Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Fri Aug 23 2024 Valid 232000Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF WESTERN MONTANA... ...SUMMARY... Strong to severe storms with severe wind gusts and some hail are possible across Montana, the Intermountain West and central Rockies, southeast Arizona to extreme southwestern New Mexico, and parts of the High Plains. ...20z Update... The primary adjustment for this update was an expansion of the Slight risk/15% wind probability southward to include more of western MT. Slowly intensifying convection across eastern ID is expected to remain relatively benign for the near-term (see MCD #1976 for additional details regarding short-term trends), but may pose a more robust severe wind threat later this afternoon/evening as convection spreads north into a deeply mixed environment across western MT. The last several HRRR solutions have captured recent convective and environmental trends well and consistently suggest the best potential for severe wind will be associated with this activity as it spreads north. The adjustment to the Slight risk area should better reflect this potential. Elsewhere, the forecast remains on track per the previous discussion (below). See MCD #1977 for the latest details regarding the severe threat across southern Arizona. ..Moore.. 08/23/2024 .PREV DISCUSSION... /ISSUED 1127 AM CDT Fri Aug 23 2024/ ...Intermountain West to northern Rockies... The lead portion of an upper trough centered along the coastal Pacific Northwest will shift north-northeastward over the northern Intermountain region in tandem with the exit region of a strengthening mid/upper-level jet. Scattered thunderstorms are expected in this regime preceding the Pacific Coast trough, with initial development over the higher terrain ahead of the surface cold front. Isolated severe gusts and marginally severe hail will be possible, with the potential for a more focused corridor of stronger wind gusts across northwest/north-central Montana late this afternoon through early evening. Additional thunderstorms should form this afternoon across east/northeast Oregon, northern/eastern Idaho, to western Wyoming, and southeastward into Utah/western Colorado, as eastern fringes of large-scale ascent preceding the Pacific Northwest trough and embedded shortwaves overlie destabilizing, elevated terrain. Throughout the corridor, sufficient deep-layer shear (30-45 kt) should exist for organized multicells and small bowing/outflow-driven clusters, and perhaps a few supercells, with some hail and severe-caliber wind gusts possible. ...High Plains... Isolated to widely scattered thunderstorms are expected to form over the central/northern Rockies, as well as near the lee trough over eastern Montana this afternoon, with another favored corridor across the central High Plains including northeast Colorado/western Nebraska. Activity should move east-northeastward across the adjoining High Plains. This convection will encounter a diurnally destabilizing, well-mixed boundary layer with steep low-level lapse rates, supporting isolated severe wind gusts. Isolated large hail also will be possible. Strongly difluent mid/upper-level flow will exist over most of this corridor, between the Pacific Northwest cyclone and the southern Plains anticyclone, with speeds generally increasing northwestward and low-level moisture greater southward across the central High Plains. Still, sufficient moisture should persist near the Montana lee trough, along with enough veering with height over the entire area to yield enough deep shear (30+ kt effective-shear magnitudes) for organized convection. ...Southeast Arizona/far southwest New Mexico... Widely scattered to scattered thunderstorms are expected to develop this afternoon with a relatively moist air mass and ample insolation. Increasing mid-level southerlies around the western rim of the anticyclone should enable 20-30 kt effective-shear magnitudes, and enough northward storm motion to augment already strong downbursts from the most intense cells locally. An instance or two of marginally severe hail could also occur. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 PM CDT Fri Aug 23 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms appear likely across the northern Plains area on Sunday, with weaker and more isolated severe potential southwestward into the southern Rockies on Sunday. ...Northern Plains... An upper trough will generally weaken as it moves from the Intermountain Region during the day and into the northern Plains through Monday morning. As the parent upper low moves from ID across MT, it will fill, with steadily decreasing flow aloft into the Plains. Despite this, sufficient shear and lift will materialize to support a severe risk centered over the northern Plains. Effective deep-layer shear on the order of 35-40 kt is forecast east of the cold front, which will exist over the central Dakotas. Heating and a moist air mass will yield 3500+ J/kg MUCAPE, and as such, severe storms are likely to develop along the cold front during the late afternoon. Overall shear looks to be marginal for supercells, given the lack of an appreciable low-level jet. However, veering winds with height may yield transient supercell structures capable of large hail. Clustering or even an MCS may develop with time as storms increase in coverage, with hodographs supporting east/southeast motion. ...Central Rockies/Plains... Modest instability and moisture will extend southwestward along the front and beneath the periphery of the stronger mid/high level winds, from western NE into CO and northern NM. Given both marginal instability and shear, only localized severe gusts are expected. Storms timed during the peak heating hours will likely have a greater risk of strong winds where the boundary layer is deeply mixed. Small hail cannot be ruled out with the strongest cells over the higher terrain of NM/CO. ..Jewell.. 08/23/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 PM CDT Fri Aug 23 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms appear likely across the northern Plains area on Sunday, with weaker and more isolated severe potential southwestward into the southern Rockies on Sunday. ...Northern Plains... An upper trough will generally weaken as it moves from the Intermountain Region during the day and into the northern Plains through Monday morning. As the parent upper low moves from ID across MT, it will fill, with steadily decreasing flow aloft into the Plains. Despite this, sufficient shear and lift will materialize to support a severe risk centered over the northern Plains. Effective deep-layer shear on the order of 35-40 kt is forecast east of the cold front, which will exist over the central Dakotas. Heating and a moist air mass will yield 3500+ J/kg MUCAPE, and as such, severe storms are likely to develop along the cold front during the late afternoon. Overall shear looks to be marginal for supercells, given the lack of an appreciable low-level jet. However, veering winds with height may yield transient supercell structures capable of large hail. Clustering or even an MCS may develop with time as storms increase in coverage, with hodographs supporting east/southeast motion. ...Central Rockies/Plains... Modest instability and moisture will extend southwestward along the front and beneath the periphery of the stronger mid/high level winds, from western NE into CO and northern NM. Given both marginal instability and shear, only localized severe gusts are expected. Storms timed during the peak heating hours will likely have a greater risk of strong winds where the boundary layer is deeply mixed. Small hail cannot be ruled out with the strongest cells over the higher terrain of NM/CO. ..Jewell.. 08/23/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 PM CDT Fri Aug 23 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms appear likely across the northern Plains area on Sunday, with weaker and more isolated severe potential southwestward into the southern Rockies on Sunday. ...Northern Plains... An upper trough will generally weaken as it moves from the Intermountain Region during the day and into the northern Plains through Monday morning. As the parent upper low moves from ID across MT, it will fill, with steadily decreasing flow aloft into the Plains. Despite this, sufficient shear and lift will materialize to support a severe risk centered over the northern Plains. Effective deep-layer shear on the order of 35-40 kt is forecast east of the cold front, which will exist over the central Dakotas. Heating and a moist air mass will yield 3500+ J/kg MUCAPE, and as such, severe storms are likely to develop along the cold front during the late afternoon. Overall shear looks to be marginal for supercells, given the lack of an appreciable low-level jet. However, veering winds with height may yield transient supercell structures capable of large hail. Clustering or even an MCS may develop with time as storms increase in coverage, with hodographs supporting east/southeast motion. ...Central Rockies/Plains... Modest instability and moisture will extend southwestward along the front and beneath the periphery of the stronger mid/high level winds, from western NE into CO and northern NM. Given both marginal instability and shear, only localized severe gusts are expected. Storms timed during the peak heating hours will likely have a greater risk of strong winds where the boundary layer is deeply mixed. Small hail cannot be ruled out with the strongest cells over the higher terrain of NM/CO. ..Jewell.. 08/23/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 PM CDT Fri Aug 23 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms appear likely across the northern Plains area on Sunday, with weaker and more isolated severe potential southwestward into the southern Rockies on Sunday. ...Northern Plains... An upper trough will generally weaken as it moves from the Intermountain Region during the day and into the northern Plains through Monday morning. As the parent upper low moves from ID across MT, it will fill, with steadily decreasing flow aloft into the Plains. Despite this, sufficient shear and lift will materialize to support a severe risk centered over the northern Plains. Effective deep-layer shear on the order of 35-40 kt is forecast east of the cold front, which will exist over the central Dakotas. Heating and a moist air mass will yield 3500+ J/kg MUCAPE, and as such, severe storms are likely to develop along the cold front during the late afternoon. Overall shear looks to be marginal for supercells, given the lack of an appreciable low-level jet. However, veering winds with height may yield transient supercell structures capable of large hail. Clustering or even an MCS may develop with time as storms increase in coverage, with hodographs supporting east/southeast motion. ...Central Rockies/Plains... Modest instability and moisture will extend southwestward along the front and beneath the periphery of the stronger mid/high level winds, from western NE into CO and northern NM. Given both marginal instability and shear, only localized severe gusts are expected. Storms timed during the peak heating hours will likely have a greater risk of strong winds where the boundary layer is deeply mixed. Small hail cannot be ruled out with the strongest cells over the higher terrain of NM/CO. ..Jewell.. 08/23/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0231 PM CDT Fri Aug 23 2024 Valid 251200Z - 261200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms appear likely across the northern Plains area on Sunday, with weaker and more isolated severe potential southwestward into the southern Rockies on Sunday. ...Northern Plains... An upper trough will generally weaken as it moves from the Intermountain Region during the day and into the northern Plains through Monday morning. As the parent upper low moves from ID across MT, it will fill, with steadily decreasing flow aloft into the Plains. Despite this, sufficient shear and lift will materialize to support a severe risk centered over the northern Plains. Effective deep-layer shear on the order of 35-40 kt is forecast east of the cold front, which will exist over the central Dakotas. Heating and a moist air mass will yield 3500+ J/kg MUCAPE, and as such, severe storms are likely to develop along the cold front during the late afternoon. Overall shear looks to be marginal for supercells, given the lack of an appreciable low-level jet. However, veering winds with height may yield transient supercell structures capable of large hail. Clustering or even an MCS may develop with time as storms increase in coverage, with hodographs supporting east/southeast motion. ...Central Rockies/Plains... Modest instability and moisture will extend southwestward along the front and beneath the periphery of the stronger mid/high level winds, from western NE into CO and northern NM. Given both marginal instability and shear, only localized severe gusts are expected. Storms timed during the peak heating hours will likely have a greater risk of strong winds where the boundary layer is deeply mixed. Small hail cannot be ruled out with the strongest cells over the higher terrain of NM/CO. ..Jewell.. 08/23/2024 Read more