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SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Mon Jul 22 2024 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE MID-ATLANTIC REGION....AND WESTERN ARIZONA TO THE LOWER COLORADO RIVER VALLEY... ...SUMMARY... Isolated severe thunderstorms will be possible this afternoon and early evening over portions of the mid-Atlantic region, as well as western Arizona to the lower Colorado River Valley. ...Mid-Atlantic states... A narrow ribbon of slightly enhanced southwesterly 500-mb flow will remain across NC/Delmarva to the southeast of a broad/weak mid-level trough centered over the Great Lakes southwestward through the Ozarks. Although large-scale forcing will be modest, a seasonably moist airmass (14-16 g/kg lowest 100-mb mean mixing ratios per 12 UTC area raobs) will gradually destabilize through the mid afternoon. Midday visible satellite imagery shows the initial stages of a building cumulus field across the Carolinas northward into eastern VA. Widely scattered to scattered thunderstorms are forecast to develop this afternoon within the moderately unstable airmass. Some strengthening in south-southwesterly 850-mb flow is progged by models later this afternoon into the early evening. A few of the stronger storms may pose a localized risk for damaging gusts (45-60 mph). If a transient supercell can develop (primarily 21-01z), a brief tornado is possible. This activity will likely diminish by mid-late evening owing to nocturnal stabilization. ...Western AZ/lower CO River Valley... Widely scattered thunderstorms are forecast to develop later this afternoon/evening as surface temperatures soar into the 100s. Although flow will be weak due to proximity to the mid- to upper-level ridge, large surface temperature-dewpoint depressions (around 50 deg F) will favor evaporative cooled downdrafts with the more robust thunderstorm cores. A few severe gusts (60-70 mph) are possible before this activity wanes by mid evening. ...Southeast New England... Model guidance indicates increased shower/thunderstorm potential late tonight (08-12 UTC) as a strengthening LLJ shifts northeastward from the Mid-Atlantic coast to near the continental shelf/deep Atlantic waters off the southeast New England coast. The latest models generally indicate meager to no surface-based buoyancy penetrating the coast, thus precluding low-severe probabilities this outlook update. ..Smith/Barnes.. 07/22/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Mon Jul 22 2024 Valid 221700Z - 231200Z Minor refinements were made to the area delineating potential for isolated dry thunderstorms across portions of the Pacific Northwest in the wake of morning convection clearing the region. Otherwise, the previous forecast remains on track. See the discussion below for more details. ..Karstens.. 07/22/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Mon Jul 22 2024/ ...Synopsis... An upper ridge centered over the Rockies will begin to weaken today under the influence of a broad mid-level trough moving onshore over the Pacific Northwest. Weak ascent, increasingly strong southwesterly flow aloft and inland moisture advection will support thunderstorms and gusty winds across the higher terrain of the Northwest and northern Rockies. Dry lightning and locally dry and breezy conditions are possible. ...Northwest, and Northern Rockies... Isolated, mostly dry, thunderstorms are expected to be ongoing at the start of the period as convection from overnight lifts north with the advancing upper trough. Additional storm development is possible later this afternoon, as peak diurnal heating and lingering mid-level moisture will support the development of weak elevated buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorms are also possible farther south across parts of the Great Basin, but higher PWATs and multiple days of prior storms suggest a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, the risk for lightning ignitions is high. In addition to the risk for lightning, gusty downslope winds are possible across parts of the Cascades and western Columbia Basin this afternoon. Increasing mid-level flow atop a hot and well-mixed boundary layer may support occasional gusts to 15-25 mph through the Cascade Gaps. However, coverage and duration of the gusty winds is expected to be limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Mon Jul 22 2024 Valid 221700Z - 231200Z Minor refinements were made to the area delineating potential for isolated dry thunderstorms across portions of the Pacific Northwest in the wake of morning convection clearing the region. Otherwise, the previous forecast remains on track. See the discussion below for more details. ..Karstens.. 07/22/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Mon Jul 22 2024/ ...Synopsis... An upper ridge centered over the Rockies will begin to weaken today under the influence of a broad mid-level trough moving onshore over the Pacific Northwest. Weak ascent, increasingly strong southwesterly flow aloft and inland moisture advection will support thunderstorms and gusty winds across the higher terrain of the Northwest and northern Rockies. Dry lightning and locally dry and breezy conditions are possible. ...Northwest, and Northern Rockies... Isolated, mostly dry, thunderstorms are expected to be ongoing at the start of the period as convection from overnight lifts north with the advancing upper trough. Additional storm development is possible later this afternoon, as peak diurnal heating and lingering mid-level moisture will support the development of weak elevated buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorms are also possible farther south across parts of the Great Basin, but higher PWATs and multiple days of prior storms suggest a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, the risk for lightning ignitions is high. In addition to the risk for lightning, gusty downslope winds are possible across parts of the Cascades and western Columbia Basin this afternoon. Increasing mid-level flow atop a hot and well-mixed boundary layer may support occasional gusts to 15-25 mph through the Cascade Gaps. However, coverage and duration of the gusty winds is expected to be limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Mon Jul 22 2024 Valid 221700Z - 231200Z Minor refinements were made to the area delineating potential for isolated dry thunderstorms across portions of the Pacific Northwest in the wake of morning convection clearing the region. Otherwise, the previous forecast remains on track. See the discussion below for more details. ..Karstens.. 07/22/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Mon Jul 22 2024/ ...Synopsis... An upper ridge centered over the Rockies will begin to weaken today under the influence of a broad mid-level trough moving onshore over the Pacific Northwest. Weak ascent, increasingly strong southwesterly flow aloft and inland moisture advection will support thunderstorms and gusty winds across the higher terrain of the Northwest and northern Rockies. Dry lightning and locally dry and breezy conditions are possible. ...Northwest, and Northern Rockies... Isolated, mostly dry, thunderstorms are expected to be ongoing at the start of the period as convection from overnight lifts north with the advancing upper trough. Additional storm development is possible later this afternoon, as peak diurnal heating and lingering mid-level moisture will support the development of weak elevated buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorms are also possible farther south across parts of the Great Basin, but higher PWATs and multiple days of prior storms suggest a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, the risk for lightning ignitions is high. In addition to the risk for lightning, gusty downslope winds are possible across parts of the Cascades and western Columbia Basin this afternoon. Increasing mid-level flow atop a hot and well-mixed boundary layer may support occasional gusts to 15-25 mph through the Cascade Gaps. However, coverage and duration of the gusty winds is expected to be limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Mon Jul 22 2024 Valid 221700Z - 231200Z Minor refinements were made to the area delineating potential for isolated dry thunderstorms across portions of the Pacific Northwest in the wake of morning convection clearing the region. Otherwise, the previous forecast remains on track. See the discussion below for more details. ..Karstens.. 07/22/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Mon Jul 22 2024/ ...Synopsis... An upper ridge centered over the Rockies will begin to weaken today under the influence of a broad mid-level trough moving onshore over the Pacific Northwest. Weak ascent, increasingly strong southwesterly flow aloft and inland moisture advection will support thunderstorms and gusty winds across the higher terrain of the Northwest and northern Rockies. Dry lightning and locally dry and breezy conditions are possible. ...Northwest, and Northern Rockies... Isolated, mostly dry, thunderstorms are expected to be ongoing at the start of the period as convection from overnight lifts north with the advancing upper trough. Additional storm development is possible later this afternoon, as peak diurnal heating and lingering mid-level moisture will support the development of weak elevated buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorms are also possible farther south across parts of the Great Basin, but higher PWATs and multiple days of prior storms suggest a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, the risk for lightning ignitions is high. In addition to the risk for lightning, gusty downslope winds are possible across parts of the Cascades and western Columbia Basin this afternoon. Increasing mid-level flow atop a hot and well-mixed boundary layer may support occasional gusts to 15-25 mph through the Cascade Gaps. However, coverage and duration of the gusty winds is expected to be limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Mon Jul 22 2024 Valid 221700Z - 231200Z Minor refinements were made to the area delineating potential for isolated dry thunderstorms across portions of the Pacific Northwest in the wake of morning convection clearing the region. Otherwise, the previous forecast remains on track. See the discussion below for more details. ..Karstens.. 07/22/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Mon Jul 22 2024/ ...Synopsis... An upper ridge centered over the Rockies will begin to weaken today under the influence of a broad mid-level trough moving onshore over the Pacific Northwest. Weak ascent, increasingly strong southwesterly flow aloft and inland moisture advection will support thunderstorms and gusty winds across the higher terrain of the Northwest and northern Rockies. Dry lightning and locally dry and breezy conditions are possible. ...Northwest, and Northern Rockies... Isolated, mostly dry, thunderstorms are expected to be ongoing at the start of the period as convection from overnight lifts north with the advancing upper trough. Additional storm development is possible later this afternoon, as peak diurnal heating and lingering mid-level moisture will support the development of weak elevated buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorms are also possible farther south across parts of the Great Basin, but higher PWATs and multiple days of prior storms suggest a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, the risk for lightning ignitions is high. In addition to the risk for lightning, gusty downslope winds are possible across parts of the Cascades and western Columbia Basin this afternoon. Increasing mid-level flow atop a hot and well-mixed boundary layer may support occasional gusts to 15-25 mph through the Cascade Gaps. However, coverage and duration of the gusty winds is expected to be limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Mon Jul 22 2024 Valid 221700Z - 231200Z Minor refinements were made to the area delineating potential for isolated dry thunderstorms across portions of the Pacific Northwest in the wake of morning convection clearing the region. Otherwise, the previous forecast remains on track. See the discussion below for more details. ..Karstens.. 07/22/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Mon Jul 22 2024/ ...Synopsis... An upper ridge centered over the Rockies will begin to weaken today under the influence of a broad mid-level trough moving onshore over the Pacific Northwest. Weak ascent, increasingly strong southwesterly flow aloft and inland moisture advection will support thunderstorms and gusty winds across the higher terrain of the Northwest and northern Rockies. Dry lightning and locally dry and breezy conditions are possible. ...Northwest, and Northern Rockies... Isolated, mostly dry, thunderstorms are expected to be ongoing at the start of the period as convection from overnight lifts north with the advancing upper trough. Additional storm development is possible later this afternoon, as peak diurnal heating and lingering mid-level moisture will support the development of weak elevated buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorms are also possible farther south across parts of the Great Basin, but higher PWATs and multiple days of prior storms suggest a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, the risk for lightning ignitions is high. In addition to the risk for lightning, gusty downslope winds are possible across parts of the Cascades and western Columbia Basin this afternoon. Increasing mid-level flow atop a hot and well-mixed boundary layer may support occasional gusts to 15-25 mph through the Cascade Gaps. However, coverage and duration of the gusty winds is expected to be limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Mon Jul 22 2024 Valid 221700Z - 231200Z Minor refinements were made to the area delineating potential for isolated dry thunderstorms across portions of the Pacific Northwest in the wake of morning convection clearing the region. Otherwise, the previous forecast remains on track. See the discussion below for more details. ..Karstens.. 07/22/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Mon Jul 22 2024/ ...Synopsis... An upper ridge centered over the Rockies will begin to weaken today under the influence of a broad mid-level trough moving onshore over the Pacific Northwest. Weak ascent, increasingly strong southwesterly flow aloft and inland moisture advection will support thunderstorms and gusty winds across the higher terrain of the Northwest and northern Rockies. Dry lightning and locally dry and breezy conditions are possible. ...Northwest, and Northern Rockies... Isolated, mostly dry, thunderstorms are expected to be ongoing at the start of the period as convection from overnight lifts north with the advancing upper trough. Additional storm development is possible later this afternoon, as peak diurnal heating and lingering mid-level moisture will support the development of weak elevated buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorms are also possible farther south across parts of the Great Basin, but higher PWATs and multiple days of prior storms suggest a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, the risk for lightning ignitions is high. In addition to the risk for lightning, gusty downslope winds are possible across parts of the Cascades and western Columbia Basin this afternoon. Increasing mid-level flow atop a hot and well-mixed boundary layer may support occasional gusts to 15-25 mph through the Cascade Gaps. However, coverage and duration of the gusty winds is expected to be limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1128 AM CDT Mon Jul 22 2024 Valid 221700Z - 231200Z Minor refinements were made to the area delineating potential for isolated dry thunderstorms across portions of the Pacific Northwest in the wake of morning convection clearing the region. Otherwise, the previous forecast remains on track. See the discussion below for more details. ..Karstens.. 07/22/2024 .PREV DISCUSSION... /ISSUED 0154 AM CDT Mon Jul 22 2024/ ...Synopsis... An upper ridge centered over the Rockies will begin to weaken today under the influence of a broad mid-level trough moving onshore over the Pacific Northwest. Weak ascent, increasingly strong southwesterly flow aloft and inland moisture advection will support thunderstorms and gusty winds across the higher terrain of the Northwest and northern Rockies. Dry lightning and locally dry and breezy conditions are possible. ...Northwest, and Northern Rockies... Isolated, mostly dry, thunderstorms are expected to be ongoing at the start of the period as convection from overnight lifts north with the advancing upper trough. Additional storm development is possible later this afternoon, as peak diurnal heating and lingering mid-level moisture will support the development of weak elevated buoyancy. Deep and well-mixed sub-cloud layers, along with moderate storm speeds, will favor low precipitation efficiency and the potential for dry lightning strikes with any storm that develops. Scattered thunderstorms are also possible farther south across parts of the Great Basin, but higher PWATs and multiple days of prior storms suggest a wetter mode is more probable. Coverage of dry storms appears highest across parts of south-central OR, extending northeastward across central ID into western MT. With receptive fuels in place over much of the Northwest and northern Rockies, the risk for lightning ignitions is high. In addition to the risk for lightning, gusty downslope winds are possible across parts of the Cascades and western Columbia Basin this afternoon. Increasing mid-level flow atop a hot and well-mixed boundary layer may support occasional gusts to 15-25 mph through the Cascade Gaps. However, coverage and duration of the gusty winds is expected to be limited. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Mon Jul 22 2024 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE MID-ATLANTIC REGION...AS WELL AS WESTERN ARIZONA TO THE LOWER COLORADO RIVER VALLEY... ...SUMMARY... Isolated severe thunderstorms will be possible today over portions of the mid-Atlantic region, as well as western Arizona to the lower Colorado River Valley. ...Synopsis... The basic mid/upper-level pattern will continue to feature mean ridging over the western CONUS, and broad but mostly weak cyclonic flow around a trough extending from the Upper Great Lakes southwestward over south TX. However, the northern part of the western ridging -- over western Canada and the northern Rockies -- will break down as: 1. A large cyclone moves eastward from the Gulf of Alaska, and 2. A strong shortwave trough in the cyclone's southeastern quadrant pivots northeastward from the Pacific across western/northern Wa to southern BC this evening and tonight. Downstream, broadly difluent and weak, mostly northerly to northwesterly flow will cover the central CONUS. A shortwave trough -- apparent in moisture-channel imagery moving into northern MN and northeastern ND from Canada -- will pivot eastward across western Lake Superior, northern WI and parts of Upper MI today. Isolated to scattered showers and multicell thunderstorms may produce small hail and strong gusts ahead of this feature, over areas surrounding western Lake Superior; however, weak deep-layer flow/shear should preclude an organized threat. Meanwhile, another shortwave trough -- initially over parts of IL/MO -- should drift eastward over IL, while weakening. Weak perturbations apparent over eastern parts of KY/TN, and over MS and western TN, will eject northeastward over the southern Appalachians. The 11Z surface analysis showed a wavy, quasistationary frontal zone from a weak low near MEM to near SHV, DAL, ABI, PRS and ELP. A warm front was drawn from the low across middle/eastern TN, southern WV, northern VA, NJ, and Long Island Sound. The warm front should drift farther northward in some areas and become stationary in others, while the western boundary segment slowly experiences frontolysis over the southern Plains to Mid-South. ...Portions of VA/NC... Widely scattered to scattered thunderstorms should form south of the front -- near outflow and differential-heating boundaries as well as a weak surface trough -- and move east-northeastward to northeastward over the outlook area through the afternoon. Once ongoing clouds/precip exit the area, diurnal heating/destabilization will act in concert with rich low-level moisture (surface dewpoints in the 70s F, PW exceeding 2 inches, mean mixing ratios near or above 17 g/kg) to offset modest mid/upper-level lapse rates and yield favorable buoyancy. MLCAPE around 1500-2500 J/kg should become common, with isolated strong/damaging gusts possible in the most intense, water-loaded downdrafts. With modest flow but well-curved low-level hodographs, and around 35 kt effective-shear magnitude ahead of the ejecting weak shortwave trough(s), and potential for boundary-storm interactions, a tornado may occur as well. ...Western AZ/lower Colorado River Valley... Widely scattered to scattered thunderstorms should form this afternoon over the western parts of the higher terrain in north-central/northwestern AZ and migrate southwestward to lower desert regions in western parts of the state -- perhaps lasting long enough to cross parts of the lower Colorado River Valley. Activity should form over well-heated higher elevations with sufficient moisture to sustain the most vigorous convection for at least a couple hours after it moves southwestward to lower deserts, deeply mixed boundary layers with hot surface temperatures and large DCAPE will favor isolated severe downbursts. A deep (700-300 mb and sometimes higher) layer of modest (5-20 kt) northerly to northeasterly flow generally is progged across the region, within the mid/upper anticyclone and southeast of the high. This will encourage preferential southward to southwestward motion of both active convection and resulting outflow pools. ..Edwards/Broyles.. 07/22/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Mon Jul 22 2024 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE MID-ATLANTIC REGION...AS WELL AS WESTERN ARIZONA TO THE LOWER COLORADO RIVER VALLEY... ...SUMMARY... Isolated severe thunderstorms will be possible today over portions of the mid-Atlantic region, as well as western Arizona to the lower Colorado River Valley. ...Synopsis... The basic mid/upper-level pattern will continue to feature mean ridging over the western CONUS, and broad but mostly weak cyclonic flow around a trough extending from the Upper Great Lakes southwestward over south TX. However, the northern part of the western ridging -- over western Canada and the northern Rockies -- will break down as: 1. A large cyclone moves eastward from the Gulf of Alaska, and 2. A strong shortwave trough in the cyclone's southeastern quadrant pivots northeastward from the Pacific across western/northern Wa to southern BC this evening and tonight. Downstream, broadly difluent and weak, mostly northerly to northwesterly flow will cover the central CONUS. A shortwave trough -- apparent in moisture-channel imagery moving into northern MN and northeastern ND from Canada -- will pivot eastward across western Lake Superior, northern WI and parts of Upper MI today. Isolated to scattered showers and multicell thunderstorms may produce small hail and strong gusts ahead of this feature, over areas surrounding western Lake Superior; however, weak deep-layer flow/shear should preclude an organized threat. Meanwhile, another shortwave trough -- initially over parts of IL/MO -- should drift eastward over IL, while weakening. Weak perturbations apparent over eastern parts of KY/TN, and over MS and western TN, will eject northeastward over the southern Appalachians. The 11Z surface analysis showed a wavy, quasistationary frontal zone from a weak low near MEM to near SHV, DAL, ABI, PRS and ELP. A warm front was drawn from the low across middle/eastern TN, southern WV, northern VA, NJ, and Long Island Sound. The warm front should drift farther northward in some areas and become stationary in others, while the western boundary segment slowly experiences frontolysis over the southern Plains to Mid-South. ...Portions of VA/NC... Widely scattered to scattered thunderstorms should form south of the front -- near outflow and differential-heating boundaries as well as a weak surface trough -- and move east-northeastward to northeastward over the outlook area through the afternoon. Once ongoing clouds/precip exit the area, diurnal heating/destabilization will act in concert with rich low-level moisture (surface dewpoints in the 70s F, PW exceeding 2 inches, mean mixing ratios near or above 17 g/kg) to offset modest mid/upper-level lapse rates and yield favorable buoyancy. MLCAPE around 1500-2500 J/kg should become common, with isolated strong/damaging gusts possible in the most intense, water-loaded downdrafts. With modest flow but well-curved low-level hodographs, and around 35 kt effective-shear magnitude ahead of the ejecting weak shortwave trough(s), and potential for boundary-storm interactions, a tornado may occur as well. ...Western AZ/lower Colorado River Valley... Widely scattered to scattered thunderstorms should form this afternoon over the western parts of the higher terrain in north-central/northwestern AZ and migrate southwestward to lower desert regions in western parts of the state -- perhaps lasting long enough to cross parts of the lower Colorado River Valley. Activity should form over well-heated higher elevations with sufficient moisture to sustain the most vigorous convection for at least a couple hours after it moves southwestward to lower deserts, deeply mixed boundary layers with hot surface temperatures and large DCAPE will favor isolated severe downbursts. A deep (700-300 mb and sometimes higher) layer of modest (5-20 kt) northerly to northeasterly flow generally is progged across the region, within the mid/upper anticyclone and southeast of the high. This will encourage preferential southward to southwestward motion of both active convection and resulting outflow pools. ..Edwards/Broyles.. 07/22/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Mon Jul 22 2024 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE MID-ATLANTIC REGION...AS WELL AS WESTERN ARIZONA TO THE LOWER COLORADO RIVER VALLEY... ...SUMMARY... Isolated severe thunderstorms will be possible today over portions of the mid-Atlantic region, as well as western Arizona to the lower Colorado River Valley. ...Synopsis... The basic mid/upper-level pattern will continue to feature mean ridging over the western CONUS, and broad but mostly weak cyclonic flow around a trough extending from the Upper Great Lakes southwestward over south TX. However, the northern part of the western ridging -- over western Canada and the northern Rockies -- will break down as: 1. A large cyclone moves eastward from the Gulf of Alaska, and 2. A strong shortwave trough in the cyclone's southeastern quadrant pivots northeastward from the Pacific across western/northern Wa to southern BC this evening and tonight. Downstream, broadly difluent and weak, mostly northerly to northwesterly flow will cover the central CONUS. A shortwave trough -- apparent in moisture-channel imagery moving into northern MN and northeastern ND from Canada -- will pivot eastward across western Lake Superior, northern WI and parts of Upper MI today. Isolated to scattered showers and multicell thunderstorms may produce small hail and strong gusts ahead of this feature, over areas surrounding western Lake Superior; however, weak deep-layer flow/shear should preclude an organized threat. Meanwhile, another shortwave trough -- initially over parts of IL/MO -- should drift eastward over IL, while weakening. Weak perturbations apparent over eastern parts of KY/TN, and over MS and western TN, will eject northeastward over the southern Appalachians. The 11Z surface analysis showed a wavy, quasistationary frontal zone from a weak low near MEM to near SHV, DAL, ABI, PRS and ELP. A warm front was drawn from the low across middle/eastern TN, southern WV, northern VA, NJ, and Long Island Sound. The warm front should drift farther northward in some areas and become stationary in others, while the western boundary segment slowly experiences frontolysis over the southern Plains to Mid-South. ...Portions of VA/NC... Widely scattered to scattered thunderstorms should form south of the front -- near outflow and differential-heating boundaries as well as a weak surface trough -- and move east-northeastward to northeastward over the outlook area through the afternoon. Once ongoing clouds/precip exit the area, diurnal heating/destabilization will act in concert with rich low-level moisture (surface dewpoints in the 70s F, PW exceeding 2 inches, mean mixing ratios near or above 17 g/kg) to offset modest mid/upper-level lapse rates and yield favorable buoyancy. MLCAPE around 1500-2500 J/kg should become common, with isolated strong/damaging gusts possible in the most intense, water-loaded downdrafts. With modest flow but well-curved low-level hodographs, and around 35 kt effective-shear magnitude ahead of the ejecting weak shortwave trough(s), and potential for boundary-storm interactions, a tornado may occur as well. ...Western AZ/lower Colorado River Valley... Widely scattered to scattered thunderstorms should form this afternoon over the western parts of the higher terrain in north-central/northwestern AZ and migrate southwestward to lower desert regions in western parts of the state -- perhaps lasting long enough to cross parts of the lower Colorado River Valley. Activity should form over well-heated higher elevations with sufficient moisture to sustain the most vigorous convection for at least a couple hours after it moves southwestward to lower deserts, deeply mixed boundary layers with hot surface temperatures and large DCAPE will favor isolated severe downbursts. A deep (700-300 mb and sometimes higher) layer of modest (5-20 kt) northerly to northeasterly flow generally is progged across the region, within the mid/upper anticyclone and southeast of the high. This will encourage preferential southward to southwestward motion of both active convection and resulting outflow pools. ..Edwards/Broyles.. 07/22/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Mon Jul 22 2024 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE MID-ATLANTIC REGION...AS WELL AS WESTERN ARIZONA TO THE LOWER COLORADO RIVER VALLEY... ...SUMMARY... Isolated severe thunderstorms will be possible today over portions of the mid-Atlantic region, as well as western Arizona to the lower Colorado River Valley. ...Synopsis... The basic mid/upper-level pattern will continue to feature mean ridging over the western CONUS, and broad but mostly weak cyclonic flow around a trough extending from the Upper Great Lakes southwestward over south TX. However, the northern part of the western ridging -- over western Canada and the northern Rockies -- will break down as: 1. A large cyclone moves eastward from the Gulf of Alaska, and 2. A strong shortwave trough in the cyclone's southeastern quadrant pivots northeastward from the Pacific across western/northern Wa to southern BC this evening and tonight. Downstream, broadly difluent and weak, mostly northerly to northwesterly flow will cover the central CONUS. A shortwave trough -- apparent in moisture-channel imagery moving into northern MN and northeastern ND from Canada -- will pivot eastward across western Lake Superior, northern WI and parts of Upper MI today. Isolated to scattered showers and multicell thunderstorms may produce small hail and strong gusts ahead of this feature, over areas surrounding western Lake Superior; however, weak deep-layer flow/shear should preclude an organized threat. Meanwhile, another shortwave trough -- initially over parts of IL/MO -- should drift eastward over IL, while weakening. Weak perturbations apparent over eastern parts of KY/TN, and over MS and western TN, will eject northeastward over the southern Appalachians. The 11Z surface analysis showed a wavy, quasistationary frontal zone from a weak low near MEM to near SHV, DAL, ABI, PRS and ELP. A warm front was drawn from the low across middle/eastern TN, southern WV, northern VA, NJ, and Long Island Sound. The warm front should drift farther northward in some areas and become stationary in others, while the western boundary segment slowly experiences frontolysis over the southern Plains to Mid-South. ...Portions of VA/NC... Widely scattered to scattered thunderstorms should form south of the front -- near outflow and differential-heating boundaries as well as a weak surface trough -- and move east-northeastward to northeastward over the outlook area through the afternoon. Once ongoing clouds/precip exit the area, diurnal heating/destabilization will act in concert with rich low-level moisture (surface dewpoints in the 70s F, PW exceeding 2 inches, mean mixing ratios near or above 17 g/kg) to offset modest mid/upper-level lapse rates and yield favorable buoyancy. MLCAPE around 1500-2500 J/kg should become common, with isolated strong/damaging gusts possible in the most intense, water-loaded downdrafts. With modest flow but well-curved low-level hodographs, and around 35 kt effective-shear magnitude ahead of the ejecting weak shortwave trough(s), and potential for boundary-storm interactions, a tornado may occur as well. ...Western AZ/lower Colorado River Valley... Widely scattered to scattered thunderstorms should form this afternoon over the western parts of the higher terrain in north-central/northwestern AZ and migrate southwestward to lower desert regions in western parts of the state -- perhaps lasting long enough to cross parts of the lower Colorado River Valley. Activity should form over well-heated higher elevations with sufficient moisture to sustain the most vigorous convection for at least a couple hours after it moves southwestward to lower deserts, deeply mixed boundary layers with hot surface temperatures and large DCAPE will favor isolated severe downbursts. A deep (700-300 mb and sometimes higher) layer of modest (5-20 kt) northerly to northeasterly flow generally is progged across the region, within the mid/upper anticyclone and southeast of the high. This will encourage preferential southward to southwestward motion of both active convection and resulting outflow pools. ..Edwards/Broyles.. 07/22/2024 Read more

740
ABPZ20 KNHC 221143
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Mon Jul 22 2024

For the eastern North Pacific...east of 140 degrees west longitude:

Central and Western East Pacific:
A tropical wave located several hundred miles south-southwest of the
southern tip of the Baja California Peninsula is producing
disorganized shower and thunderstorm activity. Environmental
conditions could become a little more conducive for some gradual
development of this system over the next several days while it moves
westward to west-northwestward at 10 to 15 mph across the central
and western portions of the basin.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 7 days...low...30 percent.

Offshore Southwestern Mexico:
Disorganized showers and thunderstorms located a few hundred miles
south-southwest of Acapulco, Mexico are associated with a surface
trough. Environmental conditions could support slight development
over the next couple of days as the system moves slowly
west-northwestward, remaining offshore of southwestern Mexico.
*Formation chance through 48 hours...low...10 percent.
*Formation chance through 7 days...low...10 percent.

$$
Forecaster Hagen/Brown

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0300 AM CDT Mon Jul 22 2024 Valid 251200Z - 301200Z ...DISCUSSION... An upper trough will move over the Northeast on Day 4/Thu and persist, albeit weakening with time, for much of the Day 4-8 period. Surface high pressure will build in the wake of a cold front moving across the Northeast on Thursday, and also persist into early next week. Some severe thunderstorm potential could develop over the Northeast states on Thursday as the cold front pushes east. However, timing of the front may be unfavorable with the diurnal cycle, and confidence is too low to include severe probabilities. Meanwhile, an upper ridge will overspread much of the Plains, while a series of upper shortwave troughs move across the Pacific Northwest vicinity. Boundary layer moisture will increase beneath the upper ridge over the Plains. With the upper trough and surface high over the Midwest/Northeast blocking progression of the upper ridge over the Plains, daily surface trough/weak low development is expected over the northern/central High Plains vicinity. However, under the influence of an amplified upper ridge, thunderstorm development each day is uncertain given a lack of large-scale ascent and likely capping concerns. Overall, severe thunderstorm potential appears low during the Day 4-8 period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0300 AM CDT Mon Jul 22 2024 Valid 251200Z - 301200Z ...DISCUSSION... An upper trough will move over the Northeast on Day 4/Thu and persist, albeit weakening with time, for much of the Day 4-8 period. Surface high pressure will build in the wake of a cold front moving across the Northeast on Thursday, and also persist into early next week. Some severe thunderstorm potential could develop over the Northeast states on Thursday as the cold front pushes east. However, timing of the front may be unfavorable with the diurnal cycle, and confidence is too low to include severe probabilities. Meanwhile, an upper ridge will overspread much of the Plains, while a series of upper shortwave troughs move across the Pacific Northwest vicinity. Boundary layer moisture will increase beneath the upper ridge over the Plains. With the upper trough and surface high over the Midwest/Northeast blocking progression of the upper ridge over the Plains, daily surface trough/weak low development is expected over the northern/central High Plains vicinity. However, under the influence of an amplified upper ridge, thunderstorm development each day is uncertain given a lack of large-scale ascent and likely capping concerns. Overall, severe thunderstorm potential appears low during the Day 4-8 period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0300 AM CDT Mon Jul 22 2024 Valid 251200Z - 301200Z ...DISCUSSION... An upper trough will move over the Northeast on Day 4/Thu and persist, albeit weakening with time, for much of the Day 4-8 period. Surface high pressure will build in the wake of a cold front moving across the Northeast on Thursday, and also persist into early next week. Some severe thunderstorm potential could develop over the Northeast states on Thursday as the cold front pushes east. However, timing of the front may be unfavorable with the diurnal cycle, and confidence is too low to include severe probabilities. Meanwhile, an upper ridge will overspread much of the Plains, while a series of upper shortwave troughs move across the Pacific Northwest vicinity. Boundary layer moisture will increase beneath the upper ridge over the Plains. With the upper trough and surface high over the Midwest/Northeast blocking progression of the upper ridge over the Plains, daily surface trough/weak low development is expected over the northern/central High Plains vicinity. However, under the influence of an amplified upper ridge, thunderstorm development each day is uncertain given a lack of large-scale ascent and likely capping concerns. Overall, severe thunderstorm potential appears low during the Day 4-8 period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0300 AM CDT Mon Jul 22 2024 Valid 251200Z - 301200Z ...DISCUSSION... An upper trough will move over the Northeast on Day 4/Thu and persist, albeit weakening with time, for much of the Day 4-8 period. Surface high pressure will build in the wake of a cold front moving across the Northeast on Thursday, and also persist into early next week. Some severe thunderstorm potential could develop over the Northeast states on Thursday as the cold front pushes east. However, timing of the front may be unfavorable with the diurnal cycle, and confidence is too low to include severe probabilities. Meanwhile, an upper ridge will overspread much of the Plains, while a series of upper shortwave troughs move across the Pacific Northwest vicinity. Boundary layer moisture will increase beneath the upper ridge over the Plains. With the upper trough and surface high over the Midwest/Northeast blocking progression of the upper ridge over the Plains, daily surface trough/weak low development is expected over the northern/central High Plains vicinity. However, under the influence of an amplified upper ridge, thunderstorm development each day is uncertain given a lack of large-scale ascent and likely capping concerns. Overall, severe thunderstorm potential appears low during the Day 4-8 period. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Mon Jul 22 2024 Valid 231200Z - 241200Z ...Synopsis... The upper trough over the Northwest is forecast to remain mostly stationary as the adjacent ridge over the Rockies begins to weaken and shift to the east. Stronger flow aloft will gradually overspread the Northwest and northern Rockies through the week. Isolated dry thunderstorms and gusty downslope winds will promote elevated fire-weather potential D2/Tuesday. ...Northwest and Northern Rockies... With the upper trough over the Northwest expected to remain fairly stationary, lingering mid-level moisture and weak ascent will continue to support mid-level destabilization and thunderstorms D2/Tuesday afternoon. Very warm surface temperatures and fast storm speeds will again favor mostly dry storms with the potential for lightning ignitions in dry fuels. Forcing for ascent should be slightly less than previous days, casting some uncertainty on storm coverage. However, at least isolated dry thunderstorms are possible over parts of eastern WA/OR and into western ID. West/southwest flow aloft is forecast to increase over the northern Rockies and Cascade Gaps ahead of the trough. This may promote several hours of gusty downslope winds across parts of eastern ID and western MT. Model guidance shows surface winds of 15-25 mph overlapping with RH values below 20%. This, along with the increase in lightning, will support the potential for elevated fire-weather conditions D2/Tuesday afternoon. ..Lyons.. 07/22/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 AM CDT Mon Jul 22 2024 Valid 231200Z - 241200Z ...Synopsis... The upper trough over the Northwest is forecast to remain mostly stationary as the adjacent ridge over the Rockies begins to weaken and shift to the east. Stronger flow aloft will gradually overspread the Northwest and northern Rockies through the week. Isolated dry thunderstorms and gusty downslope winds will promote elevated fire-weather potential D2/Tuesday. ...Northwest and Northern Rockies... With the upper trough over the Northwest expected to remain fairly stationary, lingering mid-level moisture and weak ascent will continue to support mid-level destabilization and thunderstorms D2/Tuesday afternoon. Very warm surface temperatures and fast storm speeds will again favor mostly dry storms with the potential for lightning ignitions in dry fuels. Forcing for ascent should be slightly less than previous days, casting some uncertainty on storm coverage. However, at least isolated dry thunderstorms are possible over parts of eastern WA/OR and into western ID. West/southwest flow aloft is forecast to increase over the northern Rockies and Cascade Gaps ahead of the trough. This may promote several hours of gusty downslope winds across parts of eastern ID and western MT. Model guidance shows surface winds of 15-25 mph overlapping with RH values below 20%. This, along with the increase in lightning, will support the potential for elevated fire-weather conditions D2/Tuesday afternoon. ..Lyons.. 07/22/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more