Severe Storms

MD 1935 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHERN ID...NORTHEAST NV...NORTHWEST UT
Mesoscale Discussion 1935 NWS Storm Prediction Center Norman OK 0204 PM CDT Fri Sep 06 2019 Areas affected...Southern ID...Northeast NV...Northwest UT Concerning...Severe potential...Watch unlikely Valid 061904Z - 062030Z Probability of Watch Issuance...20 percent SUMMARY...Gusty winds and marginally severe hail are expected with thunderstorms over the next few hours. Severe thunderstorm watch is not currently expected. DISCUSSION...Well-defined mid-level short-wave trough is shifting east across the northern intermountain region. Long-lived band of convection that developed over southeast OR/northwest NV has shifted downstream and new updrafts are strengthening along leading edge of thicker cloud canopy across southern ID from southern Elmore County - Twin Falls County - northern Elko County NV. As large-scale forcing interacts with higher buoyancy located over south-central ID, this activity should gradually mature, being maintained by approaching short wave. However, extensive clouds/precip currently ongoing across northern UT/eastern ID suggests strongest convection may struggle to maintain strength as it approaches weaker-buoyancy over the upper Snake River Valley. ..Darrow/Hart.. 09/06/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...SLC...PIH...BOI...LKN... LAT...LON 41461573 42241531 43241523 43881450 43551327 41891352 41311464 41461573 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0123 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...NO CRITICAL AREAS... The ongoing forecast is on track and no changes are needed. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0202 AM CDT Fri Sep 06 2019/ ...Synopsis... A negatively tilted mid-level shortwave trough will deepen across the far western CONUS throughout the Day 2/Saturday period. A surface trough will become established across the Great Basin region. As such, locally dry, breezy conditions may be observed across far western portions of the Great Basin, mainly along the lee of the Sierra. These conditions are expected to brief and patchy enough to preclude an elevated delineation. Ahead of the surface and mid-level trough axes, deep-layer ascent may encourage isolated to scattered thunderstorms across parts of northern Nevada. Nonetheless, recent accumulated rainfall from previous thunderstorm events raises concerns as to how receptive fuels will be in this area to fire spread, especially given that the forecast Day 2 storms will be predominantly wet in nature, precluding an isolated dry thunderstorm delineation at this time. Otherwise, relatively quiescent fire weather conditions are expected across the western CONUS. ...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 0123 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...NO CRITICAL AREAS... The ongoing forecast is on track and no changes are needed. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0202 AM CDT Fri Sep 06 2019/ ...Synopsis... A negatively tilted mid-level shortwave trough will deepen across the far western CONUS throughout the Day 2/Saturday period. A surface trough will become established across the Great Basin region. As such, locally dry, breezy conditions may be observed across far western portions of the Great Basin, mainly along the lee of the Sierra. These conditions are expected to brief and patchy enough to preclude an elevated delineation. Ahead of the surface and mid-level trough axes, deep-layer ascent may encourage isolated to scattered thunderstorms across parts of northern Nevada. Nonetheless, recent accumulated rainfall from previous thunderstorm events raises concerns as to how receptive fuels will be in this area to fire spread, especially given that the forecast Day 2 storms will be predominantly wet in nature, precluding an isolated dry thunderstorm delineation at this time. Otherwise, relatively quiescent fire weather conditions are expected across the western CONUS. ...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 0123 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...NO CRITICAL AREAS... The ongoing forecast is on track and no changes are needed. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0202 AM CDT Fri Sep 06 2019/ ...Synopsis... A negatively tilted mid-level shortwave trough will deepen across the far western CONUS throughout the Day 2/Saturday period. A surface trough will become established across the Great Basin region. As such, locally dry, breezy conditions may be observed across far western portions of the Great Basin, mainly along the lee of the Sierra. These conditions are expected to brief and patchy enough to preclude an elevated delineation. Ahead of the surface and mid-level trough axes, deep-layer ascent may encourage isolated to scattered thunderstorms across parts of northern Nevada. Nonetheless, recent accumulated rainfall from previous thunderstorm events raises concerns as to how receptive fuels will be in this area to fire spread, especially given that the forecast Day 2 storms will be predominantly wet in nature, precluding an isolated dry thunderstorm delineation at this time. Otherwise, relatively quiescent fire weather conditions are expected across the western CONUS. ...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 0123 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...NO CRITICAL AREAS... The ongoing forecast is on track and no changes are needed. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0202 AM CDT Fri Sep 06 2019/ ...Synopsis... A negatively tilted mid-level shortwave trough will deepen across the far western CONUS throughout the Day 2/Saturday period. A surface trough will become established across the Great Basin region. As such, locally dry, breezy conditions may be observed across far western portions of the Great Basin, mainly along the lee of the Sierra. These conditions are expected to brief and patchy enough to preclude an elevated delineation. Ahead of the surface and mid-level trough axes, deep-layer ascent may encourage isolated to scattered thunderstorms across parts of northern Nevada. Nonetheless, recent accumulated rainfall from previous thunderstorm events raises concerns as to how receptive fuels will be in this area to fire spread, especially given that the forecast Day 2 storms will be predominantly wet in nature, precluding an isolated dry thunderstorm delineation at this time. Otherwise, relatively quiescent fire weather conditions are expected across the western CONUS. ...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 0123 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...NO CRITICAL AREAS... The ongoing forecast is on track and no changes are needed. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0202 AM CDT Fri Sep 06 2019/ ...Synopsis... A negatively tilted mid-level shortwave trough will deepen across the far western CONUS throughout the Day 2/Saturday period. A surface trough will become established across the Great Basin region. As such, locally dry, breezy conditions may be observed across far western portions of the Great Basin, mainly along the lee of the Sierra. These conditions are expected to brief and patchy enough to preclude an elevated delineation. Ahead of the surface and mid-level trough axes, deep-layer ascent may encourage isolated to scattered thunderstorms across parts of northern Nevada. Nonetheless, recent accumulated rainfall from previous thunderstorm events raises concerns as to how receptive fuels will be in this area to fire spread, especially given that the forecast Day 2 storms will be predominantly wet in nature, precluding an isolated dry thunderstorm delineation at this time. Otherwise, relatively quiescent fire weather conditions are expected across the western CONUS. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Isolated strong to severe storms with gusty winds and some large hail may occur across parts of the northern and central Plains Saturday afternoon and evening. ...Northern/Central Plains... A shortwave trough over the northern Rockies/High Plains Saturday morning is forecast to move eastward across the northern/central Plains through the period. Areas of precipitation will likely be ongoing ahead of this feature across the Dakotas Saturday morning within a low-level warm air advection regime. A belt of stronger (30-40 kt) mid-level westerly flow will overspread much of the northern/central Plains by Saturday afternoon. In the wake of morning precipitation, at least weak destabilization will probably occur along/south of a surface boundary across SD. Around 30-40 kt of effective bulk shear will likely support storm organization, but overall coverage should remain quite isolated across southern SD into northern NE Saturday afternoon. Regardless, occasional large hail and strong/gusty winds could occur with any supercell storms that form in this regime. Farther south, more robust instability will likely develop along/south of a warm front near the NE/KS border since greater low-level moisture and steeper mid-level lapse rates will be present across this region. However, mid-level winds will gradually weaken with southward extent across the central Plains, and the potential for organized severe storms across southern NE into KS remains somewhat unclear. An increase in convective coverage will likely occur Saturday evening/night from north-central KS into the mid MO Valley as a southwesterly low-level jet strengthens. Tendency should be for storms to become elevated, with an isolated large hail threat possible. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Gleason.. 09/06/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Isolated strong to severe storms with gusty winds and some large hail may occur across parts of the northern and central Plains Saturday afternoon and evening. ...Northern/Central Plains... A shortwave trough over the northern Rockies/High Plains Saturday morning is forecast to move eastward across the northern/central Plains through the period. Areas of precipitation will likely be ongoing ahead of this feature across the Dakotas Saturday morning within a low-level warm air advection regime. A belt of stronger (30-40 kt) mid-level westerly flow will overspread much of the northern/central Plains by Saturday afternoon. In the wake of morning precipitation, at least weak destabilization will probably occur along/south of a surface boundary across SD. Around 30-40 kt of effective bulk shear will likely support storm organization, but overall coverage should remain quite isolated across southern SD into northern NE Saturday afternoon. Regardless, occasional large hail and strong/gusty winds could occur with any supercell storms that form in this regime. Farther south, more robust instability will likely develop along/south of a warm front near the NE/KS border since greater low-level moisture and steeper mid-level lapse rates will be present across this region. However, mid-level winds will gradually weaken with southward extent across the central Plains, and the potential for organized severe storms across southern NE into KS remains somewhat unclear. An increase in convective coverage will likely occur Saturday evening/night from north-central KS into the mid MO Valley as a southwesterly low-level jet strengthens. Tendency should be for storms to become elevated, with an isolated large hail threat possible. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Gleason.. 09/06/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Isolated strong to severe storms with gusty winds and some large hail may occur across parts of the northern and central Plains Saturday afternoon and evening. ...Northern/Central Plains... A shortwave trough over the northern Rockies/High Plains Saturday morning is forecast to move eastward across the northern/central Plains through the period. Areas of precipitation will likely be ongoing ahead of this feature across the Dakotas Saturday morning within a low-level warm air advection regime. A belt of stronger (30-40 kt) mid-level westerly flow will overspread much of the northern/central Plains by Saturday afternoon. In the wake of morning precipitation, at least weak destabilization will probably occur along/south of a surface boundary across SD. Around 30-40 kt of effective bulk shear will likely support storm organization, but overall coverage should remain quite isolated across southern SD into northern NE Saturday afternoon. Regardless, occasional large hail and strong/gusty winds could occur with any supercell storms that form in this regime. Farther south, more robust instability will likely develop along/south of a warm front near the NE/KS border since greater low-level moisture and steeper mid-level lapse rates will be present across this region. However, mid-level winds will gradually weaken with southward extent across the central Plains, and the potential for organized severe storms across southern NE into KS remains somewhat unclear. An increase in convective coverage will likely occur Saturday evening/night from north-central KS into the mid MO Valley as a southwesterly low-level jet strengthens. Tendency should be for storms to become elevated, with an isolated large hail threat possible. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Gleason.. 09/06/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Fri Sep 06 2019 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS... ...SUMMARY... Isolated strong to severe storms with gusty winds and some large hail may occur across parts of the northern and central Plains Saturday afternoon and evening. ...Northern/Central Plains... A shortwave trough over the northern Rockies/High Plains Saturday morning is forecast to move eastward across the northern/central Plains through the period. Areas of precipitation will likely be ongoing ahead of this feature across the Dakotas Saturday morning within a low-level warm air advection regime. A belt of stronger (30-40 kt) mid-level westerly flow will overspread much of the northern/central Plains by Saturday afternoon. In the wake of morning precipitation, at least weak destabilization will probably occur along/south of a surface boundary across SD. Around 30-40 kt of effective bulk shear will likely support storm organization, but overall coverage should remain quite isolated across southern SD into northern NE Saturday afternoon. Regardless, occasional large hail and strong/gusty winds could occur with any supercell storms that form in this regime. Farther south, more robust instability will likely develop along/south of a warm front near the NE/KS border since greater low-level moisture and steeper mid-level lapse rates will be present across this region. However, mid-level winds will gradually weaken with southward extent across the central Plains, and the potential for organized severe storms across southern NE into KS remains somewhat unclear. An increase in convective coverage will likely occur Saturday evening/night from north-central KS into the mid MO Valley as a southwesterly low-level jet strengthens. Tendency should be for storms to become elevated, with an isolated large hail threat possible. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Gleason.. 09/06/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1123 AM CDT Fri Sep 06 2019 Valid 061700Z - 071200Z The ongoing forecast is on track. A very low risk of isolated dry thunderstorms exists across portions of eastern Oregon, southern/central Idaho, and far southwestern Montana. Scattered thunderstorms were ongoing across southeastern Oregon and southwestern Idaho currently, and although some of these cores are likely producing wetting rainfall, peripheral lightning strikes outside of heavier cores may have potential for fire starts. Furthermore, additional thunderstorm activity is expected this afternoon as a mid-level trough provides cooling mid-level temperatures and ascent amidst modest buoyancy. PW values are expected to be relatively high throughout the day, however (around 1 inch), limiting the overall risk of dry lightning. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0146 AM CDT Fri Sep 06 2019/ ...Synopsis... A mid-level ridge will break down across the western CONUS, as the first in a series of mid-level shortwave troughs traverses the Pacific Northwest, into the central/northern Rockies regions. Deep-layer ascent associated with the impinging mid-level trough will encourage isolated to scattered thunderstorm development across much of the region, with most of the storms producing wetting rains. Towards the end of the period, as the first trough moves away from the West Coast, modest northerly low-level flow may encourage dry, breezy conditions during the early morning hours across parts of southern California, where modest potential exists for some fire spread. ...Great Basin into the Pacific Northwest, central and northern Rockies regions... Isolated to scattered thunderstorms are expected to develop during the afternoon hours. While many of the storms are expected to be relatively fast-moving and high-based in nature, precipitable water values in the 0.75-1.25 inch range suggests accumulating rainfall should be common with most storms. As such, the density of dry strikes is expected to be low enough to preclude an isolated dry thunderstorm delineation at this time. Still, at least a few dry strikes may occur along the periphery of the storm cores, atop fuels that will be at least modestly receptive to fire spread. Gusty, erratic surface winds may also accompany the stronger storms, worsening the potential for fire spread in localized areas lacking precipitation accumulation, especially in the central Rockies regions. Please see the SPC Day 1 Convective Outlook for more details on severe wind/hail potential. ...Parts of Coastal Southern California... Low-level northerly flow within the 925-850 mb layer will support a modest Sundowner event in the early morning hours across parts of the Santa Ynez mountains. Downslope flow may encourage 15-20 mph sustained northerly surface winds. Surface RH will be on the high side (20-25%) to support a more robust wildfire-spread threat, but dry fuels are in place to support some potential for fire growth, with an elevated area delineated to account for this scenario. ...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 1123 AM CDT Fri Sep 06 2019 Valid 061700Z - 071200Z The ongoing forecast is on track. A very low risk of isolated dry thunderstorms exists across portions of eastern Oregon, southern/central Idaho, and far southwestern Montana. Scattered thunderstorms were ongoing across southeastern Oregon and southwestern Idaho currently, and although some of these cores are likely producing wetting rainfall, peripheral lightning strikes outside of heavier cores may have potential for fire starts. Furthermore, additional thunderstorm activity is expected this afternoon as a mid-level trough provides cooling mid-level temperatures and ascent amidst modest buoyancy. PW values are expected to be relatively high throughout the day, however (around 1 inch), limiting the overall risk of dry lightning. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0146 AM CDT Fri Sep 06 2019/ ...Synopsis... A mid-level ridge will break down across the western CONUS, as the first in a series of mid-level shortwave troughs traverses the Pacific Northwest, into the central/northern Rockies regions. Deep-layer ascent associated with the impinging mid-level trough will encourage isolated to scattered thunderstorm development across much of the region, with most of the storms producing wetting rains. Towards the end of the period, as the first trough moves away from the West Coast, modest northerly low-level flow may encourage dry, breezy conditions during the early morning hours across parts of southern California, where modest potential exists for some fire spread. ...Great Basin into the Pacific Northwest, central and northern Rockies regions... Isolated to scattered thunderstorms are expected to develop during the afternoon hours. While many of the storms are expected to be relatively fast-moving and high-based in nature, precipitable water values in the 0.75-1.25 inch range suggests accumulating rainfall should be common with most storms. As such, the density of dry strikes is expected to be low enough to preclude an isolated dry thunderstorm delineation at this time. Still, at least a few dry strikes may occur along the periphery of the storm cores, atop fuels that will be at least modestly receptive to fire spread. Gusty, erratic surface winds may also accompany the stronger storms, worsening the potential for fire spread in localized areas lacking precipitation accumulation, especially in the central Rockies regions. Please see the SPC Day 1 Convective Outlook for more details on severe wind/hail potential. ...Parts of Coastal Southern California... Low-level northerly flow within the 925-850 mb layer will support a modest Sundowner event in the early morning hours across parts of the Santa Ynez mountains. Downslope flow may encourage 15-20 mph sustained northerly surface winds. Surface RH will be on the high side (20-25%) to support a more robust wildfire-spread threat, but dry fuels are in place to support some potential for fire growth, with an elevated area delineated to account for this scenario. ...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 1123 AM CDT Fri Sep 06 2019 Valid 061700Z - 071200Z The ongoing forecast is on track. A very low risk of isolated dry thunderstorms exists across portions of eastern Oregon, southern/central Idaho, and far southwestern Montana. Scattered thunderstorms were ongoing across southeastern Oregon and southwestern Idaho currently, and although some of these cores are likely producing wetting rainfall, peripheral lightning strikes outside of heavier cores may have potential for fire starts. Furthermore, additional thunderstorm activity is expected this afternoon as a mid-level trough provides cooling mid-level temperatures and ascent amidst modest buoyancy. PW values are expected to be relatively high throughout the day, however (around 1 inch), limiting the overall risk of dry lightning. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0146 AM CDT Fri Sep 06 2019/ ...Synopsis... A mid-level ridge will break down across the western CONUS, as the first in a series of mid-level shortwave troughs traverses the Pacific Northwest, into the central/northern Rockies regions. Deep-layer ascent associated with the impinging mid-level trough will encourage isolated to scattered thunderstorm development across much of the region, with most of the storms producing wetting rains. Towards the end of the period, as the first trough moves away from the West Coast, modest northerly low-level flow may encourage dry, breezy conditions during the early morning hours across parts of southern California, where modest potential exists for some fire spread. ...Great Basin into the Pacific Northwest, central and northern Rockies regions... Isolated to scattered thunderstorms are expected to develop during the afternoon hours. While many of the storms are expected to be relatively fast-moving and high-based in nature, precipitable water values in the 0.75-1.25 inch range suggests accumulating rainfall should be common with most storms. As such, the density of dry strikes is expected to be low enough to preclude an isolated dry thunderstorm delineation at this time. Still, at least a few dry strikes may occur along the periphery of the storm cores, atop fuels that will be at least modestly receptive to fire spread. Gusty, erratic surface winds may also accompany the stronger storms, worsening the potential for fire spread in localized areas lacking precipitation accumulation, especially in the central Rockies regions. Please see the SPC Day 1 Convective Outlook for more details on severe wind/hail potential. ...Parts of Coastal Southern California... Low-level northerly flow within the 925-850 mb layer will support a modest Sundowner event in the early morning hours across parts of the Santa Ynez mountains. Downslope flow may encourage 15-20 mph sustained northerly surface winds. Surface RH will be on the high side (20-25%) to support a more robust wildfire-spread threat, but dry fuels are in place to support some potential for fire growth, with an elevated area delineated to account for this scenario. ...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 1123 AM CDT Fri Sep 06 2019 Valid 061700Z - 071200Z The ongoing forecast is on track. A very low risk of isolated dry thunderstorms exists across portions of eastern Oregon, southern/central Idaho, and far southwestern Montana. Scattered thunderstorms were ongoing across southeastern Oregon and southwestern Idaho currently, and although some of these cores are likely producing wetting rainfall, peripheral lightning strikes outside of heavier cores may have potential for fire starts. Furthermore, additional thunderstorm activity is expected this afternoon as a mid-level trough provides cooling mid-level temperatures and ascent amidst modest buoyancy. PW values are expected to be relatively high throughout the day, however (around 1 inch), limiting the overall risk of dry lightning. See the previous discussion below for more information. ..Cook.. 09/06/2019 .PREV DISCUSSION... /ISSUED 0146 AM CDT Fri Sep 06 2019/ ...Synopsis... A mid-level ridge will break down across the western CONUS, as the first in a series of mid-level shortwave troughs traverses the Pacific Northwest, into the central/northern Rockies regions. Deep-layer ascent associated with the impinging mid-level trough will encourage isolated to scattered thunderstorm development across much of the region, with most of the storms producing wetting rains. Towards the end of the period, as the first trough moves away from the West Coast, modest northerly low-level flow may encourage dry, breezy conditions during the early morning hours across parts of southern California, where modest potential exists for some fire spread. ...Great Basin into the Pacific Northwest, central and northern Rockies regions... Isolated to scattered thunderstorms are expected to develop during the afternoon hours. While many of the storms are expected to be relatively fast-moving and high-based in nature, precipitable water values in the 0.75-1.25 inch range suggests accumulating rainfall should be common with most storms. As such, the density of dry strikes is expected to be low enough to preclude an isolated dry thunderstorm delineation at this time. Still, at least a few dry strikes may occur along the periphery of the storm cores, atop fuels that will be at least modestly receptive to fire spread. Gusty, erratic surface winds may also accompany the stronger storms, worsening the potential for fire spread in localized areas lacking precipitation accumulation, especially in the central Rockies regions. Please see the SPC Day 1 Convective Outlook for more details on severe wind/hail potential. ...Parts of Coastal Southern California... Low-level northerly flow within the 925-850 mb layer will support a modest Sundowner event in the early morning hours across parts of the Santa Ynez mountains. Downslope flow may encourage 15-20 mph sustained northerly surface winds. Surface RH will be on the high side (20-25%) to support a more robust wildfire-spread threat, but dry fuels are in place to support some potential for fire growth, with an elevated area delineated to account for this scenario. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 06 2019 Valid 061630Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN INTERMOUNTAIN REGION AND NORTHERN/CENTRAL ROCKIES... ...SUMMARY... Isolated severe thunderstorm winds and hail are possible this afternoon and evening over parts of the northern Intermountain region, northern/central Rockies and adjacent High Plains. ...ID/MT/WY... Morning water vapor imagery shows a well-defined shortwave trough moving across OR and northern CA. This feature will affect parts of ID/western MT/western WY this afternoon. Broken cloud cover will result in pockets of destabilization, with dewpoints in the 50s yielding afternoon MLCAPE values of 500-1000 J/kg. Morning CAM solutions suggest a few clusters of occasionally organized storms are possible, with gusty winds and hail possible in the strongest cells. Will maintain ongoing MRGL risk, but will monitor for the development of bowing structures later today and the potential for an upgrade. ...CO/WY... A large upper ridge is present today over the southern Rockies, with weak to moderately strong midlevel westerly flow from northern CO into WY. It appears likely that scattered afternoon thunderstorms will form in the foothills of north-central CO into southern WY, with slow eastward movement of storms into the adjacent plains this evening. A few of the storms may pose a risk of hail and gusty winds. Organized severe storms are not currently anticipated. ..Hart/Wendt.. 09/06/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 06 2019 Valid 061630Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN INTERMOUNTAIN REGION AND NORTHERN/CENTRAL ROCKIES... ...SUMMARY... Isolated severe thunderstorm winds and hail are possible this afternoon and evening over parts of the northern Intermountain region, northern/central Rockies and adjacent High Plains. ...ID/MT/WY... Morning water vapor imagery shows a well-defined shortwave trough moving across OR and northern CA. This feature will affect parts of ID/western MT/western WY this afternoon. Broken cloud cover will result in pockets of destabilization, with dewpoints in the 50s yielding afternoon MLCAPE values of 500-1000 J/kg. Morning CAM solutions suggest a few clusters of occasionally organized storms are possible, with gusty winds and hail possible in the strongest cells. Will maintain ongoing MRGL risk, but will monitor for the development of bowing structures later today and the potential for an upgrade. ...CO/WY... A large upper ridge is present today over the southern Rockies, with weak to moderately strong midlevel westerly flow from northern CO into WY. It appears likely that scattered afternoon thunderstorms will form in the foothills of north-central CO into southern WY, with slow eastward movement of storms into the adjacent plains this evening. A few of the storms may pose a risk of hail and gusty winds. Organized severe storms are not currently anticipated. ..Hart/Wendt.. 09/06/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 06 2019 Valid 061630Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN INTERMOUNTAIN REGION AND NORTHERN/CENTRAL ROCKIES... ...SUMMARY... Isolated severe thunderstorm winds and hail are possible this afternoon and evening over parts of the northern Intermountain region, northern/central Rockies and adjacent High Plains. ...ID/MT/WY... Morning water vapor imagery shows a well-defined shortwave trough moving across OR and northern CA. This feature will affect parts of ID/western MT/western WY this afternoon. Broken cloud cover will result in pockets of destabilization, with dewpoints in the 50s yielding afternoon MLCAPE values of 500-1000 J/kg. Morning CAM solutions suggest a few clusters of occasionally organized storms are possible, with gusty winds and hail possible in the strongest cells. Will maintain ongoing MRGL risk, but will monitor for the development of bowing structures later today and the potential for an upgrade. ...CO/WY... A large upper ridge is present today over the southern Rockies, with weak to moderately strong midlevel westerly flow from northern CO into WY. It appears likely that scattered afternoon thunderstorms will form in the foothills of north-central CO into southern WY, with slow eastward movement of storms into the adjacent plains this evening. A few of the storms may pose a risk of hail and gusty winds. Organized severe storms are not currently anticipated. ..Hart/Wendt.. 09/06/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 06 2019 Valid 061630Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN INTERMOUNTAIN REGION AND NORTHERN/CENTRAL ROCKIES... ...SUMMARY... Isolated severe thunderstorm winds and hail are possible this afternoon and evening over parts of the northern Intermountain region, northern/central Rockies and adjacent High Plains. ...ID/MT/WY... Morning water vapor imagery shows a well-defined shortwave trough moving across OR and northern CA. This feature will affect parts of ID/western MT/western WY this afternoon. Broken cloud cover will result in pockets of destabilization, with dewpoints in the 50s yielding afternoon MLCAPE values of 500-1000 J/kg. Morning CAM solutions suggest a few clusters of occasionally organized storms are possible, with gusty winds and hail possible in the strongest cells. Will maintain ongoing MRGL risk, but will monitor for the development of bowing structures later today and the potential for an upgrade. ...CO/WY... A large upper ridge is present today over the southern Rockies, with weak to moderately strong midlevel westerly flow from northern CO into WY. It appears likely that scattered afternoon thunderstorms will form in the foothills of north-central CO into southern WY, with slow eastward movement of storms into the adjacent plains this evening. A few of the storms may pose a risk of hail and gusty winds. Organized severe storms are not currently anticipated. ..Hart/Wendt.. 09/06/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1115 AM CDT Fri Sep 06 2019 Valid 061630Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE NORTHERN INTERMOUNTAIN REGION AND NORTHERN/CENTRAL ROCKIES... ...SUMMARY... Isolated severe thunderstorm winds and hail are possible this afternoon and evening over parts of the northern Intermountain region, northern/central Rockies and adjacent High Plains. ...ID/MT/WY... Morning water vapor imagery shows a well-defined shortwave trough moving across OR and northern CA. This feature will affect parts of ID/western MT/western WY this afternoon. Broken cloud cover will result in pockets of destabilization, with dewpoints in the 50s yielding afternoon MLCAPE values of 500-1000 J/kg. Morning CAM solutions suggest a few clusters of occasionally organized storms are possible, with gusty winds and hail possible in the strongest cells. Will maintain ongoing MRGL risk, but will monitor for the development of bowing structures later today and the potential for an upgrade. ...CO/WY... A large upper ridge is present today over the southern Rockies, with weak to moderately strong midlevel westerly flow from northern CO into WY. It appears likely that scattered afternoon thunderstorms will form in the foothills of north-central CO into southern WY, with slow eastward movement of storms into the adjacent plains this evening. A few of the storms may pose a risk of hail and gusty winds. Organized severe storms are not currently anticipated. ..Hart/Wendt.. 09/06/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0757 AM CDT Fri Sep 06 2019 Valid 061300Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PARTS OF THE NORTHERN INTERMOUNTAIN REGION...NORTHERN/CENTRAL ROCKIES AND ADJACENT HIGH PLAINS... ...SUMMARY... Isolated severe thunderstorm winds and hail are possible this afternoon and evening over parts of the northern Intermountain region, northern/central Rockies and adjacent High Plains. ...Synopsis... In mid/upper levels, an initially strong anticyclone centered over the south-central Rockies will shift southwestward and weaken as a strong shortwave trough crosses the northern Rockies. That trough -- now evident in moisture-channel imagery over western OR and northern CA -- is progged to overtake/absorb lesser vorticity lobes initially to its east across eastern OR/ID. The combined, somewhat stronger perturbation will reach the MT/ID border region and southern ID by 00Z. Thereafter, the trough will pivot eastward and east-southeastward, reaching central MT, western WY and northwestern CO by 12Z. Meanwhile, farther east, shortwave troughs now over the upper Great Lakes and northern MB will move southeastward across the Mid-Atlantic and upper Great Lakes, respectively. In response, Hurricane Dorian has commenced accelerating northeastward over/off the Outer Banks, and should eject away from the Tidewater region through the remainder of the period, per NHC forecasts. With the most thermodynamically and kinematically favorable sector for supercellular tornadoes shifting offshore, and forecast to stay southeast of the Cape Cod/Martha's Vineyard region tonight, unconditional overland tornado probabilities have been dropped. Otherwise, the surface analysis showed a low near GRB with occluded front to southeastern IA, and slow-moving cold front to a weak frontal-wave/lee low over western KS, then extending across parts of southeastern CO. The low should move southeastward across OH overnight and become poorly defined in the broader field of low pressure surrounding Dorian. Meanwhile the front should cross the Ohio Valley and stall across the southern KS/northern OK/ southeastern CO corridor. ...Northern Rockies/Intermountain region to Front Range/central High Plains... Widely scattered to scattered thunderstorms are expected to develop this afternoon into evening in three primary regimes, described below from west to east, each offering isolated severe gusts/hail, with enough spatial overlap to result in a unified outlook area: 1. A "cold-core" regime near the midlevel/500-mb thermal trough, from eastern OR across much of southern ID, potentially forming a quasi-linear band of strong/isolated severe convection over ID before weakening tonight in western WY where regime 2 below will have produced enough convection to stabilize the air mass. Diurnal heating and midlevel cooling should overlap well, steepening low/ middle-level lapse rates considerably, atop 50s F low-elevation surface dew points. This should result in MLCAPE 1000-1500 J/kg atop a well-mixed boundary layer supporting strong/locally severe gusts and survival of hail to ground level. Organization should be tempered somewhat by weakening deep-layer flow with time and proximity to the mid/upper trough, and related lack of shear. However, a conditional cold-pool aggregation potential exists, especially across parts of the Snake River Plain and southern mountains west of I-15. 2. A band of relatively maximized deep-layer ascent shifting eastward from southeastern ID and northern UT across western/central WY. A combination of lift from large-scale DCVA/cooling aloft, frontal forcing near a low-level baroclinic zone preceding that trough, and pre-frontal warm advection will support convection in this area. Buoyancy should be less in both coverage and magnitude than in regime 1, with MLCAPE mainly around 500 J/kg. Still, localized well-mixed boundary layers and marginal deep shear will promote a few strong-severe cells in the broader convective plume. 3. Heating of higher terrain, favorable low-level moisture, and resultant weak MLCINH should foster convection initiation this afternoon over the Front Range, Laramie Range, adjacent foothills, and perhaps the Bighorns. Activity then should move eastward across a diabatically destabilized strip of the central High Plains, offering damaging gusts and isolated hail before weakening. Strong surface heating and deep, strongly mixed boundary layers will support isolated severe potential with this activity before it weakens this evening in a stabilizing boundary layer, at lower elevations. ..Edwards/Smith.. 09/06/2019 Read more