Severe Storms

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Sun Sep 22 2019 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTHERN/CENTRAL ARIZONA... ...SUMMARY... Scattered storms, some of which may be severe with damaging winds and large hail, appear possible over much of Arizona on Monday. ...Arizona into Southwestern New Mexico... Embedded within large-scale upper troughing over much of the western CONUS, an upper trough/low will develop southward across the western Great Basin into the Southwest through the period. In advance of this feature, low-level moisture is forecast to rapidly increase along the CA/AZ border eastward into southern/central AZ by early Monday morning. There are some indications that isolated showers/storms may be ongoing at the start of the period Monday morning across mainly southern AZ. The effect that this possible early convection may have on destabilization and severe storm potential later in the day remains unclear. Regardless, strengthening west-southwesterly winds at mid levels in combination with increasing instability suggest that at least isolated severe storms will be possible across much of southern/central AZ Monday afternoon and evening. MLCAPE should reach to around 1000-1500 J/kg from the Mogollon Rim southward, with locally higher values possible in far western AZ. 35-50 kt of effective bulk shear will support supercells, with initial convective development probably occurring along or just east of the CA/AZ border. Isolated large hail will be possible with these mainly discrete storms, as generally straight hodographs become elongated at mid/upper levels. As storms spread eastward through the afternoon, some clustering may occur as low-level lapse rates steepen through diurnal heating and mixing of the boundary layer. Damaging winds may become an increasing concern with eastward extent across southern/central AZ into Monday evening if this upscale growth occurs. An isolated severe threat may persist Monday night into parts of southwestern NM before instability eventually wanes. Across northern AZ, both low-level moisture and related instability are forecast to be weaker, with a more isolated/marginal hail/wind threat. ...Northeast... An upper trough/low will move quickly eastward from the Great Lakes across the Northeast, OH Valley, and Mid-Atlantic on Monday. Strong mid/upper-level winds will be present across these regions in association with the upper trough/low. At the surface, a cold front will likewise sweep eastward across these regions through the day. Mid-level lapse rates over these areas are expected to remain quite meager, and widespread cloudiness will likely be present. But, surface dewpoints generally in the low to mid 60s ahead of the front and modest diurnal heating will probably support weak instability by Monday afternoon along/ahead of the front. MLCAPE should generally remain at or below 500 J/kg. This meager instability will probably temper the overall severe threat, even though strong shear will be present owing to the strengthening wind field through mid/upper levels. While some strong/gusty downdraft winds cannot be completely ruled out with rain showers or any low-topped storms that develop, the lack of stronger forecast instability precludes introduction of 5% severe probabilities for wind at this time. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Gleason.. 09/22/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Sun Sep 22 2019 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTHERN/CENTRAL ARIZONA... ...SUMMARY... Scattered storms, some of which may be severe with damaging winds and large hail, appear possible over much of Arizona on Monday. ...Arizona into Southwestern New Mexico... Embedded within large-scale upper troughing over much of the western CONUS, an upper trough/low will develop southward across the western Great Basin into the Southwest through the period. In advance of this feature, low-level moisture is forecast to rapidly increase along the CA/AZ border eastward into southern/central AZ by early Monday morning. There are some indications that isolated showers/storms may be ongoing at the start of the period Monday morning across mainly southern AZ. The effect that this possible early convection may have on destabilization and severe storm potential later in the day remains unclear. Regardless, strengthening west-southwesterly winds at mid levels in combination with increasing instability suggest that at least isolated severe storms will be possible across much of southern/central AZ Monday afternoon and evening. MLCAPE should reach to around 1000-1500 J/kg from the Mogollon Rim southward, with locally higher values possible in far western AZ. 35-50 kt of effective bulk shear will support supercells, with initial convective development probably occurring along or just east of the CA/AZ border. Isolated large hail will be possible with these mainly discrete storms, as generally straight hodographs become elongated at mid/upper levels. As storms spread eastward through the afternoon, some clustering may occur as low-level lapse rates steepen through diurnal heating and mixing of the boundary layer. Damaging winds may become an increasing concern with eastward extent across southern/central AZ into Monday evening if this upscale growth occurs. An isolated severe threat may persist Monday night into parts of southwestern NM before instability eventually wanes. Across northern AZ, both low-level moisture and related instability are forecast to be weaker, with a more isolated/marginal hail/wind threat. ...Northeast... An upper trough/low will move quickly eastward from the Great Lakes across the Northeast, OH Valley, and Mid-Atlantic on Monday. Strong mid/upper-level winds will be present across these regions in association with the upper trough/low. At the surface, a cold front will likewise sweep eastward across these regions through the day. Mid-level lapse rates over these areas are expected to remain quite meager, and widespread cloudiness will likely be present. But, surface dewpoints generally in the low to mid 60s ahead of the front and modest diurnal heating will probably support weak instability by Monday afternoon along/ahead of the front. MLCAPE should generally remain at or below 500 J/kg. This meager instability will probably temper the overall severe threat, even though strong shear will be present owing to the strengthening wind field through mid/upper levels. While some strong/gusty downdraft winds cannot be completely ruled out with rain showers or any low-topped storms that develop, the lack of stronger forecast instability precludes introduction of 5% severe probabilities for wind at this time. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% - Slight Hail: 15% - Slight ..Gleason.. 09/22/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1200 PM CDT Sun Sep 22 2019 Valid 221700Z - 231200Z ...NO CRITICAL AREAS... Current water vapor satellite imagery shows a potent mid-level trough beginning to dig into northern California. Dry air aloft is quite evident with this feature and is forecast to impact portions of the Northern Coastal Ranges during the overnight. Forecast soundings capture this dry air aloft well, though relatively efficient boundary-layer cooling in these soundings keeps this air from mixing to the surface. However, some concern exists that strong surface flow in localized areas will promote greater overnight mixing than models suggest. High-resolution guidance continues to the suggest that this will only occur on a spatially-limited basis so no highlights will be introduced. ..Wendt.. 09/22/2019 .PREV DISCUSSION... /ISSUED 0126 AM CDT Sun Sep 22 2019/ ...Synopsis... An area of mid-level ridging is forecast to move from portions of the Great Basin toward the central/northern Plains through tonight. Meanwhile, a large upstream mid/upper-level trough -- and associated area of enhanced mid-level flow -- is forecast to come onshore across portions of northern California, Oregon, and Washington late this afternoon and into the overnight. ...Nevada... A few hours of locally elevated fire weather conditions are possible this afternoon across portions of central/southwest Nevada, where sustained surface winds of 10-15 mph occur in conjunction with surface RH values near 15% and receptive fuels. However, the brief/spotty nature of these conditions precludes the introduction of a fire weather area. ...Northern California... Locally elevated fire weather conditions are possible late this evening and into tonight across eastern portions of the Northern Coast Ranges, as a tightening surface pressure gradient coupled with overlapping enhanced mid-level flow promotes increasingly gusty surface winds amidst pockets of poor overnight RH recoveries. A fire area may be needed in a future update if trends in guidance suggest greater coverage of elevated fire weather conditions. ...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 1200 PM CDT Sun Sep 22 2019 Valid 221700Z - 231200Z ...NO CRITICAL AREAS... Current water vapor satellite imagery shows a potent mid-level trough beginning to dig into northern California. Dry air aloft is quite evident with this feature and is forecast to impact portions of the Northern Coastal Ranges during the overnight. Forecast soundings capture this dry air aloft well, though relatively efficient boundary-layer cooling in these soundings keeps this air from mixing to the surface. However, some concern exists that strong surface flow in localized areas will promote greater overnight mixing than models suggest. High-resolution guidance continues to the suggest that this will only occur on a spatially-limited basis so no highlights will be introduced. ..Wendt.. 09/22/2019 .PREV DISCUSSION... /ISSUED 0126 AM CDT Sun Sep 22 2019/ ...Synopsis... An area of mid-level ridging is forecast to move from portions of the Great Basin toward the central/northern Plains through tonight. Meanwhile, a large upstream mid/upper-level trough -- and associated area of enhanced mid-level flow -- is forecast to come onshore across portions of northern California, Oregon, and Washington late this afternoon and into the overnight. ...Nevada... A few hours of locally elevated fire weather conditions are possible this afternoon across portions of central/southwest Nevada, where sustained surface winds of 10-15 mph occur in conjunction with surface RH values near 15% and receptive fuels. However, the brief/spotty nature of these conditions precludes the introduction of a fire weather area. ...Northern California... Locally elevated fire weather conditions are possible late this evening and into tonight across eastern portions of the Northern Coast Ranges, as a tightening surface pressure gradient coupled with overlapping enhanced mid-level flow promotes increasingly gusty surface winds amidst pockets of poor overnight RH recoveries. A fire area may be needed in a future update if trends in guidance suggest greater coverage of elevated fire weather conditions. ...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 1200 PM CDT Sun Sep 22 2019 Valid 221700Z - 231200Z ...NO CRITICAL AREAS... Current water vapor satellite imagery shows a potent mid-level trough beginning to dig into northern California. Dry air aloft is quite evident with this feature and is forecast to impact portions of the Northern Coastal Ranges during the overnight. Forecast soundings capture this dry air aloft well, though relatively efficient boundary-layer cooling in these soundings keeps this air from mixing to the surface. However, some concern exists that strong surface flow in localized areas will promote greater overnight mixing than models suggest. High-resolution guidance continues to the suggest that this will only occur on a spatially-limited basis so no highlights will be introduced. ..Wendt.. 09/22/2019 .PREV DISCUSSION... /ISSUED 0126 AM CDT Sun Sep 22 2019/ ...Synopsis... An area of mid-level ridging is forecast to move from portions of the Great Basin toward the central/northern Plains through tonight. Meanwhile, a large upstream mid/upper-level trough -- and associated area of enhanced mid-level flow -- is forecast to come onshore across portions of northern California, Oregon, and Washington late this afternoon and into the overnight. ...Nevada... A few hours of locally elevated fire weather conditions are possible this afternoon across portions of central/southwest Nevada, where sustained surface winds of 10-15 mph occur in conjunction with surface RH values near 15% and receptive fuels. However, the brief/spotty nature of these conditions precludes the introduction of a fire weather area. ...Northern California... Locally elevated fire weather conditions are possible late this evening and into tonight across eastern portions of the Northern Coast Ranges, as a tightening surface pressure gradient coupled with overlapping enhanced mid-level flow promotes increasingly gusty surface winds amidst pockets of poor overnight RH recoveries. A fire area may be needed in a future update if trends in guidance suggest greater coverage of elevated fire weather conditions. ...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 1117 AM CDT Sun Sep 22 2019 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EXTENDING IN A CORRIDOR FROM OKLAHOMA NORTHEASTWARD INTO ILLINOIS... ...SUMMARY... Isolated damaging winds, and perhaps a tornado or two, will be possible through this evening from parts of Oklahoma to Illinois. ...OK to IL... No changes have been made to the ongoing forecast. A band of relatively fast winds aloft extends from the southern and central Plains into the mid MS valley and Great Lakes region today. A strong shortwave trough embedded in this flow over western KS/OK will track into MO/IL during this forecast period. Considerable cloud cover and areas of precipitation will continue to affect the MRGL risk corridor this afternoon. Despite the weak instability and poor lapse rates, forecast soundings show sufficient vertical shear to pose a limited risk of a storm or two becoming intense with damaging wind potential and some tornado risk. ..Hart/Bentley.. 09/22/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1117 AM CDT Sun Sep 22 2019 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EXTENDING IN A CORRIDOR FROM OKLAHOMA NORTHEASTWARD INTO ILLINOIS... ...SUMMARY... Isolated damaging winds, and perhaps a tornado or two, will be possible through this evening from parts of Oklahoma to Illinois. ...OK to IL... No changes have been made to the ongoing forecast. A band of relatively fast winds aloft extends from the southern and central Plains into the mid MS valley and Great Lakes region today. A strong shortwave trough embedded in this flow over western KS/OK will track into MO/IL during this forecast period. Considerable cloud cover and areas of precipitation will continue to affect the MRGL risk corridor this afternoon. Despite the weak instability and poor lapse rates, forecast soundings show sufficient vertical shear to pose a limited risk of a storm or two becoming intense with damaging wind potential and some tornado risk. ..Hart/Bentley.. 09/22/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1117 AM CDT Sun Sep 22 2019 Valid 221630Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EXTENDING IN A CORRIDOR FROM OKLAHOMA NORTHEASTWARD INTO ILLINOIS... ...SUMMARY... Isolated damaging winds, and perhaps a tornado or two, will be possible through this evening from parts of Oklahoma to Illinois. ...OK to IL... No changes have been made to the ongoing forecast. A band of relatively fast winds aloft extends from the southern and central Plains into the mid MS valley and Great Lakes region today. A strong shortwave trough embedded in this flow over western KS/OK will track into MO/IL during this forecast period. Considerable cloud cover and areas of precipitation will continue to affect the MRGL risk corridor this afternoon. Despite the weak instability and poor lapse rates, forecast soundings show sufficient vertical shear to pose a limited risk of a storm or two becoming intense with damaging wind potential and some tornado risk. ..Hart/Bentley.. 09/22/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Sun Sep 22 2019 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF OK TO IL THROUGH THIS EVENING... ...SUMMARY... Isolated damaging winds, and perhaps a tornado or two, will be possible through this evening from parts of Oklahoma to Illinois. ...OK to IL through this evening... A midlevel shortwave trough with embedded perturbations over the central/northern High Plains will progress eastward to the MS Valley and Great Lakes by tonight. In advance of an embedded speed max over the central High Plains, an associated weak surface cyclone in KS this morning will develop northeastward along a front toward Lower MI by early tonight. A narrow corridor of richer low-level moisture, ranging from upper 60s dewpoints into IL to lower 70s in OK, will be maintained immediately in advance of the weak low and cold front today. A somewhat complex scenario will evolve today with widespread ongoing rainfall and some embedded thunderstorms from OK to WI. Outflow from overnight convection and differential heating today will maintain the effective boundary from northern IL into central MO. An embedded MCV is moving northeastward over southeast KS this morning, and per local VWPs and model forecasts, a 50 kt low-level jet will develop northeastward today with the weak frontal wave and ejecting midlevel trough. Though widespread rainfall will continue to limit lapse rates, the rich low-level moisture and pockets of surface heating in cloud breaks will support MLCAPE ranging from 500 J/kg this afternoon in IL to 1500 J/kg in OK. Enhanced low-midlevel flow/shear along the effective surface boundary, potentially augmented by the remnant MCV moving from KS to MO, may support some embedded rotating storms and/or small bowing segments. The threat for isolated damaging winds and a tornado or two will begin the first half of the day from southeast KS into OK, and continue into late afternoon/evening into IL. ..Thompson/Leitman.. 09/22/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Sun Sep 22 2019 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF OK TO IL THROUGH THIS EVENING... ...SUMMARY... Isolated damaging winds, and perhaps a tornado or two, will be possible through this evening from parts of Oklahoma to Illinois. ...OK to IL through this evening... A midlevel shortwave trough with embedded perturbations over the central/northern High Plains will progress eastward to the MS Valley and Great Lakes by tonight. In advance of an embedded speed max over the central High Plains, an associated weak surface cyclone in KS this morning will develop northeastward along a front toward Lower MI by early tonight. A narrow corridor of richer low-level moisture, ranging from upper 60s dewpoints into IL to lower 70s in OK, will be maintained immediately in advance of the weak low and cold front today. A somewhat complex scenario will evolve today with widespread ongoing rainfall and some embedded thunderstorms from OK to WI. Outflow from overnight convection and differential heating today will maintain the effective boundary from northern IL into central MO. An embedded MCV is moving northeastward over southeast KS this morning, and per local VWPs and model forecasts, a 50 kt low-level jet will develop northeastward today with the weak frontal wave and ejecting midlevel trough. Though widespread rainfall will continue to limit lapse rates, the rich low-level moisture and pockets of surface heating in cloud breaks will support MLCAPE ranging from 500 J/kg this afternoon in IL to 1500 J/kg in OK. Enhanced low-midlevel flow/shear along the effective surface boundary, potentially augmented by the remnant MCV moving from KS to MO, may support some embedded rotating storms and/or small bowing segments. The threat for isolated damaging winds and a tornado or two will begin the first half of the day from southeast KS into OK, and continue into late afternoon/evening into IL. ..Thompson/Leitman.. 09/22/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Sun Sep 22 2019 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF OK TO IL THROUGH THIS EVENING... ...SUMMARY... Isolated damaging winds, and perhaps a tornado or two, will be possible through this evening from parts of Oklahoma to Illinois. ...OK to IL through this evening... A midlevel shortwave trough with embedded perturbations over the central/northern High Plains will progress eastward to the MS Valley and Great Lakes by tonight. In advance of an embedded speed max over the central High Plains, an associated weak surface cyclone in KS this morning will develop northeastward along a front toward Lower MI by early tonight. A narrow corridor of richer low-level moisture, ranging from upper 60s dewpoints into IL to lower 70s in OK, will be maintained immediately in advance of the weak low and cold front today. A somewhat complex scenario will evolve today with widespread ongoing rainfall and some embedded thunderstorms from OK to WI. Outflow from overnight convection and differential heating today will maintain the effective boundary from northern IL into central MO. An embedded MCV is moving northeastward over southeast KS this morning, and per local VWPs and model forecasts, a 50 kt low-level jet will develop northeastward today with the weak frontal wave and ejecting midlevel trough. Though widespread rainfall will continue to limit lapse rates, the rich low-level moisture and pockets of surface heating in cloud breaks will support MLCAPE ranging from 500 J/kg this afternoon in IL to 1500 J/kg in OK. Enhanced low-midlevel flow/shear along the effective surface boundary, potentially augmented by the remnant MCV moving from KS to MO, may support some embedded rotating storms and/or small bowing segments. The threat for isolated damaging winds and a tornado or two will begin the first half of the day from southeast KS into OK, and continue into late afternoon/evening into IL. ..Thompson/Leitman.. 09/22/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0348 AM CDT Sun Sep 22 2019 Valid 251200Z - 301200Z ...DISCUSSION... Models are in relatively good agreement with the large-scale pattern through the D8 period, indicating at least isolated severe storm potential each day. On Wednesday/D4, a strong shortwave trough will move east from the upper MS Valley across the Great Lakes, with a cold front becoming east-west oriented as it approaches the OH Valley. This front will extend westward into MO, KS, and OK, with a moist and unstable air mass to the south. Lift with the upper trough will continue to move away from the frontal zone, but at least isolated severe storms will be possible due to heating and low-level convergence. Predictability is low in part due to potential for ongoing early-day storms. For the D5-D6 time frame, the upper low over the Southwest is expected to move across the Plains, and will aid lift and increase shear. Moisture will be in place, with a conditional threat of a few severe storms over the central Plains, but timing of this small feature is uncertain. Beyond D6, the pattern becomes quite amplified, with a large scale trough developing over the West, and an upper ridge over the East. This will result in strong southwest flow aloft over the Rockies and High Plains, while southerly surface winds maintain low-level moisture across the Plains. Lift from warm advection could potentially support a few severe storms over the northern Plains Saturday/D7 and Sunday/D8 night. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0348 AM CDT Sun Sep 22 2019 Valid 251200Z - 301200Z ...DISCUSSION... Models are in relatively good agreement with the large-scale pattern through the D8 period, indicating at least isolated severe storm potential each day. On Wednesday/D4, a strong shortwave trough will move east from the upper MS Valley across the Great Lakes, with a cold front becoming east-west oriented as it approaches the OH Valley. This front will extend westward into MO, KS, and OK, with a moist and unstable air mass to the south. Lift with the upper trough will continue to move away from the frontal zone, but at least isolated severe storms will be possible due to heating and low-level convergence. Predictability is low in part due to potential for ongoing early-day storms. For the D5-D6 time frame, the upper low over the Southwest is expected to move across the Plains, and will aid lift and increase shear. Moisture will be in place, with a conditional threat of a few severe storms over the central Plains, but timing of this small feature is uncertain. Beyond D6, the pattern becomes quite amplified, with a large scale trough developing over the West, and an upper ridge over the East. This will result in strong southwest flow aloft over the Rockies and High Plains, while southerly surface winds maintain low-level moisture across the Plains. Lift from warm advection could potentially support a few severe storms over the northern Plains Saturday/D7 and Sunday/D8 night. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0348 AM CDT Sun Sep 22 2019 Valid 251200Z - 301200Z ...DISCUSSION... Models are in relatively good agreement with the large-scale pattern through the D8 period, indicating at least isolated severe storm potential each day. On Wednesday/D4, a strong shortwave trough will move east from the upper MS Valley across the Great Lakes, with a cold front becoming east-west oriented as it approaches the OH Valley. This front will extend westward into MO, KS, and OK, with a moist and unstable air mass to the south. Lift with the upper trough will continue to move away from the frontal zone, but at least isolated severe storms will be possible due to heating and low-level convergence. Predictability is low in part due to potential for ongoing early-day storms. For the D5-D6 time frame, the upper low over the Southwest is expected to move across the Plains, and will aid lift and increase shear. Moisture will be in place, with a conditional threat of a few severe storms over the central Plains, but timing of this small feature is uncertain. Beyond D6, the pattern becomes quite amplified, with a large scale trough developing over the West, and an upper ridge over the East. This will result in strong southwest flow aloft over the Rockies and High Plains, while southerly surface winds maintain low-level moisture across the Plains. Lift from warm advection could potentially support a few severe storms over the northern Plains Saturday/D7 and Sunday/D8 night. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0348 AM CDT Sun Sep 22 2019 Valid 251200Z - 301200Z ...DISCUSSION... Models are in relatively good agreement with the large-scale pattern through the D8 period, indicating at least isolated severe storm potential each day. On Wednesday/D4, a strong shortwave trough will move east from the upper MS Valley across the Great Lakes, with a cold front becoming east-west oriented as it approaches the OH Valley. This front will extend westward into MO, KS, and OK, with a moist and unstable air mass to the south. Lift with the upper trough will continue to move away from the frontal zone, but at least isolated severe storms will be possible due to heating and low-level convergence. Predictability is low in part due to potential for ongoing early-day storms. For the D5-D6 time frame, the upper low over the Southwest is expected to move across the Plains, and will aid lift and increase shear. Moisture will be in place, with a conditional threat of a few severe storms over the central Plains, but timing of this small feature is uncertain. Beyond D6, the pattern becomes quite amplified, with a large scale trough developing over the West, and an upper ridge over the East. This will result in strong southwest flow aloft over the Rockies and High Plains, while southerly surface winds maintain low-level moisture across the Plains. Lift from warm advection could potentially support a few severe storms over the northern Plains Saturday/D7 and Sunday/D8 night. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun Sep 22 2019 Valid 241200Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF IOWA...WESTERN WISCONSIN...AND SOUTHERN MINNESOTA... ...SUMMARY... Severe storms are possible Tuesday across much of Iowa, Wisconsin, and southern Minnesota, with isolated storms from parts of the central Plains to the Upper Great Lakes. ...Synopsis... An elongated upper jet will dive southeastward across the northern Plains and into the upper MS Valley on Tuesday, with significant cooling aloft and increasing shear. The strongest lift will focus over MN, IA and WI as a cold front collides with returning low-level moisture with at least mid 60s F dewpoints. The cold front will progress eastward toward northern IL by Wed morning, while western parts of the front stall from KS into the TX Panhandle. To the west, an upper low will continue southward across western AZ and into the northern Baja, maintaining a favorable environment for scattered storms over southern AZ and NM. ...Upper MS Valley to the central Plains... Most of the area will remain free of thunderstorms for much of the day as the moist plume becomes established and temperatures aloft cool. By around 00Z, storms are expected to form along the front from southern MN into IA and perhaps eastern NE, and will expand in coverage through the evening into WI. Strong deep-layer shear perpendicular to the front will favor supercells, with steep lapse rates aloft and around 200 m2/s2 ESRH favoring very large hail and perhaps a tornado or two. Farther south into KS, strong heating of a 65-70 F dewpoint air mass will lead to over 3000 J/kg MUCAPE, with isolated severe storms expected across central and eastern KS. Hail will be possible, with localized wind damage. Parts of this area may require a categorical upgrade in later outlooks once placement of potential storm clusters is more precise. ...Southern AZ and southwest NM... Scattered to numerous storms may be ongoing Tuesday morning over southern AZ and NM in association with the upper low. Pockets of destabilization may occur once again during the day, with isolated strong to severe storms possible capable of hail or localized wind damage. ..Jewell.. 09/22/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun Sep 22 2019 Valid 241200Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF IOWA...WESTERN WISCONSIN...AND SOUTHERN MINNESOTA... ...SUMMARY... Severe storms are possible Tuesday across much of Iowa, Wisconsin, and southern Minnesota, with isolated storms from parts of the central Plains to the Upper Great Lakes. ...Synopsis... An elongated upper jet will dive southeastward across the northern Plains and into the upper MS Valley on Tuesday, with significant cooling aloft and increasing shear. The strongest lift will focus over MN, IA and WI as a cold front collides with returning low-level moisture with at least mid 60s F dewpoints. The cold front will progress eastward toward northern IL by Wed morning, while western parts of the front stall from KS into the TX Panhandle. To the west, an upper low will continue southward across western AZ and into the northern Baja, maintaining a favorable environment for scattered storms over southern AZ and NM. ...Upper MS Valley to the central Plains... Most of the area will remain free of thunderstorms for much of the day as the moist plume becomes established and temperatures aloft cool. By around 00Z, storms are expected to form along the front from southern MN into IA and perhaps eastern NE, and will expand in coverage through the evening into WI. Strong deep-layer shear perpendicular to the front will favor supercells, with steep lapse rates aloft and around 200 m2/s2 ESRH favoring very large hail and perhaps a tornado or two. Farther south into KS, strong heating of a 65-70 F dewpoint air mass will lead to over 3000 J/kg MUCAPE, with isolated severe storms expected across central and eastern KS. Hail will be possible, with localized wind damage. Parts of this area may require a categorical upgrade in later outlooks once placement of potential storm clusters is more precise. ...Southern AZ and southwest NM... Scattered to numerous storms may be ongoing Tuesday morning over southern AZ and NM in association with the upper low. Pockets of destabilization may occur once again during the day, with isolated strong to severe storms possible capable of hail or localized wind damage. ..Jewell.. 09/22/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun Sep 22 2019 Valid 241200Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF IOWA...WESTERN WISCONSIN...AND SOUTHERN MINNESOTA... ...SUMMARY... Severe storms are possible Tuesday across much of Iowa, Wisconsin, and southern Minnesota, with isolated storms from parts of the central Plains to the Upper Great Lakes. ...Synopsis... An elongated upper jet will dive southeastward across the northern Plains and into the upper MS Valley on Tuesday, with significant cooling aloft and increasing shear. The strongest lift will focus over MN, IA and WI as a cold front collides with returning low-level moisture with at least mid 60s F dewpoints. The cold front will progress eastward toward northern IL by Wed morning, while western parts of the front stall from KS into the TX Panhandle. To the west, an upper low will continue southward across western AZ and into the northern Baja, maintaining a favorable environment for scattered storms over southern AZ and NM. ...Upper MS Valley to the central Plains... Most of the area will remain free of thunderstorms for much of the day as the moist plume becomes established and temperatures aloft cool. By around 00Z, storms are expected to form along the front from southern MN into IA and perhaps eastern NE, and will expand in coverage through the evening into WI. Strong deep-layer shear perpendicular to the front will favor supercells, with steep lapse rates aloft and around 200 m2/s2 ESRH favoring very large hail and perhaps a tornado or two. Farther south into KS, strong heating of a 65-70 F dewpoint air mass will lead to over 3000 J/kg MUCAPE, with isolated severe storms expected across central and eastern KS. Hail will be possible, with localized wind damage. Parts of this area may require a categorical upgrade in later outlooks once placement of potential storm clusters is more precise. ...Southern AZ and southwest NM... Scattered to numerous storms may be ongoing Tuesday morning over southern AZ and NM in association with the upper low. Pockets of destabilization may occur once again during the day, with isolated strong to severe storms possible capable of hail or localized wind damage. ..Jewell.. 09/22/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 AM CDT Sun Sep 22 2019 Valid 241200Z - 251200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF IOWA...WESTERN WISCONSIN...AND SOUTHERN MINNESOTA... ...SUMMARY... Severe storms are possible Tuesday across much of Iowa, Wisconsin, and southern Minnesota, with isolated storms from parts of the central Plains to the Upper Great Lakes. ...Synopsis... An elongated upper jet will dive southeastward across the northern Plains and into the upper MS Valley on Tuesday, with significant cooling aloft and increasing shear. The strongest lift will focus over MN, IA and WI as a cold front collides with returning low-level moisture with at least mid 60s F dewpoints. The cold front will progress eastward toward northern IL by Wed morning, while western parts of the front stall from KS into the TX Panhandle. To the west, an upper low will continue southward across western AZ and into the northern Baja, maintaining a favorable environment for scattered storms over southern AZ and NM. ...Upper MS Valley to the central Plains... Most of the area will remain free of thunderstorms for much of the day as the moist plume becomes established and temperatures aloft cool. By around 00Z, storms are expected to form along the front from southern MN into IA and perhaps eastern NE, and will expand in coverage through the evening into WI. Strong deep-layer shear perpendicular to the front will favor supercells, with steep lapse rates aloft and around 200 m2/s2 ESRH favoring very large hail and perhaps a tornado or two. Farther south into KS, strong heating of a 65-70 F dewpoint air mass will lead to over 3000 J/kg MUCAPE, with isolated severe storms expected across central and eastern KS. Hail will be possible, with localized wind damage. Parts of this area may require a categorical upgrade in later outlooks once placement of potential storm clusters is more precise. ...Southern AZ and southwest NM... Scattered to numerous storms may be ongoing Tuesday morning over southern AZ and NM in association with the upper low. Pockets of destabilization may occur once again during the day, with isolated strong to severe storms possible capable of hail or localized wind damage. ..Jewell.. 09/22/2019 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0130 AM CDT Sun Sep 22 2019 Valid 231200Z - 241200Z ...Synopsis... A strong mid/upper-level trough -- and associated area of enhanced mid-level flow -- is forecast to gradually move southeastward from the Great Basin to the Desert Southwest Day 2/Monday. ...Northern California... Elevated to locally critical fire weather conditions are expected Day 2/Monday across portions of the Sacramento Valley (especially western portions of the valley) and adjacent North Coast Ranges, as dry/gusty low-level northerly flow -- beneath the aforementioned area of enhanced mid-level flow -- overlaps near critical minimum RH values and at least marginally receptive fuels. Elevated fire weather conditions may also persist into the overnight due to poor RH recoveries and lingering gusty/breezy surface winds -- especially in terrain favored areas of the North Coast Ranges. ...Southern California... While a combination of increasing offshore surface flow and poor overnight RH recoveries may promote at least locally elevated fire weather conditions late overnight Day 2/Monday, the uncertainty regarding timing/coverage of any fire weather conditions precludes a fire weather area at this time. ..Elliott.. 09/22/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more