Severe Storms

WW 638 SEVERE TSTM CO 082055Z - 090300Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 638 NWS Storm Prediction Center Norman OK 255 PM MDT Sun Sep 8 2019 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Central and Northeastern Colorado * Effective this Sunday afternoon and evening from 255 PM until 900 PM MDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Thunderstorms over the high terrain of central Colorado will intensify as it moves eastward into the High Plains. Damaging wind gusts are the main concern with the strongest cells, along with some risk of hail. The severe thunderstorm watch area is approximately along and 75 statute miles east and west of a line from 40 miles north northwest of Fort Collins CO to 15 miles southeast of Pueblo CO. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU8). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 26030. ...Hart Read more

WW 0638 Status Updates
STATUS FOR WATCH 0638 HAS NOT BEEN ISSUED YET Read more

WW 0638 Status Updates
STATUS FOR WATCH 0638 HAS NOT BEEN ISSUED YET Read more

MD 1939 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR MUCH OF EASTERN COLORADO
Mesoscale Discussion 1939 NWS Storm Prediction Center Norman OK 0340 PM CDT Sun Sep 08 2019 Areas affected...Much of eastern Colorado Concerning...Severe potential...Watch likely Valid 082040Z - 082215Z Probability of Watch Issuance...80 percent SUMMARY...Strong thunderstorms are expected to develop across much of eastern Colorado later this afternoon. Severe wind gusts and hail are expected with the more organized convection. DISCUSSION...Leading edge of large-scale forcing for ascent is spreading across the central Rockies early this afternoon. Latest satellite imagery depicts this well with an arcing band of deep convection extending from southwest WY - northwest CO - into the San Juan Mountains. Over the last few hours, low clouds have gradually thinned over lower elevations of northeast CO but a notable surface boundary remains draped along the I-70 corridor which is maintaining easterly low-level flow. Strongly-forcing band of convection has already generated locally severe wind gusts over the higher terrain and this activity is expected to grow upscale as it encounters more buoyant air mass downstream. Latest diagnostic data suggest surface parcels remain capped east of the Front Range, but continued heating should ease inhibition over the next few hours. Maturing organized thunderstorms with wind/hail should progress across much of eastern CO late this afternoon/evening. ..Darrow/Hart.. 09/08/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GLD...PUB...BOU... LAT...LON 37870365 38860505 39940538 40820517 40900374 40100285 39540209 38080219 37870365 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sun Sep 08 2019 Valid 082000Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN CO...FAR SOUTHEASTERN WY...AND THE NE PANHANDLE... ...SUMMARY... Severe thunderstorms with strong/gusty winds and hail remain possible across parts of the central Rockies and adjacent High Plains this afternoon and evening. Other strong storms may affect parts of southeast Virginia and northeast North Carolina. ...20Z Update... Storms have begun to increase in coverage across the higher terrain of central CO ahead of a northeastward-moving upper trough over the Great Basin. As this activity spreads eastward and encounters greater low-level moisture across northeastern CO and vicinity later this afternoon and evening, isolated severe thunderstorms may occur. Damaging winds still appear to be the main threat as storms will likely grow upscale into a small cluster this evening, but marginally severe hail may also occur early in the convective life cycle. Ongoing forecast still appears on track, and no changes have been made to the Marginal/Slight risk areas across this region. ..Gleason.. 09/08/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Sep 08 2019/ ...Central Rockies into High Plains... Morning water vapor loop shows a strong and progressive upper trough moving across parts of NV/UT. This feature will track into WY/CO later today, with an associated zone of enhanced forcing for ascent overspreading the region. Strong daytime heating is occurring over much of the mountains and foothills of CO, where steep low-level lapse rates will develop and scattered thunderstorms are expected. As these storms move off the higher terrain late this afternoon and early evening, continued easterly low-level winds will help to establish an axis of sufficient CAPE for a few robust updrafts/downdrafts capable of damaging winds and some hail. Vertical shear profiles are sufficient for supercell/bowing structures. This activity will spread northeastward across the SLGT risk area during the evening. ...VA/NC... The southern fringe of stronger westerly flow aloft has sagged into southeast VA/northeast NC today, where a very moist and potentially unstable air mass is present. Dewpoints in the mid 70s and strong heating will lead to moderate CAPE values and the development of a few afternoon thunderstorms. Low-level winds are weak, suggesting that storms will be rather disorganized. However, sufficient midlevel winds and favorable thermodynamic parameters indicate a low risk of gusty winds in the stronger cells. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sun Sep 08 2019 Valid 082000Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN CO...FAR SOUTHEASTERN WY...AND THE NE PANHANDLE... ...SUMMARY... Severe thunderstorms with strong/gusty winds and hail remain possible across parts of the central Rockies and adjacent High Plains this afternoon and evening. Other strong storms may affect parts of southeast Virginia and northeast North Carolina. ...20Z Update... Storms have begun to increase in coverage across the higher terrain of central CO ahead of a northeastward-moving upper trough over the Great Basin. As this activity spreads eastward and encounters greater low-level moisture across northeastern CO and vicinity later this afternoon and evening, isolated severe thunderstorms may occur. Damaging winds still appear to be the main threat as storms will likely grow upscale into a small cluster this evening, but marginally severe hail may also occur early in the convective life cycle. Ongoing forecast still appears on track, and no changes have been made to the Marginal/Slight risk areas across this region. ..Gleason.. 09/08/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Sep 08 2019/ ...Central Rockies into High Plains... Morning water vapor loop shows a strong and progressive upper trough moving across parts of NV/UT. This feature will track into WY/CO later today, with an associated zone of enhanced forcing for ascent overspreading the region. Strong daytime heating is occurring over much of the mountains and foothills of CO, where steep low-level lapse rates will develop and scattered thunderstorms are expected. As these storms move off the higher terrain late this afternoon and early evening, continued easterly low-level winds will help to establish an axis of sufficient CAPE for a few robust updrafts/downdrafts capable of damaging winds and some hail. Vertical shear profiles are sufficient for supercell/bowing structures. This activity will spread northeastward across the SLGT risk area during the evening. ...VA/NC... The southern fringe of stronger westerly flow aloft has sagged into southeast VA/northeast NC today, where a very moist and potentially unstable air mass is present. Dewpoints in the mid 70s and strong heating will lead to moderate CAPE values and the development of a few afternoon thunderstorms. Low-level winds are weak, suggesting that storms will be rather disorganized. However, sufficient midlevel winds and favorable thermodynamic parameters indicate a low risk of gusty winds in the stronger cells. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sun Sep 08 2019 Valid 082000Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN CO...FAR SOUTHEASTERN WY...AND THE NE PANHANDLE... ...SUMMARY... Severe thunderstorms with strong/gusty winds and hail remain possible across parts of the central Rockies and adjacent High Plains this afternoon and evening. Other strong storms may affect parts of southeast Virginia and northeast North Carolina. ...20Z Update... Storms have begun to increase in coverage across the higher terrain of central CO ahead of a northeastward-moving upper trough over the Great Basin. As this activity spreads eastward and encounters greater low-level moisture across northeastern CO and vicinity later this afternoon and evening, isolated severe thunderstorms may occur. Damaging winds still appear to be the main threat as storms will likely grow upscale into a small cluster this evening, but marginally severe hail may also occur early in the convective life cycle. Ongoing forecast still appears on track, and no changes have been made to the Marginal/Slight risk areas across this region. ..Gleason.. 09/08/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Sep 08 2019/ ...Central Rockies into High Plains... Morning water vapor loop shows a strong and progressive upper trough moving across parts of NV/UT. This feature will track into WY/CO later today, with an associated zone of enhanced forcing for ascent overspreading the region. Strong daytime heating is occurring over much of the mountains and foothills of CO, where steep low-level lapse rates will develop and scattered thunderstorms are expected. As these storms move off the higher terrain late this afternoon and early evening, continued easterly low-level winds will help to establish an axis of sufficient CAPE for a few robust updrafts/downdrafts capable of damaging winds and some hail. Vertical shear profiles are sufficient for supercell/bowing structures. This activity will spread northeastward across the SLGT risk area during the evening. ...VA/NC... The southern fringe of stronger westerly flow aloft has sagged into southeast VA/northeast NC today, where a very moist and potentially unstable air mass is present. Dewpoints in the mid 70s and strong heating will lead to moderate CAPE values and the development of a few afternoon thunderstorms. Low-level winds are weak, suggesting that storms will be rather disorganized. However, sufficient midlevel winds and favorable thermodynamic parameters indicate a low risk of gusty winds in the stronger cells. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sun Sep 08 2019 Valid 082000Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN CO...FAR SOUTHEASTERN WY...AND THE NE PANHANDLE... ...SUMMARY... Severe thunderstorms with strong/gusty winds and hail remain possible across parts of the central Rockies and adjacent High Plains this afternoon and evening. Other strong storms may affect parts of southeast Virginia and northeast North Carolina. ...20Z Update... Storms have begun to increase in coverage across the higher terrain of central CO ahead of a northeastward-moving upper trough over the Great Basin. As this activity spreads eastward and encounters greater low-level moisture across northeastern CO and vicinity later this afternoon and evening, isolated severe thunderstorms may occur. Damaging winds still appear to be the main threat as storms will likely grow upscale into a small cluster this evening, but marginally severe hail may also occur early in the convective life cycle. Ongoing forecast still appears on track, and no changes have been made to the Marginal/Slight risk areas across this region. ..Gleason.. 09/08/2019 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sun Sep 08 2019/ ...Central Rockies into High Plains... Morning water vapor loop shows a strong and progressive upper trough moving across parts of NV/UT. This feature will track into WY/CO later today, with an associated zone of enhanced forcing for ascent overspreading the region. Strong daytime heating is occurring over much of the mountains and foothills of CO, where steep low-level lapse rates will develop and scattered thunderstorms are expected. As these storms move off the higher terrain late this afternoon and early evening, continued easterly low-level winds will help to establish an axis of sufficient CAPE for a few robust updrafts/downdrafts capable of damaging winds and some hail. Vertical shear profiles are sufficient for supercell/bowing structures. This activity will spread northeastward across the SLGT risk area during the evening. ...VA/NC... The southern fringe of stronger westerly flow aloft has sagged into southeast VA/northeast NC today, where a very moist and potentially unstable air mass is present. Dewpoints in the mid 70s and strong heating will lead to moderate CAPE values and the development of a few afternoon thunderstorms. Low-level winds are weak, suggesting that storms will be rather disorganized. However, sufficient midlevel winds and favorable thermodynamic parameters indicate a low risk of gusty winds in the stronger cells. Read more

No watches are valid as of Sun Sep 8 19:08:07 UTC 2019.

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0205 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z The ongoing forecast is on track. Locally critical conditions can be expected across much of eastern/southern Nevada and western Utah, with minimum RH values (15-25%) being a limiting factor for a higher fire-weather threat. Southern California will also remain in a regime favoring Sundowner winds, with low RH values favoring elevated to locally critical fire weather conditions. More details are in the previous forecast discussion below. ..Cook.. 09/08/2019 .PREV DISCUSSION... /ISSUED 0148 AM CDT Sun Sep 08 2019/ ...Synopsis... Mid/upper-level longwave troughing is forecast to remain/deepen over much of the western CONUS Day 2/Monday. As this occurs, an area of enhanced mid-level flow is forecast to overspread portions of southern California, the Southwest, and the southern Great Basin. ...Nevada/Utah/Arizona... Downward mixing of the aforementioned enhanced mid-level flow should foster sustained surface winds of 15-20 mph (locally greater) Day 2/Monday afternoon/evening over portions of the southern Great Basin and vicinity. Elevated to locally critical fire weather conditions are forecast to develop as these surface winds overlap near-critical RH values and at least marginally receptive fuels. At this time, uncertainty regarding coverage/duration of sustained surface winds > 20 mph and critically-lowered RH values precludes the introduction of a critical fire weather area. ...Southern California: Santa Barbara and western Ventura County... Elevated fire weather conditions may be ongoing at higher elevations (e.g., > 1 kft) of eastern Santa Barbara and western Ventura Counties at 12Z Day 2/Monday due to poor overnight RH recoveries and gusty Sundowner winds. While surface winds are forecast to weaken and become less gusty during the late morning and early afternoon, elevated fire weather conditions are expected to redevelop as surface winds increase during the afternoon/evening. Elevated fire weather conditions may continue through the Day 2/Monday overnight as poor overnight RH recoveries and gusty winds persist. ...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 0205 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z The ongoing forecast is on track. Locally critical conditions can be expected across much of eastern/southern Nevada and western Utah, with minimum RH values (15-25%) being a limiting factor for a higher fire-weather threat. Southern California will also remain in a regime favoring Sundowner winds, with low RH values favoring elevated to locally critical fire weather conditions. More details are in the previous forecast discussion below. ..Cook.. 09/08/2019 .PREV DISCUSSION... /ISSUED 0148 AM CDT Sun Sep 08 2019/ ...Synopsis... Mid/upper-level longwave troughing is forecast to remain/deepen over much of the western CONUS Day 2/Monday. As this occurs, an area of enhanced mid-level flow is forecast to overspread portions of southern California, the Southwest, and the southern Great Basin. ...Nevada/Utah/Arizona... Downward mixing of the aforementioned enhanced mid-level flow should foster sustained surface winds of 15-20 mph (locally greater) Day 2/Monday afternoon/evening over portions of the southern Great Basin and vicinity. Elevated to locally critical fire weather conditions are forecast to develop as these surface winds overlap near-critical RH values and at least marginally receptive fuels. At this time, uncertainty regarding coverage/duration of sustained surface winds > 20 mph and critically-lowered RH values precludes the introduction of a critical fire weather area. ...Southern California: Santa Barbara and western Ventura County... Elevated fire weather conditions may be ongoing at higher elevations (e.g., > 1 kft) of eastern Santa Barbara and western Ventura Counties at 12Z Day 2/Monday due to poor overnight RH recoveries and gusty Sundowner winds. While surface winds are forecast to weaken and become less gusty during the late morning and early afternoon, elevated fire weather conditions are expected to redevelop as surface winds increase during the afternoon/evening. Elevated fire weather conditions may continue through the Day 2/Monday overnight as poor overnight RH recoveries and gusty winds persist. ...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 0205 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z The ongoing forecast is on track. Locally critical conditions can be expected across much of eastern/southern Nevada and western Utah, with minimum RH values (15-25%) being a limiting factor for a higher fire-weather threat. Southern California will also remain in a regime favoring Sundowner winds, with low RH values favoring elevated to locally critical fire weather conditions. More details are in the previous forecast discussion below. ..Cook.. 09/08/2019 .PREV DISCUSSION... /ISSUED 0148 AM CDT Sun Sep 08 2019/ ...Synopsis... Mid/upper-level longwave troughing is forecast to remain/deepen over much of the western CONUS Day 2/Monday. As this occurs, an area of enhanced mid-level flow is forecast to overspread portions of southern California, the Southwest, and the southern Great Basin. ...Nevada/Utah/Arizona... Downward mixing of the aforementioned enhanced mid-level flow should foster sustained surface winds of 15-20 mph (locally greater) Day 2/Monday afternoon/evening over portions of the southern Great Basin and vicinity. Elevated to locally critical fire weather conditions are forecast to develop as these surface winds overlap near-critical RH values and at least marginally receptive fuels. At this time, uncertainty regarding coverage/duration of sustained surface winds > 20 mph and critically-lowered RH values precludes the introduction of a critical fire weather area. ...Southern California: Santa Barbara and western Ventura County... Elevated fire weather conditions may be ongoing at higher elevations (e.g., > 1 kft) of eastern Santa Barbara and western Ventura Counties at 12Z Day 2/Monday due to poor overnight RH recoveries and gusty Sundowner winds. While surface winds are forecast to weaken and become less gusty during the late morning and early afternoon, elevated fire weather conditions are expected to redevelop as surface winds increase during the afternoon/evening. Elevated fire weather conditions may continue through the Day 2/Monday overnight as poor overnight RH recoveries and gusty winds persist. ...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 0205 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z The ongoing forecast is on track. Locally critical conditions can be expected across much of eastern/southern Nevada and western Utah, with minimum RH values (15-25%) being a limiting factor for a higher fire-weather threat. Southern California will also remain in a regime favoring Sundowner winds, with low RH values favoring elevated to locally critical fire weather conditions. More details are in the previous forecast discussion below. ..Cook.. 09/08/2019 .PREV DISCUSSION... /ISSUED 0148 AM CDT Sun Sep 08 2019/ ...Synopsis... Mid/upper-level longwave troughing is forecast to remain/deepen over much of the western CONUS Day 2/Monday. As this occurs, an area of enhanced mid-level flow is forecast to overspread portions of southern California, the Southwest, and the southern Great Basin. ...Nevada/Utah/Arizona... Downward mixing of the aforementioned enhanced mid-level flow should foster sustained surface winds of 15-20 mph (locally greater) Day 2/Monday afternoon/evening over portions of the southern Great Basin and vicinity. Elevated to locally critical fire weather conditions are forecast to develop as these surface winds overlap near-critical RH values and at least marginally receptive fuels. At this time, uncertainty regarding coverage/duration of sustained surface winds > 20 mph and critically-lowered RH values precludes the introduction of a critical fire weather area. ...Southern California: Santa Barbara and western Ventura County... Elevated fire weather conditions may be ongoing at higher elevations (e.g., > 1 kft) of eastern Santa Barbara and western Ventura Counties at 12Z Day 2/Monday due to poor overnight RH recoveries and gusty Sundowner winds. While surface winds are forecast to weaken and become less gusty during the late morning and early afternoon, elevated fire weather conditions are expected to redevelop as surface winds increase during the afternoon/evening. Elevated fire weather conditions may continue through the Day 2/Monday overnight as poor overnight RH recoveries and gusty winds persist. ...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 1230 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS INTO THE UPPER MS VALLEY... ...SUMMARY... Thunderstorms capable of producing isolated tornadoes, large hail, and strong/gusty winds will be possible across parts of the northern Plains and upper Mississippi Valley Monday afternoon and evening. ...Northern/Central Plains into the Upper Mississippi Valley... An upper trough will continue to develop northeastward across the northern Plains into the Upper Midwest on Monday. A surface low initially over the northern/central High Plains should consolidate over SD by Monday evening. A warm front extending eastward from the low will shift northward across the upper MS Valley through the day, with upper 60 to lower 70s dewpoints likely present across the warm sector. Scattered to numerous showers and thunderstorms will likely be ongoing across parts of the northern/central Plains Monday morning in a low-level warm air advection regime ahead of the upper trough. This may delay diurnal destabilization south of the front through the morning, but weak to moderate instability should eventually develop with modest daytime heating and gradual steepening of mid-level lapse rates as the upper trough moves northeastward. There is still some uncertainty in the placement of the warm front by late Monday afternoon in model guidance. But, any storms that can form south of the warm front, move northeastward, and subsequently cross the front will have the potential to produce isolated tornadoes given strong low-level shear that will be present. In addition, there should be enough effective bulk shear (around 35-45 kt) to support supercells initially. At this time, it appears that parts of central/northern IA into far southeastern SD and southern MN will have the best potential for isolated to scattered surface-based storm coverage as large-scale ascent associated with the upper trough encourages convective development by Monday afternoon. Isolated large hail may also occur, although mid-level lapse rates become more modest with eastward extent. A low-level jet is forecast to strengthen Monday evening from IA into MN, which will likely support the northward advance of the warm front overnight across the Upper Midwest, with an isolated large hail threat persisting with mainly elevated storms. Farther south into NE/KS, overall convective coverage is more questionable. Still, any storms that can form along/ahead of a surface trough may be capable of isolated hail and strong/gusty winds given the presence of moderate to strong instability and sufficient mid-level flow for some updraft organization. ...Virginia/North Carolina... Isolated to widely scattered storms may form by Monday afternoon as a weak shortwave trough moves over the Mid-Atlantic. Modestly enhanced mid-level flow and at least moderate instability along/south of a surface boundary across central/southern VA may support occasionally organized updrafts capable of producing both isolated large hail and strong to damaging wind gusts. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 5% - Marginal Hail: 15% - Slight ..Gleason.. 09/08/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS INTO THE UPPER MS VALLEY... ...SUMMARY... Thunderstorms capable of producing isolated tornadoes, large hail, and strong/gusty winds will be possible across parts of the northern Plains and upper Mississippi Valley Monday afternoon and evening. ...Northern/Central Plains into the Upper Mississippi Valley... An upper trough will continue to develop northeastward across the northern Plains into the Upper Midwest on Monday. A surface low initially over the northern/central High Plains should consolidate over SD by Monday evening. A warm front extending eastward from the low will shift northward across the upper MS Valley through the day, with upper 60 to lower 70s dewpoints likely present across the warm sector. Scattered to numerous showers and thunderstorms will likely be ongoing across parts of the northern/central Plains Monday morning in a low-level warm air advection regime ahead of the upper trough. This may delay diurnal destabilization south of the front through the morning, but weak to moderate instability should eventually develop with modest daytime heating and gradual steepening of mid-level lapse rates as the upper trough moves northeastward. There is still some uncertainty in the placement of the warm front by late Monday afternoon in model guidance. But, any storms that can form south of the warm front, move northeastward, and subsequently cross the front will have the potential to produce isolated tornadoes given strong low-level shear that will be present. In addition, there should be enough effective bulk shear (around 35-45 kt) to support supercells initially. At this time, it appears that parts of central/northern IA into far southeastern SD and southern MN will have the best potential for isolated to scattered surface-based storm coverage as large-scale ascent associated with the upper trough encourages convective development by Monday afternoon. Isolated large hail may also occur, although mid-level lapse rates become more modest with eastward extent. A low-level jet is forecast to strengthen Monday evening from IA into MN, which will likely support the northward advance of the warm front overnight across the Upper Midwest, with an isolated large hail threat persisting with mainly elevated storms. Farther south into NE/KS, overall convective coverage is more questionable. Still, any storms that can form along/ahead of a surface trough may be capable of isolated hail and strong/gusty winds given the presence of moderate to strong instability and sufficient mid-level flow for some updraft organization. ...Virginia/North Carolina... Isolated to widely scattered storms may form by Monday afternoon as a weak shortwave trough moves over the Mid-Atlantic. Modestly enhanced mid-level flow and at least moderate instability along/south of a surface boundary across central/southern VA may support occasionally organized updrafts capable of producing both isolated large hail and strong to damaging wind gusts. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 5% - Marginal Hail: 15% - Slight ..Gleason.. 09/08/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS INTO THE UPPER MS VALLEY... ...SUMMARY... Thunderstorms capable of producing isolated tornadoes, large hail, and strong/gusty winds will be possible across parts of the northern Plains and upper Mississippi Valley Monday afternoon and evening. ...Northern/Central Plains into the Upper Mississippi Valley... An upper trough will continue to develop northeastward across the northern Plains into the Upper Midwest on Monday. A surface low initially over the northern/central High Plains should consolidate over SD by Monday evening. A warm front extending eastward from the low will shift northward across the upper MS Valley through the day, with upper 60 to lower 70s dewpoints likely present across the warm sector. Scattered to numerous showers and thunderstorms will likely be ongoing across parts of the northern/central Plains Monday morning in a low-level warm air advection regime ahead of the upper trough. This may delay diurnal destabilization south of the front through the morning, but weak to moderate instability should eventually develop with modest daytime heating and gradual steepening of mid-level lapse rates as the upper trough moves northeastward. There is still some uncertainty in the placement of the warm front by late Monday afternoon in model guidance. But, any storms that can form south of the warm front, move northeastward, and subsequently cross the front will have the potential to produce isolated tornadoes given strong low-level shear that will be present. In addition, there should be enough effective bulk shear (around 35-45 kt) to support supercells initially. At this time, it appears that parts of central/northern IA into far southeastern SD and southern MN will have the best potential for isolated to scattered surface-based storm coverage as large-scale ascent associated with the upper trough encourages convective development by Monday afternoon. Isolated large hail may also occur, although mid-level lapse rates become more modest with eastward extent. A low-level jet is forecast to strengthen Monday evening from IA into MN, which will likely support the northward advance of the warm front overnight across the Upper Midwest, with an isolated large hail threat persisting with mainly elevated storms. Farther south into NE/KS, overall convective coverage is more questionable. Still, any storms that can form along/ahead of a surface trough may be capable of isolated hail and strong/gusty winds given the presence of moderate to strong instability and sufficient mid-level flow for some updraft organization. ...Virginia/North Carolina... Isolated to widely scattered storms may form by Monday afternoon as a weak shortwave trough moves over the Mid-Atlantic. Modestly enhanced mid-level flow and at least moderate instability along/south of a surface boundary across central/southern VA may support occasionally organized updrafts capable of producing both isolated large hail and strong to damaging wind gusts. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 5% - Marginal Hail: 15% - Slight ..Gleason.. 09/08/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS INTO THE UPPER MS VALLEY... ...SUMMARY... Thunderstorms capable of producing isolated tornadoes, large hail, and strong/gusty winds will be possible across parts of the northern Plains and upper Mississippi Valley Monday afternoon and evening. ...Northern/Central Plains into the Upper Mississippi Valley... An upper trough will continue to develop northeastward across the northern Plains into the Upper Midwest on Monday. A surface low initially over the northern/central High Plains should consolidate over SD by Monday evening. A warm front extending eastward from the low will shift northward across the upper MS Valley through the day, with upper 60 to lower 70s dewpoints likely present across the warm sector. Scattered to numerous showers and thunderstorms will likely be ongoing across parts of the northern/central Plains Monday morning in a low-level warm air advection regime ahead of the upper trough. This may delay diurnal destabilization south of the front through the morning, but weak to moderate instability should eventually develop with modest daytime heating and gradual steepening of mid-level lapse rates as the upper trough moves northeastward. There is still some uncertainty in the placement of the warm front by late Monday afternoon in model guidance. But, any storms that can form south of the warm front, move northeastward, and subsequently cross the front will have the potential to produce isolated tornadoes given strong low-level shear that will be present. In addition, there should be enough effective bulk shear (around 35-45 kt) to support supercells initially. At this time, it appears that parts of central/northern IA into far southeastern SD and southern MN will have the best potential for isolated to scattered surface-based storm coverage as large-scale ascent associated with the upper trough encourages convective development by Monday afternoon. Isolated large hail may also occur, although mid-level lapse rates become more modest with eastward extent. A low-level jet is forecast to strengthen Monday evening from IA into MN, which will likely support the northward advance of the warm front overnight across the Upper Midwest, with an isolated large hail threat persisting with mainly elevated storms. Farther south into NE/KS, overall convective coverage is more questionable. Still, any storms that can form along/ahead of a surface trough may be capable of isolated hail and strong/gusty winds given the presence of moderate to strong instability and sufficient mid-level flow for some updraft organization. ...Virginia/North Carolina... Isolated to widely scattered storms may form by Monday afternoon as a weak shortwave trough moves over the Mid-Atlantic. Modestly enhanced mid-level flow and at least moderate instability along/south of a surface boundary across central/southern VA may support occasionally organized updrafts capable of producing both isolated large hail and strong to damaging wind gusts. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 5% - Marginal Hail: 15% - Slight ..Gleason.. 09/08/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sun Sep 08 2019 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN PLAINS INTO THE UPPER MS VALLEY... ...SUMMARY... Thunderstorms capable of producing isolated tornadoes, large hail, and strong/gusty winds will be possible across parts of the northern Plains and upper Mississippi Valley Monday afternoon and evening. ...Northern/Central Plains into the Upper Mississippi Valley... An upper trough will continue to develop northeastward across the northern Plains into the Upper Midwest on Monday. A surface low initially over the northern/central High Plains should consolidate over SD by Monday evening. A warm front extending eastward from the low will shift northward across the upper MS Valley through the day, with upper 60 to lower 70s dewpoints likely present across the warm sector. Scattered to numerous showers and thunderstorms will likely be ongoing across parts of the northern/central Plains Monday morning in a low-level warm air advection regime ahead of the upper trough. This may delay diurnal destabilization south of the front through the morning, but weak to moderate instability should eventually develop with modest daytime heating and gradual steepening of mid-level lapse rates as the upper trough moves northeastward. There is still some uncertainty in the placement of the warm front by late Monday afternoon in model guidance. But, any storms that can form south of the warm front, move northeastward, and subsequently cross the front will have the potential to produce isolated tornadoes given strong low-level shear that will be present. In addition, there should be enough effective bulk shear (around 35-45 kt) to support supercells initially. At this time, it appears that parts of central/northern IA into far southeastern SD and southern MN will have the best potential for isolated to scattered surface-based storm coverage as large-scale ascent associated with the upper trough encourages convective development by Monday afternoon. Isolated large hail may also occur, although mid-level lapse rates become more modest with eastward extent. A low-level jet is forecast to strengthen Monday evening from IA into MN, which will likely support the northward advance of the warm front overnight across the Upper Midwest, with an isolated large hail threat persisting with mainly elevated storms. Farther south into NE/KS, overall convective coverage is more questionable. Still, any storms that can form along/ahead of a surface trough may be capable of isolated hail and strong/gusty winds given the presence of moderate to strong instability and sufficient mid-level flow for some updraft organization. ...Virginia/North Carolina... Isolated to widely scattered storms may form by Monday afternoon as a weak shortwave trough moves over the Mid-Atlantic. Modestly enhanced mid-level flow and at least moderate instability along/south of a surface boundary across central/southern VA may support occasionally organized updrafts capable of producing both isolated large hail and strong to damaging wind gusts. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 5% - Marginal Hail: 15% - Slight ..Gleason.. 09/08/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Sep 08 2019 Valid 081630Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF EASTERN COLORADO...SOUTHEAST WYOMING...AND THE NEBRASKA PANHANDLE... ...SUMMARY... Severe thunderstorms with strong/gusty winds and hail will be possible across parts of the central Rockies and adjacent High Plains this afternoon and evening. Other strong storms may affect parts of southeast Virginia and northeast North Carolina. ...Central Rockies into High Plains... Morning water vapor loop shows a strong and progressive upper trough moving across parts of NV/UT. This feature will track into WY/CO later today, with an associated zone of enhanced forcing for ascent overspreading the region. Strong daytime heating is occurring over much of the mountains and foothills of CO, where steep low-level lapse rates will develop and scattered thunderstorms are expected. As these storms move off the higher terrain late this afternoon and early evening, continued easterly low-level winds will help to establish an axis of sufficient CAPE for a few robust updrafts/downdrafts capable of damaging winds and some hail. Vertical shear profiles are sufficient for supercell/bowing structures. This activity will spread northeastward across the SLGT risk area during the evening. ...VA/NC... The southern fringe of stronger westerly flow aloft has sagged into southeast VA/northeast NC today, where a very moist and potentially unstable air mass is present. Dewpoints in the mid 70s and strong heating will lead to moderate CAPE values and the development of a few afternoon thunderstorms. Low-level winds are weak, suggesting that storms will be rather disorganized. However, sufficient midlevel winds and favorable thermodynamic parameters indicate a low risk of gusty winds in the stronger cells. ..Hart/Wendt.. 09/08/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Sep 08 2019 Valid 081630Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF EASTERN COLORADO...SOUTHEAST WYOMING...AND THE NEBRASKA PANHANDLE... ...SUMMARY... Severe thunderstorms with strong/gusty winds and hail will be possible across parts of the central Rockies and adjacent High Plains this afternoon and evening. Other strong storms may affect parts of southeast Virginia and northeast North Carolina. ...Central Rockies into High Plains... Morning water vapor loop shows a strong and progressive upper trough moving across parts of NV/UT. This feature will track into WY/CO later today, with an associated zone of enhanced forcing for ascent overspreading the region. Strong daytime heating is occurring over much of the mountains and foothills of CO, where steep low-level lapse rates will develop and scattered thunderstorms are expected. As these storms move off the higher terrain late this afternoon and early evening, continued easterly low-level winds will help to establish an axis of sufficient CAPE for a few robust updrafts/downdrafts capable of damaging winds and some hail. Vertical shear profiles are sufficient for supercell/bowing structures. This activity will spread northeastward across the SLGT risk area during the evening. ...VA/NC... The southern fringe of stronger westerly flow aloft has sagged into southeast VA/northeast NC today, where a very moist and potentially unstable air mass is present. Dewpoints in the mid 70s and strong heating will lead to moderate CAPE values and the development of a few afternoon thunderstorms. Low-level winds are weak, suggesting that storms will be rather disorganized. However, sufficient midlevel winds and favorable thermodynamic parameters indicate a low risk of gusty winds in the stronger cells. ..Hart/Wendt.. 09/08/2019 Read more