Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Tue Sep 03 2019 Valid 032000Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE UPPER GREAT LAKES/MIDWEST... ...SUMMARY... Scattered severe thunderstorms are expected this afternoon and evening across parts of the Great Lakes and Midwest. A few tornadoes, large hail, and damaging winds remain possible. ...Discussion... Little change appears necessary to the ongoing outlook at this time, with the largest adjustment being to decrease the size of the MRGL and SLGT risk areas on the southern and western fringes. Otherwise, widespread cloud cover persists across a large portion of the SLGT risk area, which continues to temper destabilization, and fairly substantial capping is also evident from area 18z special RAOBs. These factors continue to cast uncertainty with respect to the degree of severe risk, and as such, upgrade to ENH risk (as was mentioned in prior outlooks) appears unwarranted at this time. Otherwise, the outlook appears to remain on track, with no other appreciable changes necessary at this time. ..Goss.. 09/03/2019 .PREV DISCUSSION... /ISSUED 1139 AM CDT Tue Sep 03 2019/ ...Midwest/Great Lakes... An upgrade to Enhanced Risk could still be warranted for portions of the region later today pending convective/observational trends. However, as mentioned in the prior (13Z) Outlook discussion, short-term guidance continues to generally sub-optimally depict and/or remains slow to adjust to the influence of ongoing convection, which casts some uncertainty regarding the convective scenario later today. This is principally with respect to the thermodynamic environment and related likelihood and north-northeastward extent of appreciable moistening and destabilization later today, coincident with a notable deep-layer wind field. Morning observations including 12Z sounding and WSR-88D VWP data sample deep-layer winds that are very strong by late-summer standards, particularly at a latitude around southern Lake Michigan and northward including Wisconsin/Michigan. Beneath a respectable elevated mixed layer, seasonably rich low-level moisture (with around 70F surface dewpoints) is prevalent at late morning across eastern Iowa, southern Wisconsin, western Illinois near and ahead of an eastward-advancing cold front. This moisture will steadily advect eastward today, with the morning convection/residual cloud cover potentially effectively reinforcing/delaying an eastward-shifting warm front toward and across Lower Michigan and northern Indiana. Boundary-layer heating will probably be of more limited duration with north/northeast extent across Lower Michigan, but will be greater with southwest extent into Illinois. A strongly unstable air mass should develop initially near Lake Michigan southwestward across Illinois, with greater uncertainty in the degree of buoyancy farther north across Lower Michigan. At least isolated, mid-to-late afternoon deep convective redevelopment will probably occur with the approach of a cold front from western Lower Michigan into northern Illinois, with deep-layer winds well-supportive (40-50 kt effective) of initial supercells. Hail/damaging wind potential aside, low-level shear/SRH will be maximized near the effective warm front and within the increasingly narrow warm sector with northward extent across Lower Michigan. Although short-term forecast uncertainty lingers as previously discussed, on presumed/probable air mass recovery a respectable potential does exist for a couple of tornadoes, including some possibility of a strong tornado, aside from an increasing risk for damaging winds this evening. Severe risks currently appear most probable to occur across northern Indiana and southern Lower Michigan, and possibly into northern/western Ohio late tonight. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast Florida Coast... Hurricane Dorian is forecast to move northward and remain offshore; reference NHC for the latest details. This will maintain most of the Florida Atlantic Coast in the tornado-unfavorable western periphery of Dorian. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple of rotating cells capable of a brief tornado through tonight. ...Deep South Texas... Reference NHC for the latest details regarding Tropical Depression Seven, which may gradually strengthen/organize over the far western Gulf of Mexico. A modest low-level strengthening of easterly winds on its northern periphery could influence low-topped supercell potential and possibly some tornado risk into Wednesday. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Tue Sep 03 2019 Valid 032000Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE UPPER GREAT LAKES/MIDWEST... ...SUMMARY... Scattered severe thunderstorms are expected this afternoon and evening across parts of the Great Lakes and Midwest. A few tornadoes, large hail, and damaging winds remain possible. ...Discussion... Little change appears necessary to the ongoing outlook at this time, with the largest adjustment being to decrease the size of the MRGL and SLGT risk areas on the southern and western fringes. Otherwise, widespread cloud cover persists across a large portion of the SLGT risk area, which continues to temper destabilization, and fairly substantial capping is also evident from area 18z special RAOBs. These factors continue to cast uncertainty with respect to the degree of severe risk, and as such, upgrade to ENH risk (as was mentioned in prior outlooks) appears unwarranted at this time. Otherwise, the outlook appears to remain on track, with no other appreciable changes necessary at this time. ..Goss.. 09/03/2019 .PREV DISCUSSION... /ISSUED 1139 AM CDT Tue Sep 03 2019/ ...Midwest/Great Lakes... An upgrade to Enhanced Risk could still be warranted for portions of the region later today pending convective/observational trends. However, as mentioned in the prior (13Z) Outlook discussion, short-term guidance continues to generally sub-optimally depict and/or remains slow to adjust to the influence of ongoing convection, which casts some uncertainty regarding the convective scenario later today. This is principally with respect to the thermodynamic environment and related likelihood and north-northeastward extent of appreciable moistening and destabilization later today, coincident with a notable deep-layer wind field. Morning observations including 12Z sounding and WSR-88D VWP data sample deep-layer winds that are very strong by late-summer standards, particularly at a latitude around southern Lake Michigan and northward including Wisconsin/Michigan. Beneath a respectable elevated mixed layer, seasonably rich low-level moisture (with around 70F surface dewpoints) is prevalent at late morning across eastern Iowa, southern Wisconsin, western Illinois near and ahead of an eastward-advancing cold front. This moisture will steadily advect eastward today, with the morning convection/residual cloud cover potentially effectively reinforcing/delaying an eastward-shifting warm front toward and across Lower Michigan and northern Indiana. Boundary-layer heating will probably be of more limited duration with north/northeast extent across Lower Michigan, but will be greater with southwest extent into Illinois. A strongly unstable air mass should develop initially near Lake Michigan southwestward across Illinois, with greater uncertainty in the degree of buoyancy farther north across Lower Michigan. At least isolated, mid-to-late afternoon deep convective redevelopment will probably occur with the approach of a cold front from western Lower Michigan into northern Illinois, with deep-layer winds well-supportive (40-50 kt effective) of initial supercells. Hail/damaging wind potential aside, low-level shear/SRH will be maximized near the effective warm front and within the increasingly narrow warm sector with northward extent across Lower Michigan. Although short-term forecast uncertainty lingers as previously discussed, on presumed/probable air mass recovery a respectable potential does exist for a couple of tornadoes, including some possibility of a strong tornado, aside from an increasing risk for damaging winds this evening. Severe risks currently appear most probable to occur across northern Indiana and southern Lower Michigan, and possibly into northern/western Ohio late tonight. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast Florida Coast... Hurricane Dorian is forecast to move northward and remain offshore; reference NHC for the latest details. This will maintain most of the Florida Atlantic Coast in the tornado-unfavorable western periphery of Dorian. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple of rotating cells capable of a brief tornado through tonight. ...Deep South Texas... Reference NHC for the latest details regarding Tropical Depression Seven, which may gradually strengthen/organize over the far western Gulf of Mexico. A modest low-level strengthening of easterly winds on its northern periphery could influence low-topped supercell potential and possibly some tornado risk into Wednesday. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Tue Sep 03 2019 Valid 032000Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE UPPER GREAT LAKES/MIDWEST... ...SUMMARY... Scattered severe thunderstorms are expected this afternoon and evening across parts of the Great Lakes and Midwest. A few tornadoes, large hail, and damaging winds remain possible. ...Discussion... Little change appears necessary to the ongoing outlook at this time, with the largest adjustment being to decrease the size of the MRGL and SLGT risk areas on the southern and western fringes. Otherwise, widespread cloud cover persists across a large portion of the SLGT risk area, which continues to temper destabilization, and fairly substantial capping is also evident from area 18z special RAOBs. These factors continue to cast uncertainty with respect to the degree of severe risk, and as such, upgrade to ENH risk (as was mentioned in prior outlooks) appears unwarranted at this time. Otherwise, the outlook appears to remain on track, with no other appreciable changes necessary at this time. ..Goss.. 09/03/2019 .PREV DISCUSSION... /ISSUED 1139 AM CDT Tue Sep 03 2019/ ...Midwest/Great Lakes... An upgrade to Enhanced Risk could still be warranted for portions of the region later today pending convective/observational trends. However, as mentioned in the prior (13Z) Outlook discussion, short-term guidance continues to generally sub-optimally depict and/or remains slow to adjust to the influence of ongoing convection, which casts some uncertainty regarding the convective scenario later today. This is principally with respect to the thermodynamic environment and related likelihood and north-northeastward extent of appreciable moistening and destabilization later today, coincident with a notable deep-layer wind field. Morning observations including 12Z sounding and WSR-88D VWP data sample deep-layer winds that are very strong by late-summer standards, particularly at a latitude around southern Lake Michigan and northward including Wisconsin/Michigan. Beneath a respectable elevated mixed layer, seasonably rich low-level moisture (with around 70F surface dewpoints) is prevalent at late morning across eastern Iowa, southern Wisconsin, western Illinois near and ahead of an eastward-advancing cold front. This moisture will steadily advect eastward today, with the morning convection/residual cloud cover potentially effectively reinforcing/delaying an eastward-shifting warm front toward and across Lower Michigan and northern Indiana. Boundary-layer heating will probably be of more limited duration with north/northeast extent across Lower Michigan, but will be greater with southwest extent into Illinois. A strongly unstable air mass should develop initially near Lake Michigan southwestward across Illinois, with greater uncertainty in the degree of buoyancy farther north across Lower Michigan. At least isolated, mid-to-late afternoon deep convective redevelopment will probably occur with the approach of a cold front from western Lower Michigan into northern Illinois, with deep-layer winds well-supportive (40-50 kt effective) of initial supercells. Hail/damaging wind potential aside, low-level shear/SRH will be maximized near the effective warm front and within the increasingly narrow warm sector with northward extent across Lower Michigan. Although short-term forecast uncertainty lingers as previously discussed, on presumed/probable air mass recovery a respectable potential does exist for a couple of tornadoes, including some possibility of a strong tornado, aside from an increasing risk for damaging winds this evening. Severe risks currently appear most probable to occur across northern Indiana and southern Lower Michigan, and possibly into northern/western Ohio late tonight. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast Florida Coast... Hurricane Dorian is forecast to move northward and remain offshore; reference NHC for the latest details. This will maintain most of the Florida Atlantic Coast in the tornado-unfavorable western periphery of Dorian. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple of rotating cells capable of a brief tornado through tonight. ...Deep South Texas... Reference NHC for the latest details regarding Tropical Depression Seven, which may gradually strengthen/organize over the far western Gulf of Mexico. A modest low-level strengthening of easterly winds on its northern periphery could influence low-topped supercell potential and possibly some tornado risk into Wednesday. Read more

MD 1920 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR EASTERN/SOUTHERN WI
Mesoscale Discussion 1920 NWS Storm Prediction Center Norman OK 0157 PM CDT Tue Sep 03 2019 Areas affected...Eastern/Southern WI Concerning...Severe potential...Watch unlikely Valid 031857Z - 032100Z Probability of Watch Issuance...20 percent SUMMARY...Storm coverage is expected to increase over the next few hours along the front moving through eastern WI. A few severe storms are possible. DISCUSSION...Recent visible satellite imagery has shown increasingly deep cumulus towers along the cold front moving eastward across eastern WI. Cloudiness has limited diurnal heating and destabilization further south (across far southern WI and northern IL) but portions of eastern WI have reached the upper 70s/low 80s. Ample low-level moisture also exists, with dewpoints ranging from the low 70s across southern WI to the upper 60s just south of Green Bay. Steep mid-level lapse rates have also pushed into the region. All of this factors result in moderately buoyant thermodynamic environment. However, residual capping inversion may hinder overall updraft strength and contribute to a somewhat disorganized storm mode initially (i.e. during the next hour or so). Lift from the approaching shortwave trough should help cool these mid-level temperatures and allow for stronger, more persistent updrafts. Enhanced mid-level flow attendant to an approaching shortwave trough is contributing to strong vertical shear, with mesoanalysis estimated effective bulk shear from 50 to 60 kt. Once more persistent updrafts become established, a few more organized storms are possible. Primary severe threat is strong wind gusts. Uncertainty regarding storm coverage limits higher watch probability but trends will be monitored closely. ..Mosier/Guyer.. 09/03/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GRB...MKX...ARX... LAT...LON 43098797 42678866 42699040 43788955 44698852 44948770 44788730 44178759 43898765 43098797 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Tue Sep 03 2019 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST...THE SOUTHEASTERN U.S. COAST...AND DEEP SOUTH TEXAS... ...SUMMARY... A couple of tornadoes are possible along the Georgia and south Carolina coastal areas Wednesday afternoon through Wednesday night in association with Hurricane Dorian. A brief tornado or two will also be possible over deep south Texas, as Tropical Depression 7 strengthens and moves gradually onshore over northeastern Mexico. Otherwise, isolated damaging gusts are possible Wednesday afternoon from the Middle Atlantic through New England. ...Synopsis... The upper pattern across the U.S. will be characterized by a large ridge, affecting much of the Rockies and into the Plains states. A weak upper low/trough is forecast to remain just off the West Coast, while a stronger short-wave trough progresses eastward across the Northeast. Meanwhile, Hurricane Dorian is forecast to advance slowly northward just off the Southeast U.S. Coast, while Tropical Depression #7 moves westward across the western Gulf of Mexico. At the surface, a cold front, accompanying the Northeast U.S. upper system, will advance across the Northeast through the period, while high pressure prevails across the central U.S. and into the Rockies. ...New England southwestward to the northern Chesapeake Bay vicinity... A cold front is forecast to advance across the Northeast Wednesday, ahead of a parent mid-level short-wave trough. While mid- to high-level cloud cover from remnant/prior storms is expected to hinder insolation/subsequent destabilization across parts of the area, enough instability should evolve during the afternoon to permit scattered to isolated storm development ahead of the advancing front. With a relatively strong, southwesterly/westerly flow field aloft expected atop the region, potential for fast-moving cells, and possibly a few semi-organized bands of storms, is apparent. While the overall severe risk still appears likely to be limited by modest destabilization potential during the afternoon, an upgrade to slight risk could be required in later forecasts if potential for slightly greater afternoon destabilization becomes apparent. ...Southeast U.S. Coast... Latest forecasts from the National Hurricane Center depict that Hurricane Dorian -- which should lie off the Florida Coast Wednesday morning -- will move northward/northwestward along the southeastern Atlantic Coast, to a position east of the southern South Carolina Coast late. With east to northeast low-level flow near the coast, north of the storm's center, veering slightly with height, a shear profile supportive of low-level rotation is expected. Therefore, the risk for a tornado or two will expand gradually northward in conjunction with Dorian's progression, reaching roughly the vicinity of the North Carolina/South Carolina border by sunrise Thursday. ...Deep south Texas... As Tropical Depression #7, now over the western Gulf of Mexico, moves westward with time, slow strengthening -- possibly to Tropical Storm intensity -- is forecast (please see the latest forecasts from the National Hurricane Center). With a corresponding increase in the wind field surrounding the low, low-level shear may be sufficient to support limited risk for a brief tornado spin-up or two -- which may linger through much of the period as the storm moves inland over northeast Mexico during latter stages of the period. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 09/03/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Tue Sep 03 2019 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST...THE SOUTHEASTERN U.S. COAST...AND DEEP SOUTH TEXAS... ...SUMMARY... A couple of tornadoes are possible along the Georgia and south Carolina coastal areas Wednesday afternoon through Wednesday night in association with Hurricane Dorian. A brief tornado or two will also be possible over deep south Texas, as Tropical Depression 7 strengthens and moves gradually onshore over northeastern Mexico. Otherwise, isolated damaging gusts are possible Wednesday afternoon from the Middle Atlantic through New England. ...Synopsis... The upper pattern across the U.S. will be characterized by a large ridge, affecting much of the Rockies and into the Plains states. A weak upper low/trough is forecast to remain just off the West Coast, while a stronger short-wave trough progresses eastward across the Northeast. Meanwhile, Hurricane Dorian is forecast to advance slowly northward just off the Southeast U.S. Coast, while Tropical Depression #7 moves westward across the western Gulf of Mexico. At the surface, a cold front, accompanying the Northeast U.S. upper system, will advance across the Northeast through the period, while high pressure prevails across the central U.S. and into the Rockies. ...New England southwestward to the northern Chesapeake Bay vicinity... A cold front is forecast to advance across the Northeast Wednesday, ahead of a parent mid-level short-wave trough. While mid- to high-level cloud cover from remnant/prior storms is expected to hinder insolation/subsequent destabilization across parts of the area, enough instability should evolve during the afternoon to permit scattered to isolated storm development ahead of the advancing front. With a relatively strong, southwesterly/westerly flow field aloft expected atop the region, potential for fast-moving cells, and possibly a few semi-organized bands of storms, is apparent. While the overall severe risk still appears likely to be limited by modest destabilization potential during the afternoon, an upgrade to slight risk could be required in later forecasts if potential for slightly greater afternoon destabilization becomes apparent. ...Southeast U.S. Coast... Latest forecasts from the National Hurricane Center depict that Hurricane Dorian -- which should lie off the Florida Coast Wednesday morning -- will move northward/northwestward along the southeastern Atlantic Coast, to a position east of the southern South Carolina Coast late. With east to northeast low-level flow near the coast, north of the storm's center, veering slightly with height, a shear profile supportive of low-level rotation is expected. Therefore, the risk for a tornado or two will expand gradually northward in conjunction with Dorian's progression, reaching roughly the vicinity of the North Carolina/South Carolina border by sunrise Thursday. ...Deep south Texas... As Tropical Depression #7, now over the western Gulf of Mexico, moves westward with time, slow strengthening -- possibly to Tropical Storm intensity -- is forecast (please see the latest forecasts from the National Hurricane Center). With a corresponding increase in the wind field surrounding the low, low-level shear may be sufficient to support limited risk for a brief tornado spin-up or two -- which may linger through much of the period as the storm moves inland over northeast Mexico during latter stages of the period. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 09/03/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Tue Sep 03 2019 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST...THE SOUTHEASTERN U.S. COAST...AND DEEP SOUTH TEXAS... ...SUMMARY... A couple of tornadoes are possible along the Georgia and south Carolina coastal areas Wednesday afternoon through Wednesday night in association with Hurricane Dorian. A brief tornado or two will also be possible over deep south Texas, as Tropical Depression 7 strengthens and moves gradually onshore over northeastern Mexico. Otherwise, isolated damaging gusts are possible Wednesday afternoon from the Middle Atlantic through New England. ...Synopsis... The upper pattern across the U.S. will be characterized by a large ridge, affecting much of the Rockies and into the Plains states. A weak upper low/trough is forecast to remain just off the West Coast, while a stronger short-wave trough progresses eastward across the Northeast. Meanwhile, Hurricane Dorian is forecast to advance slowly northward just off the Southeast U.S. Coast, while Tropical Depression #7 moves westward across the western Gulf of Mexico. At the surface, a cold front, accompanying the Northeast U.S. upper system, will advance across the Northeast through the period, while high pressure prevails across the central U.S. and into the Rockies. ...New England southwestward to the northern Chesapeake Bay vicinity... A cold front is forecast to advance across the Northeast Wednesday, ahead of a parent mid-level short-wave trough. While mid- to high-level cloud cover from remnant/prior storms is expected to hinder insolation/subsequent destabilization across parts of the area, enough instability should evolve during the afternoon to permit scattered to isolated storm development ahead of the advancing front. With a relatively strong, southwesterly/westerly flow field aloft expected atop the region, potential for fast-moving cells, and possibly a few semi-organized bands of storms, is apparent. While the overall severe risk still appears likely to be limited by modest destabilization potential during the afternoon, an upgrade to slight risk could be required in later forecasts if potential for slightly greater afternoon destabilization becomes apparent. ...Southeast U.S. Coast... Latest forecasts from the National Hurricane Center depict that Hurricane Dorian -- which should lie off the Florida Coast Wednesday morning -- will move northward/northwestward along the southeastern Atlantic Coast, to a position east of the southern South Carolina Coast late. With east to northeast low-level flow near the coast, north of the storm's center, veering slightly with height, a shear profile supportive of low-level rotation is expected. Therefore, the risk for a tornado or two will expand gradually northward in conjunction with Dorian's progression, reaching roughly the vicinity of the North Carolina/South Carolina border by sunrise Thursday. ...Deep south Texas... As Tropical Depression #7, now over the western Gulf of Mexico, moves westward with time, slow strengthening -- possibly to Tropical Storm intensity -- is forecast (please see the latest forecasts from the National Hurricane Center). With a corresponding increase in the wind field surrounding the low, low-level shear may be sufficient to support limited risk for a brief tornado spin-up or two -- which may linger through much of the period as the storm moves inland over northeast Mexico during latter stages of the period. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 09/03/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Tue Sep 03 2019 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST...THE SOUTHEASTERN U.S. COAST...AND DEEP SOUTH TEXAS... ...SUMMARY... A couple of tornadoes are possible along the Georgia and south Carolina coastal areas Wednesday afternoon through Wednesday night in association with Hurricane Dorian. A brief tornado or two will also be possible over deep south Texas, as Tropical Depression 7 strengthens and moves gradually onshore over northeastern Mexico. Otherwise, isolated damaging gusts are possible Wednesday afternoon from the Middle Atlantic through New England. ...Synopsis... The upper pattern across the U.S. will be characterized by a large ridge, affecting much of the Rockies and into the Plains states. A weak upper low/trough is forecast to remain just off the West Coast, while a stronger short-wave trough progresses eastward across the Northeast. Meanwhile, Hurricane Dorian is forecast to advance slowly northward just off the Southeast U.S. Coast, while Tropical Depression #7 moves westward across the western Gulf of Mexico. At the surface, a cold front, accompanying the Northeast U.S. upper system, will advance across the Northeast through the period, while high pressure prevails across the central U.S. and into the Rockies. ...New England southwestward to the northern Chesapeake Bay vicinity... A cold front is forecast to advance across the Northeast Wednesday, ahead of a parent mid-level short-wave trough. While mid- to high-level cloud cover from remnant/prior storms is expected to hinder insolation/subsequent destabilization across parts of the area, enough instability should evolve during the afternoon to permit scattered to isolated storm development ahead of the advancing front. With a relatively strong, southwesterly/westerly flow field aloft expected atop the region, potential for fast-moving cells, and possibly a few semi-organized bands of storms, is apparent. While the overall severe risk still appears likely to be limited by modest destabilization potential during the afternoon, an upgrade to slight risk could be required in later forecasts if potential for slightly greater afternoon destabilization becomes apparent. ...Southeast U.S. Coast... Latest forecasts from the National Hurricane Center depict that Hurricane Dorian -- which should lie off the Florida Coast Wednesday morning -- will move northward/northwestward along the southeastern Atlantic Coast, to a position east of the southern South Carolina Coast late. With east to northeast low-level flow near the coast, north of the storm's center, veering slightly with height, a shear profile supportive of low-level rotation is expected. Therefore, the risk for a tornado or two will expand gradually northward in conjunction with Dorian's progression, reaching roughly the vicinity of the North Carolina/South Carolina border by sunrise Thursday. ...Deep south Texas... As Tropical Depression #7, now over the western Gulf of Mexico, moves westward with time, slow strengthening -- possibly to Tropical Storm intensity -- is forecast (please see the latest forecasts from the National Hurricane Center). With a corresponding increase in the wind field surrounding the low, low-level shear may be sufficient to support limited risk for a brief tornado spin-up or two -- which may linger through much of the period as the storm moves inland over northeast Mexico during latter stages of the period. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 09/03/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1228 PM CDT Tue Sep 03 2019 Valid 041200Z - 051200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST...THE SOUTHEASTERN U.S. COAST...AND DEEP SOUTH TEXAS... ...SUMMARY... A couple of tornadoes are possible along the Georgia and south Carolina coastal areas Wednesday afternoon through Wednesday night in association with Hurricane Dorian. A brief tornado or two will also be possible over deep south Texas, as Tropical Depression 7 strengthens and moves gradually onshore over northeastern Mexico. Otherwise, isolated damaging gusts are possible Wednesday afternoon from the Middle Atlantic through New England. ...Synopsis... The upper pattern across the U.S. will be characterized by a large ridge, affecting much of the Rockies and into the Plains states. A weak upper low/trough is forecast to remain just off the West Coast, while a stronger short-wave trough progresses eastward across the Northeast. Meanwhile, Hurricane Dorian is forecast to advance slowly northward just off the Southeast U.S. Coast, while Tropical Depression #7 moves westward across the western Gulf of Mexico. At the surface, a cold front, accompanying the Northeast U.S. upper system, will advance across the Northeast through the period, while high pressure prevails across the central U.S. and into the Rockies. ...New England southwestward to the northern Chesapeake Bay vicinity... A cold front is forecast to advance across the Northeast Wednesday, ahead of a parent mid-level short-wave trough. While mid- to high-level cloud cover from remnant/prior storms is expected to hinder insolation/subsequent destabilization across parts of the area, enough instability should evolve during the afternoon to permit scattered to isolated storm development ahead of the advancing front. With a relatively strong, southwesterly/westerly flow field aloft expected atop the region, potential for fast-moving cells, and possibly a few semi-organized bands of storms, is apparent. While the overall severe risk still appears likely to be limited by modest destabilization potential during the afternoon, an upgrade to slight risk could be required in later forecasts if potential for slightly greater afternoon destabilization becomes apparent. ...Southeast U.S. Coast... Latest forecasts from the National Hurricane Center depict that Hurricane Dorian -- which should lie off the Florida Coast Wednesday morning -- will move northward/northwestward along the southeastern Atlantic Coast, to a position east of the southern South Carolina Coast late. With east to northeast low-level flow near the coast, north of the storm's center, veering slightly with height, a shear profile supportive of low-level rotation is expected. Therefore, the risk for a tornado or two will expand gradually northward in conjunction with Dorian's progression, reaching roughly the vicinity of the North Carolina/South Carolina border by sunrise Thursday. ...Deep south Texas... As Tropical Depression #7, now over the western Gulf of Mexico, moves westward with time, slow strengthening -- possibly to Tropical Storm intensity -- is forecast (please see the latest forecasts from the National Hurricane Center). With a corresponding increase in the wind field surrounding the low, low-level shear may be sufficient to support limited risk for a brief tornado spin-up or two -- which may linger through much of the period as the storm moves inland over northeast Mexico during latter stages of the period. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 5% - Marginal Hail: 5% - Marginal ..Goss.. 09/03/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1152 AM CDT Tue Sep 03 2019 Valid 031700Z - 041200Z Changes have been made to the ISODRYT area across portions of the northern/central Great Basin. Water vapor satellite imagery indicates that a weak shortwave trough was located in the vicinity of the northern NV/UT border. The 12Z LKN soundings shows subsidence occurring in the wake of this feature. Given no appreciable mid-level cooling expected, convection occurring in northeastern Nevada is questionable this afternoon. Farther to the south and east, GPS PWAT observations show a plume of monsoonal moisture moving northward. A steady increase in PWAT values through the afternoon/evening lends doubt to how dry storms will be, particularly across central/western Utah. Lastly, mean flow within the cloud-bearing layer on forecast soundings is around 10-15 mph which would suggest at least a mixed-mode of wet/dry storms with a relatively quick transition to wet in some locations. For these reasons, the ISODRYT area has been relegated to east-central Nevada on the edge of moisture plume. While uncertainty still remains, this area appears to have the greatest probability of a few dry lighting strikes. ..Wendt.. 09/03/2019 .PREV DISCUSSION... /ISSUED 0112 AM CDT Tue Sep 03 2019/ ...Synopsis... A mid-level ridge will remain in place across the western CONUS, with an embedded shortwave trough propagating around the ridge across the Pacific Northwest. Mildly dry and breezy conditions may occur east of the Cascades as the stronger flow aloft attempts to mix downward to the surface. Mid-level monsoonal moisture will also be present across parts of the Great Basin, fueling isolated thunderstorms, with a few dry strikes possible. ...Pacific Northwest... By afternoon peak heating, boundary layer mixing, in conjunction with downslope flow along the lee of the Cascades, will contribute to westerly winds reaching 15 mph at times, particularly in the Harney Basin area, with RH dropping into the 15-25% range. As winds exceeding 15 mph will be brief and confined to mainly terrain favoring locations, an elevated delineation has been withheld at this time. ...Portions of the Great Basin... Mid-level moisture will meander northwestward into central parts of the Great Basin (including parts of Nevada into western Utah), where afternoon heating will provide enough buoyancy and lift to induce isolated thunderstorms. Though these storms will be slow moving, cells are expected to be high based in nature (i.e. rooted atop a sfc-500 mb dry sub-cloud layer), and are expected to occur over fuels that are near-critical to critically receptive to fire spread, warranting the addition of an isolated dry thunderstorm delineation. ...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 1152 AM CDT Tue Sep 03 2019 Valid 031700Z - 041200Z Changes have been made to the ISODRYT area across portions of the northern/central Great Basin. Water vapor satellite imagery indicates that a weak shortwave trough was located in the vicinity of the northern NV/UT border. The 12Z LKN soundings shows subsidence occurring in the wake of this feature. Given no appreciable mid-level cooling expected, convection occurring in northeastern Nevada is questionable this afternoon. Farther to the south and east, GPS PWAT observations show a plume of monsoonal moisture moving northward. A steady increase in PWAT values through the afternoon/evening lends doubt to how dry storms will be, particularly across central/western Utah. Lastly, mean flow within the cloud-bearing layer on forecast soundings is around 10-15 mph which would suggest at least a mixed-mode of wet/dry storms with a relatively quick transition to wet in some locations. For these reasons, the ISODRYT area has been relegated to east-central Nevada on the edge of moisture plume. While uncertainty still remains, this area appears to have the greatest probability of a few dry lighting strikes. ..Wendt.. 09/03/2019 .PREV DISCUSSION... /ISSUED 0112 AM CDT Tue Sep 03 2019/ ...Synopsis... A mid-level ridge will remain in place across the western CONUS, with an embedded shortwave trough propagating around the ridge across the Pacific Northwest. Mildly dry and breezy conditions may occur east of the Cascades as the stronger flow aloft attempts to mix downward to the surface. Mid-level monsoonal moisture will also be present across parts of the Great Basin, fueling isolated thunderstorms, with a few dry strikes possible. ...Pacific Northwest... By afternoon peak heating, boundary layer mixing, in conjunction with downslope flow along the lee of the Cascades, will contribute to westerly winds reaching 15 mph at times, particularly in the Harney Basin area, with RH dropping into the 15-25% range. As winds exceeding 15 mph will be brief and confined to mainly terrain favoring locations, an elevated delineation has been withheld at this time. ...Portions of the Great Basin... Mid-level moisture will meander northwestward into central parts of the Great Basin (including parts of Nevada into western Utah), where afternoon heating will provide enough buoyancy and lift to induce isolated thunderstorms. Though these storms will be slow moving, cells are expected to be high based in nature (i.e. rooted atop a sfc-500 mb dry sub-cloud layer), and are expected to occur over fuels that are near-critical to critically receptive to fire spread, warranting the addition of an isolated dry thunderstorm delineation. ...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 1152 AM CDT Tue Sep 03 2019 Valid 031700Z - 041200Z Changes have been made to the ISODRYT area across portions of the northern/central Great Basin. Water vapor satellite imagery indicates that a weak shortwave trough was located in the vicinity of the northern NV/UT border. The 12Z LKN soundings shows subsidence occurring in the wake of this feature. Given no appreciable mid-level cooling expected, convection occurring in northeastern Nevada is questionable this afternoon. Farther to the south and east, GPS PWAT observations show a plume of monsoonal moisture moving northward. A steady increase in PWAT values through the afternoon/evening lends doubt to how dry storms will be, particularly across central/western Utah. Lastly, mean flow within the cloud-bearing layer on forecast soundings is around 10-15 mph which would suggest at least a mixed-mode of wet/dry storms with a relatively quick transition to wet in some locations. For these reasons, the ISODRYT area has been relegated to east-central Nevada on the edge of moisture plume. While uncertainty still remains, this area appears to have the greatest probability of a few dry lighting strikes. ..Wendt.. 09/03/2019 .PREV DISCUSSION... /ISSUED 0112 AM CDT Tue Sep 03 2019/ ...Synopsis... A mid-level ridge will remain in place across the western CONUS, with an embedded shortwave trough propagating around the ridge across the Pacific Northwest. Mildly dry and breezy conditions may occur east of the Cascades as the stronger flow aloft attempts to mix downward to the surface. Mid-level monsoonal moisture will also be present across parts of the Great Basin, fueling isolated thunderstorms, with a few dry strikes possible. ...Pacific Northwest... By afternoon peak heating, boundary layer mixing, in conjunction with downslope flow along the lee of the Cascades, will contribute to westerly winds reaching 15 mph at times, particularly in the Harney Basin area, with RH dropping into the 15-25% range. As winds exceeding 15 mph will be brief and confined to mainly terrain favoring locations, an elevated delineation has been withheld at this time. ...Portions of the Great Basin... Mid-level moisture will meander northwestward into central parts of the Great Basin (including parts of Nevada into western Utah), where afternoon heating will provide enough buoyancy and lift to induce isolated thunderstorms. Though these storms will be slow moving, cells are expected to be high based in nature (i.e. rooted atop a sfc-500 mb dry sub-cloud layer), and are expected to occur over fuels that are near-critical to critically receptive to fire spread, warranting the addition of an isolated dry thunderstorm delineation. ...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 1152 AM CDT Tue Sep 03 2019 Valid 031700Z - 041200Z Changes have been made to the ISODRYT area across portions of the northern/central Great Basin. Water vapor satellite imagery indicates that a weak shortwave trough was located in the vicinity of the northern NV/UT border. The 12Z LKN soundings shows subsidence occurring in the wake of this feature. Given no appreciable mid-level cooling expected, convection occurring in northeastern Nevada is questionable this afternoon. Farther to the south and east, GPS PWAT observations show a plume of monsoonal moisture moving northward. A steady increase in PWAT values through the afternoon/evening lends doubt to how dry storms will be, particularly across central/western Utah. Lastly, mean flow within the cloud-bearing layer on forecast soundings is around 10-15 mph which would suggest at least a mixed-mode of wet/dry storms with a relatively quick transition to wet in some locations. For these reasons, the ISODRYT area has been relegated to east-central Nevada on the edge of moisture plume. While uncertainty still remains, this area appears to have the greatest probability of a few dry lighting strikes. ..Wendt.. 09/03/2019 .PREV DISCUSSION... /ISSUED 0112 AM CDT Tue Sep 03 2019/ ...Synopsis... A mid-level ridge will remain in place across the western CONUS, with an embedded shortwave trough propagating around the ridge across the Pacific Northwest. Mildly dry and breezy conditions may occur east of the Cascades as the stronger flow aloft attempts to mix downward to the surface. Mid-level monsoonal moisture will also be present across parts of the Great Basin, fueling isolated thunderstorms, with a few dry strikes possible. ...Pacific Northwest... By afternoon peak heating, boundary layer mixing, in conjunction with downslope flow along the lee of the Cascades, will contribute to westerly winds reaching 15 mph at times, particularly in the Harney Basin area, with RH dropping into the 15-25% range. As winds exceeding 15 mph will be brief and confined to mainly terrain favoring locations, an elevated delineation has been withheld at this time. ...Portions of the Great Basin... Mid-level moisture will meander northwestward into central parts of the Great Basin (including parts of Nevada into western Utah), where afternoon heating will provide enough buoyancy and lift to induce isolated thunderstorms. Though these storms will be slow moving, cells are expected to be high based in nature (i.e. rooted atop a sfc-500 mb dry sub-cloud layer), and are expected to occur over fuels that are near-critical to critically receptive to fire spread, warranting the addition of an isolated dry thunderstorm delineation. ...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 1139 AM CDT Tue Sep 03 2019 Valid 031630Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MIDWEST AND GREAT LAKES... ...SUMMARY... Scattered severe thunderstorms are expected mainly during the late afternoon to evening hours across parts of the Great Lakes and Midwest. A few tornadoes, large hail, and damaging winds are all possible. ...Midwest/Great Lakes... An upgrade to Enhanced Risk could still be warranted for portions of the region later today pending convective/observational trends. However, as mentioned in the prior (13Z) Outlook discussion, short-term guidance continues to generally sub-optimally depict and/or remains slow to adjust to the influence of ongoing convection, which casts some uncertainty regarding the convective scenario later today. This is principally with respect to the thermodynamic environment and related likelihood and north-northeastward extent of appreciable moistening and destabilization later today, coincident with a notable deep-layer wind field. Morning observations including 12Z sounding and WSR-88D VWP data sample deep-layer winds that are very strong by late-summer standards, particularly at a latitude around southern Lake Michigan and northward including Wisconsin/Michigan. Beneath a respectable elevated mixed layer, seasonably rich low-level moisture (with around 70F surface dewpoints) is prevalent at late morning across eastern Iowa, southern Wisconsin, western Illinois near and ahead of an eastward-advancing cold front. This moisture will steadily advect eastward today, with the morning convection/residual cloud cover potentially effectively reinforcing/delaying an eastward-shifting warm front toward and across Lower Michigan and northern Indiana. Boundary-layer heating will probably be of more limited duration with north/northeast extent across Lower Michigan, but will be greater with southwest extent into Illinois. A strongly unstable air mass should develop initially near Lake Michigan southwestward across Illinois, with greater uncertainty in the degree of buoyancy farther north across Lower Michigan. At least isolated, mid-to-late afternoon deep convective redevelopment will probably occur with the approach of a cold front from western Lower Michigan into northern Illinois, with deep-layer winds well-supportive (40-50 kt effective) of initial supercells. Hail/damaging wind potential aside, low-level shear/SRH will be maximized near the effective warm front and within the increasingly narrow warm sector with northward extent across Lower Michigan. Although short-term forecast uncertainty lingers as previously discussed, on presumed/probable air mass recovery a respectable potential does exist for a couple of tornadoes, including some possibility of a strong tornado, aside from an increasing risk for damaging winds this evening. Severe risks currently appear most probable to occur across northern Indiana and southern Lower Michigan, and possibly into northern/western Ohio late tonight. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast Florida Coast... Hurricane Dorian is forecast to move northward and remain offshore; reference NHC for the latest details. This will maintain most of the Florida Atlantic Coast in the tornado-unfavorable western periphery of Dorian. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple of rotating cells capable of a brief tornado through tonight. ...Deep South Texas... Reference NHC for the latest details regarding Tropical Depression Seven, which may gradually strengthen/organize over the far western Gulf of Mexico. A modest low-level strengthening of easterly winds on its northern periphery could influence low-topped supercell potential and possibly some tornado risk into Wednesday. ..Guyer/Nauslar.. 09/03/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1139 AM CDT Tue Sep 03 2019 Valid 031630Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MIDWEST AND GREAT LAKES... ...SUMMARY... Scattered severe thunderstorms are expected mainly during the late afternoon to evening hours across parts of the Great Lakes and Midwest. A few tornadoes, large hail, and damaging winds are all possible. ...Midwest/Great Lakes... An upgrade to Enhanced Risk could still be warranted for portions of the region later today pending convective/observational trends. However, as mentioned in the prior (13Z) Outlook discussion, short-term guidance continues to generally sub-optimally depict and/or remains slow to adjust to the influence of ongoing convection, which casts some uncertainty regarding the convective scenario later today. This is principally with respect to the thermodynamic environment and related likelihood and north-northeastward extent of appreciable moistening and destabilization later today, coincident with a notable deep-layer wind field. Morning observations including 12Z sounding and WSR-88D VWP data sample deep-layer winds that are very strong by late-summer standards, particularly at a latitude around southern Lake Michigan and northward including Wisconsin/Michigan. Beneath a respectable elevated mixed layer, seasonably rich low-level moisture (with around 70F surface dewpoints) is prevalent at late morning across eastern Iowa, southern Wisconsin, western Illinois near and ahead of an eastward-advancing cold front. This moisture will steadily advect eastward today, with the morning convection/residual cloud cover potentially effectively reinforcing/delaying an eastward-shifting warm front toward and across Lower Michigan and northern Indiana. Boundary-layer heating will probably be of more limited duration with north/northeast extent across Lower Michigan, but will be greater with southwest extent into Illinois. A strongly unstable air mass should develop initially near Lake Michigan southwestward across Illinois, with greater uncertainty in the degree of buoyancy farther north across Lower Michigan. At least isolated, mid-to-late afternoon deep convective redevelopment will probably occur with the approach of a cold front from western Lower Michigan into northern Illinois, with deep-layer winds well-supportive (40-50 kt effective) of initial supercells. Hail/damaging wind potential aside, low-level shear/SRH will be maximized near the effective warm front and within the increasingly narrow warm sector with northward extent across Lower Michigan. Although short-term forecast uncertainty lingers as previously discussed, on presumed/probable air mass recovery a respectable potential does exist for a couple of tornadoes, including some possibility of a strong tornado, aside from an increasing risk for damaging winds this evening. Severe risks currently appear most probable to occur across northern Indiana and southern Lower Michigan, and possibly into northern/western Ohio late tonight. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast Florida Coast... Hurricane Dorian is forecast to move northward and remain offshore; reference NHC for the latest details. This will maintain most of the Florida Atlantic Coast in the tornado-unfavorable western periphery of Dorian. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple of rotating cells capable of a brief tornado through tonight. ...Deep South Texas... Reference NHC for the latest details regarding Tropical Depression Seven, which may gradually strengthen/organize over the far western Gulf of Mexico. A modest low-level strengthening of easterly winds on its northern periphery could influence low-topped supercell potential and possibly some tornado risk into Wednesday. ..Guyer/Nauslar.. 09/03/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1139 AM CDT Tue Sep 03 2019 Valid 031630Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MIDWEST AND GREAT LAKES... ...SUMMARY... Scattered severe thunderstorms are expected mainly during the late afternoon to evening hours across parts of the Great Lakes and Midwest. A few tornadoes, large hail, and damaging winds are all possible. ...Midwest/Great Lakes... An upgrade to Enhanced Risk could still be warranted for portions of the region later today pending convective/observational trends. However, as mentioned in the prior (13Z) Outlook discussion, short-term guidance continues to generally sub-optimally depict and/or remains slow to adjust to the influence of ongoing convection, which casts some uncertainty regarding the convective scenario later today. This is principally with respect to the thermodynamic environment and related likelihood and north-northeastward extent of appreciable moistening and destabilization later today, coincident with a notable deep-layer wind field. Morning observations including 12Z sounding and WSR-88D VWP data sample deep-layer winds that are very strong by late-summer standards, particularly at a latitude around southern Lake Michigan and northward including Wisconsin/Michigan. Beneath a respectable elevated mixed layer, seasonably rich low-level moisture (with around 70F surface dewpoints) is prevalent at late morning across eastern Iowa, southern Wisconsin, western Illinois near and ahead of an eastward-advancing cold front. This moisture will steadily advect eastward today, with the morning convection/residual cloud cover potentially effectively reinforcing/delaying an eastward-shifting warm front toward and across Lower Michigan and northern Indiana. Boundary-layer heating will probably be of more limited duration with north/northeast extent across Lower Michigan, but will be greater with southwest extent into Illinois. A strongly unstable air mass should develop initially near Lake Michigan southwestward across Illinois, with greater uncertainty in the degree of buoyancy farther north across Lower Michigan. At least isolated, mid-to-late afternoon deep convective redevelopment will probably occur with the approach of a cold front from western Lower Michigan into northern Illinois, with deep-layer winds well-supportive (40-50 kt effective) of initial supercells. Hail/damaging wind potential aside, low-level shear/SRH will be maximized near the effective warm front and within the increasingly narrow warm sector with northward extent across Lower Michigan. Although short-term forecast uncertainty lingers as previously discussed, on presumed/probable air mass recovery a respectable potential does exist for a couple of tornadoes, including some possibility of a strong tornado, aside from an increasing risk for damaging winds this evening. Severe risks currently appear most probable to occur across northern Indiana and southern Lower Michigan, and possibly into northern/western Ohio late tonight. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast Florida Coast... Hurricane Dorian is forecast to move northward and remain offshore; reference NHC for the latest details. This will maintain most of the Florida Atlantic Coast in the tornado-unfavorable western periphery of Dorian. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple of rotating cells capable of a brief tornado through tonight. ...Deep South Texas... Reference NHC for the latest details regarding Tropical Depression Seven, which may gradually strengthen/organize over the far western Gulf of Mexico. A modest low-level strengthening of easterly winds on its northern periphery could influence low-topped supercell potential and possibly some tornado risk into Wednesday. ..Guyer/Nauslar.. 09/03/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1139 AM CDT Tue Sep 03 2019 Valid 031630Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MIDWEST AND GREAT LAKES... ...SUMMARY... Scattered severe thunderstorms are expected mainly during the late afternoon to evening hours across parts of the Great Lakes and Midwest. A few tornadoes, large hail, and damaging winds are all possible. ...Midwest/Great Lakes... An upgrade to Enhanced Risk could still be warranted for portions of the region later today pending convective/observational trends. However, as mentioned in the prior (13Z) Outlook discussion, short-term guidance continues to generally sub-optimally depict and/or remains slow to adjust to the influence of ongoing convection, which casts some uncertainty regarding the convective scenario later today. This is principally with respect to the thermodynamic environment and related likelihood and north-northeastward extent of appreciable moistening and destabilization later today, coincident with a notable deep-layer wind field. Morning observations including 12Z sounding and WSR-88D VWP data sample deep-layer winds that are very strong by late-summer standards, particularly at a latitude around southern Lake Michigan and northward including Wisconsin/Michigan. Beneath a respectable elevated mixed layer, seasonably rich low-level moisture (with around 70F surface dewpoints) is prevalent at late morning across eastern Iowa, southern Wisconsin, western Illinois near and ahead of an eastward-advancing cold front. This moisture will steadily advect eastward today, with the morning convection/residual cloud cover potentially effectively reinforcing/delaying an eastward-shifting warm front toward and across Lower Michigan and northern Indiana. Boundary-layer heating will probably be of more limited duration with north/northeast extent across Lower Michigan, but will be greater with southwest extent into Illinois. A strongly unstable air mass should develop initially near Lake Michigan southwestward across Illinois, with greater uncertainty in the degree of buoyancy farther north across Lower Michigan. At least isolated, mid-to-late afternoon deep convective redevelopment will probably occur with the approach of a cold front from western Lower Michigan into northern Illinois, with deep-layer winds well-supportive (40-50 kt effective) of initial supercells. Hail/damaging wind potential aside, low-level shear/SRH will be maximized near the effective warm front and within the increasingly narrow warm sector with northward extent across Lower Michigan. Although short-term forecast uncertainty lingers as previously discussed, on presumed/probable air mass recovery a respectable potential does exist for a couple of tornadoes, including some possibility of a strong tornado, aside from an increasing risk for damaging winds this evening. Severe risks currently appear most probable to occur across northern Indiana and southern Lower Michigan, and possibly into northern/western Ohio late tonight. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast Florida Coast... Hurricane Dorian is forecast to move northward and remain offshore; reference NHC for the latest details. This will maintain most of the Florida Atlantic Coast in the tornado-unfavorable western periphery of Dorian. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple of rotating cells capable of a brief tornado through tonight. ...Deep South Texas... Reference NHC for the latest details regarding Tropical Depression Seven, which may gradually strengthen/organize over the far western Gulf of Mexico. A modest low-level strengthening of easterly winds on its northern periphery could influence low-topped supercell potential and possibly some tornado risk into Wednesday. ..Guyer/Nauslar.. 09/03/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Tue Sep 03 2019 Valid 031300Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE GREAT LAKES AND MIDWEST... ...SUMMARY... Scattered severe thunderstorms are expected mainly during the late afternoon to mid-evening across parts of the Great Lakes and Midwest regions. A few tornadoes, large hail, and damaging winds are all possible. ...Great Lakes and Midwest... Expansive stratiform and convective swaths are ongoing from northern Lower MI to eastern WI and northern IL. The leading convection is associated with an eastward-moving MCV, while upstream activity is being forced by robust low-level warm advection ahead of a vigorous shortwave trough over northern MN. The cluster over far northern IL may pose an isolated severe threat through midday as it spreads towards northern IN. Latest guidance is largely underestimating the extent of ongoing convection (especially the 06Z NAM). The 06Z ESRL-HRRR and GFS appear closer to reality compared with the 00Z HREF members/ECMWF and 06Z HRRR. This yields continued uncertainty in how the convective scenario will play out later this afternoon and evening. As such, while potential exists for a significant tornado, an upgrade to a category 3-Enhanced Slight Risk has been deferred. Seasonably rich low-level moisture is prevalent upstream of the warm-advection driven convection across IA/southern MN/southwest WI, characterized by near 70 surface dew points. This rich moisture will advect eastward in the wake of this morning activity beneath an elevated mixed layer. Boundary-layer heating will probably be of more limited duration with northeast extent across Lower MI, but will be greater with southwest extent into IL. A strongly unstable air mass should develop near and southwest of Lake Michigan with greater uncertainty in the degree of buoyancy farther northeast. At least isolated, mid to late afternoon convective redevelopment will probably occur with approach of a cold front from western Lower MI into northern IL. Deep-layer shear will be strongest northeast compared to more veered flow and less enlargement to hodographs with southwest extent. With some indications of veer-back-veer wind profiles, convective mode may tend to evolve into a few clusters with embedded supercell structures. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast FL Coast... Hurricane Dorian is forecast to move northward and remain offshore. This will place most of the FL Atlantic Coast in the unfavorable northwest quadrant for tornadoes. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple rotating cells capable of a brief tornado through tonight. ..Grams/Smith.. 09/03/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Tue Sep 03 2019 Valid 031300Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE GREAT LAKES AND MIDWEST... ...SUMMARY... Scattered severe thunderstorms are expected mainly during the late afternoon to mid-evening across parts of the Great Lakes and Midwest regions. A few tornadoes, large hail, and damaging winds are all possible. ...Great Lakes and Midwest... Expansive stratiform and convective swaths are ongoing from northern Lower MI to eastern WI and northern IL. The leading convection is associated with an eastward-moving MCV, while upstream activity is being forced by robust low-level warm advection ahead of a vigorous shortwave trough over northern MN. The cluster over far northern IL may pose an isolated severe threat through midday as it spreads towards northern IN. Latest guidance is largely underestimating the extent of ongoing convection (especially the 06Z NAM). The 06Z ESRL-HRRR and GFS appear closer to reality compared with the 00Z HREF members/ECMWF and 06Z HRRR. This yields continued uncertainty in how the convective scenario will play out later this afternoon and evening. As such, while potential exists for a significant tornado, an upgrade to a category 3-Enhanced Slight Risk has been deferred. Seasonably rich low-level moisture is prevalent upstream of the warm-advection driven convection across IA/southern MN/southwest WI, characterized by near 70 surface dew points. This rich moisture will advect eastward in the wake of this morning activity beneath an elevated mixed layer. Boundary-layer heating will probably be of more limited duration with northeast extent across Lower MI, but will be greater with southwest extent into IL. A strongly unstable air mass should develop near and southwest of Lake Michigan with greater uncertainty in the degree of buoyancy farther northeast. At least isolated, mid to late afternoon convective redevelopment will probably occur with approach of a cold front from western Lower MI into northern IL. Deep-layer shear will be strongest northeast compared to more veered flow and less enlargement to hodographs with southwest extent. With some indications of veer-back-veer wind profiles, convective mode may tend to evolve into a few clusters with embedded supercell structures. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast FL Coast... Hurricane Dorian is forecast to move northward and remain offshore. This will place most of the FL Atlantic Coast in the unfavorable northwest quadrant for tornadoes. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple rotating cells capable of a brief tornado through tonight. ..Grams/Smith.. 09/03/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0738 AM CDT Tue Sep 03 2019 Valid 031300Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE GREAT LAKES AND MIDWEST... ...SUMMARY... Scattered severe thunderstorms are expected mainly during the late afternoon to mid-evening across parts of the Great Lakes and Midwest regions. A few tornadoes, large hail, and damaging winds are all possible. ...Great Lakes and Midwest... Expansive stratiform and convective swaths are ongoing from northern Lower MI to eastern WI and northern IL. The leading convection is associated with an eastward-moving MCV, while upstream activity is being forced by robust low-level warm advection ahead of a vigorous shortwave trough over northern MN. The cluster over far northern IL may pose an isolated severe threat through midday as it spreads towards northern IN. Latest guidance is largely underestimating the extent of ongoing convection (especially the 06Z NAM). The 06Z ESRL-HRRR and GFS appear closer to reality compared with the 00Z HREF members/ECMWF and 06Z HRRR. This yields continued uncertainty in how the convective scenario will play out later this afternoon and evening. As such, while potential exists for a significant tornado, an upgrade to a category 3-Enhanced Slight Risk has been deferred. Seasonably rich low-level moisture is prevalent upstream of the warm-advection driven convection across IA/southern MN/southwest WI, characterized by near 70 surface dew points. This rich moisture will advect eastward in the wake of this morning activity beneath an elevated mixed layer. Boundary-layer heating will probably be of more limited duration with northeast extent across Lower MI, but will be greater with southwest extent into IL. A strongly unstable air mass should develop near and southwest of Lake Michigan with greater uncertainty in the degree of buoyancy farther northeast. At least isolated, mid to late afternoon convective redevelopment will probably occur with approach of a cold front from western Lower MI into northern IL. Deep-layer shear will be strongest northeast compared to more veered flow and less enlargement to hodographs with southwest extent. With some indications of veer-back-veer wind profiles, convective mode may tend to evolve into a few clusters with embedded supercell structures. The severe threat should wane overnight as the primary shortwave trough becomes increasingly separated from the lingering buoyancy plume over the Midwest. ...East-central/northeast FL Coast... Hurricane Dorian is forecast to move northward and remain offshore. This will place most of the FL Atlantic Coast in the unfavorable northwest quadrant for tornadoes. Nevertheless, some enlargement to the low-level hodograph combined with weak instability might support a couple rotating cells capable of a brief tornado through tonight. ..Grams/Smith.. 09/03/2019 Read more