Severe Storms

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0139 AM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...NO CRITICAL AREAS... ...Synopsis... The upper-level ridge over the western CONUS will continue to amplify into western Canada tomorrow with an upper-level shortwave trough approaching the Pacific Northwest. Subtropical moisture will begin to move into the Southwest as the ridge builds and into southern Montana/northern Wyoming with easterly low-level flow extending westward from the northern Plains. Isolated dry thunderstorms may develop across southern Montana and northern Wyoming. However, fuel conditions and uncertainty regarding thunderstorm coverage preclude introducing an isolated dry thunderstorm area at this time. ..Nauslar.. 08/19/2019 ...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 0139 AM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...NO CRITICAL AREAS... ...Synopsis... The upper-level ridge over the western CONUS will continue to amplify into western Canada tomorrow with an upper-level shortwave trough approaching the Pacific Northwest. Subtropical moisture will begin to move into the Southwest as the ridge builds and into southern Montana/northern Wyoming with easterly low-level flow extending westward from the northern Plains. Isolated dry thunderstorms may develop across southern Montana and northern Wyoming. However, fuel conditions and uncertainty regarding thunderstorm coverage preclude introducing an isolated dry thunderstorm area at this time. ..Nauslar.. 08/19/2019 ...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 0139 AM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...NO CRITICAL AREAS... ...Synopsis... The upper-level ridge over the western CONUS will continue to amplify into western Canada tomorrow with an upper-level shortwave trough approaching the Pacific Northwest. Subtropical moisture will begin to move into the Southwest as the ridge builds and into southern Montana/northern Wyoming with easterly low-level flow extending westward from the northern Plains. Isolated dry thunderstorms may develop across southern Montana and northern Wyoming. However, fuel conditions and uncertainty regarding thunderstorm coverage preclude introducing an isolated dry thunderstorm area at this time. ..Nauslar.. 08/19/2019 ...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 0139 AM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...NO CRITICAL AREAS... ...Synopsis... The upper-level ridge over the western CONUS will continue to amplify into western Canada tomorrow with an upper-level shortwave trough approaching the Pacific Northwest. Subtropical moisture will begin to move into the Southwest as the ridge builds and into southern Montana/northern Wyoming with easterly low-level flow extending westward from the northern Plains. Isolated dry thunderstorms may develop across southern Montana and northern Wyoming. However, fuel conditions and uncertainty regarding thunderstorm coverage preclude introducing an isolated dry thunderstorm area at this time. ..Nauslar.. 08/19/2019 ...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 0131 AM CDT Mon Aug 19 2019 Valid 191200Z - 201200Z ...Synopsis... Upper-level ridging will continue to strengthen and amplify over the western CONUS today. Much of the Intermountain West will remain hot/dry, and large-scale flow will be relatively weak across the much of the region. However, some residual stronger mid-level flow will remain over the northern Rockies/vicinity, and a weak mid-level shortwave trough is forecast to move over the northern Rockies as well. An elevated area was added across portions of southern and central Wyoming. West-southwest sustained surface winds of 12-20 mph with gusts of 25-30 mph and RH values of 8-15% are expected this afternoon and into the evening across the area. Additionally, very deep (10,000+ ft), dry, and unstable boundary layers will develop. This will be the fifth consecutive day of dry/breezy conditions with ERCs rising across portions of southern/western/central Wyoming (70-90th percentiles). ..Nauslar.. 08/19/2019 ...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 0131 AM CDT Mon Aug 19 2019 Valid 191200Z - 201200Z ...Synopsis... Upper-level ridging will continue to strengthen and amplify over the western CONUS today. Much of the Intermountain West will remain hot/dry, and large-scale flow will be relatively weak across the much of the region. However, some residual stronger mid-level flow will remain over the northern Rockies/vicinity, and a weak mid-level shortwave trough is forecast to move over the northern Rockies as well. An elevated area was added across portions of southern and central Wyoming. West-southwest sustained surface winds of 12-20 mph with gusts of 25-30 mph and RH values of 8-15% are expected this afternoon and into the evening across the area. Additionally, very deep (10,000+ ft), dry, and unstable boundary layers will develop. This will be the fifth consecutive day of dry/breezy conditions with ERCs rising across portions of southern/western/central Wyoming (70-90th percentiles). ..Nauslar.. 08/19/2019 ...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 0131 AM CDT Mon Aug 19 2019 Valid 191200Z - 201200Z ...Synopsis... Upper-level ridging will continue to strengthen and amplify over the western CONUS today. Much of the Intermountain West will remain hot/dry, and large-scale flow will be relatively weak across the much of the region. However, some residual stronger mid-level flow will remain over the northern Rockies/vicinity, and a weak mid-level shortwave trough is forecast to move over the northern Rockies as well. An elevated area was added across portions of southern and central Wyoming. West-southwest sustained surface winds of 12-20 mph with gusts of 25-30 mph and RH values of 8-15% are expected this afternoon and into the evening across the area. Additionally, very deep (10,000+ ft), dry, and unstable boundary layers will develop. This will be the fifth consecutive day of dry/breezy conditions with ERCs rising across portions of southern/western/central Wyoming (70-90th percentiles). ..Nauslar.. 08/19/2019 ...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 0131 AM CDT Mon Aug 19 2019 Valid 191200Z - 201200Z ...Synopsis... Upper-level ridging will continue to strengthen and amplify over the western CONUS today. Much of the Intermountain West will remain hot/dry, and large-scale flow will be relatively weak across the much of the region. However, some residual stronger mid-level flow will remain over the northern Rockies/vicinity, and a weak mid-level shortwave trough is forecast to move over the northern Rockies as well. An elevated area was added across portions of southern and central Wyoming. West-southwest sustained surface winds of 12-20 mph with gusts of 25-30 mph and RH values of 8-15% are expected this afternoon and into the evening across the area. Additionally, very deep (10,000+ ft), dry, and unstable boundary layers will develop. This will be the fifth consecutive day of dry/breezy conditions with ERCs rising across portions of southern/western/central Wyoming (70-90th percentiles). ..Nauslar.. 08/19/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0125 AM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM ILLINOIS AND FAR WESTERN INDIANA WESTWARD INTO NEBRASKA... CORRECTED FOR GEOGRAPHIC SPELLING ERROR IN HEADLINE ...SUMMARY... Severe storms with damaging winds are possible over Illinois and parts of surrounding states on Tuesday. Severe storms with hail and wind are also expected over much of Nebraska. ...Synopsis... A shortwave trough will move southeastward across MB and ON, with 35-45 kt midlevel winds across the Upper MS Valley and Great Lakes. Heights will gradually lower from the mid MO Valley across the OH Valley and toward the Mid Atlantic by Wed morning. Cool temperatures aloft with -10 C at 500 mb will spread southeastward across MO and IL atop a moist and unstable air mass. Strong instability will also extend westward over much of the central Plains, with an east-west front along the KS/NE border and low pressure developing along the CO/KS border. This boundary will provide a focus for storms during the evening as the low-level jet develops and aids lift. ...IA/MO/IL/IN... Models indicate that an MCS will develop early in the morning over IA in a zone of warm advection with 40 kt west/southwest 850 mb winds, and will continue southeastward over IL and MO during the day. While much of this event may occur prior to peak heating, a very moist air mass and a few hours of heating will lead to 3000-4000 J/kg MUCAPE. Winds aloft will not be particularly strong this far south of the upper trough, but sufficient to aid forward propagation of an MCS. Damaging winds will be the primary concern. Western portions of this MCS will likely affect eastern MO, and may persist as far south as northeast AR. A higher probability threat corridor may need to be added in later outlooks once the MCS timing and position are better known. ...Eastern WY and northeast CO into NE... Strong heating will occur over WY, CO, and much of KS, but will be tempered along and north of the front into NE. Increasing easterly surface winds in the vicinity of the front will maintain 60s to 70s F dewpoints over NE, with near 60 F into northeast CO. Storms are expected to initiate within the well heated air mass of eastern CO and WY during the late afternoon, with increasing coverage north of the front in NE overnight. Damaging winds and hail will be the primary concerns. Deep-layer shear over NE may be sufficient for elevated supercells capable of very large hail given the large instability. An MCS could also develop into Wednesday morning over eastern NE into northwest MO. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% SIG - Slight Hail: 15% SIG - Slight ..Jewell.. 08/19/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0125 AM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM ILLINOIS AND FAR WESTERN INDIANA WESTWARD INTO NEBRASKA... CORRECTED FOR GEOGRAPHIC SPELLING ERROR IN HEADLINE ...SUMMARY... Severe storms with damaging winds are possible over Illinois and parts of surrounding states on Tuesday. Severe storms with hail and wind are also expected over much of Nebraska. ...Synopsis... A shortwave trough will move southeastward across MB and ON, with 35-45 kt midlevel winds across the Upper MS Valley and Great Lakes. Heights will gradually lower from the mid MO Valley across the OH Valley and toward the Mid Atlantic by Wed morning. Cool temperatures aloft with -10 C at 500 mb will spread southeastward across MO and IL atop a moist and unstable air mass. Strong instability will also extend westward over much of the central Plains, with an east-west front along the KS/NE border and low pressure developing along the CO/KS border. This boundary will provide a focus for storms during the evening as the low-level jet develops and aids lift. ...IA/MO/IL/IN... Models indicate that an MCS will develop early in the morning over IA in a zone of warm advection with 40 kt west/southwest 850 mb winds, and will continue southeastward over IL and MO during the day. While much of this event may occur prior to peak heating, a very moist air mass and a few hours of heating will lead to 3000-4000 J/kg MUCAPE. Winds aloft will not be particularly strong this far south of the upper trough, but sufficient to aid forward propagation of an MCS. Damaging winds will be the primary concern. Western portions of this MCS will likely affect eastern MO, and may persist as far south as northeast AR. A higher probability threat corridor may need to be added in later outlooks once the MCS timing and position are better known. ...Eastern WY and northeast CO into NE... Strong heating will occur over WY, CO, and much of KS, but will be tempered along and north of the front into NE. Increasing easterly surface winds in the vicinity of the front will maintain 60s to 70s F dewpoints over NE, with near 60 F into northeast CO. Storms are expected to initiate within the well heated air mass of eastern CO and WY during the late afternoon, with increasing coverage north of the front in NE overnight. Damaging winds and hail will be the primary concerns. Deep-layer shear over NE may be sufficient for elevated supercells capable of very large hail given the large instability. An MCS could also develop into Wednesday morning over eastern NE into northwest MO. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% SIG - Slight Hail: 15% SIG - Slight ..Jewell.. 08/19/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0125 AM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM ILLINOIS AND FAR WESTERN INDIANA WESTWARD INTO NEBRASKA... CORRECTED FOR GEOGRAPHIC SPELLING ERROR IN HEADLINE ...SUMMARY... Severe storms with damaging winds are possible over Illinois and parts of surrounding states on Tuesday. Severe storms with hail and wind are also expected over much of Nebraska. ...Synopsis... A shortwave trough will move southeastward across MB and ON, with 35-45 kt midlevel winds across the Upper MS Valley and Great Lakes. Heights will gradually lower from the mid MO Valley across the OH Valley and toward the Mid Atlantic by Wed morning. Cool temperatures aloft with -10 C at 500 mb will spread southeastward across MO and IL atop a moist and unstable air mass. Strong instability will also extend westward over much of the central Plains, with an east-west front along the KS/NE border and low pressure developing along the CO/KS border. This boundary will provide a focus for storms during the evening as the low-level jet develops and aids lift. ...IA/MO/IL/IN... Models indicate that an MCS will develop early in the morning over IA in a zone of warm advection with 40 kt west/southwest 850 mb winds, and will continue southeastward over IL and MO during the day. While much of this event may occur prior to peak heating, a very moist air mass and a few hours of heating will lead to 3000-4000 J/kg MUCAPE. Winds aloft will not be particularly strong this far south of the upper trough, but sufficient to aid forward propagation of an MCS. Damaging winds will be the primary concern. Western portions of this MCS will likely affect eastern MO, and may persist as far south as northeast AR. A higher probability threat corridor may need to be added in later outlooks once the MCS timing and position are better known. ...Eastern WY and northeast CO into NE... Strong heating will occur over WY, CO, and much of KS, but will be tempered along and north of the front into NE. Increasing easterly surface winds in the vicinity of the front will maintain 60s to 70s F dewpoints over NE, with near 60 F into northeast CO. Storms are expected to initiate within the well heated air mass of eastern CO and WY during the late afternoon, with increasing coverage north of the front in NE overnight. Damaging winds and hail will be the primary concerns. Deep-layer shear over NE may be sufficient for elevated supercells capable of very large hail given the large instability. An MCS could also develop into Wednesday morning over eastern NE into northwest MO. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% SIG - Slight Hail: 15% SIG - Slight ..Jewell.. 08/19/2019 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 0125 AM CDT Mon Aug 19 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM ILLINOIS AND FAR WESTERN INDIANA WESTWARD INTO NEBRASKA... CORRECTED FOR GEOGRAPHIC SPELLING ERROR IN HEADLINE ...SUMMARY... Severe storms with damaging winds are possible over Illinois and parts of surrounding states on Tuesday. Severe storms with hail and wind are also expected over much of Nebraska. ...Synopsis... A shortwave trough will move southeastward across MB and ON, with 35-45 kt midlevel winds across the Upper MS Valley and Great Lakes. Heights will gradually lower from the mid MO Valley across the OH Valley and toward the Mid Atlantic by Wed morning. Cool temperatures aloft with -10 C at 500 mb will spread southeastward across MO and IL atop a moist and unstable air mass. Strong instability will also extend westward over much of the central Plains, with an east-west front along the KS/NE border and low pressure developing along the CO/KS border. This boundary will provide a focus for storms during the evening as the low-level jet develops and aids lift. ...IA/MO/IL/IN... Models indicate that an MCS will develop early in the morning over IA in a zone of warm advection with 40 kt west/southwest 850 mb winds, and will continue southeastward over IL and MO during the day. While much of this event may occur prior to peak heating, a very moist air mass and a few hours of heating will lead to 3000-4000 J/kg MUCAPE. Winds aloft will not be particularly strong this far south of the upper trough, but sufficient to aid forward propagation of an MCS. Damaging winds will be the primary concern. Western portions of this MCS will likely affect eastern MO, and may persist as far south as northeast AR. A higher probability threat corridor may need to be added in later outlooks once the MCS timing and position are better known. ...Eastern WY and northeast CO into NE... Strong heating will occur over WY, CO, and much of KS, but will be tempered along and north of the front into NE. Increasing easterly surface winds in the vicinity of the front will maintain 60s to 70s F dewpoints over NE, with near 60 F into northeast CO. Storms are expected to initiate within the well heated air mass of eastern CO and WY during the late afternoon, with increasing coverage north of the front in NE overnight. Damaging winds and hail will be the primary concerns. Deep-layer shear over NE may be sufficient for elevated supercells capable of very large hail given the large instability. An MCS could also develop into Wednesday morning over eastern NE into northwest MO. ...MAXIMUM RISK BY HAZARD... Tornado: 2% - Marginal Wind: 15% SIG - Slight Hail: 15% SIG - Slight ..Jewell.. 08/19/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Mon Aug 19 2019 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS AND MIDDLE MO VALLEY....AND OVER THE CENTRAL HIGH PLAINS...AND ACROSS NEW ENGLAND... ...SUMMARY... Isolated severe storms are possible over parts of the northern Plains and Middle Missouri Valley Monday evening and overnight. Isolated severe storms are possible across the central High Plains and New England. ...Synopsis... Overall upper pattern across the northern third of the CONUS will continue to trend more zonal as the shortwave trough currently moving through Ontario progresses eastward and upper ridging centered over the southern Plains builds. An additional shortwave trough is expected to move across Canadian Prairie Provinces during the second half of the period, helping to push a cold front through the much of the northern Plains by early Tuesday morning. Before this cold front moves through, the surface pattern will be dominated by high pressure gradually shifting northeastward across the Upper Midwest and Upper Great Lakes. Southerly flow around this high will allow the very moist air mass across the central Plains to advect northward into the northern Plains. ...Northern Plains into the Mid MO Valley... Moisture advection is anticipated across the region throughout the day, with dewpoints in the mid to upper 60s (isolated low 70s) by the late afternoon/early evening. At the same time, strong diurnal heating will lead to deep boundary-layer mixing and temperatures into the upper 80s and 90s across the western Dakotas. Large-scale forcing for ascent will be negligible (with minor height rises anticipated) but with little convective inhibition and surface convergence near a weak surface low over western ND, thunderstorm initiation is possible. If initiation can occur, the air mass across the western Dakotas (and downstream across the central Dakotas) will support strong updrafts capable of hail and strong wind gusts. Southeasterly low-level flow also supports low-probability tornado threat. Steep low-level lapse rates and relatively dry mid-levels also suggest an environment favorable for strong cold pools and a resulting potential for upscale growth into an organized, forward-propagating MCS. A strengthening low-level jet would provide the moisture needed for MCS maintenance. Main uncertainty regarding this scenario is the initiation of surface-based storms during late afternoon across the western Dakotas. Guidance has shown high run-to-run variability regarding initiation. Upgrades may be needed in subsequent outlooks if initiation appears likely. Additionally, a strengthening low-level jet and resulting warm-air advection is expected to promote elevated thunderstorm development across IA late today/early Tuesday morning. Hail is possible within the strongest updrafts. ...Central High Plains... Isolated thunderstorm development is possible along the lee trough extending across the region. Most probable location for initiation is across northeast CO where a lee low will likely exist. Given the deeply mixed boundary-layer, strong wind gusts are possible with a few of these high-based storms. Some isolated hail is also possible with the strongest updrafts. ...New England... Isolated showers and thunderstorms are expected this morning, but air mass recovery is still anticipated ahead of an approaching shortwave trough and attendant surface trough. The strongest shear will be confined to ME, where the potential for a few supercells exists. Modest flow aloft will exist farther south, but bowing line segments capable of isolated damaging wind gusts are still expected. ..Mosier/Nauslar.. 08/19/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Mon Aug 19 2019 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS AND MIDDLE MO VALLEY....AND OVER THE CENTRAL HIGH PLAINS...AND ACROSS NEW ENGLAND... ...SUMMARY... Isolated severe storms are possible over parts of the northern Plains and Middle Missouri Valley Monday evening and overnight. Isolated severe storms are possible across the central High Plains and New England. ...Synopsis... Overall upper pattern across the northern third of the CONUS will continue to trend more zonal as the shortwave trough currently moving through Ontario progresses eastward and upper ridging centered over the southern Plains builds. An additional shortwave trough is expected to move across Canadian Prairie Provinces during the second half of the period, helping to push a cold front through the much of the northern Plains by early Tuesday morning. Before this cold front moves through, the surface pattern will be dominated by high pressure gradually shifting northeastward across the Upper Midwest and Upper Great Lakes. Southerly flow around this high will allow the very moist air mass across the central Plains to advect northward into the northern Plains. ...Northern Plains into the Mid MO Valley... Moisture advection is anticipated across the region throughout the day, with dewpoints in the mid to upper 60s (isolated low 70s) by the late afternoon/early evening. At the same time, strong diurnal heating will lead to deep boundary-layer mixing and temperatures into the upper 80s and 90s across the western Dakotas. Large-scale forcing for ascent will be negligible (with minor height rises anticipated) but with little convective inhibition and surface convergence near a weak surface low over western ND, thunderstorm initiation is possible. If initiation can occur, the air mass across the western Dakotas (and downstream across the central Dakotas) will support strong updrafts capable of hail and strong wind gusts. Southeasterly low-level flow also supports low-probability tornado threat. Steep low-level lapse rates and relatively dry mid-levels also suggest an environment favorable for strong cold pools and a resulting potential for upscale growth into an organized, forward-propagating MCS. A strengthening low-level jet would provide the moisture needed for MCS maintenance. Main uncertainty regarding this scenario is the initiation of surface-based storms during late afternoon across the western Dakotas. Guidance has shown high run-to-run variability regarding initiation. Upgrades may be needed in subsequent outlooks if initiation appears likely. Additionally, a strengthening low-level jet and resulting warm-air advection is expected to promote elevated thunderstorm development across IA late today/early Tuesday morning. Hail is possible within the strongest updrafts. ...Central High Plains... Isolated thunderstorm development is possible along the lee trough extending across the region. Most probable location for initiation is across northeast CO where a lee low will likely exist. Given the deeply mixed boundary-layer, strong wind gusts are possible with a few of these high-based storms. Some isolated hail is also possible with the strongest updrafts. ...New England... Isolated showers and thunderstorms are expected this morning, but air mass recovery is still anticipated ahead of an approaching shortwave trough and attendant surface trough. The strongest shear will be confined to ME, where the potential for a few supercells exists. Modest flow aloft will exist farther south, but bowing line segments capable of isolated damaging wind gusts are still expected. ..Mosier/Nauslar.. 08/19/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Mon Aug 19 2019 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS AND MIDDLE MO VALLEY....AND OVER THE CENTRAL HIGH PLAINS...AND ACROSS NEW ENGLAND... ...SUMMARY... Isolated severe storms are possible over parts of the northern Plains and Middle Missouri Valley Monday evening and overnight. Isolated severe storms are possible across the central High Plains and New England. ...Synopsis... Overall upper pattern across the northern third of the CONUS will continue to trend more zonal as the shortwave trough currently moving through Ontario progresses eastward and upper ridging centered over the southern Plains builds. An additional shortwave trough is expected to move across Canadian Prairie Provinces during the second half of the period, helping to push a cold front through the much of the northern Plains by early Tuesday morning. Before this cold front moves through, the surface pattern will be dominated by high pressure gradually shifting northeastward across the Upper Midwest and Upper Great Lakes. Southerly flow around this high will allow the very moist air mass across the central Plains to advect northward into the northern Plains. ...Northern Plains into the Mid MO Valley... Moisture advection is anticipated across the region throughout the day, with dewpoints in the mid to upper 60s (isolated low 70s) by the late afternoon/early evening. At the same time, strong diurnal heating will lead to deep boundary-layer mixing and temperatures into the upper 80s and 90s across the western Dakotas. Large-scale forcing for ascent will be negligible (with minor height rises anticipated) but with little convective inhibition and surface convergence near a weak surface low over western ND, thunderstorm initiation is possible. If initiation can occur, the air mass across the western Dakotas (and downstream across the central Dakotas) will support strong updrafts capable of hail and strong wind gusts. Southeasterly low-level flow also supports low-probability tornado threat. Steep low-level lapse rates and relatively dry mid-levels also suggest an environment favorable for strong cold pools and a resulting potential for upscale growth into an organized, forward-propagating MCS. A strengthening low-level jet would provide the moisture needed for MCS maintenance. Main uncertainty regarding this scenario is the initiation of surface-based storms during late afternoon across the western Dakotas. Guidance has shown high run-to-run variability regarding initiation. Upgrades may be needed in subsequent outlooks if initiation appears likely. Additionally, a strengthening low-level jet and resulting warm-air advection is expected to promote elevated thunderstorm development across IA late today/early Tuesday morning. Hail is possible within the strongest updrafts. ...Central High Plains... Isolated thunderstorm development is possible along the lee trough extending across the region. Most probable location for initiation is across northeast CO where a lee low will likely exist. Given the deeply mixed boundary-layer, strong wind gusts are possible with a few of these high-based storms. Some isolated hail is also possible with the strongest updrafts. ...New England... Isolated showers and thunderstorms are expected this morning, but air mass recovery is still anticipated ahead of an approaching shortwave trough and attendant surface trough. The strongest shear will be confined to ME, where the potential for a few supercells exists. Modest flow aloft will exist farther south, but bowing line segments capable of isolated damaging wind gusts are still expected. ..Mosier/Nauslar.. 08/19/2019 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Mon Aug 19 2019 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN PLAINS AND MIDDLE MO VALLEY....AND OVER THE CENTRAL HIGH PLAINS...AND ACROSS NEW ENGLAND... ...SUMMARY... Isolated severe storms are possible over parts of the northern Plains and Middle Missouri Valley Monday evening and overnight. Isolated severe storms are possible across the central High Plains and New England. ...Synopsis... Overall upper pattern across the northern third of the CONUS will continue to trend more zonal as the shortwave trough currently moving through Ontario progresses eastward and upper ridging centered over the southern Plains builds. An additional shortwave trough is expected to move across Canadian Prairie Provinces during the second half of the period, helping to push a cold front through the much of the northern Plains by early Tuesday morning. Before this cold front moves through, the surface pattern will be dominated by high pressure gradually shifting northeastward across the Upper Midwest and Upper Great Lakes. Southerly flow around this high will allow the very moist air mass across the central Plains to advect northward into the northern Plains. ...Northern Plains into the Mid MO Valley... Moisture advection is anticipated across the region throughout the day, with dewpoints in the mid to upper 60s (isolated low 70s) by the late afternoon/early evening. At the same time, strong diurnal heating will lead to deep boundary-layer mixing and temperatures into the upper 80s and 90s across the western Dakotas. Large-scale forcing for ascent will be negligible (with minor height rises anticipated) but with little convective inhibition and surface convergence near a weak surface low over western ND, thunderstorm initiation is possible. If initiation can occur, the air mass across the western Dakotas (and downstream across the central Dakotas) will support strong updrafts capable of hail and strong wind gusts. Southeasterly low-level flow also supports low-probability tornado threat. Steep low-level lapse rates and relatively dry mid-levels also suggest an environment favorable for strong cold pools and a resulting potential for upscale growth into an organized, forward-propagating MCS. A strengthening low-level jet would provide the moisture needed for MCS maintenance. Main uncertainty regarding this scenario is the initiation of surface-based storms during late afternoon across the western Dakotas. Guidance has shown high run-to-run variability regarding initiation. Upgrades may be needed in subsequent outlooks if initiation appears likely. Additionally, a strengthening low-level jet and resulting warm-air advection is expected to promote elevated thunderstorm development across IA late today/early Tuesday morning. Hail is possible within the strongest updrafts. ...Central High Plains... Isolated thunderstorm development is possible along the lee trough extending across the region. Most probable location for initiation is across northeast CO where a lee low will likely exist. Given the deeply mixed boundary-layer, strong wind gusts are possible with a few of these high-based storms. Some isolated hail is also possible with the strongest updrafts. ...New England... Isolated showers and thunderstorms are expected this morning, but air mass recovery is still anticipated ahead of an approaching shortwave trough and attendant surface trough. The strongest shear will be confined to ME, where the potential for a few supercells exists. Modest flow aloft will exist farther south, but bowing line segments capable of isolated damaging wind gusts are still expected. ..Mosier/Nauslar.. 08/19/2019 Read more

WW 0599 Status Updates
STATUS REPORT ON WW 599 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 40 S MIE TO 35 WNW DAY TO 20 E FWA TO 20 SE DTW TO 50 ESE MTC TO 30 NNW ZZV. WW 599 WILL BE ALLOWED TO EXPIRE AT 190200Z. FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 1798 ..GLEASON..08/19/19 ATTN...WFO...IWX...ILN...CLE... STATUS REPORT FOR WS 599 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS INC041-047-161-177-190200- IN . INDIANA COUNTIES INCLUDED ARE FAYETTE FRANKLIN UNION WAYNE OHC003-005-011-017-021-023-033-037-039-041-043-063-065-069-077- 083-091-093-095-101-107-109-113-117-123-125-135-137-139-143-147- 149-159-161-173-175-190200- OH . OHIO COUNTIES INCLUDED ARE ALLEN ASHLAND AUGLAIZE BUTLER CHAMPAIGN CLARK CRAWFORD DARKE DEFIANCE DELAWARE ERIE HANCOCK HARDIN HENRY HURON Read more

WW 599 SEVERE TSTM IN OH PA LE 181925Z - 190200Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 599 NWS Storm Prediction Center Norman OK 325 PM EDT Sun Aug 18 2019 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Parts of east central and northeast Indiana Western and northern Ohio Extreme northwest Pennsylvania Lake Erie * Effective this Sunday afternoon and evening from 325 PM until 1000 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1.5 inches in diameter possible SUMMARY...Scattered thunderstorms are ongoing from northwest Ohio across Lake Erie along a remnant thunderstorm outflow boundary, and more storms will likely form through the afternoon farther south and west. The storm environment favors multicell clusters, and potentially marginal supercells, capable of producing damaging winds and isolated large hail through this evening. The severe thunderstorm watch area is approximately along and 45 statute miles north and south of a line from 10 miles north northwest of Muncie IN to 15 miles east northeast of Erie PA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). 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. && OTHER WATCH INFORMATION...CONTINUE...WW 598... 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 550. Mean storm motion vector 27025. ...Thompson Read more

MD 1798 CONCERNING SEVERE THUNDERSTORM WATCH 599... FOR PORTIONS OF CENTRAL/EASTERN IN AND WESTERN/CENTRAL OH
Mesoscale Discussion 1798 NWS Storm Prediction Center Norman OK 0802 PM CDT Sun Aug 18 2019 Areas affected...Portions of central/eastern IN and western/central OH Concerning...Severe Thunderstorm Watch 599... Valid 190102Z - 190200Z The severe weather threat for Severe Thunderstorm Watch 599 continues. SUMMARY...An isolated strong/gusty wind threat should continue across Severe Thunderstorm Watch 599 this evening. A gradual weakening trend with ongoing storms should occur over the next couple of hours. DISCUSSION...A line of storms ahead of a cold front will continue eastward across parts of the OH Valley this evening. This convection produced multiple measured severe and damaging wind gusts earlier this evening across central IN. However, recent radar imagery has shown outflow surging ahead of the line across east-central IN into west-central OH. A reservoir of weak to moderate instability exists downstream of this ongoing activity, but a gradual reduction of MLCAPE is expected this evening with the loss of daytime heating. In addition, stronger mid-level flow associated with a shortwave trough over the Great Lakes will remain mostly displaced to the north of this region, which should limit effective bulk shear and overall storm intensity. Still, isolated strong/gusty winds producing occasional damage remain possible over the next couple of hours across mainly western portions of Severe Thunderstorm Watch 599 (far eastern IN and western OH). ..Gleason.. 08/19/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CLE...ILN...IWX...IND... LAT...LON 39588595 39788564 40118546 40788542 41628443 41778294 41668260 40828277 39888364 39318451 39328578 39588595 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 PM CDT Sun Aug 18 2019 Valid 190100Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER OHIO VALLEY INTO THE LOWER GREAT LAKES... ...SUMMARY... Isolated to widely scattered damaging winds are possible from the lower Ohio Valley northeast into the lower Great Lakes this evening. ...01Z Update... ...OH Valley into the Lower Great Lakes... A line of thunderstorms currently extends along a cold front from southeastern Lower MI southwestward through central IL. Occasionally strong updrafts have been noted within this much of line with the most organized storms along its southern periphery across central IN. Isolated strong wind gusts remain possible along the length of this line for the next few hours. ...Elsewhere... The outlook was trimmed elsewhere based on recent trends. Isolated storms across far northwest TX and southwest OK will pose a risk for isolated strong wind gusts (discussed in more detail in MCD 1797). A few water-loaded downbursts are also possible across the Mid-South and southern New England. ..Mosier.. 08/19/2019 Read more