Severe Storms

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Thu Sep 19 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms are possible on Friday across the northern Plains, with isolated activity into the central and southern High Plains. ...Synopsis... The large upper trough currently extending from Alberta into central CA is expected to gradually drift eastward, reaching the Great Basin by early Friday morning. A shortwave trough rotating through the base of this parent upper trough is then expected to continue eastward/northeastward through the northern/central Rockies and into the northern Plains. By early Saturday, broad upper troughing will still be in place across much of the western CONUS with the previously mentioned shortwave trough likely over western portions of the northern Plains. The surface pattern early Friday morning will likely be characterized by a well-defined trough extending from eastern MT into eastern CO, separating the moist, southerly return flow across the Plains from the drier, more westerly/southwesterly flow across the central/southern High Plains. As the shortwave trough progresses eastward/northeastward, this surface trough is expected to also move eastward into more of the central Plains while its parent surface low moves into the Dakotas. Convergence along this boundary as well as near the surface low is expected to contribute to afternoon/evening thunderstorm development across the northern and central Plains. ...Northern/Central Plains...Northern High Plains... A moist air mass will be in place over the region early Friday, with further moistening expected amidst the modest moisture advection anticipated throughout the day. Steep mid-level lapse rates are also expected to be present across the region. The combination of these factors will result in moderate to strong buoyancy with afternoon/evening MLCAPE expected to range from around 3000 J/kg across ND to 1500 J/kg across western NE. Surface low and attendant trough mentioned in the synopsis are expected to interact with the buoyant and destabilizing air mass, contributing to the development of late afternoon thunderstorms. Overall environment supports the potential for supercells with this first round of thunderstorms, but the linear forcing for ascent and deep unidirectional shear profiles both suggest a quick linear transition and a predominantly linear mode. Strong wind gusts and large hail are the primary threats but a couple tornadoes are also possible with any more discrete storms. Additional thunderstorm development is expected Friday afternoon farther west across eastern WY and southeast MT, just ahead of the approaching shortwave trough. Scant low-level moisture is anticipated in this region but cool mid-level temperatures will still result in enough buoyancy to support thunderstorms amidst the strong forcing for ascent. These storms will likely organize/intensify with eastern extent as they move into a more buoyant environment across the northern Plains. A more organized MCS may result from these storms, supported by a strengthening low-level jet and ample low-level moisture. ...Central/Southern High Plains... Thunderstorms are expected to develop along the lee trough on Friday afternoon. Shear profiles support the potential for a few supercells, but a more clustered/linear storm mode will likely limit the number of discrete storms. Current expectation is for multicell line segments to be main storm mode, with strong downbursts as the primary severe threat. Even so, a few supercells capable of strong wind gusts and large hail are possible, particularly across western portions of the region. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 15% - Slight Hail: 15% - Slight ..Mosier.. 09/19/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Thu Sep 19 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms are possible on Friday across the northern Plains, with isolated activity into the central and southern High Plains. ...Synopsis... The large upper trough currently extending from Alberta into central CA is expected to gradually drift eastward, reaching the Great Basin by early Friday morning. A shortwave trough rotating through the base of this parent upper trough is then expected to continue eastward/northeastward through the northern/central Rockies and into the northern Plains. By early Saturday, broad upper troughing will still be in place across much of the western CONUS with the previously mentioned shortwave trough likely over western portions of the northern Plains. The surface pattern early Friday morning will likely be characterized by a well-defined trough extending from eastern MT into eastern CO, separating the moist, southerly return flow across the Plains from the drier, more westerly/southwesterly flow across the central/southern High Plains. As the shortwave trough progresses eastward/northeastward, this surface trough is expected to also move eastward into more of the central Plains while its parent surface low moves into the Dakotas. Convergence along this boundary as well as near the surface low is expected to contribute to afternoon/evening thunderstorm development across the northern and central Plains. ...Northern/Central Plains...Northern High Plains... A moist air mass will be in place over the region early Friday, with further moistening expected amidst the modest moisture advection anticipated throughout the day. Steep mid-level lapse rates are also expected to be present across the region. The combination of these factors will result in moderate to strong buoyancy with afternoon/evening MLCAPE expected to range from around 3000 J/kg across ND to 1500 J/kg across western NE. Surface low and attendant trough mentioned in the synopsis are expected to interact with the buoyant and destabilizing air mass, contributing to the development of late afternoon thunderstorms. Overall environment supports the potential for supercells with this first round of thunderstorms, but the linear forcing for ascent and deep unidirectional shear profiles both suggest a quick linear transition and a predominantly linear mode. Strong wind gusts and large hail are the primary threats but a couple tornadoes are also possible with any more discrete storms. Additional thunderstorm development is expected Friday afternoon farther west across eastern WY and southeast MT, just ahead of the approaching shortwave trough. Scant low-level moisture is anticipated in this region but cool mid-level temperatures will still result in enough buoyancy to support thunderstorms amidst the strong forcing for ascent. These storms will likely organize/intensify with eastern extent as they move into a more buoyant environment across the northern Plains. A more organized MCS may result from these storms, supported by a strengthening low-level jet and ample low-level moisture. ...Central/Southern High Plains... Thunderstorms are expected to develop along the lee trough on Friday afternoon. Shear profiles support the potential for a few supercells, but a more clustered/linear storm mode will likely limit the number of discrete storms. Current expectation is for multicell line segments to be main storm mode, with strong downbursts as the primary severe threat. Even so, a few supercells capable of strong wind gusts and large hail are possible, particularly across western portions of the region. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 15% - Slight Hail: 15% - Slight ..Mosier.. 09/19/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Thu Sep 19 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms are possible on Friday across the northern Plains, with isolated activity into the central and southern High Plains. ...Synopsis... The large upper trough currently extending from Alberta into central CA is expected to gradually drift eastward, reaching the Great Basin by early Friday morning. A shortwave trough rotating through the base of this parent upper trough is then expected to continue eastward/northeastward through the northern/central Rockies and into the northern Plains. By early Saturday, broad upper troughing will still be in place across much of the western CONUS with the previously mentioned shortwave trough likely over western portions of the northern Plains. The surface pattern early Friday morning will likely be characterized by a well-defined trough extending from eastern MT into eastern CO, separating the moist, southerly return flow across the Plains from the drier, more westerly/southwesterly flow across the central/southern High Plains. As the shortwave trough progresses eastward/northeastward, this surface trough is expected to also move eastward into more of the central Plains while its parent surface low moves into the Dakotas. Convergence along this boundary as well as near the surface low is expected to contribute to afternoon/evening thunderstorm development across the northern and central Plains. ...Northern/Central Plains...Northern High Plains... A moist air mass will be in place over the region early Friday, with further moistening expected amidst the modest moisture advection anticipated throughout the day. Steep mid-level lapse rates are also expected to be present across the region. The combination of these factors will result in moderate to strong buoyancy with afternoon/evening MLCAPE expected to range from around 3000 J/kg across ND to 1500 J/kg across western NE. Surface low and attendant trough mentioned in the synopsis are expected to interact with the buoyant and destabilizing air mass, contributing to the development of late afternoon thunderstorms. Overall environment supports the potential for supercells with this first round of thunderstorms, but the linear forcing for ascent and deep unidirectional shear profiles both suggest a quick linear transition and a predominantly linear mode. Strong wind gusts and large hail are the primary threats but a couple tornadoes are also possible with any more discrete storms. Additional thunderstorm development is expected Friday afternoon farther west across eastern WY and southeast MT, just ahead of the approaching shortwave trough. Scant low-level moisture is anticipated in this region but cool mid-level temperatures will still result in enough buoyancy to support thunderstorms amidst the strong forcing for ascent. These storms will likely organize/intensify with eastern extent as they move into a more buoyant environment across the northern Plains. A more organized MCS may result from these storms, supported by a strengthening low-level jet and ample low-level moisture. ...Central/Southern High Plains... Thunderstorms are expected to develop along the lee trough on Friday afternoon. Shear profiles support the potential for a few supercells, but a more clustered/linear storm mode will likely limit the number of discrete storms. Current expectation is for multicell line segments to be main storm mode, with strong downbursts as the primary severe threat. Even so, a few supercells capable of strong wind gusts and large hail are possible, particularly across western portions of the region. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 15% - Slight Hail: 15% - Slight ..Mosier.. 09/19/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Thu Sep 19 2019 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE NORTHERN PLAINS... ...SUMMARY... Scattered severe storms are possible on Friday across the northern Plains, with isolated activity into the central and southern High Plains. ...Synopsis... The large upper trough currently extending from Alberta into central CA is expected to gradually drift eastward, reaching the Great Basin by early Friday morning. A shortwave trough rotating through the base of this parent upper trough is then expected to continue eastward/northeastward through the northern/central Rockies and into the northern Plains. By early Saturday, broad upper troughing will still be in place across much of the western CONUS with the previously mentioned shortwave trough likely over western portions of the northern Plains. The surface pattern early Friday morning will likely be characterized by a well-defined trough extending from eastern MT into eastern CO, separating the moist, southerly return flow across the Plains from the drier, more westerly/southwesterly flow across the central/southern High Plains. As the shortwave trough progresses eastward/northeastward, this surface trough is expected to also move eastward into more of the central Plains while its parent surface low moves into the Dakotas. Convergence along this boundary as well as near the surface low is expected to contribute to afternoon/evening thunderstorm development across the northern and central Plains. ...Northern/Central Plains...Northern High Plains... A moist air mass will be in place over the region early Friday, with further moistening expected amidst the modest moisture advection anticipated throughout the day. Steep mid-level lapse rates are also expected to be present across the region. The combination of these factors will result in moderate to strong buoyancy with afternoon/evening MLCAPE expected to range from around 3000 J/kg across ND to 1500 J/kg across western NE. Surface low and attendant trough mentioned in the synopsis are expected to interact with the buoyant and destabilizing air mass, contributing to the development of late afternoon thunderstorms. Overall environment supports the potential for supercells with this first round of thunderstorms, but the linear forcing for ascent and deep unidirectional shear profiles both suggest a quick linear transition and a predominantly linear mode. Strong wind gusts and large hail are the primary threats but a couple tornadoes are also possible with any more discrete storms. Additional thunderstorm development is expected Friday afternoon farther west across eastern WY and southeast MT, just ahead of the approaching shortwave trough. Scant low-level moisture is anticipated in this region but cool mid-level temperatures will still result in enough buoyancy to support thunderstorms amidst the strong forcing for ascent. These storms will likely organize/intensify with eastern extent as they move into a more buoyant environment across the northern Plains. A more organized MCS may result from these storms, supported by a strengthening low-level jet and ample low-level moisture. ...Central/Southern High Plains... Thunderstorms are expected to develop along the lee trough on Friday afternoon. Shear profiles support the potential for a few supercells, but a more clustered/linear storm mode will likely limit the number of discrete storms. Current expectation is for multicell line segments to be main storm mode, with strong downbursts as the primary severe threat. Even so, a few supercells capable of strong wind gusts and large hail are possible, particularly across western portions of the region. ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind: 15% - Slight Hail: 15% - Slight ..Mosier.. 09/19/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1137 AM CDT Thu Sep 19 2019 Valid 191700Z - 201200Z ...CRITICAL FIRE WEATHER AREA FOR FAR SOUTHEAST NEVADA...NORTHWEST ARIZONA...AND A LARGE PORTION OF UTAH... No changes are needed to the ongoing forecast of critical fire weather conditions across portions of southeastern Nevada, northwestern Arizona, and Utah (see previous discussion below). Strong insolation ahead of an approaching upper-level trough has already resulted in some locations reporting RH values this morning below 20% along with wind gusts approaching 30 mph. As boundary layer mixing continues through the afternoon, widespread critical fire weather conditions are expected across the region with the potential for strong wind gusts (i.e., approaching 50 mph). ..Jirak.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1246 AM CDT Thu Sep 19 2019/ ...Synopsis... A strong mid-level jet will spread across the Great Basin today ahead of a mid-level closed low. Some of these strong winds are expected to transport toward the surface through deep vertical mixing. Surface winds could be quite strong (30 to 35 mph) in northwest Arizona and southwest Utah with some gusts approaching 50 mph. In addition, this pre-frontal airmass will feature dry surface conditions and RH values around 10 to 20 percent. 20 to 30 mph surface winds are expected farther northeast into most of Wyoming where relative humidity will also be in the 15 to 20 percent range. Isolated critical conditions will be possible in this region, but no critical area was added here due to borderline relative humidity and relatively sparse fuels. ...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 1137 AM CDT Thu Sep 19 2019 Valid 191700Z - 201200Z ...CRITICAL FIRE WEATHER AREA FOR FAR SOUTHEAST NEVADA...NORTHWEST ARIZONA...AND A LARGE PORTION OF UTAH... No changes are needed to the ongoing forecast of critical fire weather conditions across portions of southeastern Nevada, northwestern Arizona, and Utah (see previous discussion below). Strong insolation ahead of an approaching upper-level trough has already resulted in some locations reporting RH values this morning below 20% along with wind gusts approaching 30 mph. As boundary layer mixing continues through the afternoon, widespread critical fire weather conditions are expected across the region with the potential for strong wind gusts (i.e., approaching 50 mph). ..Jirak.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1246 AM CDT Thu Sep 19 2019/ ...Synopsis... A strong mid-level jet will spread across the Great Basin today ahead of a mid-level closed low. Some of these strong winds are expected to transport toward the surface through deep vertical mixing. Surface winds could be quite strong (30 to 35 mph) in northwest Arizona and southwest Utah with some gusts approaching 50 mph. In addition, this pre-frontal airmass will feature dry surface conditions and RH values around 10 to 20 percent. 20 to 30 mph surface winds are expected farther northeast into most of Wyoming where relative humidity will also be in the 15 to 20 percent range. Isolated critical conditions will be possible in this region, but no critical area was added here due to borderline relative humidity and relatively sparse fuels. ...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 1137 AM CDT Thu Sep 19 2019 Valid 191700Z - 201200Z ...CRITICAL FIRE WEATHER AREA FOR FAR SOUTHEAST NEVADA...NORTHWEST ARIZONA...AND A LARGE PORTION OF UTAH... No changes are needed to the ongoing forecast of critical fire weather conditions across portions of southeastern Nevada, northwestern Arizona, and Utah (see previous discussion below). Strong insolation ahead of an approaching upper-level trough has already resulted in some locations reporting RH values this morning below 20% along with wind gusts approaching 30 mph. As boundary layer mixing continues through the afternoon, widespread critical fire weather conditions are expected across the region with the potential for strong wind gusts (i.e., approaching 50 mph). ..Jirak.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1246 AM CDT Thu Sep 19 2019/ ...Synopsis... A strong mid-level jet will spread across the Great Basin today ahead of a mid-level closed low. Some of these strong winds are expected to transport toward the surface through deep vertical mixing. Surface winds could be quite strong (30 to 35 mph) in northwest Arizona and southwest Utah with some gusts approaching 50 mph. In addition, this pre-frontal airmass will feature dry surface conditions and RH values around 10 to 20 percent. 20 to 30 mph surface winds are expected farther northeast into most of Wyoming where relative humidity will also be in the 15 to 20 percent range. Isolated critical conditions will be possible in this region, but no critical area was added here due to borderline relative humidity and relatively sparse fuels. ...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 1108 AM CDT Thu Sep 19 2019 Valid 191630Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE HIGH PLAINS...AND OVER PORTIONS OF THE TEXAS AND LOUISIANA COAST.... ...SUMMARY... Thunderstorms capable of isolated damaging winds and marginally severe hail will be possible in parts of the central and southern High Plains this afternoon and evening. A brief tornado or two will also be possible near the upper Texas and southwest Louisiana coast. ...High Plains... A large upper trough is present over the western states today, while a broad upper ridge dominates the weather in the east. Southwesterly flow aloft persists over the High Plains, where full sunshine and dewpoints in the 60s will result in steep low-level lapse rates and moderate CAPE. A weak midlevel impulse over NM will likely aid in the development of scattered thunderstorms by mid-afternoon over southeast CO and western portions of the TX/OK Panhandles. This activity will spread northeastward into western KS during the evening. Midlevel winds are relatively weak, which may limit overall organization of the storms. However, potential exists for gusty/damaging winds and hail in the strongest cells through the early evening. ...LA/TX... TD Imelda continues to affect portions of the upper TX and southwest LA coastal region. Transient rotating storms have been noted this morning near the Sabine river. Increasingly discrete convection on the southwest flank of the circulation may also pose a risk of a brief spin-up or two farther south along the upper/middle TX coast later today. ..Hart/Gleason.. 09/19/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1108 AM CDT Thu Sep 19 2019 Valid 191630Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE HIGH PLAINS...AND OVER PORTIONS OF THE TEXAS AND LOUISIANA COAST.... ...SUMMARY... Thunderstorms capable of isolated damaging winds and marginally severe hail will be possible in parts of the central and southern High Plains this afternoon and evening. A brief tornado or two will also be possible near the upper Texas and southwest Louisiana coast. ...High Plains... A large upper trough is present over the western states today, while a broad upper ridge dominates the weather in the east. Southwesterly flow aloft persists over the High Plains, where full sunshine and dewpoints in the 60s will result in steep low-level lapse rates and moderate CAPE. A weak midlevel impulse over NM will likely aid in the development of scattered thunderstorms by mid-afternoon over southeast CO and western portions of the TX/OK Panhandles. This activity will spread northeastward into western KS during the evening. Midlevel winds are relatively weak, which may limit overall organization of the storms. However, potential exists for gusty/damaging winds and hail in the strongest cells through the early evening. ...LA/TX... TD Imelda continues to affect portions of the upper TX and southwest LA coastal region. Transient rotating storms have been noted this morning near the Sabine river. Increasingly discrete convection on the southwest flank of the circulation may also pose a risk of a brief spin-up or two farther south along the upper/middle TX coast later today. ..Hart/Gleason.. 09/19/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1108 AM CDT Thu Sep 19 2019 Valid 191630Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE HIGH PLAINS...AND OVER PORTIONS OF THE TEXAS AND LOUISIANA COAST.... ...SUMMARY... Thunderstorms capable of isolated damaging winds and marginally severe hail will be possible in parts of the central and southern High Plains this afternoon and evening. A brief tornado or two will also be possible near the upper Texas and southwest Louisiana coast. ...High Plains... A large upper trough is present over the western states today, while a broad upper ridge dominates the weather in the east. Southwesterly flow aloft persists over the High Plains, where full sunshine and dewpoints in the 60s will result in steep low-level lapse rates and moderate CAPE. A weak midlevel impulse over NM will likely aid in the development of scattered thunderstorms by mid-afternoon over southeast CO and western portions of the TX/OK Panhandles. This activity will spread northeastward into western KS during the evening. Midlevel winds are relatively weak, which may limit overall organization of the storms. However, potential exists for gusty/damaging winds and hail in the strongest cells through the early evening. ...LA/TX... TD Imelda continues to affect portions of the upper TX and southwest LA coastal region. Transient rotating storms have been noted this morning near the Sabine river. Increasingly discrete convection on the southwest flank of the circulation may also pose a risk of a brief spin-up or two farther south along the upper/middle TX coast later today. ..Hart/Gleason.. 09/19/2019 Read more

MD 1984 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR EXTREME SOUTHEAST TEXAS AND SOUTHWEST LOUISIANA
Mesoscale Discussion 1984 NWS Storm Prediction Center Norman OK 0911 AM CDT Thu Sep 19 2019 Areas affected...extreme southeast Texas and southwest Louisiana Concerning...Severe potential...Watch possible Valid 191411Z - 191615Z Probability of Watch Issuance...40 percent SUMMARY...Threat for isolated tornadoes should persist through the morning and possibly into the early afternoon from extreme southeast TX into southwest LA. The spatial extent of threat is expected to remain small, but trends are being monitored. DISCUSSION...As of mid morning a warm front extends from near the southwest LA coast northwestward to a surface low in southeast TX. These features are associated with tropical depression Imelda that is located over east TX and moving very slowly north at around 5 mph. Storms continue developing along a convergence band over southeast TX with more discrete mini supercells developing ahead of the line moving northward onto the southwest LA coast. The greatest potential for a few brief tornadoes will be as these mini supercells move north and interact with the warm front across southwest LA where 0-1 km storm relative helicity ranges from 150-250 m2/s2. The spatial extent of the threat area is expected to remain limited, but some of these storms might eventually affect the city of Lake Charles. ..Dial/Hart.. 09/19/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LCH... LAT...LON 30299331 29839283 29569301 29829407 30419388 30299331 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0727 AM CDT Thu Sep 19 2019 Valid 191300Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY NEAR THE UPPER TX COAST...AND THIS AFTERNOON/EVENING FOR PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated damaging winds and marginally severe hail will be possible in parts of the central and southern High Plains this afternoon and evening. A brief tornado or two will also be possible near the upper Texas coast. ...Central/southern High Plains this afternoon/evening... A midlevel trough will move eastward over NV/ID and UT by tonight, with subtle/diffuse speed maxima preceding the trough from the southern Rockies to the central High Plains. An associated broad surface low will form in WY and move toward the northern High Plains by early Friday, with a lee trough extending southeastward into eastern CO. Surface heating and boundary-layer dewpoints in the 60s east of the lee trough will contribute to MLCAPE near 2000 J/kg this afternoon/evening. Forcing for ascent will be weak at best on the larger scale, with storm initiation relying on surface heating to remove convective inhibition. Still, scattered thunderstorms are expected to form this afternoon and persist into this evening along and east of the lee trough, and along the northwest edge of a midlevel moisture plume across the southern High Plains. Steep lapse rates will promote some potential for strong outflow winds with downbursts, as well as marginally severe hail. Deep-layer vertical shear will be weak across western KS where multicell clusters will be the main storm mode, and slightly stronger across the TX Panhandle where some transient supercell structures will be possible. ...Southeast TX today... Extreme rainfall has occurred overnight between Houston and Beaumont with training convection which has been maintained by 35 kt south-southwesterly inflow of 100 mb mean mixing ratios near 19 g/kg (77-80 F dewpoints) into a stationary, rain-reinforced boundary. Back-building to the west will become more probable during the day with the stronger low-level inflow focused into the west flank of the ongoing convection, and as surface heating occurs to the west. There will still be sufficient low-level shear/hodograph curvature for a few rotating storms and a brief/weak tornado or two in this band the first half of the day, with a gradual decrease in low-level flow/shear is expected by later this afternoon. ...Northern High Plains through tonight... The richer low-level moisture is confined to NE/KS this morning, and moisture is likely to remain limited across eastern WY through most of the afternoon. Moisture will increase farther west and north tonight, but this will also be accompanied by a capped boundary layer. Since the limited moisture will likewise limit buoyancy during the diurnal heating cycle, severe storms appear unlikely this afternoon. The cap and only weak forcing for ascent until Friday morning also suggests that any severe threat overnight will remain too low to warrant an outlook area. ..Thompson/Kerr.. 09/19/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0727 AM CDT Thu Sep 19 2019 Valid 191300Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY NEAR THE UPPER TX COAST...AND THIS AFTERNOON/EVENING FOR PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated damaging winds and marginally severe hail will be possible in parts of the central and southern High Plains this afternoon and evening. A brief tornado or two will also be possible near the upper Texas coast. ...Central/southern High Plains this afternoon/evening... A midlevel trough will move eastward over NV/ID and UT by tonight, with subtle/diffuse speed maxima preceding the trough from the southern Rockies to the central High Plains. An associated broad surface low will form in WY and move toward the northern High Plains by early Friday, with a lee trough extending southeastward into eastern CO. Surface heating and boundary-layer dewpoints in the 60s east of the lee trough will contribute to MLCAPE near 2000 J/kg this afternoon/evening. Forcing for ascent will be weak at best on the larger scale, with storm initiation relying on surface heating to remove convective inhibition. Still, scattered thunderstorms are expected to form this afternoon and persist into this evening along and east of the lee trough, and along the northwest edge of a midlevel moisture plume across the southern High Plains. Steep lapse rates will promote some potential for strong outflow winds with downbursts, as well as marginally severe hail. Deep-layer vertical shear will be weak across western KS where multicell clusters will be the main storm mode, and slightly stronger across the TX Panhandle where some transient supercell structures will be possible. ...Southeast TX today... Extreme rainfall has occurred overnight between Houston and Beaumont with training convection which has been maintained by 35 kt south-southwesterly inflow of 100 mb mean mixing ratios near 19 g/kg (77-80 F dewpoints) into a stationary, rain-reinforced boundary. Back-building to the west will become more probable during the day with the stronger low-level inflow focused into the west flank of the ongoing convection, and as surface heating occurs to the west. There will still be sufficient low-level shear/hodograph curvature for a few rotating storms and a brief/weak tornado or two in this band the first half of the day, with a gradual decrease in low-level flow/shear is expected by later this afternoon. ...Northern High Plains through tonight... The richer low-level moisture is confined to NE/KS this morning, and moisture is likely to remain limited across eastern WY through most of the afternoon. Moisture will increase farther west and north tonight, but this will also be accompanied by a capped boundary layer. Since the limited moisture will likewise limit buoyancy during the diurnal heating cycle, severe storms appear unlikely this afternoon. The cap and only weak forcing for ascent until Friday morning also suggests that any severe threat overnight will remain too low to warrant an outlook area. ..Thompson/Kerr.. 09/19/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0727 AM CDT Thu Sep 19 2019 Valid 191300Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY NEAR THE UPPER TX COAST...AND THIS AFTERNOON/EVENING FOR PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated damaging winds and marginally severe hail will be possible in parts of the central and southern High Plains this afternoon and evening. A brief tornado or two will also be possible near the upper Texas coast. ...Central/southern High Plains this afternoon/evening... A midlevel trough will move eastward over NV/ID and UT by tonight, with subtle/diffuse speed maxima preceding the trough from the southern Rockies to the central High Plains. An associated broad surface low will form in WY and move toward the northern High Plains by early Friday, with a lee trough extending southeastward into eastern CO. Surface heating and boundary-layer dewpoints in the 60s east of the lee trough will contribute to MLCAPE near 2000 J/kg this afternoon/evening. Forcing for ascent will be weak at best on the larger scale, with storm initiation relying on surface heating to remove convective inhibition. Still, scattered thunderstorms are expected to form this afternoon and persist into this evening along and east of the lee trough, and along the northwest edge of a midlevel moisture plume across the southern High Plains. Steep lapse rates will promote some potential for strong outflow winds with downbursts, as well as marginally severe hail. Deep-layer vertical shear will be weak across western KS where multicell clusters will be the main storm mode, and slightly stronger across the TX Panhandle where some transient supercell structures will be possible. ...Southeast TX today... Extreme rainfall has occurred overnight between Houston and Beaumont with training convection which has been maintained by 35 kt south-southwesterly inflow of 100 mb mean mixing ratios near 19 g/kg (77-80 F dewpoints) into a stationary, rain-reinforced boundary. Back-building to the west will become more probable during the day with the stronger low-level inflow focused into the west flank of the ongoing convection, and as surface heating occurs to the west. There will still be sufficient low-level shear/hodograph curvature for a few rotating storms and a brief/weak tornado or two in this band the first half of the day, with a gradual decrease in low-level flow/shear is expected by later this afternoon. ...Northern High Plains through tonight... The richer low-level moisture is confined to NE/KS this morning, and moisture is likely to remain limited across eastern WY through most of the afternoon. Moisture will increase farther west and north tonight, but this will also be accompanied by a capped boundary layer. Since the limited moisture will likewise limit buoyancy during the diurnal heating cycle, severe storms appear unlikely this afternoon. The cap and only weak forcing for ascent until Friday morning also suggests that any severe threat overnight will remain too low to warrant an outlook area. ..Thompson/Kerr.. 09/19/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0727 AM CDT Thu Sep 19 2019 Valid 191300Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY NEAR THE UPPER TX COAST...AND THIS AFTERNOON/EVENING FOR PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms capable of isolated damaging winds and marginally severe hail will be possible in parts of the central and southern High Plains this afternoon and evening. A brief tornado or two will also be possible near the upper Texas coast. ...Central/southern High Plains this afternoon/evening... A midlevel trough will move eastward over NV/ID and UT by tonight, with subtle/diffuse speed maxima preceding the trough from the southern Rockies to the central High Plains. An associated broad surface low will form in WY and move toward the northern High Plains by early Friday, with a lee trough extending southeastward into eastern CO. Surface heating and boundary-layer dewpoints in the 60s east of the lee trough will contribute to MLCAPE near 2000 J/kg this afternoon/evening. Forcing for ascent will be weak at best on the larger scale, with storm initiation relying on surface heating to remove convective inhibition. Still, scattered thunderstorms are expected to form this afternoon and persist into this evening along and east of the lee trough, and along the northwest edge of a midlevel moisture plume across the southern High Plains. Steep lapse rates will promote some potential for strong outflow winds with downbursts, as well as marginally severe hail. Deep-layer vertical shear will be weak across western KS where multicell clusters will be the main storm mode, and slightly stronger across the TX Panhandle where some transient supercell structures will be possible. ...Southeast TX today... Extreme rainfall has occurred overnight between Houston and Beaumont with training convection which has been maintained by 35 kt south-southwesterly inflow of 100 mb mean mixing ratios near 19 g/kg (77-80 F dewpoints) into a stationary, rain-reinforced boundary. Back-building to the west will become more probable during the day with the stronger low-level inflow focused into the west flank of the ongoing convection, and as surface heating occurs to the west. There will still be sufficient low-level shear/hodograph curvature for a few rotating storms and a brief/weak tornado or two in this band the first half of the day, with a gradual decrease in low-level flow/shear is expected by later this afternoon. ...Northern High Plains through tonight... The richer low-level moisture is confined to NE/KS this morning, and moisture is likely to remain limited across eastern WY through most of the afternoon. Moisture will increase farther west and north tonight, but this will also be accompanied by a capped boundary layer. Since the limited moisture will likewise limit buoyancy during the diurnal heating cycle, severe storms appear unlikely this afternoon. The cap and only weak forcing for ascent until Friday morning also suggests that any severe threat overnight will remain too low to warrant an outlook area. ..Thompson/Kerr.. 09/19/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CDT Thu Sep 19 2019 Valid 221200Z - 271200Z ...DISCUSSION... On Sunday/D4, a shortwave trough is forecast to move across the upper Mississippi Valley and Great Lakes, though models differ on speed and amplification. Regardless, thunderstorms are likely along the cold front, roughly from Lower Michigan into Missouri. Unidirectional southwest winds along the front suggest a degree of wind threat, though predictability is currently low. This trough will continue eastward into Monday/D5, but instability will be low over the Ohio Valley and Northeast. Meanwhile to the west, good model agreement exists with an upper low that is forecast to drop south across Nevada and into Arizona on Monday/D5. Increasing winds aloft as well as upslope along the rim with gulf moisture suggest a few severe storms are possible. Veering winds with height, good speed shear aloft and MLCAPE of 1000-1500 J/kg also indicate supercell potential or bowing segments. If model trends persist, severe probabilities may be added in future outlooks. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CDT Thu Sep 19 2019 Valid 221200Z - 271200Z ...DISCUSSION... On Sunday/D4, a shortwave trough is forecast to move across the upper Mississippi Valley and Great Lakes, though models differ on speed and amplification. Regardless, thunderstorms are likely along the cold front, roughly from Lower Michigan into Missouri. Unidirectional southwest winds along the front suggest a degree of wind threat, though predictability is currently low. This trough will continue eastward into Monday/D5, but instability will be low over the Ohio Valley and Northeast. Meanwhile to the west, good model agreement exists with an upper low that is forecast to drop south across Nevada and into Arizona on Monday/D5. Increasing winds aloft as well as upslope along the rim with gulf moisture suggest a few severe storms are possible. Veering winds with height, good speed shear aloft and MLCAPE of 1000-1500 J/kg also indicate supercell potential or bowing segments. If model trends persist, severe probabilities may be added in future outlooks. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CDT Thu Sep 19 2019 Valid 221200Z - 271200Z ...DISCUSSION... On Sunday/D4, a shortwave trough is forecast to move across the upper Mississippi Valley and Great Lakes, though models differ on speed and amplification. Regardless, thunderstorms are likely along the cold front, roughly from Lower Michigan into Missouri. Unidirectional southwest winds along the front suggest a degree of wind threat, though predictability is currently low. This trough will continue eastward into Monday/D5, but instability will be low over the Ohio Valley and Northeast. Meanwhile to the west, good model agreement exists with an upper low that is forecast to drop south across Nevada and into Arizona on Monday/D5. Increasing winds aloft as well as upslope along the rim with gulf moisture suggest a few severe storms are possible. Veering winds with height, good speed shear aloft and MLCAPE of 1000-1500 J/kg also indicate supercell potential or bowing segments. If model trends persist, severe probabilities may be added in future outlooks. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CDT Thu Sep 19 2019 Valid 221200Z - 271200Z ...DISCUSSION... On Sunday/D4, a shortwave trough is forecast to move across the upper Mississippi Valley and Great Lakes, though models differ on speed and amplification. Regardless, thunderstorms are likely along the cold front, roughly from Lower Michigan into Missouri. Unidirectional southwest winds along the front suggest a degree of wind threat, though predictability is currently low. This trough will continue eastward into Monday/D5, but instability will be low over the Ohio Valley and Northeast. Meanwhile to the west, good model agreement exists with an upper low that is forecast to drop south across Nevada and into Arizona on Monday/D5. Increasing winds aloft as well as upslope along the rim with gulf moisture suggest a few severe storms are possible. Veering winds with height, good speed shear aloft and MLCAPE of 1000-1500 J/kg also indicate supercell potential or bowing segments. If model trends persist, severe probabilities may be added in future outlooks. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0232 AM CDT Thu Sep 19 2019 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS KANSAS...NORTHERN MISSOURI AND IOWA... ...SUMMARY... Severe storms are possible across parts of the Plains on Saturday, most notably from Kansas into Iowa. ...Synopsis... An upper trough will move east across the northern Plains and toward the Great Lakes, with a broad zone of strong southwest winds aloft encompassing much of the central and northern Plains, upper MS valley and Great Lakes. The primary surface trough will extend from northern ND and MN into Ontario, with a cold front roughly from MN to KS by Saturday afternoon. Ahead of this front, mid to upper 60s F dewpoints will be widespread, and will contribute to areas of moderate instability. The most favorable combination of instability, lift, and shear appears to be from KS northeastward into IA and northern MO, although severe storm potential exists as far north as MN and WI. ...Central Plains... Upper 60s to near 70 F dewpoints are forecast to move north over OK, KS, MO and IA, with a cold front roughly from central KS into western IA by peak heating. Given the very moist air mass, capping will be minimal and storms may form early in the day from KS into MO in the moist sector with isolated severe possible. Veering winds with height and favorable effective SRH may favor a couple supercells producing either strong wind gusts or a brief/weak tornado. The most likely time for concentrated severe storms will be during the late afternoon and evening, beneath a strengthening 40-50 kt low-level jet centered over KS. Good model agreement exists within the zone from KS into northern MO and IA depicting significant storm coverage. Damaging wind appears to be the main concern during the evening, and storms may persist into IA and even western IL given strong westerlies aloft. ...Upper Mississippi Valley... Scattered storms are expected throughout the day from MN into WI. Early day storms may be associated with warm advection at 850 mb, with a secondary area of storms along the cold front as it moves across MN during the day. Marginal instability is forecast, with long hodographs suggesting a wind or marginal hail threat. It appears that a dry slot will move over the region during the day, with veering winds above the surface. In addition, 850 mb wind convergence will focus farther north into Ontario, with some models showing speed divergence over MN. Therefore at this time, only isolated severe storms are forecast. ..Jewell.. 09/19/2019 Read more