Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Thu Sep 19 2019 Valid 192000Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE SOUTHERN AND CENTRAL HIGH PLAINS...AND OVER PORTIONS OF THE TEXAS 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 middle/upper Texas coast. ...20Z Update.. ...Central/Southern High Plains... Thunderstorm coverage is increasing across the region and a few severe thunderstorms are still anticipated. See MCD 1985 for more short-term details. ...LA/TX... TD Imelda remains centered over southeast TX (about 25 miles south of CLL). Tornado threat east/southeast of the center appears limited given the lack of instability. More cellular activity continues southwest of the center over the middle TX Coast. In this area, steep low-level lapse rates are in place, but generally modest low-level shear will keep the tornado potential low. Later this evening, strengthening southeasterly surface winds may contribute to a modest increase in the tornado potential. ..Mosier.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1108 AM CDT Thu Sep 19 2019/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Thu Sep 19 2019 Valid 192000Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE SOUTHERN AND CENTRAL HIGH PLAINS...AND OVER PORTIONS OF THE TEXAS 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 middle/upper Texas coast. ...20Z Update.. ...Central/Southern High Plains... Thunderstorm coverage is increasing across the region and a few severe thunderstorms are still anticipated. See MCD 1985 for more short-term details. ...LA/TX... TD Imelda remains centered over southeast TX (about 25 miles south of CLL). Tornado threat east/southeast of the center appears limited given the lack of instability. More cellular activity continues southwest of the center over the middle TX Coast. In this area, steep low-level lapse rates are in place, but generally modest low-level shear will keep the tornado potential low. Later this evening, strengthening southeasterly surface winds may contribute to a modest increase in the tornado potential. ..Mosier.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1108 AM CDT Thu Sep 19 2019/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Thu Sep 19 2019 Valid 192000Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE SOUTHERN AND CENTRAL HIGH PLAINS...AND OVER PORTIONS OF THE TEXAS 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 middle/upper Texas coast. ...20Z Update.. ...Central/Southern High Plains... Thunderstorm coverage is increasing across the region and a few severe thunderstorms are still anticipated. See MCD 1985 for more short-term details. ...LA/TX... TD Imelda remains centered over southeast TX (about 25 miles south of CLL). Tornado threat east/southeast of the center appears limited given the lack of instability. More cellular activity continues southwest of the center over the middle TX Coast. In this area, steep low-level lapse rates are in place, but generally modest low-level shear will keep the tornado potential low. Later this evening, strengthening southeasterly surface winds may contribute to a modest increase in the tornado potential. ..Mosier.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1108 AM CDT Thu Sep 19 2019/ ...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. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Thu Sep 19 2019 Valid 192000Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE SOUTHERN AND CENTRAL HIGH PLAINS...AND OVER PORTIONS OF THE TEXAS 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 middle/upper Texas coast. ...20Z Update.. ...Central/Southern High Plains... Thunderstorm coverage is increasing across the region and a few severe thunderstorms are still anticipated. See MCD 1985 for more short-term details. ...LA/TX... TD Imelda remains centered over southeast TX (about 25 miles south of CLL). Tornado threat east/southeast of the center appears limited given the lack of instability. More cellular activity continues southwest of the center over the middle TX Coast. In this area, steep low-level lapse rates are in place, but generally modest low-level shear will keep the tornado potential low. Later this evening, strengthening southeasterly surface winds may contribute to a modest increase in the tornado potential. ..Mosier.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1108 AM CDT Thu Sep 19 2019/ ...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. Read more

MD 1985 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF THE SOUTHERN AND CENTRAL HIGH PLAINS
Mesoscale Discussion 1985 NWS Storm Prediction Center Norman OK 0248 PM CDT Thu Sep 19 2019 Areas affected...Portions of the southern and central High Plains Concerning...Severe potential...Watch unlikely Valid 191948Z - 192215Z Probability of Watch Issuance...20 percent SUMMARY...Strong/gusty winds and large hail may occur on an isolated basis with storms this afternoon and early evening. Watch issuance is unlikely at this time. DISCUSSION...Weak low-level convergence along a surface trough combined with modest large-scale ascent associated with a subtle shortwave trough over NM has encouraged recent convective development across parts of the southern and central High Plains. Low-level moisture increases with eastward extent across this region, with mid 50s to mid 60s surface dewpoints present. An EML plume extends across this area from higher terrain to the west, and MLCAPE of 1000-2000+ J/kg has developed along/east of the surface trough from southern NE into eastern CO/western KS, far eastern NM, and the TX/OK Panhandles. The main limiting factor that should keep the overall severe threat fairly isolated remains modest low/mid-level winds. Only about 25-30 kt of effective bulk shear will be present across the warm sector through the remainder of the afternoon and into the early evening. This marginal shear will likely promote occasional storm organization, with some large hail and strong/gusty winds possible as storms spread slowly eastward and potentially grow upscale into one or more small clusters. This isolated severe threat is expected to wane this evening with eastward extent across the southern/central High Plains as convective inhibition increases with the loss of daytime heating. ..Gleason/Hart.. 09/19/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LBF...DDC...GLD...LUB...AMA...PUB...ABQ... LAT...LON 34330329 36820310 39260251 39400251 40870170 40690051 40020022 38220013 35850026 34080100 33350164 33350261 33590303 34330329 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0143 PM CDT Thu Sep 19 2019 Valid 201200Z - 211200Z The ongoing forecast for elevated fire weather conditions across the Four Corners Region and portions of the central Rockies and central High Plains on Friday generally remains on track (see previous discussion below). Overall, the highest confidence/greatest model agreement for overlapping strong winds and low RH extends from northeastern Arizona into the Four Corners Region. In contrast, there is less confidence in meeting elevated conditions across eastern Colorado, owing to uncertainty in lee cyclogenesis location/strength/evolution. Given these considerations, only minor changes were made to the areal extent of the elevated delineation in this update. ..Jirak.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1247 AM CDT Thu Sep 19 2019/ ...Synopsis... The mid-level trough from Day1/Thursday will shift east on Friday which will increase fire weather concerns in portions of the central Rockies and the central High Plains. Deep mixing will strengthen surface winds across much of this region with wind speeds of 20 to 30 mph expected. Relative humidity will vary across the area from around 15 percent up to 30 percent. Locally critical fire weather conditions are possible within the broader elevated delineation, but the highest likelihood of critical conditions remains ambiguous at this time. Winds are expected to be strongest in Wyoming where relative humidity will be the highest, and lightest in eastern Utah where relative humidity will be the lowest. In eastern Colorado, both winds and relative humidity are expected to be borderline critical. Will continue to monitor the forecast for potential critical additions, especially if forecast guidance is drier or lee cyclogenesis is stronger, both of which would likely increase the likelihood of critical fire weather conditions. ...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 0143 PM CDT Thu Sep 19 2019 Valid 201200Z - 211200Z The ongoing forecast for elevated fire weather conditions across the Four Corners Region and portions of the central Rockies and central High Plains on Friday generally remains on track (see previous discussion below). Overall, the highest confidence/greatest model agreement for overlapping strong winds and low RH extends from northeastern Arizona into the Four Corners Region. In contrast, there is less confidence in meeting elevated conditions across eastern Colorado, owing to uncertainty in lee cyclogenesis location/strength/evolution. Given these considerations, only minor changes were made to the areal extent of the elevated delineation in this update. ..Jirak.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1247 AM CDT Thu Sep 19 2019/ ...Synopsis... The mid-level trough from Day1/Thursday will shift east on Friday which will increase fire weather concerns in portions of the central Rockies and the central High Plains. Deep mixing will strengthen surface winds across much of this region with wind speeds of 20 to 30 mph expected. Relative humidity will vary across the area from around 15 percent up to 30 percent. Locally critical fire weather conditions are possible within the broader elevated delineation, but the highest likelihood of critical conditions remains ambiguous at this time. Winds are expected to be strongest in Wyoming where relative humidity will be the highest, and lightest in eastern Utah where relative humidity will be the lowest. In eastern Colorado, both winds and relative humidity are expected to be borderline critical. Will continue to monitor the forecast for potential critical additions, especially if forecast guidance is drier or lee cyclogenesis is stronger, both of which would likely increase the likelihood of critical fire weather conditions. ...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 0143 PM CDT Thu Sep 19 2019 Valid 201200Z - 211200Z The ongoing forecast for elevated fire weather conditions across the Four Corners Region and portions of the central Rockies and central High Plains on Friday generally remains on track (see previous discussion below). Overall, the highest confidence/greatest model agreement for overlapping strong winds and low RH extends from northeastern Arizona into the Four Corners Region. In contrast, there is less confidence in meeting elevated conditions across eastern Colorado, owing to uncertainty in lee cyclogenesis location/strength/evolution. Given these considerations, only minor changes were made to the areal extent of the elevated delineation in this update. ..Jirak.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1247 AM CDT Thu Sep 19 2019/ ...Synopsis... The mid-level trough from Day1/Thursday will shift east on Friday which will increase fire weather concerns in portions of the central Rockies and the central High Plains. Deep mixing will strengthen surface winds across much of this region with wind speeds of 20 to 30 mph expected. Relative humidity will vary across the area from around 15 percent up to 30 percent. Locally critical fire weather conditions are possible within the broader elevated delineation, but the highest likelihood of critical conditions remains ambiguous at this time. Winds are expected to be strongest in Wyoming where relative humidity will be the highest, and lightest in eastern Utah where relative humidity will be the lowest. In eastern Colorado, both winds and relative humidity are expected to be borderline critical. Will continue to monitor the forecast for potential critical additions, especially if forecast guidance is drier or lee cyclogenesis is stronger, both of which would likely increase the likelihood of critical fire weather conditions. ...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 0143 PM CDT Thu Sep 19 2019 Valid 201200Z - 211200Z The ongoing forecast for elevated fire weather conditions across the Four Corners Region and portions of the central Rockies and central High Plains on Friday generally remains on track (see previous discussion below). Overall, the highest confidence/greatest model agreement for overlapping strong winds and low RH extends from northeastern Arizona into the Four Corners Region. In contrast, there is less confidence in meeting elevated conditions across eastern Colorado, owing to uncertainty in lee cyclogenesis location/strength/evolution. Given these considerations, only minor changes were made to the areal extent of the elevated delineation in this update. ..Jirak.. 09/19/2019 .PREV DISCUSSION... /ISSUED 1247 AM CDT Thu Sep 19 2019/ ...Synopsis... The mid-level trough from Day1/Thursday will shift east on Friday which will increase fire weather concerns in portions of the central Rockies and the central High Plains. Deep mixing will strengthen surface winds across much of this region with wind speeds of 20 to 30 mph expected. Relative humidity will vary across the area from around 15 percent up to 30 percent. Locally critical fire weather conditions are possible within the broader elevated delineation, but the highest likelihood of critical conditions remains ambiguous at this time. Winds are expected to be strongest in Wyoming where relative humidity will be the highest, and lightest in eastern Utah where relative humidity will be the lowest. In eastern Colorado, both winds and relative humidity are expected to be borderline critical. Will continue to monitor the forecast for potential critical additions, especially if forecast guidance is drier or lee cyclogenesis is stronger, both of which would likely increase the likelihood of critical fire weather conditions. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 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