Severe Storms

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1111 AM CDT Mon Sep 23 2019 Valid 231630Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF WESTERN ARIZONA... ...SUMMARY... Thunderstorms with very large hail and damaging winds will be possible today across parts of southwest and central Arizona. Storms with a few strong wind gusts will be possible in parts of the Northeast. ...AZ... Morning water vapor loop shows an intense upper trough digging into CA/NV. Midlevel height falls, cooling temperatures aloft, and large scale forcing are overspreading AZ in advance of this system. This should lead to multiple rounds of thunderstorms today and tonight over the region. Morning convection and clouds are reinforcing a baroclinic zone that extends across central AZ. This boundary should be the focus of thunderstorms though the day, with ample CAPE and weak CIN over southern AZ. Vertical shear profiles are sufficient for a few supercell storms capable of very large hail and damaging wind gusts. An isolated tornado cannot be ruled out. ...Northeast... A low-amplitude and progressive shortwave trough is moving across the Great Lakes region today, with an associated cold front approaching western NY/PA. Widespread clouds are present today across much of NY into VT, which should limit daytime heating/destabilization in the area of strongest forcing and convective potential. This is expected to keep the overall severe risk in this area MRGL. Have extended the MRGL risk area farther south in parts of central PA where stronger heating is occurring and at least isolated afternoon thunderstorms are possible. Despite the weak instability throughout the risk area, strong winds aloft and large-scale forcing suggest a risk of gusty/damaging wind gusts in the strongest storms. ..Hart/Bentley.. 09/23/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1111 AM CDT Mon Sep 23 2019 Valid 231630Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF WESTERN ARIZONA... ...SUMMARY... Thunderstorms with very large hail and damaging winds will be possible today across parts of southwest and central Arizona. Storms with a few strong wind gusts will be possible in parts of the Northeast. ...AZ... Morning water vapor loop shows an intense upper trough digging into CA/NV. Midlevel height falls, cooling temperatures aloft, and large scale forcing are overspreading AZ in advance of this system. This should lead to multiple rounds of thunderstorms today and tonight over the region. Morning convection and clouds are reinforcing a baroclinic zone that extends across central AZ. This boundary should be the focus of thunderstorms though the day, with ample CAPE and weak CIN over southern AZ. Vertical shear profiles are sufficient for a few supercell storms capable of very large hail and damaging wind gusts. An isolated tornado cannot be ruled out. ...Northeast... A low-amplitude and progressive shortwave trough is moving across the Great Lakes region today, with an associated cold front approaching western NY/PA. Widespread clouds are present today across much of NY into VT, which should limit daytime heating/destabilization in the area of strongest forcing and convective potential. This is expected to keep the overall severe risk in this area MRGL. Have extended the MRGL risk area farther south in parts of central PA where stronger heating is occurring and at least isolated afternoon thunderstorms are possible. Despite the weak instability throughout the risk area, strong winds aloft and large-scale forcing suggest a risk of gusty/damaging wind gusts in the strongest storms. ..Hart/Bentley.. 09/23/2019 Read more

No watches are valid as of Mon Sep 23 16:19:02 UTC 2019.

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1050 AM CDT Mon Sep 23 2019 Valid 231700Z - 241200Z No changes to the ongoing forecast. Please see the previous discussion for more details. ..Wendt.. 09/23/2019 .PREV DISCUSSION... /ISSUED 0145 AM CDT Mon Sep 23 2019/ ...Synopsis... A strong mid/upper-level trough is forecast to become cutoff from the main flow as it moves from the Great Basin southeastward to the Southwest Desert through tonight. As this occurs, an area of enhanced northerly mid-level flow -- located on the west side of the trough -- will overspread much of California as it shifts southward through the day. ...Northern California... Breezy northerly low-level flow is forecast to develop during the early afternoon across portions of the Sacramento Valley and adjacent Coastal Mountains behind the aforementioned mid-level trough. While sustained surface winds are forecast to generally remain around 10-20 mph (locally greater), wind gusts of 30-40 mph are possible. Elevated to locally critical fire weather conditions are likely as these winds overlap minimum RH values of 15-20% (locally lower) and at least marginally receptive fuels. Poor overnight RH recoveries (15-25%) and lingering breezy/gusty northerly winds should continue to foster elevated to locally critical fire weather conditions late this evening and into tonight across the higher elevations (e.g., > 1 kft) of the North/East Bay Hills, the Diablo Range, and the Northern Coast Mountains. Additionally, gusty northeasterly downslope winds (gusts up to 50 mph) on the western slopes of the Northern Sierra's and adjacent foothills should promote elevated to locally critical fire weather conditions late this evening/tonight amidst poor overnight RH recoveries (around 20-25%). ...Southern California... A dry offshore low-level flow is forecast to increase late tonight over the mountains of Ventura, Los Angeles, and Santa Barbara Counties as the aforementioned area of enhanced mid-level flow overspreads the area. While the timing of the stronger winds and RH reductions remains somewhat uncertain, at least a few hours of elevated to locally critical fire weather conditions are possible late tonight. ...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 1050 AM CDT Mon Sep 23 2019 Valid 231700Z - 241200Z No changes to the ongoing forecast. Please see the previous discussion for more details. ..Wendt.. 09/23/2019 .PREV DISCUSSION... /ISSUED 0145 AM CDT Mon Sep 23 2019/ ...Synopsis... A strong mid/upper-level trough is forecast to become cutoff from the main flow as it moves from the Great Basin southeastward to the Southwest Desert through tonight. As this occurs, an area of enhanced northerly mid-level flow -- located on the west side of the trough -- will overspread much of California as it shifts southward through the day. ...Northern California... Breezy northerly low-level flow is forecast to develop during the early afternoon across portions of the Sacramento Valley and adjacent Coastal Mountains behind the aforementioned mid-level trough. While sustained surface winds are forecast to generally remain around 10-20 mph (locally greater), wind gusts of 30-40 mph are possible. Elevated to locally critical fire weather conditions are likely as these winds overlap minimum RH values of 15-20% (locally lower) and at least marginally receptive fuels. Poor overnight RH recoveries (15-25%) and lingering breezy/gusty northerly winds should continue to foster elevated to locally critical fire weather conditions late this evening and into tonight across the higher elevations (e.g., > 1 kft) of the North/East Bay Hills, the Diablo Range, and the Northern Coast Mountains. Additionally, gusty northeasterly downslope winds (gusts up to 50 mph) on the western slopes of the Northern Sierra's and adjacent foothills should promote elevated to locally critical fire weather conditions late this evening/tonight amidst poor overnight RH recoveries (around 20-25%). ...Southern California... A dry offshore low-level flow is forecast to increase late tonight over the mountains of Ventura, Los Angeles, and Santa Barbara Counties as the aforementioned area of enhanced mid-level flow overspreads the area. While the timing of the stronger winds and RH reductions remains somewhat uncertain, at least a few hours of elevated to locally critical fire weather conditions are possible late tonight. ...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 1050 AM CDT Mon Sep 23 2019 Valid 231700Z - 241200Z No changes to the ongoing forecast. Please see the previous discussion for more details. ..Wendt.. 09/23/2019 .PREV DISCUSSION... /ISSUED 0145 AM CDT Mon Sep 23 2019/ ...Synopsis... A strong mid/upper-level trough is forecast to become cutoff from the main flow as it moves from the Great Basin southeastward to the Southwest Desert through tonight. As this occurs, an area of enhanced northerly mid-level flow -- located on the west side of the trough -- will overspread much of California as it shifts southward through the day. ...Northern California... Breezy northerly low-level flow is forecast to develop during the early afternoon across portions of the Sacramento Valley and adjacent Coastal Mountains behind the aforementioned mid-level trough. While sustained surface winds are forecast to generally remain around 10-20 mph (locally greater), wind gusts of 30-40 mph are possible. Elevated to locally critical fire weather conditions are likely as these winds overlap minimum RH values of 15-20% (locally lower) and at least marginally receptive fuels. Poor overnight RH recoveries (15-25%) and lingering breezy/gusty northerly winds should continue to foster elevated to locally critical fire weather conditions late this evening and into tonight across the higher elevations (e.g., > 1 kft) of the North/East Bay Hills, the Diablo Range, and the Northern Coast Mountains. Additionally, gusty northeasterly downslope winds (gusts up to 50 mph) on the western slopes of the Northern Sierra's and adjacent foothills should promote elevated to locally critical fire weather conditions late this evening/tonight amidst poor overnight RH recoveries (around 20-25%). ...Southern California... A dry offshore low-level flow is forecast to increase late tonight over the mountains of Ventura, Los Angeles, and Santa Barbara Counties as the aforementioned area of enhanced mid-level flow overspreads the area. While the timing of the stronger winds and RH reductions remains somewhat uncertain, at least a few hours of elevated to locally critical fire weather conditions are possible late tonight. ...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 1050 AM CDT Mon Sep 23 2019 Valid 231700Z - 241200Z No changes to the ongoing forecast. Please see the previous discussion for more details. ..Wendt.. 09/23/2019 .PREV DISCUSSION... /ISSUED 0145 AM CDT Mon Sep 23 2019/ ...Synopsis... A strong mid/upper-level trough is forecast to become cutoff from the main flow as it moves from the Great Basin southeastward to the Southwest Desert through tonight. As this occurs, an area of enhanced northerly mid-level flow -- located on the west side of the trough -- will overspread much of California as it shifts southward through the day. ...Northern California... Breezy northerly low-level flow is forecast to develop during the early afternoon across portions of the Sacramento Valley and adjacent Coastal Mountains behind the aforementioned mid-level trough. While sustained surface winds are forecast to generally remain around 10-20 mph (locally greater), wind gusts of 30-40 mph are possible. Elevated to locally critical fire weather conditions are likely as these winds overlap minimum RH values of 15-20% (locally lower) and at least marginally receptive fuels. Poor overnight RH recoveries (15-25%) and lingering breezy/gusty northerly winds should continue to foster elevated to locally critical fire weather conditions late this evening and into tonight across the higher elevations (e.g., > 1 kft) of the North/East Bay Hills, the Diablo Range, and the Northern Coast Mountains. Additionally, gusty northeasterly downslope winds (gusts up to 50 mph) on the western slopes of the Northern Sierra's and adjacent foothills should promote elevated to locally critical fire weather conditions late this evening/tonight amidst poor overnight RH recoveries (around 20-25%). ...Southern California... A dry offshore low-level flow is forecast to increase late tonight over the mountains of Ventura, Los Angeles, and Santa Barbara Counties as the aforementioned area of enhanced mid-level flow overspreads the area. While the timing of the stronger winds and RH reductions remains somewhat uncertain, at least a few hours of elevated to locally critical fire weather conditions are possible late tonight. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2001 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR SOUTHWEST/SOUTH-CENTRAL AZ
Mesoscale Discussion 2001 NWS Storm Prediction Center Norman OK 0959 AM CDT Mon Sep 23 2019 Areas affected...Southwest/South-Central AZ Concerning...Severe potential...Watch likely Valid 231459Z - 231700Z Probability of Watch Issuance...80 percent SUMMARY...Multiple rounds of thunderstorms are expected across southwest/south-central AZ today, including supercells. Primary threat is large hail but strong wind gusts and an isolated tornado are also possible. A watch will likely be needed over the next few hours. DISCUSSION...12Z Yuma (1Y7) sounding sampled an usually moist air mass across the region, with a surface dewpoint of 70 deg F and a PW value of 1.86 inches. This area of ample low-level moisture extends throughout much of the Lower AZ Desert, with surface dewpoints in the 70s southwest of the Mogollon Rim. Warm surface temperatures coupled with this ample low-level moisture and relatively cool temperatures aloft result in an air mass already characterized by little to no convective inhibition and moderate buoyancy (i.e. 1500-2000 J/kg of MLCAPE). In addition to this buoyancy, the shortwave trough digging southward into southern CA has promoted increased mid-level flow, resulting in strong deep-layer vertical shear across much of the region. Recent mesoanalysis estimated effective bulk shear is currently 40-50 kt. This thermodynamic environment coupled with ascent from the approaching shortwave trough will result in widespread thunderstorms across the region. Multiple rounds of storms are anticipated. Additionally, the strong vertical shear in place is expected to promote severe thunderstorm development, some of which could produce very large hail (i.e. greater than 2" in diameter). Strong wind gusts and a tornado or two are also possible. Convective trends will be monitored closely for likely watch issuance over the next few hours. ..Mosier/Hart.. 09/23/2019 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...TWC...FGZ...PSR...VEF... LAT...LON 33641483 34291432 34641336 34481126 33201076 31881089 31641202 32431468 33641483 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Mon Sep 23 2019 Valid 231300Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THROUGH LATE EVENING ACROSS A SMALL PART OF SOUTHWEST AZ... ...SUMMARY... Thunderstorms with very large hail and damaging winds will be possible today across parts of southwest and central Arizona. Storms with a few strong wind gusts will be possible in parts of the Northeast. ...AZ through tonight... A transition season severe weather episode is expected today into tonight across AZ. A midlevel shortwave trough over northwest NV this morning will dig south-southeastward toward the lower CO River valley and evolve into a closed low by Tuesday morning. Low-level mass response to the approaching midlevel trough will result in northward transport of moisture from southwest/south central AZ to the rim through the day. Some slightly elevated convection is ongoing along the north edge of the returning moisture, and this convection may persist through the morning and pose a marginal hail threat. The background environment will become favorable for additional thunderstorms through the day as ascent and midlevel cooling develop southeastward into AZ. Daytime heating across southwest AZ will support surface-based thunderstorm development by late morning (17-18z) along a pseudo-dryline near the CO River, and storms will spread eastward near the rim through the afternoon and into this evening. Surface dewpoints have increased to 70-76 F across southwest AZ with a moisture surge from the Gulf of CA. After accounting for some daytime heating/mixing, boundary-layer dewpoints of 65-70 F beneath midlevel lapse rates near 7 C/km will result in MLCAPE of 1500-2500 J/kg and minimal convective inhibition. Effective bulk shear of 40-50 kt and relatively long/straight hodographs will favor splitting supercells capable of producing isolated very large hail near 2 inches in diameter, and there is some potential for clustering of hail events west of Phoenix this afternoon. The stronger supercells, as well as eventual upscale growth into small clusters, will pose a threat for damaging winds. Otherwise, an isolated tornado cannot be ruled out, but this threat will be secondary given relatively weak low-level flow/shear. Convection should persist into the overnight hours, with at least a low-end threat for hail/wind continuing. ...NY and vicinity this afternoon/evening... A midlevel shortwave trough and associated surface cold front will move eastward across NY by late afternoon into early tonight. Clouds and poor lapse rates in the pre-frontal warm sector will limit buoyancy, with MLCAPE likely to remain near 500 J/kg. Still, an increase in midlevel flow with the approach of the shortwave trough could support isolated strong gusts with downward momentum transfer in convection near the front this afternoon/evening. ..Thompson/Leitman.. 09/23/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Mon Sep 23 2019 Valid 231300Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THROUGH LATE EVENING ACROSS A SMALL PART OF SOUTHWEST AZ... ...SUMMARY... Thunderstorms with very large hail and damaging winds will be possible today across parts of southwest and central Arizona. Storms with a few strong wind gusts will be possible in parts of the Northeast. ...AZ through tonight... A transition season severe weather episode is expected today into tonight across AZ. A midlevel shortwave trough over northwest NV this morning will dig south-southeastward toward the lower CO River valley and evolve into a closed low by Tuesday morning. Low-level mass response to the approaching midlevel trough will result in northward transport of moisture from southwest/south central AZ to the rim through the day. Some slightly elevated convection is ongoing along the north edge of the returning moisture, and this convection may persist through the morning and pose a marginal hail threat. The background environment will become favorable for additional thunderstorms through the day as ascent and midlevel cooling develop southeastward into AZ. Daytime heating across southwest AZ will support surface-based thunderstorm development by late morning (17-18z) along a pseudo-dryline near the CO River, and storms will spread eastward near the rim through the afternoon and into this evening. Surface dewpoints have increased to 70-76 F across southwest AZ with a moisture surge from the Gulf of CA. After accounting for some daytime heating/mixing, boundary-layer dewpoints of 65-70 F beneath midlevel lapse rates near 7 C/km will result in MLCAPE of 1500-2500 J/kg and minimal convective inhibition. Effective bulk shear of 40-50 kt and relatively long/straight hodographs will favor splitting supercells capable of producing isolated very large hail near 2 inches in diameter, and there is some potential for clustering of hail events west of Phoenix this afternoon. The stronger supercells, as well as eventual upscale growth into small clusters, will pose a threat for damaging winds. Otherwise, an isolated tornado cannot be ruled out, but this threat will be secondary given relatively weak low-level flow/shear. Convection should persist into the overnight hours, with at least a low-end threat for hail/wind continuing. ...NY and vicinity this afternoon/evening... A midlevel shortwave trough and associated surface cold front will move eastward across NY by late afternoon into early tonight. Clouds and poor lapse rates in the pre-frontal warm sector will limit buoyancy, with MLCAPE likely to remain near 500 J/kg. Still, an increase in midlevel flow with the approach of the shortwave trough could support isolated strong gusts with downward momentum transfer in convection near the front this afternoon/evening. ..Thompson/Leitman.. 09/23/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Mon Sep 23 2019 Valid 231300Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THROUGH LATE EVENING ACROSS A SMALL PART OF SOUTHWEST AZ... ...SUMMARY... Thunderstorms with very large hail and damaging winds will be possible today across parts of southwest and central Arizona. Storms with a few strong wind gusts will be possible in parts of the Northeast. ...AZ through tonight... A transition season severe weather episode is expected today into tonight across AZ. A midlevel shortwave trough over northwest NV this morning will dig south-southeastward toward the lower CO River valley and evolve into a closed low by Tuesday morning. Low-level mass response to the approaching midlevel trough will result in northward transport of moisture from southwest/south central AZ to the rim through the day. Some slightly elevated convection is ongoing along the north edge of the returning moisture, and this convection may persist through the morning and pose a marginal hail threat. The background environment will become favorable for additional thunderstorms through the day as ascent and midlevel cooling develop southeastward into AZ. Daytime heating across southwest AZ will support surface-based thunderstorm development by late morning (17-18z) along a pseudo-dryline near the CO River, and storms will spread eastward near the rim through the afternoon and into this evening. Surface dewpoints have increased to 70-76 F across southwest AZ with a moisture surge from the Gulf of CA. After accounting for some daytime heating/mixing, boundary-layer dewpoints of 65-70 F beneath midlevel lapse rates near 7 C/km will result in MLCAPE of 1500-2500 J/kg and minimal convective inhibition. Effective bulk shear of 40-50 kt and relatively long/straight hodographs will favor splitting supercells capable of producing isolated very large hail near 2 inches in diameter, and there is some potential for clustering of hail events west of Phoenix this afternoon. The stronger supercells, as well as eventual upscale growth into small clusters, will pose a threat for damaging winds. Otherwise, an isolated tornado cannot be ruled out, but this threat will be secondary given relatively weak low-level flow/shear. Convection should persist into the overnight hours, with at least a low-end threat for hail/wind continuing. ...NY and vicinity this afternoon/evening... A midlevel shortwave trough and associated surface cold front will move eastward across NY by late afternoon into early tonight. Clouds and poor lapse rates in the pre-frontal warm sector will limit buoyancy, with MLCAPE likely to remain near 500 J/kg. Still, an increase in midlevel flow with the approach of the shortwave trough could support isolated strong gusts with downward momentum transfer in convection near the front this afternoon/evening. ..Thompson/Leitman.. 09/23/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Mon Sep 23 2019 Valid 231300Z - 241200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THROUGH LATE EVENING ACROSS A SMALL PART OF SOUTHWEST AZ... ...SUMMARY... Thunderstorms with very large hail and damaging winds will be possible today across parts of southwest and central Arizona. Storms with a few strong wind gusts will be possible in parts of the Northeast. ...AZ through tonight... A transition season severe weather episode is expected today into tonight across AZ. A midlevel shortwave trough over northwest NV this morning will dig south-southeastward toward the lower CO River valley and evolve into a closed low by Tuesday morning. Low-level mass response to the approaching midlevel trough will result in northward transport of moisture from southwest/south central AZ to the rim through the day. Some slightly elevated convection is ongoing along the north edge of the returning moisture, and this convection may persist through the morning and pose a marginal hail threat. The background environment will become favorable for additional thunderstorms through the day as ascent and midlevel cooling develop southeastward into AZ. Daytime heating across southwest AZ will support surface-based thunderstorm development by late morning (17-18z) along a pseudo-dryline near the CO River, and storms will spread eastward near the rim through the afternoon and into this evening. Surface dewpoints have increased to 70-76 F across southwest AZ with a moisture surge from the Gulf of CA. After accounting for some daytime heating/mixing, boundary-layer dewpoints of 65-70 F beneath midlevel lapse rates near 7 C/km will result in MLCAPE of 1500-2500 J/kg and minimal convective inhibition. Effective bulk shear of 40-50 kt and relatively long/straight hodographs will favor splitting supercells capable of producing isolated very large hail near 2 inches in diameter, and there is some potential for clustering of hail events west of Phoenix this afternoon. The stronger supercells, as well as eventual upscale growth into small clusters, will pose a threat for damaging winds. Otherwise, an isolated tornado cannot be ruled out, but this threat will be secondary given relatively weak low-level flow/shear. Convection should persist into the overnight hours, with at least a low-end threat for hail/wind continuing. ...NY and vicinity this afternoon/evening... A midlevel shortwave trough and associated surface cold front will move eastward across NY by late afternoon into early tonight. Clouds and poor lapse rates in the pre-frontal warm sector will limit buoyancy, with MLCAPE likely to remain near 500 J/kg. Still, an increase in midlevel flow with the approach of the shortwave trough could support isolated strong gusts with downward momentum transfer in convection near the front this afternoon/evening. ..Thompson/Leitman.. 09/23/2019 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0343 AM CDT Mon Sep 23 2019 Valid 261200Z - 011200Z ...DISCUSSION... For the D4-D6 period, thunderstorms will be concentrated from the mid MO Valley to the upper MS Valley, as the flow regime becomes more zonal across the northern tier of states. These storms will mainly be driven by warm advection, except on D6 when the southwestern low finally ejects east across the Plains. In all cases, the severe threat appears marginal for mainly wind. For the D7 and D8 period, a large upper trough is forecast to amplify over the West, with increasing southwest winds aloft gradually overspreading the central and northern Plains. Low-level moisture will be in place over much of the Plains, due to an expansive 30-50 kt southerly low-level jet. If this scenario occurs, severe storms will be likely across the northern Plains. Given the positive-tilt to the upper trough, storms would likely be focused along a cold front, with orientation suggesting damaging winds the main threat. At this time predictability is too low to demarcate the greatest threat area, but severe probabilities may be required in later outlooks as the event become more predictable. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0343 AM CDT Mon Sep 23 2019 Valid 261200Z - 011200Z ...DISCUSSION... For the D4-D6 period, thunderstorms will be concentrated from the mid MO Valley to the upper MS Valley, as the flow regime becomes more zonal across the northern tier of states. These storms will mainly be driven by warm advection, except on D6 when the southwestern low finally ejects east across the Plains. In all cases, the severe threat appears marginal for mainly wind. For the D7 and D8 period, a large upper trough is forecast to amplify over the West, with increasing southwest winds aloft gradually overspreading the central and northern Plains. Low-level moisture will be in place over much of the Plains, due to an expansive 30-50 kt southerly low-level jet. If this scenario occurs, severe storms will be likely across the northern Plains. Given the positive-tilt to the upper trough, storms would likely be focused along a cold front, with orientation suggesting damaging winds the main threat. At this time predictability is too low to demarcate the greatest threat area, but severe probabilities may be required in later outlooks as the event become more predictable. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0343 AM CDT Mon Sep 23 2019 Valid 261200Z - 011200Z ...DISCUSSION... For the D4-D6 period, thunderstorms will be concentrated from the mid MO Valley to the upper MS Valley, as the flow regime becomes more zonal across the northern tier of states. These storms will mainly be driven by warm advection, except on D6 when the southwestern low finally ejects east across the Plains. In all cases, the severe threat appears marginal for mainly wind. For the D7 and D8 period, a large upper trough is forecast to amplify over the West, with increasing southwest winds aloft gradually overspreading the central and northern Plains. Low-level moisture will be in place over much of the Plains, due to an expansive 30-50 kt southerly low-level jet. If this scenario occurs, severe storms will be likely across the northern Plains. Given the positive-tilt to the upper trough, storms would likely be focused along a cold front, with orientation suggesting damaging winds the main threat. At this time predictability is too low to demarcate the greatest threat area, but severe probabilities may be required in later outlooks as the event become more predictable. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0208 AM CDT Mon Sep 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS... ...SUMMARY... A few strong storms are possible over parts of southern Kansas/Missouri, and northern Oklahoma/Arkansas on Wednesday. ...Synopsis... A strong upper jet will develop east across the Great lakes, with the upper trough taking on a negative tilt as it approaches the Northeast overnight. High pressure will build eastward across the northern Plains and Midwest, with a cold front becoming east-west oriented from KS to the OH River. South of the stalled front, a moist and unstable air mass will exist across the central Plains with mid to upper 60s F dewpoints. Farther east along the front, little if any instability will be present to support more than general thunderstorms from the OH Valley into the Great Lakes. Elsewhere, an upper low will remain over the Southwest, and will support sporadic thunderstorms through the period. ...KS/OK/MO/AR... Convergence near the front or any outflow boundaries from antecedent storms will provide a focus for daytime storms. Although moderately unstable, this zone will be just south of the stronger winds aloft, thus effective shear will not be strong, but perhaps sufficient for a few southeastward-moving clusters of storms capable of marginal hail and wind. ...AZ... An upper low will remain over the northern Gulf of CA, drifting slowly north Wednesday night. While cool temperatures aloft will remain with this system, several days of rain and storms will likely reduce overall lapse rates and instability. Several hundred J/kg MUCAPE and daytime heating will likely lead to scattered storms, but the severe threat appears low at this time. However, strong wind gusts or small hail are possible. ..Jewell.. 09/23/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0208 AM CDT Mon Sep 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS... ...SUMMARY... A few strong storms are possible over parts of southern Kansas/Missouri, and northern Oklahoma/Arkansas on Wednesday. ...Synopsis... A strong upper jet will develop east across the Great lakes, with the upper trough taking on a negative tilt as it approaches the Northeast overnight. High pressure will build eastward across the northern Plains and Midwest, with a cold front becoming east-west oriented from KS to the OH River. South of the stalled front, a moist and unstable air mass will exist across the central Plains with mid to upper 60s F dewpoints. Farther east along the front, little if any instability will be present to support more than general thunderstorms from the OH Valley into the Great Lakes. Elsewhere, an upper low will remain over the Southwest, and will support sporadic thunderstorms through the period. ...KS/OK/MO/AR... Convergence near the front or any outflow boundaries from antecedent storms will provide a focus for daytime storms. Although moderately unstable, this zone will be just south of the stronger winds aloft, thus effective shear will not be strong, but perhaps sufficient for a few southeastward-moving clusters of storms capable of marginal hail and wind. ...AZ... An upper low will remain over the northern Gulf of CA, drifting slowly north Wednesday night. While cool temperatures aloft will remain with this system, several days of rain and storms will likely reduce overall lapse rates and instability. Several hundred J/kg MUCAPE and daytime heating will likely lead to scattered storms, but the severe threat appears low at this time. However, strong wind gusts or small hail are possible. ..Jewell.. 09/23/2019 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0208 AM CDT Mon Sep 23 2019 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS... ...SUMMARY... A few strong storms are possible over parts of southern Kansas/Missouri, and northern Oklahoma/Arkansas on Wednesday. ...Synopsis... A strong upper jet will develop east across the Great lakes, with the upper trough taking on a negative tilt as it approaches the Northeast overnight. High pressure will build eastward across the northern Plains and Midwest, with a cold front becoming east-west oriented from KS to the OH River. South of the stalled front, a moist and unstable air mass will exist across the central Plains with mid to upper 60s F dewpoints. Farther east along the front, little if any instability will be present to support more than general thunderstorms from the OH Valley into the Great Lakes. Elsewhere, an upper low will remain over the Southwest, and will support sporadic thunderstorms through the period. ...KS/OK/MO/AR... Convergence near the front or any outflow boundaries from antecedent storms will provide a focus for daytime storms. Although moderately unstable, this zone will be just south of the stronger winds aloft, thus effective shear will not be strong, but perhaps sufficient for a few southeastward-moving clusters of storms capable of marginal hail and wind. ...AZ... An upper low will remain over the northern Gulf of CA, drifting slowly north Wednesday night. While cool temperatures aloft will remain with this system, several days of rain and storms will likely reduce overall lapse rates and instability. Several hundred J/kg MUCAPE and daytime heating will likely lead to scattered storms, but the severe threat appears low at this time. However, strong wind gusts or small hail are possible. ..Jewell.. 09/23/2019 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0147 AM CDT Mon Sep 23 2019 Valid 241200Z - 251200Z ...Synopsis... A closed mid/upper-level low is forecast to gradually shift from the Desert Southwest to Baja California through Day 2/Tuesday. ...Southern California... Pockets of elevated to locally critical fire weather conditions will likely be ongoing early Day 2/Tuesday across the mountains of Ventura, Los Angeles, and Santa Barbara Counties as increasing offshore surface winds overlap areas with poor overnight RH recoveries. While winds are forecast to weaken through the day as upper-level support associated with the aforementioned upper low shifts away from the area, elevated fire weather conditions should remain as RH values continue to decrease. At least locally elevated fire weather conditions are possible into Day 2/Tuesday night as RH recoveries remain poor amidst breezy winds. ...Northern California... Pockets of elevated to locally critical fire weather conditions will likely be ongoing across the higher elevations (e.g., > 1 kft) of the North/East Bay Hills, the Diablo Range, the Northern Coast Mountains, and the western slopes of the Northern Sierra's and adjacent foothills Day 2/Tuesday morning as poor overnight RH recoveries occur in conjunction with gusty surface winds. By afternoon, elevated fire weather conditions should spread to the lower elevations of the Sacramento Valley as sustained surface winds of around 15 mph develop in conjunction with near critical RH values. At least locally elevated fire weather conditions are possible at higher elevations (e.g., > 1 kft) into Day 2/Tuesday night as RH recoveries remain poor amidst breezy winds. ..Elliott.. 09/23/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0147 AM CDT Mon Sep 23 2019 Valid 241200Z - 251200Z ...Synopsis... A closed mid/upper-level low is forecast to gradually shift from the Desert Southwest to Baja California through Day 2/Tuesday. ...Southern California... Pockets of elevated to locally critical fire weather conditions will likely be ongoing early Day 2/Tuesday across the mountains of Ventura, Los Angeles, and Santa Barbara Counties as increasing offshore surface winds overlap areas with poor overnight RH recoveries. While winds are forecast to weaken through the day as upper-level support associated with the aforementioned upper low shifts away from the area, elevated fire weather conditions should remain as RH values continue to decrease. At least locally elevated fire weather conditions are possible into Day 2/Tuesday night as RH recoveries remain poor amidst breezy winds. ...Northern California... Pockets of elevated to locally critical fire weather conditions will likely be ongoing across the higher elevations (e.g., > 1 kft) of the North/East Bay Hills, the Diablo Range, the Northern Coast Mountains, and the western slopes of the Northern Sierra's and adjacent foothills Day 2/Tuesday morning as poor overnight RH recoveries occur in conjunction with gusty surface winds. By afternoon, elevated fire weather conditions should spread to the lower elevations of the Sacramento Valley as sustained surface winds of around 15 mph develop in conjunction with near critical RH values. At least locally elevated fire weather conditions are possible at higher elevations (e.g., > 1 kft) into Day 2/Tuesday night as RH recoveries remain poor amidst breezy winds. ..Elliott.. 09/23/2019 ...Please see www.spc.noaa.gov/fire for graphic product... Read more