Severe Storms

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 PM CDT Sun Sep 15 2019 Valid 160100Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the contiguous U.S. today. ...01z Update... Thunder has been removed from the Midwestern U.S. Earlier thunderstorm activity has diminished with loss of daytime heating and due to a less favorable airmass downstream across the upper OH Valley and central Appalachians. Diurnally driven thunderstorm probabilities have also been removed across AL/GA and portions of TX/LA eastward to the coastal Carolinas/southeast VA. Isolated storms will continue to be possible along the TX/LA coastal vicinity as a broad area of low pressure continues to shift westward across the Gulf of Mexico. Isolated thunderstorms also are possible across parts of southern/central FL and the FL east coast as Tropical Storm Humberto continue to pivot north/northeast tonight well offshore of the southeastern U.S. coast. Thunderstorm activity will persist a few more hours across parts of AZ/NM and vicinity as a weak mid/upper low lifts northeast across the region. Finally, a few thunderstorms are possible overnight along the WA/OR coast as a shortwave trough moves toward the Pacific coast. ..Leitman.. 09/16/2019 Read more

No watches are valid as of Sun Sep 15 22:29:01 UTC 2019.

No Mesoscale Discussions are in effect as of Sun Sep 15 22:29:01 UTC 2019.

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0250 PM CDT Sun Sep 15 2019 Valid 152000Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the contiguous U.S. today. ...Discussion... Primary change to current outlook has been to trim general thunderstorm area over the Great Lakes and OH Valley. In wake of shortwave trough, forcing for ascent will be limited to weak convergence and weak warm advection along and in advance of a southeast-moving cold front the remainder of the period. As a result, coverage of any additional thunderstorms is expected to be sparse. ..Dial.. 09/15/2019 .PREV DISCUSSION... /ISSUED 1052 AM CDT Sun Sep 15 2019/ ...Far southeast AZ and southwest NM... A couple stronger storms are possible near the southeast AZ/southwest NM/international border area to the south of a low-amplitude shortwave impulse slowly moving from the Mogollon Rim to the southern Rockies. Pockets of greater insolation should be confined to the international border with abundant cloud coverage/remnant stratiform rain farther north closer to the shortwave impulse. Scattered thunderstorms will develop later this afternoon as destabilization occurs within the cloud breaks. Moderate buoyancy with MLCAPE of 1000-1500 J/kg in conjunction with effective shear around 25 kt may support a couple updrafts possessing weak/transient mid-level rotation. Amid modest mid-level lapse rates, this setup would most likely yield small hail and locally strong gusts. Overall threat appears too limited to warrant a severe risk area. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0250 PM CDT Sun Sep 15 2019 Valid 152000Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the contiguous U.S. today. ...Discussion... Primary change to current outlook has been to trim general thunderstorm area over the Great Lakes and OH Valley. In wake of shortwave trough, forcing for ascent will be limited to weak convergence and weak warm advection along and in advance of a southeast-moving cold front the remainder of the period. As a result, coverage of any additional thunderstorms is expected to be sparse. ..Dial.. 09/15/2019 .PREV DISCUSSION... /ISSUED 1052 AM CDT Sun Sep 15 2019/ ...Far southeast AZ and southwest NM... A couple stronger storms are possible near the southeast AZ/southwest NM/international border area to the south of a low-amplitude shortwave impulse slowly moving from the Mogollon Rim to the southern Rockies. Pockets of greater insolation should be confined to the international border with abundant cloud coverage/remnant stratiform rain farther north closer to the shortwave impulse. Scattered thunderstorms will develop later this afternoon as destabilization occurs within the cloud breaks. Moderate buoyancy with MLCAPE of 1000-1500 J/kg in conjunction with effective shear around 25 kt may support a couple updrafts possessing weak/transient mid-level rotation. Amid modest mid-level lapse rates, this setup would most likely yield small hail and locally strong gusts. Overall threat appears too limited to warrant a severe risk area. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0250 PM CDT Sun Sep 15 2019 Valid 152000Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the contiguous U.S. today. ...Discussion... Primary change to current outlook has been to trim general thunderstorm area over the Great Lakes and OH Valley. In wake of shortwave trough, forcing for ascent will be limited to weak convergence and weak warm advection along and in advance of a southeast-moving cold front the remainder of the period. As a result, coverage of any additional thunderstorms is expected to be sparse. ..Dial.. 09/15/2019 .PREV DISCUSSION... /ISSUED 1052 AM CDT Sun Sep 15 2019/ ...Far southeast AZ and southwest NM... A couple stronger storms are possible near the southeast AZ/southwest NM/international border area to the south of a low-amplitude shortwave impulse slowly moving from the Mogollon Rim to the southern Rockies. Pockets of greater insolation should be confined to the international border with abundant cloud coverage/remnant stratiform rain farther north closer to the shortwave impulse. Scattered thunderstorms will develop later this afternoon as destabilization occurs within the cloud breaks. Moderate buoyancy with MLCAPE of 1000-1500 J/kg in conjunction with effective shear around 25 kt may support a couple updrafts possessing weak/transient mid-level rotation. Amid modest mid-level lapse rates, this setup would most likely yield small hail and locally strong gusts. Overall threat appears too limited to warrant a severe risk area. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0214 PM CDT Sun Sep 15 2019 Valid 161200Z - 171200Z ...CRITICAL FIRE WEATHER AREA FOR MUCH OF NV...WESTERN UT...EXTREME NORTHWEST AZ... ...Southern California: Wind/RH... The primary change with this forecast update was to extend the Elevated fire weather area farther westward into the mountains of Los Angeles and Ventura counties and southward along/near the coastal ranges east of San Diego. While low-level flow will be onshore across these areas, RH values are forecast to remain reduced at higher elevations, with minimum values of 10-20% amidst sustained surface winds of 15-20 mph. Elevated (to locally critical) fire weather conditions may also continue overnight due to poor overnight RH recoveries and lingering gusty winds. ...Central/Eastern Utah: Dry Thunderstorms... Forecast soundings across portions of central/eastern Utah tomorrow afternoon suggest a potential for relatively high-based thunderstorms with fast storm motions. While precipitable water values are forecast to be somewhat marginal for isolated dry thunderstorms (e.g., 0.75"+), the fast storm motions and relatively dry fuels may be enough to compensate and allow for lightning ignitions -- especially on the periphery of storm cores. While a dry thunderstorm area was withheld with this outlook due to uncertainties regarding thunderstorm coverage, one may be needed in future outlooks. Otherwise, the forecast remains on track, with only minor changes needed based on the latest ensemble forecast guidance. Please see the previous discussion below for more information on tomorrow's fire weather forecast. ..Elliott.. 09/15/2019 .PREV DISCUSSION... /ISSUED 0113 AM CDT Sun Sep 15 2019/ ...Synopsis... A strong upper trough is forecast to move across the Great Basin into portions of the Intermountain West from Monday into Monday night. In conjunction with this trough, a cold front will sweep across portions of the interior Northwest and Great Basin. ...Great Basin and vicinity... A broad area of elevated to critical conditions is again expected over portions of the Great Basin and vicinity on Monday, with the area of greatest threat shifted eastward compared to D1/Sunday. Poor overnight RH recovery into Monday morning may allow critical conditions to develop early in the day ahead of the cold front. Critical conditions will become widespread across much of NV into portions of western UT and perhaps northwest AZ by the afternoon, as sustained winds increase to 20-30 mph and RH values drop below 15%. The northwestern extent of critical conditions will be determined by the timing of the cold front. Some areas northwest of the current critical delineation may see at least brief critical conditions before the front passes. An abrupt wind shift will accompany the front, which will impact the behavior of any ongoing fires, though RH values should rise fairly quickly in the wake of the front. The eastern portion of the critical area, where the front is not expected until Monday night, will see poor RH recovery during the evening and a more prolonged period of critical 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 0214 PM CDT Sun Sep 15 2019 Valid 161200Z - 171200Z ...CRITICAL FIRE WEATHER AREA FOR MUCH OF NV...WESTERN UT...EXTREME NORTHWEST AZ... ...Southern California: Wind/RH... The primary change with this forecast update was to extend the Elevated fire weather area farther westward into the mountains of Los Angeles and Ventura counties and southward along/near the coastal ranges east of San Diego. While low-level flow will be onshore across these areas, RH values are forecast to remain reduced at higher elevations, with minimum values of 10-20% amidst sustained surface winds of 15-20 mph. Elevated (to locally critical) fire weather conditions may also continue overnight due to poor overnight RH recoveries and lingering gusty winds. ...Central/Eastern Utah: Dry Thunderstorms... Forecast soundings across portions of central/eastern Utah tomorrow afternoon suggest a potential for relatively high-based thunderstorms with fast storm motions. While precipitable water values are forecast to be somewhat marginal for isolated dry thunderstorms (e.g., 0.75"+), the fast storm motions and relatively dry fuels may be enough to compensate and allow for lightning ignitions -- especially on the periphery of storm cores. While a dry thunderstorm area was withheld with this outlook due to uncertainties regarding thunderstorm coverage, one may be needed in future outlooks. Otherwise, the forecast remains on track, with only minor changes needed based on the latest ensemble forecast guidance. Please see the previous discussion below for more information on tomorrow's fire weather forecast. ..Elliott.. 09/15/2019 .PREV DISCUSSION... /ISSUED 0113 AM CDT Sun Sep 15 2019/ ...Synopsis... A strong upper trough is forecast to move across the Great Basin into portions of the Intermountain West from Monday into Monday night. In conjunction with this trough, a cold front will sweep across portions of the interior Northwest and Great Basin. ...Great Basin and vicinity... A broad area of elevated to critical conditions is again expected over portions of the Great Basin and vicinity on Monday, with the area of greatest threat shifted eastward compared to D1/Sunday. Poor overnight RH recovery into Monday morning may allow critical conditions to develop early in the day ahead of the cold front. Critical conditions will become widespread across much of NV into portions of western UT and perhaps northwest AZ by the afternoon, as sustained winds increase to 20-30 mph and RH values drop below 15%. The northwestern extent of critical conditions will be determined by the timing of the cold front. Some areas northwest of the current critical delineation may see at least brief critical conditions before the front passes. An abrupt wind shift will accompany the front, which will impact the behavior of any ongoing fires, though RH values should rise fairly quickly in the wake of the front. The eastern portion of the critical area, where the front is not expected until Monday night, will see poor RH recovery during the evening and a more prolonged period of critical 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 0214 PM CDT Sun Sep 15 2019 Valid 161200Z - 171200Z ...CRITICAL FIRE WEATHER AREA FOR MUCH OF NV...WESTERN UT...EXTREME NORTHWEST AZ... ...Southern California: Wind/RH... The primary change with this forecast update was to extend the Elevated fire weather area farther westward into the mountains of Los Angeles and Ventura counties and southward along/near the coastal ranges east of San Diego. While low-level flow will be onshore across these areas, RH values are forecast to remain reduced at higher elevations, with minimum values of 10-20% amidst sustained surface winds of 15-20 mph. Elevated (to locally critical) fire weather conditions may also continue overnight due to poor overnight RH recoveries and lingering gusty winds. ...Central/Eastern Utah: Dry Thunderstorms... Forecast soundings across portions of central/eastern Utah tomorrow afternoon suggest a potential for relatively high-based thunderstorms with fast storm motions. While precipitable water values are forecast to be somewhat marginal for isolated dry thunderstorms (e.g., 0.75"+), the fast storm motions and relatively dry fuels may be enough to compensate and allow for lightning ignitions -- especially on the periphery of storm cores. While a dry thunderstorm area was withheld with this outlook due to uncertainties regarding thunderstorm coverage, one may be needed in future outlooks. Otherwise, the forecast remains on track, with only minor changes needed based on the latest ensemble forecast guidance. Please see the previous discussion below for more information on tomorrow's fire weather forecast. ..Elliott.. 09/15/2019 .PREV DISCUSSION... /ISSUED 0113 AM CDT Sun Sep 15 2019/ ...Synopsis... A strong upper trough is forecast to move across the Great Basin into portions of the Intermountain West from Monday into Monday night. In conjunction with this trough, a cold front will sweep across portions of the interior Northwest and Great Basin. ...Great Basin and vicinity... A broad area of elevated to critical conditions is again expected over portions of the Great Basin and vicinity on Monday, with the area of greatest threat shifted eastward compared to D1/Sunday. Poor overnight RH recovery into Monday morning may allow critical conditions to develop early in the day ahead of the cold front. Critical conditions will become widespread across much of NV into portions of western UT and perhaps northwest AZ by the afternoon, as sustained winds increase to 20-30 mph and RH values drop below 15%. The northwestern extent of critical conditions will be determined by the timing of the cold front. Some areas northwest of the current critical delineation may see at least brief critical conditions before the front passes. An abrupt wind shift will accompany the front, which will impact the behavior of any ongoing fires, though RH values should rise fairly quickly in the wake of the front. The eastern portion of the critical area, where the front is not expected until Monday night, will see poor RH recovery during the evening and a more prolonged period of critical 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 1226 PM CDT Sun Sep 15 2019 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE GREAT BASIN... ...SUMMARY... A few thunderstorms with locally strong wind gusts may impact portions of the Great Basin Monday afternoon and night. ...Great Basin region... An amplifying upper trough currently over the eastern Pacific will move through the Great Basin region Monday afternoon and Monday night. This feature will be accompanied by a strong cold front that should extend from eastern OR into northern CA early Monday and from southeast ID through western UT by the end of this period. Primary limiting factor for a more robust severe threat will be limited low-level moisture and instability, with MLCAPE generally less than 500 J/kg. Inverted-V boundary layers will exist in the pre-frontal warm sector across northwestern NV where at least 200-300 J/kg MLCAPE will exist during the afternoon. Storms are expected to develop within frontal zone where strong deep-layer winds accompanying the upper trough will exist. A few of these storms could produce locally strong wind gusts during the afternoon and evening. Additional more isolated storms will be possible over central and eastern UT during the afternoon within corridor of slightly greater moisture and 300-500 J/kg MLCAPE. These storms will reside within 30-35 kt effective bulk shear at least marginally supportive of mid-level updraft rotation. A few locally strong wind gusts and small hail will be possible. Overnight, a band of storms may increase along the front as it intercepts slightly better low-level moisture across UT. This activity will be embedded within strong deep-layer winds, and a dry-sub cloud layer will promote transfer of higher momentum air to the surface. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: 5% - Marginal Hail: <5% - None ..Dial.. 09/15/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1226 PM CDT Sun Sep 15 2019 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE GREAT BASIN... ...SUMMARY... A few thunderstorms with locally strong wind gusts may impact portions of the Great Basin Monday afternoon and night. ...Great Basin region... An amplifying upper trough currently over the eastern Pacific will move through the Great Basin region Monday afternoon and Monday night. This feature will be accompanied by a strong cold front that should extend from eastern OR into northern CA early Monday and from southeast ID through western UT by the end of this period. Primary limiting factor for a more robust severe threat will be limited low-level moisture and instability, with MLCAPE generally less than 500 J/kg. Inverted-V boundary layers will exist in the pre-frontal warm sector across northwestern NV where at least 200-300 J/kg MLCAPE will exist during the afternoon. Storms are expected to develop within frontal zone where strong deep-layer winds accompanying the upper trough will exist. A few of these storms could produce locally strong wind gusts during the afternoon and evening. Additional more isolated storms will be possible over central and eastern UT during the afternoon within corridor of slightly greater moisture and 300-500 J/kg MLCAPE. These storms will reside within 30-35 kt effective bulk shear at least marginally supportive of mid-level updraft rotation. A few locally strong wind gusts and small hail will be possible. Overnight, a band of storms may increase along the front as it intercepts slightly better low-level moisture across UT. This activity will be embedded within strong deep-layer winds, and a dry-sub cloud layer will promote transfer of higher momentum air to the surface. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: 5% - Marginal Hail: <5% - None ..Dial.. 09/15/2019 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1226 PM CDT Sun Sep 15 2019 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION OF THE GREAT BASIN... ...SUMMARY... A few thunderstorms with locally strong wind gusts may impact portions of the Great Basin Monday afternoon and night. ...Great Basin region... An amplifying upper trough currently over the eastern Pacific will move through the Great Basin region Monday afternoon and Monday night. This feature will be accompanied by a strong cold front that should extend from eastern OR into northern CA early Monday and from southeast ID through western UT by the end of this period. Primary limiting factor for a more robust severe threat will be limited low-level moisture and instability, with MLCAPE generally less than 500 J/kg. Inverted-V boundary layers will exist in the pre-frontal warm sector across northwestern NV where at least 200-300 J/kg MLCAPE will exist during the afternoon. Storms are expected to develop within frontal zone where strong deep-layer winds accompanying the upper trough will exist. A few of these storms could produce locally strong wind gusts during the afternoon and evening. Additional more isolated storms will be possible over central and eastern UT during the afternoon within corridor of slightly greater moisture and 300-500 J/kg MLCAPE. These storms will reside within 30-35 kt effective bulk shear at least marginally supportive of mid-level updraft rotation. A few locally strong wind gusts and small hail will be possible. Overnight, a band of storms may increase along the front as it intercepts slightly better low-level moisture across UT. This activity will be embedded within strong deep-layer winds, and a dry-sub cloud layer will promote transfer of higher momentum air to the surface. ...MAXIMUM RISK BY HAZARD... Tornado: <2% - None Wind: 5% - Marginal Hail: <5% - None ..Dial.. 09/15/2019 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1109 AM CDT Sun Sep 15 2019 Valid 151700Z - 161200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST NV...NORTHEAST CA...SOUTHEAST OR...SOUTHWEST ID...... ...CRITICAL FIRE WEATHER AREA FOR CENTRAL/EASTERN NV... Higher-end critical meteorological fire weather conditions are likely this afternoon/evening across portions of far northeast California, far northwest Nevada, and far southeast Oregon. At 12Z, the upstream MFR RAOB sampled southwest winds of around 60 mph near 15 kft along the leading edge of an area of enhanced mid-level flow associated with a vigorous mid/upper-level trough located just offshore. This area of enhanced flow aloft is forecast to overspread far northeast California and vicinity this afternoon/evening and be reasonably well timed with peak heating. Forecast soundings suggest relatively steep low-level lapse rates, which should foster efficient downward mixing of the stronger flow from aloft, with sustained surface winds of 20-30 mph developing by mid/late afternoon (localized gusts 40+ mph). While high-level clouds -- currently observed on satellite imagery -- may temper surface warming somewhat, high temperatures in the mid/upper 70s coupled with a very dry air mass (surface dewpoints in the low teens) will allow for minimum RH values of 8-15%. The higher-end critical conditions are most likely to occur between 2-7 pm PDT. Overall, the forecast remains on track, with only minimal changes needed to reflect the latest observations and ensemble guidance. Please see the discussion below for more information on today's fire weather forecast. ..Elliott.. 09/15/2019 .PREV DISCUSSION... /ISSUED 0112 AM CDT Sun Sep 15 2019/ ...Synopsis... A vigorous upper trough is forecast to amplify and shift eastward across the Pacific Coast into the Great Basin/interior Northwest by Monday morning. At the surface, low pressure will deepen from the northern Great Basin into portions of the northern High Plains, with a surface trough extending southward into the central/southern High Plains. ...Great Basin and vicinity... As low/midlevel flow increases in advance of the strong upper trough, a broad area of elevated to potentially critical fire weather conditions is forecast to develop from the Great Basin and vicinity eastward into portions of southern WY. High-end critical conditions are likely over northwest NV and adjacent portions of northeast CA, southeast OR, and far southwest ID. In this area, sustained winds of 20-30 mph will combine with minimum RH values of 8-15%, with localized areas of extremely critical conditions possible. Another area of critical conditions is forecast over portions of central/eastern NV, where sustained winds of 15-25 mph are forecast in conjunction with minimum RH values of 10-15%. Poor overnight RH recovery is expected across both critical areas, and critical conditions may persist through late tonight in some areas. Elsewhere, critically low RH is expected over the remainder of the elevated area, though slightly weaker winds and/or less receptive fuels preclude any critical upgrade for those regions. Elevated to locally critical wind/RH will also likely develop across portions of eastern ID into southwest MT, but fuels are currently expected to be mostly unreceptive, so no delineation was included for that area. ...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 1109 AM CDT Sun Sep 15 2019 Valid 151700Z - 161200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST NV...NORTHEAST CA...SOUTHEAST OR...SOUTHWEST ID...... ...CRITICAL FIRE WEATHER AREA FOR CENTRAL/EASTERN NV... Higher-end critical meteorological fire weather conditions are likely this afternoon/evening across portions of far northeast California, far northwest Nevada, and far southeast Oregon. At 12Z, the upstream MFR RAOB sampled southwest winds of around 60 mph near 15 kft along the leading edge of an area of enhanced mid-level flow associated with a vigorous mid/upper-level trough located just offshore. This area of enhanced flow aloft is forecast to overspread far northeast California and vicinity this afternoon/evening and be reasonably well timed with peak heating. Forecast soundings suggest relatively steep low-level lapse rates, which should foster efficient downward mixing of the stronger flow from aloft, with sustained surface winds of 20-30 mph developing by mid/late afternoon (localized gusts 40+ mph). While high-level clouds -- currently observed on satellite imagery -- may temper surface warming somewhat, high temperatures in the mid/upper 70s coupled with a very dry air mass (surface dewpoints in the low teens) will allow for minimum RH values of 8-15%. The higher-end critical conditions are most likely to occur between 2-7 pm PDT. Overall, the forecast remains on track, with only minimal changes needed to reflect the latest observations and ensemble guidance. Please see the discussion below for more information on today's fire weather forecast. ..Elliott.. 09/15/2019 .PREV DISCUSSION... /ISSUED 0112 AM CDT Sun Sep 15 2019/ ...Synopsis... A vigorous upper trough is forecast to amplify and shift eastward across the Pacific Coast into the Great Basin/interior Northwest by Monday morning. At the surface, low pressure will deepen from the northern Great Basin into portions of the northern High Plains, with a surface trough extending southward into the central/southern High Plains. ...Great Basin and vicinity... As low/midlevel flow increases in advance of the strong upper trough, a broad area of elevated to potentially critical fire weather conditions is forecast to develop from the Great Basin and vicinity eastward into portions of southern WY. High-end critical conditions are likely over northwest NV and adjacent portions of northeast CA, southeast OR, and far southwest ID. In this area, sustained winds of 20-30 mph will combine with minimum RH values of 8-15%, with localized areas of extremely critical conditions possible. Another area of critical conditions is forecast over portions of central/eastern NV, where sustained winds of 15-25 mph are forecast in conjunction with minimum RH values of 10-15%. Poor overnight RH recovery is expected across both critical areas, and critical conditions may persist through late tonight in some areas. Elsewhere, critically low RH is expected over the remainder of the elevated area, though slightly weaker winds and/or less receptive fuels preclude any critical upgrade for those regions. Elevated to locally critical wind/RH will also likely develop across portions of eastern ID into southwest MT, but fuels are currently expected to be mostly unreceptive, so no delineation was included for that area. ...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 1109 AM CDT Sun Sep 15 2019 Valid 151700Z - 161200Z ...CRITICAL FIRE WEATHER AREA FOR NORTHWEST NV...NORTHEAST CA...SOUTHEAST OR...SOUTHWEST ID...... ...CRITICAL FIRE WEATHER AREA FOR CENTRAL/EASTERN NV... Higher-end critical meteorological fire weather conditions are likely this afternoon/evening across portions of far northeast California, far northwest Nevada, and far southeast Oregon. At 12Z, the upstream MFR RAOB sampled southwest winds of around 60 mph near 15 kft along the leading edge of an area of enhanced mid-level flow associated with a vigorous mid/upper-level trough located just offshore. This area of enhanced flow aloft is forecast to overspread far northeast California and vicinity this afternoon/evening and be reasonably well timed with peak heating. Forecast soundings suggest relatively steep low-level lapse rates, which should foster efficient downward mixing of the stronger flow from aloft, with sustained surface winds of 20-30 mph developing by mid/late afternoon (localized gusts 40+ mph). While high-level clouds -- currently observed on satellite imagery -- may temper surface warming somewhat, high temperatures in the mid/upper 70s coupled with a very dry air mass (surface dewpoints in the low teens) will allow for minimum RH values of 8-15%. The higher-end critical conditions are most likely to occur between 2-7 pm PDT. Overall, the forecast remains on track, with only minimal changes needed to reflect the latest observations and ensemble guidance. Please see the discussion below for more information on today's fire weather forecast. ..Elliott.. 09/15/2019 .PREV DISCUSSION... /ISSUED 0112 AM CDT Sun Sep 15 2019/ ...Synopsis... A vigorous upper trough is forecast to amplify and shift eastward across the Pacific Coast into the Great Basin/interior Northwest by Monday morning. At the surface, low pressure will deepen from the northern Great Basin into portions of the northern High Plains, with a surface trough extending southward into the central/southern High Plains. ...Great Basin and vicinity... As low/midlevel flow increases in advance of the strong upper trough, a broad area of elevated to potentially critical fire weather conditions is forecast to develop from the Great Basin and vicinity eastward into portions of southern WY. High-end critical conditions are likely over northwest NV and adjacent portions of northeast CA, southeast OR, and far southwest ID. In this area, sustained winds of 20-30 mph will combine with minimum RH values of 8-15%, with localized areas of extremely critical conditions possible. Another area of critical conditions is forecast over portions of central/eastern NV, where sustained winds of 15-25 mph are forecast in conjunction with minimum RH values of 10-15%. Poor overnight RH recovery is expected across both critical areas, and critical conditions may persist through late tonight in some areas. Elsewhere, critically low RH is expected over the remainder of the elevated area, though slightly weaker winds and/or less receptive fuels preclude any critical upgrade for those regions. Elevated to locally critical wind/RH will also likely develop across portions of eastern ID into southwest MT, but fuels are currently expected to be mostly unreceptive, so no delineation was included for that area. ...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 1052 AM CDT Sun Sep 15 2019 Valid 151630Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the contiguous U.S. today. ...Far southeast AZ and southwest NM... A couple stronger storms are possible near the southeast AZ/southwest NM/international border area to the south of a low-amplitude shortwave impulse slowly moving from the Mogollon Rim to the southern Rockies. Pockets of greater insolation should be confined to the international border with abundant cloud coverage/remnant stratiform rain farther north closer to the shortwave impulse. Scattered thunderstorms will develop later this afternoon as destabilization occurs within the cloud breaks. Moderate buoyancy with MLCAPE of 1000-1500 J/kg in conjunction with effective shear around 25 kt may support a couple updrafts possessing weak/transient mid-level rotation. Amid modest mid-level lapse rates, this setup would most likely yield small hail and locally strong gusts. Overall threat appears too limited to warrant a severe risk area. ..Grams/Karstens.. 09/15/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1052 AM CDT Sun Sep 15 2019 Valid 151630Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the contiguous U.S. today. ...Far southeast AZ and southwest NM... A couple stronger storms are possible near the southeast AZ/southwest NM/international border area to the south of a low-amplitude shortwave impulse slowly moving from the Mogollon Rim to the southern Rockies. Pockets of greater insolation should be confined to the international border with abundant cloud coverage/remnant stratiform rain farther north closer to the shortwave impulse. Scattered thunderstorms will develop later this afternoon as destabilization occurs within the cloud breaks. Moderate buoyancy with MLCAPE of 1000-1500 J/kg in conjunction with effective shear around 25 kt may support a couple updrafts possessing weak/transient mid-level rotation. Amid modest mid-level lapse rates, this setup would most likely yield small hail and locally strong gusts. Overall threat appears too limited to warrant a severe risk area. ..Grams/Karstens.. 09/15/2019 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1052 AM CDT Sun Sep 15 2019 Valid 151630Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the contiguous U.S. today. ...Far southeast AZ and southwest NM... A couple stronger storms are possible near the southeast AZ/southwest NM/international border area to the south of a low-amplitude shortwave impulse slowly moving from the Mogollon Rim to the southern Rockies. Pockets of greater insolation should be confined to the international border with abundant cloud coverage/remnant stratiform rain farther north closer to the shortwave impulse. Scattered thunderstorms will develop later this afternoon as destabilization occurs within the cloud breaks. Moderate buoyancy with MLCAPE of 1000-1500 J/kg in conjunction with effective shear around 25 kt may support a couple updrafts possessing weak/transient mid-level rotation. Amid modest mid-level lapse rates, this setup would most likely yield small hail and locally strong gusts. Overall threat appears too limited to warrant a severe risk area. ..Grams/Karstens.. 09/15/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0720 AM CDT Sun Sep 15 2019 Valid 151300Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the U.S. today. ...Synopsis... On the larger scale, a trough will amplify near the Pacific Northwest coast through tonight, while downstream heights will rise across the northern Plains and upper MS Valley. Isolated lightning strikes may occur along the coasts of WA/OR as the midlevel thermal trough and steeper lapse rates spread inland tonight. Farther east, a low-amplitude shortwave trough will continue eastward over the upper Great Lakes today. Clusters of mostly elevated thunderstorms are ongoing across northern IL within a zone of low-level warm advection associated with the upper Great Lakes trough. There is a low chance for hail with the strongest storms this morning, though the warm advection will weaken and shift eastward later today, with an associated decrease in storm coverage/intensity expected. South of the main belt of westerlies, a midlevel low is moving slowly westward over the northwest Gulf of Mexico, and will continue to support a threat for additional storms near the coast along the north edge of the richer tropical moisture. A separate midlevel low will continue to move slowly northeastward from southeast AZ toward the Four Corners through tonight. Scattered thunderstorms are expected with diurnal heating in cloud breaks over the high terrain and in the zone of ascent north through east of the low. Vertical shear and buoyancy may become sufficient for a strong storm or two in the vicinity of extreme southwest NM this afternoon, though the threat for damaging winds appears too low to warrant an outlook area. ..Thompson/Gleason.. 09/15/2019 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0720 AM CDT Sun Sep 15 2019 Valid 151300Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected across the U.S. today. ...Synopsis... On the larger scale, a trough will amplify near the Pacific Northwest coast through tonight, while downstream heights will rise across the northern Plains and upper MS Valley. Isolated lightning strikes may occur along the coasts of WA/OR as the midlevel thermal trough and steeper lapse rates spread inland tonight. Farther east, a low-amplitude shortwave trough will continue eastward over the upper Great Lakes today. Clusters of mostly elevated thunderstorms are ongoing across northern IL within a zone of low-level warm advection associated with the upper Great Lakes trough. There is a low chance for hail with the strongest storms this morning, though the warm advection will weaken and shift eastward later today, with an associated decrease in storm coverage/intensity expected. South of the main belt of westerlies, a midlevel low is moving slowly westward over the northwest Gulf of Mexico, and will continue to support a threat for additional storms near the coast along the north edge of the richer tropical moisture. A separate midlevel low will continue to move slowly northeastward from southeast AZ toward the Four Corners through tonight. Scattered thunderstorms are expected with diurnal heating in cloud breaks over the high terrain and in the zone of ascent north through east of the low. Vertical shear and buoyancy may become sufficient for a strong storm or two in the vicinity of extreme southwest NM this afternoon, though the threat for damaging winds appears too low to warrant an outlook area. ..Thompson/Gleason.. 09/15/2019 Read more