SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0132 PM CST Tue Jan 21 2025 Valid 212000Z - 221200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across the U.S. through tonight. ...20z... No changes were made. Widespread winter precipitation is ongoing along the Gulf Coast. High pressure over the interior of the central CONUS will continue to support very cold, dry and stable conditions with offshore flow. This will negate sufficient buoyancy for thunderstorm potential. See the prior outlook for more info. ..Lyons.. 01/21/2025 .PREV DISCUSSION... /ISSUED 1012 AM CST Tue Jan 21 2025/ ...Synopsis... Expansive high pressure associated with a polar airmass is in place across is in place east of Rockies. This high, which is currently centered over eastern OK/western AR, is expected to shift eastward/northeastward throughout the day, ending the period over the Ohio Valley. Associated cold, dry, and stable conditions will preclude thunderstorm development. A similar environment is anticipated across the western CONUS, with high pressure and associated stability dominating the sensible weather. A deepening surface low will continue to shift eastward across the Gulf of Mexico, with strong warm-air advection throughout its warm sector contributing to a broad precipitation field across the Gulf Coast. A few lightning flashes were observed over Acadia Parish in south-central LA over the past hour, but these flashes were most likely created by the self-initiated upward leader process. Given the continuing windy conditions and potential for mixed-phase hydrometeors at low levels, some additional self-initiated flashes are possible throughout the period. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0132 PM CST Tue Jan 21 2025 Valid 212000Z - 221200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across the U.S. through tonight. ...20z... No changes were made. Widespread winter precipitation is ongoing along the Gulf Coast. High pressure over the interior of the central CONUS will continue to support very cold, dry and stable conditions with offshore flow. This will negate sufficient buoyancy for thunderstorm potential. See the prior outlook for more info. ..Lyons.. 01/21/2025 .PREV DISCUSSION... /ISSUED 1012 AM CST Tue Jan 21 2025/ ...Synopsis... Expansive high pressure associated with a polar airmass is in place across is in place east of Rockies. This high, which is currently centered over eastern OK/western AR, is expected to shift eastward/northeastward throughout the day, ending the period over the Ohio Valley. Associated cold, dry, and stable conditions will preclude thunderstorm development. A similar environment is anticipated across the western CONUS, with high pressure and associated stability dominating the sensible weather. A deepening surface low will continue to shift eastward across the Gulf of Mexico, with strong warm-air advection throughout its warm sector contributing to a broad precipitation field across the Gulf Coast. A few lightning flashes were observed over Acadia Parish in south-central LA over the past hour, but these flashes were most likely created by the self-initiated upward leader process. Given the continuing windy conditions and potential for mixed-phase hydrometeors at low levels, some additional self-initiated flashes are possible throughout the period. Read more

MD 0049 CONCERNING HEAVY SNOW FOR SOUTHERN JEFFERSON AND NORTHERN LEWIS COUNTIES DOWNSTREAM OF LAKE ONTARIO
Mesoscale Discussion 0049 NWS Storm Prediction Center Norman OK 1028 AM CST Tue Jan 21 2025 Areas affected...Southern Jefferson and northern Lewis counties downstream of Lake Ontario Concerning...Heavy snow Valid 211628Z - 212230Z SUMMARY...Heavy lake-effect snow to continue downstream of Lake Ontario to continue for another 10 to 12 hours. Snowfall rates of 2+ inches per hour expected. DISCUSSION...A strong lake-effect snow band which developed yesterday evening and slowly shifted north has now stalled over the same location since around 10Z this morning with snowfall rates in excess of 2 inches per hour. Forecast soundings show a similar wind direction and EL depth which should support similar intensity through at least 00Z. After this time, winds become more erratic and the depth of the convective layer will become more shallow which will likely result in a weaker, more erratic snow band. However, until that time, 2+ inch per hour snowfall rates are expected to persist through the afternoon and into the early evening across the same area across southern Jefferson and northern Lewis counties. ..Bentley.. 01/21/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BUF... LAT...LON 43947628 44037579 44007543 43897536 43767560 43717592 43697613 43707625 43847635 43947628 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 1248 PM CST Tue Jan 21 2025 Valid 231200Z - 241200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast on Thursday. ...Synopsis... A large mid/upper-level trough will persist from the south-central Great Plains into the eastern CONUS on Thursday, as multiple embedded shortwaves move southeastward through the larger-scale trough. Generally dry and stable conditions in the wake of a significant cold intrusion should continue to limit thunderstorm potential through the period. ..Dean.. 01/21/2025 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 1248 PM CST Tue Jan 21 2025 Valid 231200Z - 241200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast on Thursday. ...Synopsis... A large mid/upper-level trough will persist from the south-central Great Plains into the eastern CONUS on Thursday, as multiple embedded shortwaves move southeastward through the larger-scale trough. Generally dry and stable conditions in the wake of a significant cold intrusion should continue to limit thunderstorm potential through the period. ..Dean.. 01/21/2025 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1124 AM CST Tue Jan 21 2025 Valid 221200Z - 231200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected on Wednesday. ...Synopsis... A deep mid/upper-level trough will remain in place over most of the CONUS on Wednesday. Anomalously cold conditions are expected from the Great Plains to the Eastern Seaboard, in the wake of a strong cold front. Weak MUCAPE may persist across far south FL and the Keys very early in the forecast period, but deep convection appears unlikely due to warm temperatures aloft and decreasing large-scale ascent with time. Elsewhere, dry and stable conditions will limit thunderstorm potential. ..Dean.. 01/21/2025 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1100 AM CST Tue Jan 21 2025 Valid 211700Z - 221200Z ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR THE SAN GABRIEL MOUNTAINS WEST TOWARDS THE MALIBU COAST... ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SAN JACINTO TO LAGUNA MOUNTAIN RANGES... ...CRITICAL FIRE WEATHER AREA FOR MUCH OF SOUTHERN CALIFORNIA... The previous forecast (see below) remains on track, and only minor changes were made to the Extremely Critical highlights in Los Angeles County and Ventura County -- based on the latest surface observations and high-resolution guidance. The offshore pressure gradient should be peaking over the next few hours (latest LAX-DAG gradient around -6.5 mb), and this will be the period of strongest offshore winds and potential for extremely critical conditions. Thereafter, critical conditions should persist into this evening, when an overall decrease in the pressure gradient and surface winds is expected. ..Weinman.. 01/21/2025 .PREV DISCUSSION... /ISSUED 0156 AM CST Tue Jan 21 2025/ ...Synopsis... A mid-level trough across the southwest U.S. will rapidly track eastward toward the Southeast while surface high pressure persists over the Great Basin through the period. Strong offshore flow will persist from the Ventura Valley to the Laguna Mountains, with widespread 20-30 mph sustained winds and 10 percent RH expected during the day into early Wednesday morning, warranting the maintenance of Critical highlights across much of the far southern California shoreline. Furthermore, the latest high-resolution guidance consensus shows sustained winds exceeding 40 mph, coinciding with single-digit RH, from the Ventura Valley to the San Bernardino Mountains, as well as the San Jacinto to Laguna Mountain ranges, where Extremely Critical highlights were maintained. The best chance for Extremely Critical conditions will be during the morning into early afternoon hours. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 0048 CONCERNING HEAVY SNOW FOR SOUTHEAST LOUISIANA...SOUTHERN MISSISSIPPI AND FAR SOUTHERN ALABAMA
Mesoscale Discussion 0048 NWS Storm Prediction Center Norman OK 0846 AM CST Tue Jan 21 2025 Areas affected...Southeast Louisiana...southern Mississippi and far southern Alabama Concerning...Heavy snow Valid 211446Z - 211845Z SUMMARY...Moderate to heavy snow to continue this morning and through the afternoon. Some blowing and drifting is also expected. DISCUSSION...An expansive region of light to occasionally moderate snow has spread across much of the central Gulf coast this morning. Expect precipitation rates to increase through the late morning and afternoon with widespread moderate to occasionally heavy snowfall rates expected. In addition, some stronger winds, particularly closer to the coast will lead to some blowing and drifting. Areas with northward exposure (ex. southern short of Lake Pontchartrain) may see some localized blizzard conditions through the day. Some mixed precipitation is being observed from southern Terrebonne Parish to southern St. Bernard Parish where a warm nose (seen just below 700mb on the LIX 12Z RAOB) is slightly above freezing. 60 knots of southwesterly flow in this warm nose will attempt to maintain its presence across the region while temperatures aloft continue to cool. Expect the cold air to eventually win out with snow likely across all of southern Louisiana by later this afternoon. ..Bentley.. 01/21/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...MOB...JAN...LIX...LCH... LAT...LON 31019159 31519076 31608898 31238781 30798754 30218756 30198828 30138865 29938871 29528885 29078901 28908909 28948999 29049087 29309164 29419195 30419196 31019159 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1012 AM CST Tue Jan 21 2025 Valid 211630Z - 221200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across the U.S. today through tonight. ...Synopsis... Expansive high pressure associated with a polar airmass is in place across is in place east of Rockies. This high, which is currently centered over eastern OK/western AR, is expected to shift eastward/northeastward throughout the day, ending the period over the Ohio Valley. Associated cold, dry, and stable conditions will preclude thunderstorm development. A similar environment is anticipated across the western CONUS, with high pressure and associated stability dominating the sensible weather. A deepening surface low will continue to shift eastward across the Gulf of Mexico, with strong warm-air advection throughout its warm sector contributing to a broad precipitation field across the Gulf Coast. A few lightning flashes were observed over Acadia Parish in south-central LA over the past hour, but these flashes were most likely created by the self-initiated upward leader process. Given the continuing windy conditions and potential for mixed-phase hydrometeors at low levels, some additional self-initiated flashes are possible throughout the period. ..Mosier/Thornton.. 01/21/2025 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1012 AM CST Tue Jan 21 2025 Valid 211630Z - 221200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across the U.S. today through tonight. ...Synopsis... Expansive high pressure associated with a polar airmass is in place across is in place east of Rockies. This high, which is currently centered over eastern OK/western AR, is expected to shift eastward/northeastward throughout the day, ending the period over the Ohio Valley. Associated cold, dry, and stable conditions will preclude thunderstorm development. A similar environment is anticipated across the western CONUS, with high pressure and associated stability dominating the sensible weather. A deepening surface low will continue to shift eastward across the Gulf of Mexico, with strong warm-air advection throughout its warm sector contributing to a broad precipitation field across the Gulf Coast. A few lightning flashes were observed over Acadia Parish in south-central LA over the past hour, but these flashes were most likely created by the self-initiated upward leader process. Given the continuing windy conditions and potential for mixed-phase hydrometeors at low levels, some additional self-initiated flashes are possible throughout the period. ..Mosier/Thornton.. 01/21/2025 Read more

MD 0047 CONCERNING HEAVY SNOW FOR FAR SOUTHEAST TEXAS INTO SOUTH-CENTRAL LOUISIANA
Mesoscale Discussion 0047 NWS Storm Prediction Center Norman OK 0447 AM CST Tue Jan 21 2025 Areas affected...Far southeast Texas into south-central Louisiana Concerning...Heavy snow Valid 211047Z - 211515Z SUMMARY...Moderate snowfall with embedded heavier bands will become more likely over the next several hours in southern Louisiana. DISCUSSION...The broad upper-level trough across the central/eastern U.S. is in the process of intensifying this morning. As this occurs, the upper-level jet along eastern flank of the trough will also intensify. Increasing mid/upper-level ascent as well as at least weak lower-level frontogenesis (850-700 mb or so) will promote favorable conditions for dendritic growth. Moderate snowfall has already been observed at several stations in southwestern Louisiana over the last hour. With the most favorable synoptic conditions expected to occur around mid/late morning, moderate snowfall should become increasingly prevalent across southern Louisiana in particular. Some banded structures will be possible which could produce heavier snowfall rates (0.5-1 in/hr) at least locally. ..Wendt.. 01/21/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LIX...LCH... LAT...LON 29749396 29999432 30579416 30979267 31019185 30809148 30689122 29949132 29709181 29669242 29709266 29749396 Read more

MD 0046 CONCERNING WINTER MIXED PRECIPITATION FOR PORTIONS OF THE MIDDLE AND UPPER TEXAS COAST VICINITY
Mesoscale Discussion 0046 NWS Storm Prediction Center Norman OK 0256 AM CST Tue Jan 21 2025 Areas affected...Portions of the Middle and Upper Texas Coast Vicinity Concerning...Winter mixed precipitation Valid 210856Z - 211330Z SUMMARY...A mix of sleet and light freezing rain/drizzle will remain possible through daybreak. A gradual shift to snow (from north to south) will also occur with time. DISCUSSION...A mix of winter precipitation continues within and north the Middle/Upper Texas Coast regions. Based on reported precipitation and model sounding data, a mixture of sleet and lighter freezing rain/drizzle is most likely. Given the presence of steep lapse rates at cloud top (both noted in regional observed soundings and model soundings), some convective elements are possible and would be more efficient sleet producers. With time, additional large-scale ascent will cool the atmospheric column such that precipitation should continue to switch to all snow by daybreak and beyond. Should freezing rain/drizzle linger, this is most likely to be nearer the coast where the cold air may be shallow enough to support it. ..Wendt.. 01/21/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...HGX...CRP...EWX... LAT...LON 28049692 27649732 27679765 27819799 28169817 29139788 29569711 30089523 30039480 29439466 28049692 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0649 AM CST Tue Jan 21 2025 Valid 211300Z - 221200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across the U.S. today through tonight. A large surface high dominates the weather across the CONUS today, with cold, dry, and stable conditions preventing thunderstorms. A strengthening surface low off the Gulf coast may provide isolated thunderstorms offshore later today and tonight, but lightning activity is expected to remain well south of the coast. ..Hart/Wendt.. 01/21/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0649 AM CST Tue Jan 21 2025 Valid 211300Z - 221200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across the U.S. today through tonight. A large surface high dominates the weather across the CONUS today, with cold, dry, and stable conditions preventing thunderstorms. A strengthening surface low off the Gulf coast may provide isolated thunderstorms offshore later today and tonight, but lightning activity is expected to remain well south of the coast. ..Hart/Wendt.. 01/21/2025 Read more

MD 0045 CONCERNING HEAVY SNOW FOR PORTIONS OF FAR WESTERN NEW YORK
Mesoscale Discussion 0045 NWS Storm Prediction Center Norman OK 1030 PM CST Mon Jan 20 2025 Areas affected...portions of far western New York Concerning...Heavy snow Valid 210430Z - 211030Z SUMMARY...At least 2-3 inch/hour snowfall rates should continue past sunrise with an intense lake-effect snow band. DISCUSSION...MRMS mosaic and KTYX radar imagery show an intense, steady-state lake-effect snow band persisting across Jefferson and Lewis Counties in far western NY. This snow-band is benefiting from an optimal fetch of moisture off of Lake Ontario, where 8+ C/km 0-3 km lapse rates are in place. As such, convective snowfall within this lake-effect band should persist past sunrise, as shown by the latest high-resolution guidance consensus. Furthermore, given the convective nature of the band, and degree of saturation in the dendritic growth zone, snowfall rates at least in the 2-3 inch/hour range are expected through the remainder of tonight. ..Squitieri.. 01/21/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BUF... LAT...LON 43977634 44027567 43947519 43697514 43547540 43587581 43617612 43647630 43977634 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0302 AM CST Tue Jan 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... An amplified and progressive upper trough will move quickly from the MS Valley to the East Coast on Friday/D4, with zonal flow developing behind this system. High pressure will follow, maintaining dry offshore winds across the Southeast. Models remain in relatively good agreement with the large-scale pattern through the weekend, depicting a positive-tilt upper trough over the southwestern states. A broad fetch of west/southwest flow aloft is forecast to extend across the southern Plains and into much of the East, with the deep upper low over eastern Canada. Sufficient instability is forecast to develop across parts of southern and eastern TX into the lower MS Valley Saturday/D5 Night into Sunday/D6. Given the antecedent cool air at the surface, substantial clouds and precipitation appear likely, reducing overall destabilization and severe potential. Models diverge around Monday/D7, with uncertainly regarding whether another wave will develop into the northern Plains and Great Lakes as disturbances rotate around the large-scale low. To the west, the trough/low over the Southwest may eventually eject east, but timing for this is uncertain as well with low predictability at this time frame. In any case, severe potential is forecast to be low through the period. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0302 AM CST Tue Jan 21 2025 Valid 241200Z - 291200Z ...DISCUSSION... An amplified and progressive upper trough will move quickly from the MS Valley to the East Coast on Friday/D4, with zonal flow developing behind this system. High pressure will follow, maintaining dry offshore winds across the Southeast. Models remain in relatively good agreement with the large-scale pattern through the weekend, depicting a positive-tilt upper trough over the southwestern states. A broad fetch of west/southwest flow aloft is forecast to extend across the southern Plains and into much of the East, with the deep upper low over eastern Canada. Sufficient instability is forecast to develop across parts of southern and eastern TX into the lower MS Valley Saturday/D5 Night into Sunday/D6. Given the antecedent cool air at the surface, substantial clouds and precipitation appear likely, reducing overall destabilization and severe potential. Models diverge around Monday/D7, with uncertainly regarding whether another wave will develop into the northern Plains and Great Lakes as disturbances rotate around the large-scale low. To the west, the trough/low over the Southwest may eventually eject east, but timing for this is uncertain as well with low predictability at this time frame. In any case, severe potential is forecast to be low through the period. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0157 AM CST Tue Jan 21 2025 Valid 221200Z - 231200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA... ...Synopsis... A surface pressure gradient will persist across southern California, with some strengthening of the gradient likely by late Wednesday afternoon as another in a series of mid-level troughs overspread the Great Basin tomorrow (Wednesday). Another day of offshore flow capable of supporting rapid wildfire spread is expected. By afternoon peak heating, widespread sustained 20-30 mph wind speeds are likely, along with RH dropping to at least the 10-15 percent range. Locally higher wind speeds/gusts are also likely in terrain-favoring areas. Anywhere from the Ventura Valley region to the Laguna Mountains may experience the aforementioned meteorological surface conditions, necessitating the introduction of Critical fire weather highlights this outlook. ..Squitieri.. 01/21/2025 ...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 0156 AM CST Tue Jan 21 2025 Valid 211200Z - 221200Z ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE VENTURA VALLEY TO THE SAN BERNARDINO MOUNTAINS IN SOUTHERN CALIFORNIA... ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE SAN JACINTO TO LAGUNA MOUNTAIN RANGES... ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF SOUTHERN CALIFORNIA... ...Synopsis... A mid-level trough across the southwest U.S. will rapidly track eastward toward the Southeast while surface high pressure persists over the Great Basin through the period. Strong offshore flow will persist from the Ventura Valley to the Laguna Mountains, with widespread 20-30 mph sustained winds and 10 percent RH expected during the day into early Wednesday morning, warranting the maintenance of Critical highlights across much of the far southern California shoreline. Furthermore, the latest high-resolution guidance consensus shows sustained winds exceeding 40 mph, coinciding with single-digit RH, from the Ventura Valley to the San Bernardino Mountains, as well as the San Jacinto to Laguna Mountain ranges, where Extremely Critical highlights were maintained. The best chance for Extremely Critical conditions will be during the morning into early afternoon hours. ..Squitieri.. 01/21/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0117 AM CST Tue Jan 21 2025 Valid 231200Z - 241200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast on Thursday. ...Synopsis... A cool and stable pattern will persist on Thursday across the CONUS with an expansive upper trough over much of the central states and into the Great Lakes. This trough may amplify as it becomes more progressive and moves into the MS Valley by 12Z Friday. A strongly cyclonic speed max will exist along the northern Gulf Coast, with cooling aloft to the north. At the surface, another installment of high pressure will push into the Gulf of Mexico, with further drying. Any appreciable low-level moisture will remain east of the FL Peninsula, and as such, thunderstorms are not forecast. ..Jewell.. 01/21/2025 Read more