SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1028 AM CST Mon Jan 20 2025 Valid 201630Z - 211200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... No thunderstorms are expected across the U.S. through tonight. ...Synopsis... Another surge of cold air is anticipated across the CONUS, reinforcing the polar airmass already in place. This will result in a maintenance of dry and stable conditions, with no thunderstorms anticipated. Some deeper convection is possible late tonight/early tomorrow along the middle/upper TX Coast as warm-air advection strengthens throughout the warm sector of surface low developing over the western Gulf of Mexico. Model forecast soundings have thermodynamic profiles with scant (and shallow) buoyancy between around 800 to 500 mb. These profiles also suggest sleet will be the predominant precipitation type, with mixed-phase parcels combining with the modest buoyancy to support a few lightning flashes. Even so, the overall thunderstorm probabilities are still expected to be less than 10 percent. ..Mosier.. 01/20/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0642 AM CST Mon Jan 20 2025 Valid 201300Z - 211200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... No thunderstorms are expected across the U.S. through tonight. Relatively dry and stable conditions will prevail across the CONUS today, with no thunderstorms expected. ..Hart/Wendt.. 01/20/2025 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0642 AM CST Mon Jan 20 2025 Valid 201300Z - 211200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... No thunderstorms are expected across the U.S. through tonight. Relatively dry and stable conditions will prevail across the CONUS today, with no thunderstorms expected. ..Hart/Wendt.. 01/20/2025 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0342 AM CST Mon Jan 20 2025 Valid 231200Z - 281200Z ...DISCUSSION... For Thursday/D4 into Friday/D5, a large positive-tilt upper trough will move from central parts of the CONUS toward the East Coast, exiting land late Friday. Although strong winds aloft will overspread the southeastern states, northerly winds are forecast to hold over land. Behind that system, high pressure will maintain stable conditions over the eastern CONUS into Saturday/D6, although more of a zonal flow regime is forecast thereafter. As a result of this possible transition to the pattern, minimal low-level moisture return with low 60s F dewpoints may return to parts of the TX Coast as surface pressure lowers briefly. Beyond the D6 time frame, model spread is large, but the general signal is for the ongoing large trough pattern over the central and eastern CONUS to at least shift northeastward into eastern Canada and the northeastern states, allowing for gradual warming across the South. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0342 AM CST Mon Jan 20 2025 Valid 231200Z - 281200Z ...DISCUSSION... For Thursday/D4 into Friday/D5, a large positive-tilt upper trough will move from central parts of the CONUS toward the East Coast, exiting land late Friday. Although strong winds aloft will overspread the southeastern states, northerly winds are forecast to hold over land. Behind that system, high pressure will maintain stable conditions over the eastern CONUS into Saturday/D6, although more of a zonal flow regime is forecast thereafter. As a result of this possible transition to the pattern, minimal low-level moisture return with low 60s F dewpoints may return to parts of the TX Coast as surface pressure lowers briefly. Beyond the D6 time frame, model spread is large, but the general signal is for the ongoing large trough pattern over the central and eastern CONUS to at least shift northeastward into eastern Canada and the northeastern states, allowing for gradual warming across the South. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0208 AM CST Mon Jan 20 2025 Valid 211200Z - 221200Z ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR THE SAN GABRIEL MOUNTAINS WEST TOWARDS THE SANTA MONICA MOUNTAINS AND SANTA SUSANA MOUNTAINS... INCLUDING THE MALIBU COAST... ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR PORTIONS OF THE EASTERN SAN DIEGO FOOTHILLS INTO THE WESTERN SAN JACINTO MOUNTAINS... ...CRITICAL FIRE WEATHER AREA FOR MUCH OF SOUTHERN CALIFORNIA... ...Synopsis... A strong Santa Ana wind event beginning Monday afternoon will persist well into Tuesday afternoon and evening, resulting in widespread Critical and Extremely Critical fire-weather conditions across much of Southern California. ...Extremely Critical fire-weather conditions for the San Gabriel, Santa Monica, and Santa Susana Mountains... Extremely Critical fire-weather conditions will persist from the Day 1 outlook period (Mon) well into Day 2 (Tues). Sustained winds of 40-45 MPH (gusting 70-100 MPH on mountains, 50-80 MPH in the valleys/coastal regions) with single-digit relative humidity values as low as 2%-5% will be ongoing at the start of the period, subsiding by late Tuesday afternoon/early Tuesday evening. For more details, see the current Day 1 fire-weather outlook. ...Extremely Critical fire-weather conditions for portions of the eastern San Diego foothills into the western San Jacinto Mountains... Confidence has increased in strong, dry offshore flow across far Southern California, particularly portions of the eastern San Diego foothills into the San Jacinto Mountains. Recent 00Z HREF guidance shows ensemble mean sustained surface winds as high as 50-55 MPH, with the ensemble maximum as high as 60 MPH and gusts as high as 80 MPH. Coupled with single-digit relative humidities, this will result in several hours of Extremely Critical fire-weather conditions supportive of rapid wildfire onset and spread, subsiding by late Tuesday evening into Wednesday morning. ..Halbert.. 01/20/2025 ...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 0208 AM CST Mon Jan 20 2025 Valid 201200Z - 211200Z ...EXTREMELY CRITICAL FIRE WEATHER AREA FOR THE SAN GABRIEL MOUNTAINS WEST TOWARDS THE SANTA MONICA MOUNTAINS AND SANTA SUSANA MOUNTAINS... INCLUDING THE MALIBU COAST... ...CRITICAL FIRE WEATHER AREA FOR MUCH OF SOUTHERN CALIFORNIA... ...Synopsis... While most of the CONUS is dominated by cold air and high pressure, a strong, positively-tilted mid-level trough will move southward across California, with a highly amplified mid-level Pacific ridge following behind it. As the trough axis reaches southern California Monday afternoon, intensifying surface pressure gradients will result in the development of strong Santa Ana winds. The 00Z HREF guidance and global ensembles continue to forecast strong LAX->DAG pressure gradients ranging from -8 mb to -11 mb, with wind speeds trending upward to 40-45 MPH sustained (gusting 70 - 100 MPH on the mountains, 50 - 80 MPH in the valleys/coastal regions). In addition to the upward trend in wind speed and gust forecasts, relative humidity values have trended significantly drier, with values as low as 2%-5%. These Extremely Critical fire-weather conditions, supporting rapid wildfire onset and spread, will begin Monday afternoon and reach peak intensity Monday evening into Tuesday morning. The area of greatest risk lies from the San Gabriel Mountains westward into the Santa Monica Mountains, the Malibu Coast, and the Santa Susana Mountains. Elsewhere, Critical fire-weather conditions extend southward to the U.S./Mexico border, where strong (and critically dry) offshore winds will persist overnight into Tuesday morning. ..Halbert.. 01/20/2025 ...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 1254 AM CST Mon Jan 20 2025 Valid 221200Z - 231200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast on Wednesday. ...Synopsis... An elongated upper trough will exit the East Coast early in the day, as another positive-tilt trough moves into the central CONUS. This trough will extend roughly from the upper Great Lakes into the southern Plains. Meanwhile, an upper ridge will exist along the West Coast, with additional disturbances diving south into the northern Rockies. At the surface, a stable air mass in terms of convection will exist due to high pressure. A weak surface low may form from the FL Straits toward the Bahamas, avoiding the FL Peninsula where the air mass will remain stable. As such, little to no lightning activity is forecast across the USA on Wednesday due to the stable air mass over land. ..Jewell.. 01/20/2025 Read more

SPC 0830Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 1254 AM CST Mon Jan 20 2025 Valid 221200Z - 231200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast on Wednesday. ...Synopsis... An elongated upper trough will exit the East Coast early in the day, as another positive-tilt trough moves into the central CONUS. This trough will extend roughly from the upper Great Lakes into the southern Plains. Meanwhile, an upper ridge will exist along the West Coast, with additional disturbances diving south into the northern Rockies. At the surface, a stable air mass in terms of convection will exist due to high pressure. A weak surface low may form from the FL Straits toward the Bahamas, avoiding the FL Peninsula where the air mass will remain stable. As such, little to no lightning activity is forecast across the USA on Wednesday due to the stable air mass over land. ..Jewell.. 01/20/2025 Read more

MD 0040 CONCERNING HEAVY SNOW FOR COASTAL MAINE
Mesoscale Discussion 0040 NWS Storm Prediction Center Norman OK 0923 PM CST Sun Jan 19 2025 Areas affected...Coastal Maine Concerning...Heavy snow Valid 200323Z - 200930Z SUMMARY...Heavy snowfall with rates at or exceeding 1"/hour are expected across coastal Maine through 09Z as a surface cyclone tracks northeastward off the coast of New England. DISCUSSION...As a rapidly deepening surface low tracks northeastward off the coast of New England, strong isentropic ascent and lift in the dendritic growth zone will result in heavy snowfall across portions of coastal Maine. Short-term guidance from the 00Z HREF, along with surface pressure falls in recent observations, have increased confidence that some areas on the coast could meet or exceed 1"/hour snowfall rates. The greatest chance for heavy snowfall rates will be north and east of Rockland, and the combination of strong winds and heavy snowfall rates will result in low visibility conditions (at or below 0.5 mi). These conditions are expected to subside in southern Maine starting around 06Z, and exiting northeast Maine by 08-09Z. ..Halbert.. 01/20/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CAR...GYX... LAT...LON 44217093 44517034 44936946 45416838 45336758 45086701 44776675 44396714 44026793 43726904 43606987 43147044 43007066 43197106 43487131 44027122 44217093 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1149 PM CST Sun Jan 19 2025 Valid 211200Z - 221200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast on Tuesday. ...Synopsis... A large positive-tilt upper trough will stretch from the upper Great Lakes into the southern High Plains Tuesday morning, and will progress toward the East Coast by 12Z Wednesday. Behind this wave, another lobe of vorticity will drop south across the Rockies and toward the Plains late. At the surface, a strong high pressure ridge will extend from the Great Basin all the way to the Mid Atlantic Tuesday morning, with this high consolidating across the eastern states and toward the lower MS Valley overnight. Another area of high pressure will develop southward across the Pacific Northwest and northern Rockies, in association with the second upper wave. While 60s F dewpoints will remain from the FL Straits toward the Bahamas, little destabilization is expected over the mainland. Thunderstorms may occur over parts of the central Gulf of Mexico along the surging cold front, with little impact to land expected. ..Jewell.. 01/20/2025 Read more

SPC 0700Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1149 PM CST Sun Jan 19 2025 Valid 211200Z - 221200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not forecast on Tuesday. ...Synopsis... A large positive-tilt upper trough will stretch from the upper Great Lakes into the southern High Plains Tuesday morning, and will progress toward the East Coast by 12Z Wednesday. Behind this wave, another lobe of vorticity will drop south across the Rockies and toward the Plains late. At the surface, a strong high pressure ridge will extend from the Great Basin all the way to the Mid Atlantic Tuesday morning, with this high consolidating across the eastern states and toward the lower MS Valley overnight. Another area of high pressure will develop southward across the Pacific Northwest and northern Rockies, in association with the second upper wave. While 60s F dewpoints will remain from the FL Straits toward the Bahamas, little destabilization is expected over the mainland. Thunderstorms may occur over parts of the central Gulf of Mexico along the surging cold front, with little impact to land expected. ..Jewell.. 01/20/2025 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1101 PM CST Sun Jan 19 2025 Valid 201200Z - 211200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for thunderstorms appears negligible across the U.S. today through tonight. ...Discussion... A significant short wave perturbation is forecast to continue progressing through the crest of blocking larger-scale mid-level ridging centered over the northeastern Pacific, eventually digging across the Canadian Rockies and adjacent Pacific Northwest by late tonight. Downstream, short wave ridging likely will overspread the Canadian Prairies, northern U.S. Rockies and Great Basin, in the wake of digging short wave troughing across the northern Great Plains through upper Mississippi Valley/Great Lakes region and across the Southwest/southern Rockies and adjacent international border vicinity. Farther east, it appears that strong, confluent southwesterly mid/upper flow will be maintained between a prominent ridge centered over the subtropical western Atlantic and a broad, cold cyclonic circulation centered east-northeast of Hudson Bay. Beneath this regime, surface troughing likely will develop and deepen across the Canadian Prairies into the lee of the northern U.S. Rockies. Otherwise, though its center is forecast to shift from the lee of the northern through southern Rockies, expansive cold surface ridging will generally be maintained across much of the interior U.S, with another high center building across the Allegheny Mountains/Mid Atlantic vicinity. The frontal zone demarcating the leading edge of this cold intrusion probably will begin to stall and weaken east/southeast of the Florida Peninsula into the southeastern Gulf of Mexico, well in the wake of a rapidly deepening cyclone migrating across and northeast of the Canadian Maritimes. ...Texas coastal areas... Models do indicate that weak troughing will form on the southern flank of the cold surface ridge, from the southwestern toward northwestern Gulf of Mexico today through tonight. Any associated boundary-layer destabilization likely will remain focused well offshore of the lower Texas coast. However, elevated moisture return may contribute to weak CAPE rooted around the 700 mb level as far north as the upper Texas coast by 12Z Tuesday. RAP and NAM forecast soundings suggest that it might not be out of the question that convection, supported by ascent associated with lower/mid-tropospheric warm advection, might become capable of producing some lightning. But, due to lingering uncertainties, thunderstorm probabilities will be maintained at less than 10 percent, at least for now. ..Kerr.. 01/20/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0637 PM CST Sun Jan 19 2025 Valid 200100Z - 201200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for additional thunderstorm development across the southern Florida Peninsula and Keys appears negligible through the remainder of tonight. ...01z Update... The cold front is still in the process of advancing across the southern Florida Peninsula. However, stronger low-level convergence is now generally focused near and offshore of coastal areas to the south through east of the Palm Beach vicinity, and probabilities for additional thunderstorm development are becoming increasingly negligible beneath lingering warm and dry layers aloft. Based on latest observational data, the risk for thunderstorms will generally remain focused well offshore of the Atlantic coast, and south of the Florida Keys, through the remainder of tonight. ..Kerr.. 01/20/2025 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0637 PM CST Sun Jan 19 2025 Valid 200100Z - 201200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for additional thunderstorm development across the southern Florida Peninsula and Keys appears negligible through the remainder of tonight. ...01z Update... The cold front is still in the process of advancing across the southern Florida Peninsula. However, stronger low-level convergence is now generally focused near and offshore of coastal areas to the south through east of the Palm Beach vicinity, and probabilities for additional thunderstorm development are becoming increasingly negligible beneath lingering warm and dry layers aloft. Based on latest observational data, the risk for thunderstorms will generally remain focused well offshore of the Atlantic coast, and south of the Florida Keys, through the remainder of tonight. ..Kerr.. 01/20/2025 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0355 PM CST Sun Jan 19 2025 Valid 211200Z - 271200Z ...Southern California - Day 3/Tuesday... Critical to extremely critical fire-weather conditions will be ongoing across southern CA at the start of the Day 3/Tuesday period, as the offshore pressure gradient will be at peak magnitudes (LAX-DAG gradient around -8 to -10 mb). This gradient, coupled with continued upper-level support through at least 15Z, will result in very strong/gusty northeasterly surface winds and single-digit RH across much of southern CA. The strongest winds should remain focused over the wind-prone Santa Ana corridor of northern/western Los Angeles County into eastern Ventura County -- where the greatest risk of Extremely Critical conditions will persist through at least 15Z. Thereafter, the positive-tilt shortwave trough and strong winds aloft that were providing upper-level support for the strong Santa Ana event on Day 3/Tuesday will continue east-southeastward into the central CONUS. However, strong surface high pressure will persist across the Intermountain West, favoring continued dry offshore flow across southern CA on Day 4/Wednesday through Day 5/Thursday. Current indications are that the offshore pressure gradient will yield elevated to locally critical fire-weather conditions both days/mornings, though the lack of upper-level support limits confidence in any more than locally critical conditions -- precluding 70-percent probabilities at this time. ..Weinman.. 01/19/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0355 PM CST Sun Jan 19 2025 Valid 211200Z - 271200Z ...Southern California - Day 3/Tuesday... Critical to extremely critical fire-weather conditions will be ongoing across southern CA at the start of the Day 3/Tuesday period, as the offshore pressure gradient will be at peak magnitudes (LAX-DAG gradient around -8 to -10 mb). This gradient, coupled with continued upper-level support through at least 15Z, will result in very strong/gusty northeasterly surface winds and single-digit RH across much of southern CA. The strongest winds should remain focused over the wind-prone Santa Ana corridor of northern/western Los Angeles County into eastern Ventura County -- where the greatest risk of Extremely Critical conditions will persist through at least 15Z. Thereafter, the positive-tilt shortwave trough and strong winds aloft that were providing upper-level support for the strong Santa Ana event on Day 3/Tuesday will continue east-southeastward into the central CONUS. However, strong surface high pressure will persist across the Intermountain West, favoring continued dry offshore flow across southern CA on Day 4/Wednesday through Day 5/Thursday. Current indications are that the offshore pressure gradient will yield elevated to locally critical fire-weather conditions both days/mornings, though the lack of upper-level support limits confidence in any more than locally critical conditions -- precluding 70-percent probabilities at this time. ..Weinman.. 01/19/2025 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Sun Jan 19 22:01:02 UTC 2025.

MD 0039 CONCERNING HEAVY SNOW FOR PORTIONS OF THE MID-ATLANTIC AND NORTHEAST
Mesoscale Discussion 0039 NWS Storm Prediction Center Norman OK 0334 PM CST Sun Jan 19 2025 Areas affected...Portions of the Mid-Atlantic and Northeast Concerning...Heavy snow Valid 192134Z - 200100Z SUMMARY...Heavy snowfall will continue to shift northeastward this evening across portions of the Mid-Atlantic and Northeast with rates of >=1" per hour possible. DISCUSSION...The latest water vapor imagery indicates that the mid/upper-level speed max is exiting the coast. As a result, the surface low is deepening off of Delmarva and is forecast to continue strengthening offshore and move quickly to the northeast. Low-level frontogenesis will continue to support upward vertical motion and precipitation banding. Precipitation type is more uncertain near the coast where strong low-level warm air advection will act to offset cooling by evaporation and melting over the next few hours. Thus, the corridor with the highest confidence of 1"+ snowfall rates over the next few hours has been highlighted. ..Jirak/Mosier.. 01/19/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GYX...BOX...OKX...ALY...PHI...BGM... LAT...LON 41857286 41487335 41127372 40807419 40527458 40357527 40617574 41167540 41777467 42177422 42537378 42897315 43077272 43187218 42867184 42477217 42307238 41857286 Read more

MD 0038 CONCERNING HEAVY SNOW FOR PORTIONS OF MID-ATLANTIC STATES
Mesoscale Discussion 0038 NWS Storm Prediction Center Norman OK 1200 PM CST Sun Jan 19 2025 Areas affected...Portions of Mid-Atlantic States Concerning...Heavy snow Valid 191800Z - 192230Z SUMMARY...Snowfall will continue to increase from southwest to northeast across portions of West Virginia, Maryland, and Pennsylvania this afternoon with rates exceeding 1" per hour. DISCUSSION...An upper-level trough and associated speed max rotating around a low near Hudson Bay are moving toward the East Coast this afternoon. In response at the surface, a low over North Carolina is forecast to deepen and shift northeastward through the afternoon. To the north to northwest of the surface low, low-level frontogenesis will promote upward vertical motion and precipitation banding. Given these favorable factors and cold vertical profiles, snowfall rates of >=1" per hour are likely this afternoon with higher rates possible in banded structures. ..Jirak/Mosier.. 01/19/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...PHI...CTP...LWX...RNK...PBZ...RLX... LAT...LON 39687582 39517657 39347767 39067877 38717917 38377961 38078019 38018068 38168091 38788077 39448031 40117977 40437925 40867841 40947721 40887643 40637544 40257509 39927529 39687582 Read more