Severe Storms

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1043 AM CST Sat Nov 19 2022 Valid 191700Z - 201200Z No changes have been made to the current forecast. Offshore flow should linger through this evening before weakening overnight. Occasional elevated fire-weather conditions are possible. See the previous discussion for more information. ..Lyons.. 11/19/2022 .PREV DISCUSSION... /ISSUED 0114 AM CST Sat Nov 19 2022/ ...Synopsis... Surface high pressure and associated cold air should envelop much of the CONUS, limiting significant wildfire-spread potential. Some fire-spread potential may exist across higher-terrain areas of southern California with continued dry and strong offshore flow, mainly during the first half of the period, with low-end Elevated highlights maintained. The main limiting factor to more robust wildfire-spread potential continues to be poorly receptive fuels. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1021 AM CST Sat Nov 19 2022 Valid 191630Z - 201200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected through tonight. ...Synopsis... Upper troughing is forecast to dig east-southeastward across the Upper Great Lakes/Midwest region today, and then sweep eastward across the Lower Lakes and into the Northeast/New England overnight. Meanwhile, in the West, a weak trough will drift across the southwestern deserts, while ridging prevails across the West Coast states and into the Great Basin. At the surface, cold high pressure will largely prevail across the country, though a reinforcing/arctic cold front will cross the northeastern quarter of the country through the period. A few lightning flashes will be possible across the Great Lakes region today, as the reinforcing surge of cold air spreads across the still-warm lakes, resulting in low-topped convective snow showers/bands. A couple of flashes may also persist across parts of coastal southern Texas, and a flash or two may also occur with isolated convection over southern Florida and the Keys. Elsewhere, stable conditions will preclude thunder potential. ..Goss.. 11/19/2022 Read more

No watches are valid as of Fri Nov 18 18:01:01 UTC 2022.

MD 1959 CONCERNING HEAVY SNOW FOR AREAS NORTHEAST OF LAKE ERIE ACROSS THE SOUTHERN PORTION OF THE BUFFALO METRO
Mesoscale Discussion 1959 NWS Storm Prediction Center Norman OK 1159 AM CST Fri Nov 18 2022 Areas affected...Areas northeast of Lake Erie across the southern portion of the Buffalo Metro Concerning...Heavy snow Valid 181759Z - 182200Z SUMMARY...A lake-effect snow band is likely to persist through the afternoon with snow rates 2+ inches per hour. DISCUSSION...A persistent band of lake-effect snow, around 230 km long, across Lake Erie has made a slight shift southward through the morning. Upstream, a shortwave trough is rotating within the main open wave trough with increasing DCVA and large scale ascent across the Ohio River Valley progged to shift northward into New York by 20-21z. Ahead of this feature, southwesterly winds and long moisture fetch continues across Lake Erie. Lake induced 0-3 km lapse rates of 9+ C/km will continue through afternoon as colder air aloft interacts with warm lake water below. The primary snow band is currently located across the area of greatest surface convergence, which has been shifting southward through the morning. This band should see an uptick in intensity over the next couple of hours with rates 2+ inches per hour primarily across the southern Buffalo Metro extending northward into northwestern Wyoming County. Near zero visibility will be possible at times with dangerous travel conditions likely. ..Thornton/Guyer.. 11/18/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BUF... LAT...LON 42927853 42897889 42837910 42727914 42627916 42577900 42587870 42607855 42657839 42727816 42807811 42907821 42927853 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1116 AM CST Fri Nov 18 2022 Valid 191200Z - 201200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk for severe thunderstorms appears negligible across the U.S. Saturday through Saturday night. ...Synopsis... Cyclonic flow aloft will persist across the CONUS on Saturday. A pair of shortwave troughs will progress through this cyclonic flow, with the northernmost wave moving from the Upper Midwest eastward across the Great Lakes, OH Valley, and Northeast. The southernmost shortwave will be less progressive, gradually moving from southern CA/Lower CO River Valley eastward/southeastward into more of the Southwest and northern Mexico. Progression of the northern shortwave and an associated cold front will reinforce the stable continental air mass in place over the majority of central and eastern CONUS. This should preclude thunderstorm development east of the Rockies, with the exception of a few localized areas. One area is along the TX Coast, where showers and a few embedded thunderstorms are possible early Saturday morning. Isolated thunderstorms are also possible Saturday night into Sunday morning across south FL and the FL Keys amid modest low-level moisture return and easterly low-level flow. Lastly, a few flashes are possible over and in the immediate lee of Lakes Erie and Ontario, where warm lake waters and convective heavy snow bands could result in isolated lightning flashes. ..Mosier.. 11/18/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1039 AM CST Fri Nov 18 2022 Valid 181700Z - 191200Z ...Southern California... Light offshore winds and dry surface conditions are expected much of today ahead of an advancing mid-level trough. While gusts may occasionally reach 15-20 mph in the higher terrain, widespread elevated fire-weather conditions are not expected through the daytime hours. Stronger pressure gradients will increase overnight and into early Saturday as the trough and enhanced mid-level northeasterly flow move over southern CA. Terrain enhanced gusts to 30 mph and humidity below 20% are possible, supporting some risk for elevated to locally critical fire-weather conditions. However, fuels remain only marginally supportive. See the previous discussion for additional information. ..Lyons.. 11/18/2022 .PREV DISCUSSION... /ISSUED 1147 PM CST Thu Nov 17 2022/ ...Synopsis... A broad, positively tilted mid-level trough will encourage deep-layer northwesterly flow and at/below freezing surface temperatures across much of the central and northern CONUS, mitigating widespread significant wildfire-spread potential. However, northerly, offshore deep-layer flow is expected to develop along the southern California coastline. As such, dry and breezy conditions may develop in higher-terrain areas of the transverse ranges toward the end of the period (i.e. 06-12Z Saturday). Elevated highlights have been introduced. However, these highlights delineate what is expected to be a lower-end event since fuels currently appear poorly to (at best) marginally receptive to wildfire spread. ...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 1030 AM CST Fri Nov 18 2022 Valid 181630Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected through tonight. ...Discussion... Most of the CONUS will be influenced by longwave troughing and associated cool/cold continental trajectories. Related to a belt of southern-stream westerlies, weak cyclogenesis is expected over the northwest Gulf of Mexico late tonight, with increasing warm advection and the gradual development of weak elevated buoyancy near the Texas coast. This may support isolated thunderstorm development late tonight/early Saturday. Occasional lightning flashes will also continue through this evening, particularly in vicinity of Lake Erie and Lake Ontario in association with lake-effect snow bands. This convective potential should somewhat diminish late tonight. ..Guyer/Thornton.. 11/18/2022 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1117 AM CST Thu Nov 17 2022 Valid 181200Z - 191200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected on Friday. ...Synopsis... Broad upper troughing will be maintained across the CONUS on Friday as a series of shortwave troughs move through the northern stream from the northern Plains across the mid/upper MS Valley, Great Lakes, and Northeast. Another shortwave trough is expected to become displaced from the main branch as it moves southward across CA. Persistent upper troughing will help maintain a stable, continental air mass across the CONUS throughout the period. The aforementioned series of shortwaves result in cooling mid-level temperatures above the still-warm Lower Great Lakes. This will contribute to additional steepening of low-level lapse rates, enhancing evolving bands of sustained low-topped lake-effect convection. Thermodynamic profiles may become conducive to charge separation and occasional lightning flashes in the more vigorous activity. Some moisture return is anticipated across deep South TX, with surface cyclogenesis beginning just off the coast early Saturday morning. The warm sector will likely remain offshore, but warm air advection Friday night/Saturday morning will result in showers along the coast, with a few embedded thunderstorms possible. ..Mosier.. 11/17/2022 Read more

No watches are valid as of Thu Nov 17 17:22:02 UTC 2022.

No Mesoscale Discussions are in effect as of Thu Nov 17 17:22:02 UTC 2022.

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1007 AM CST Thu Nov 17 2022 Valid 171630Z - 181200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Sporadic lightning flashes are possible across parts of the lower Great Lakes within lake-effect snowbands. ...Lower Great Lakes... A negatively tilted midlevel shortwave trough currently tracking east-southeastward across the upper Great Lakes will continue eastward across Lower Michigan and the lower Great Lakes into the overnight hours. Current regional VWP data shows west-northwesterly low-level flow over the lower Great Lakes vicinity, and this flow will back/strengthen to a west-southwesterly component in response to the approaching shortwave trough this evening. This mean low-level flow parallel to the long axis of Lake Erie and eventually Lake Ontario will support intense/persistent lake-effect snowbands through the overnight hours. Cold midlevel temperatures accompanying the shortwave trough atop relatively warm lake waters will yield sufficiently cold/high EL temperatures (at or above 3.5 km AGL) for mixed-phase convective clouds and sporadic lightning flashes within the deeper/persistent snowbands downwind of Lakes Erie and Ontario. ..Weinman/Thompson.. 11/17/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0912 AM CST Thu Nov 17 2022 Valid 171700Z - 181200Z ...NO CRITICAL AREAS... Fire weather concerns remain limited today. Localized elevated conditions are noted within the higher terrain of Los Angeles and Ventura counties in southern CA, and may persist through 20 UTC based on latest ensemble guidance. However, these conditions will remain too localized for highlights. See the previous discussion below for additional details. ..Moore.. 11/17/2022 .PREV DISCUSSION... /ISSUED 1054 PM CST Wed Nov 16 2022/ ...Synopsis... A longwave trough will be present across the entire CONUS today. An expansive surface high pressure system will stretch from the Northwest into the Southeast. A modest coastal trough will develop through the period in southern California. Cool/cold temperatures and weak surface winds will keep fire weather concerns very low during the period. Some locally elevated conditions remain possible early this morning in LA/Ventura Counties before Santa Ana winds fully subside by late morning. ...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 1120 AM CST Wed Nov 16 2022 Valid 171200Z - 181200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected over the continental U.S. on Thursday. ...Synopsis... Several shortwave troughs are expected to move within the broad upper troughing forecast to persist across the CONUS on Thursday, particularly within the northern stream from the northern Plains across the Great Lakes into the Northeast. This progression will help reinforce the dry, continental air mass already in place. Stable conditions associated with this air mass will preclude thunderstorm development across the majority of the CONUS Thursday. The only exception is in the immediate lee of the Lower Great Lakes, where a flash or two is possible within the shallow lake-effect squalls. Lightning coverage over land areas is expected to remain less than 10%. ..Mosier.. 11/16/2022 Read more

No watches are valid as of Wed Nov 16 17:25:01 UTC 2022.

MD 1954 CONCERNING HEAVY SNOW FOR PORTIONS OF NORTHERN ME
Mesoscale Discussion 1954 NWS Storm Prediction Center Norman OK 1036 AM CST Wed Nov 16 2022 Areas affected...Portions of northern ME Concerning...Heavy snow Valid 161636Z - 162200Z SUMMARY...Heavy snow, with rates around 1 inch per hour, should occur through the afternoon across parts of northern Maine. DISCUSSION...A shortwave trough over northern NY and southern Ontario/Quebec will progress northeastward today. Strong large-scale ascent associated with this feature will overspread northern New England through the afternoon. A band of precipitation associated with pronounced frontogenesis in the 700-500 mb layer currently exists over southern Quebec into northern ME. Based on the 12Z sounding from CAR and latest RAP forecast soundings, expectations are for the bulk of this precipitation to fall as snow across northern ME over the next several hours. Strong ascent through the saturated dendritic growth zone should support a band of heavy snow, with rates around 1 inch per hour, mainly across northern ME through this afternoon. Locally higher rates may occur within the most intense portions of the heavy snow band. The stronger forcing aloft will eventually shift into Canada by this evening, with the heavy snow also developing northward and away from northern ME. A mix of freezing rain and sleet may occur on the southern fringe of the precipitation band, where low-level warm advection will support some melting of frozen hydrometeors. ..Gleason.. 11/16/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CAR... LAT...LON 47526927 47476897 47256888 47426833 47326804 47036771 46386774 46086883 45996970 45997036 46357029 46477008 46747003 47526927 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1018 AM CST Wed Nov 16 2022 Valid 161700Z - 171200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHERN CALIFORNIA COAST... Morning observations from along the southern CA coast show a strong Santa Ana wind event underway with RH values in the single digits to low 20s and winds gusting to 50-60 mph (occasionally up to 70 mph within the LA/Ventura county mountains). Several more hours of elevated to critical fire weather conditions are expected before winds gradually abate this evening. Elevated wind/RH conditions will likely develop within the lower CO river valley amid deep diurnal mixing, but limited fuel status for most of the region precludes an expansion of the risk area. See the previous discussion for additional details. ..Moore.. 11/16/2022 .PREV DISCUSSION... /ISSUED 1136 PM CST Tue Nov 15 2022/ ...Synopsis... A broad upper-level trough will be in place across much of the U.S. today. A compact shortwave trough along the southern California coast will phase with the large trough to the east early in the period. Surface high pressure will strengthen in the Great Basin before slowly weakening through the day. ...Southern California... A strong Santa Ana wind event will be ongoing on early this morning. The offshore pressure gradient will be maximized during the early/mid-morning and slowly relax thereafter. Stronger winds aloft, associated with the passing shortwave, will also be most favorably aligned with the offshore gradient during the same period. Winds of 20-30 mph will be possible away from the terrain with 40-60 mph possible in wind-prone areas. Given the upper-level wind support for this event, higher gusts can be expected as well. RH of 10-20% is probable in the typical Santa Ana wind corridors and will become more widespread by afternoon. The main limiting factor for a more significant event will be the moisture levels of the heavier fuels. Fine fuels, however, will be receptive to fire spread. ...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 1011 AM CST Wed Nov 16 2022 Valid 161630Z - 171200Z ...NO THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are not expected across the contiguous U.S. through tonight. ...Synopsis... Broad large-scale troughing will persist over the eastern two-thirds of the CONUS, while an embedded cyclonic impulse lifts northeastward across the Saint Lawrence Valley. An associated surface cyclone will track northeastward off the New England coast, while a cold front extends south-southwestward off the Eastern Seaboard into the central/southern Florida Peninsula. A plume of strong warm air advection ahead of the surface cyclone combined with weak elevated buoyancy could support an isolated lightning flash near eastern ME this afternoon, though this activity looks too isolated for thunder probabilities. Farther south, an isolated storm cannot be ruled out over southwest FL and eventually southeastern FL along the diffuse cold front, though storms should generally remain offshore. Over the Great Lakes, a lightning flash or two is possible with the more intense/persistent lake effect snowbands given a modestly deep convective boundary layer, though coverage appears too limited for thunder probabilities here. ..Weinman/Thompson.. 11/16/2022 Read more

No watches are valid as of Tue Nov 15 17:24:01 UTC 2022.

No Mesoscale Discussions are in effect as of Tue Nov 15 17:24:01 UTC 2022.

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1113 AM CST Tue Nov 15 2022 Valid 161200Z - 171200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The risk of severe thunderstorms appears low across the U.S. Wednesday through Wednesday night. ...Synopsis... A deep upper trough will remain in place over much of the CONUS on Wednesday. A surface low is forecast to deepen as it moves from offshore of the Mid Atlantic northeastward toward the Canadian Maritimes. A cold front attendant to this surface low will continue moving southward across the Gulf of Mexico and FL Peninsula. In the wake of the cold front and under the influence of an expansive surface ridge, dry/stable conditions are expected across most of the CONUS, with minimal thunderstorm risk. ...Coastal New England... The primary convective risk is expected across coastal portions of southern New England, where some increase in low-level moisture and instability is expected near the track of the surface low. Wind profiles will become conditionally favorable for organized convection along/ahead of the low track, but with surface-based instability expected to remain quite limited, severe-thunderstorm potential still appears low. ..Dean.. 11/15/2022 Read more