Severe Storms

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

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1022 AM CST Tue Nov 15 2022 Valid 151630Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorms are not expected across the contiguous United States through tonight. ...Synopsis... Broadly cyclonic/enhanced midlevel flow will persist across the eastern CONUS through the period, while several embedded impulses (evident in water vapor imagery) track northeastward through the flow. This weak large-scale ascent, coupled with a plume of warm advection and cold midlevel temperatures, will support sporadic/embedded lightning flashes within a larger precipitation field along/east of the Appalachians into the overnight hours. At the surface, a baroclinic zone is draped along the GA/Carolinas coast, with upper 60s boundary-layer dewpoints just offshore. This boundary and high theta-e airmass will make little inland progression today owing to the aforementioned widespread precipitation and related cloud coverage west of the boundary. However, current indications are that a weak frontal wave will develop northeastward along the Mid-Atlantic coast, which could favor somewhat greater surface-based instability over immediate coastal areas into the overnight hours. While the enhanced midlevel flow/veering wind profile will support surface-based supercell structures over the Atlantic waters, east-northeastward storm motions should generally keep this activity away from the aforementioned coastal areas. Therefore, the risk of surface-based storms over land appears too conditional for low severe probabilities at this time. ..Weinman/Hart.. 11/15/2022 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0902 AM CST Tue Nov 15 2022 Valid 151700Z - 161200Z The forecast remains on track with localized elevated conditions expected to develop late tonight into early Wednesday morning along parts of the southern CA coast. Cool temperature and widespread rain/snow chances will mitigate fire concerns elsewhere across the CONUS. See the previous discussion below for additional details. ..Moore.. 11/15/2022 .PREV DISCUSSION... /ISSUED 1143 PM CST Mon Nov 14 2022/ ...Synopsis... For today, a large upper-level trough will continue to strengthen in the East. Along the West Coast, another shortwave trough will dig southward along the California coast through the day. At the surface, high pressure in the Great Basin will strengthen into Wednesday morning. Winds across parts of Los Angeles/Ventura Counties will begin to increase during the evening and into Wednesday morning. RH will take some time to fall. Values below 20% appear possible for a few hours late in the period. Winds of 20 mph could extend to the coast, particularly in Ventura County. Winds up to 40 mph are possible within the more wind-prone areas of the terrain. Fuel dryness remains rather marginal after recent rains, but some elevated fire weather can be expected where fuels are locally drier. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Mon Nov 14 17:50:01 UTC 2022.

MD 1952 CONCERNING HEAVY SNOW FOR SOUTH-CENTRAL AND SOUTHWESTERN OK
Mesoscale Discussion 1952 NWS Storm Prediction Center Norman OK 1141 AM CST Mon Nov 14 2022 Areas affected...south-central and southwestern OK Concerning...Heavy snow Valid 141741Z - 142045Z SUMMARY...Heavy snow with rates near 1 inch per hour will continue across west-central OK this afternoon, and possibly spread east-southeastward across south-central OK in the next few hours. DISCUSSION...Latest water vapor loops show strong DCVA overspreading western OK ahead of a compact midlevel shortwave trough approaching west TX. Cold/saturated deep-layer thermodynamic profiles over west TX (sampled by the 12z AMA observed sounding) coupled with the strengthening large-scale ascent are supporting areas of heavy snow across parts of western OK. As the DCVA continues to overspread a weak ENE-WSW-oriented midlevel thermal gradient across this area, frontogenetic forcing should aid in a somewhat focused corridor of snowfall rates near 1 inch per hour given a modestly deep and saturated dendritic growth zone. However, mesoscale ascent is not particularly strong here, so confidence in prolonged heavy rates in any given area is limited at this time. Over southwest OK, surface temperatures remain above freezing, though continued showers and related moistening of the boundary-layer should yield a transition to snow during the next couple hours. Farther east, regional VWP data depicts an increasing southerly low-level jet over north-central TX which will gradually impinge on a WSW-ENE-oriented low/mid-level baroclinic zone over south-central OK. As the aforementioned shortwave trough continues eastward this afternoon, strong mesoscale ascent -- aided by the larger-scale ascent -- will develop through this corridor by 20Z. This strong/focused ascent would conditionally support snowfall rates of 1 inch per hour (locally higher) for a few hours this afternoon. The main question across this corridor is the degree of surface cooling, as surface temperatures remain in the middle/upper 30s F. However, current indications are that continued wet-bulb cooling and descent of the melting layer could support additional surface cooling and a band of heavy snow. ..Weinman.. 11/14/2022 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...OUN... LAT...LON 34959961 35719972 36049958 36209929 36209904 36089869 35469854 35199802 34779698 34519703 34589752 34639816 34739874 34809923 34959961 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1116 AM CST Mon Nov 14 2022 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL GULF COAST TUESDAY MORNING... ...SUMMARY... Strong thunderstorms may impact portions of immediate central Gulf coastal areas Tuesday morning into afternoon, accompanied by at least some risk for severe weather. ...Synopsis... Several shortwave troughs will be embedded within the cyclonic flow aloft expected to cover the CONUS early Tuesday morning. The lead shortwave trough should be over mid MS Valley Tuesday morning, before then ejecting quickly northeastward through the OH Valley. Another shortwave will follow in the wake of this lead wave, moving from the central Plains across the Mid MS Valley and Lower/Middle OH Valley. Evolution of these shortwaves will encourage eastward expansion of the strong mid-level flow initially over the southern Plains and Lower/Mid MS Valley. By late Tuesday, moderate to strong mid-level flow is forecast to extend from the southern Plains eastward/northeastward across much of the eastern CONUS. At the same time, strong southerly low-level flow is expected to initially extend from the central Gulf Coast into the TN Valley. This corridor of stronger low-level flow should spread eastward/northeastward throughout the day, likely stretching from the Southeast Coast through VA by Tuesday evening. ...Central Gulf Coast... A surface low will likely near the immediate coastal areas of southern MS/AL. Location of this low will have a large influence on the downstream severe threat across southern AL into the western FL Panhandle. A more northerly location would likely result in more inland penetration of the warm sector. Thunderstorms will likely be ongoing near the surface low early Tuesday morning, with convergence in the vicinity of the low and attendant frontal zone continuing to support storms in the warm sector throughout the morning. Low-level shear profiles suggest isolated gusts and a few tornadoes are possible with these storms. Weakening low-level convergence and displacement south of the stronger large-scale forcing for ascent should lead to gradually diminishing thunderstorm coverage and intensity with eastern extent into more of GA and central FL Peninsula. ...Mid-Atlantic... Strong low-level flow mentioned in the synopsis will extend across the region by the late afternoon/early evening. This strong low-level flow may overlay modest low-level moisture from far northeast SC into the NC Outer Banks from Tuesday evening into Wednesday morning. Current expectation is for the more supportive thermodynamic environment to remain just offshore, limiting the severe potential over land areas. If guidance trends towards a more westerly position of the developing surface low, a small area of low severe probabilities may be needed in later outlooks. ..Mosier.. 11/14/2022 Read more