Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0200 PM CST Sat Mar 11 2023 Valid 112000Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF EASTERN OKLAHOMA INTO NORTHERN MISSISSIPPI... ...SUMMARY... Scattered severe thunderstorms, capable of large to very large hail, will remain possible this evening and overnight across eastern Oklahoma into Arkansas. ...20Z Update... The primary change to this outlook was to expand the Slight Risk farther east into northern MS for tonight. Some of the latest high-resolution guidance have been trending upwards in intensity of a bowing segment of convection originating from earlier supercells across AR. After 06Z, this line of storms may progress across northern MS with a threat of damaging gusts. The severe hail threat remains on track across eastern OK into western AR for this evening. Multiple hail producing supercells are likely, and a few instances of up to baseball sized hail is possible. The primary limiting factor to a more widespread severe hail threat is the potential for a rapid upscale growth of storms, which may occur after storms achieve supercell status, hence limiting the coverage of significant-severe hail. Another change to the outlook was to add a Category 1/Marginal Risk for portions of the central valley region of CA. Current observations depict upper 50s to low 60s F surface dewpoints amid warming surface temperatures. Continued diurnal heating will foster a well-mixed but moist boundary layer and associated steep low-level lapse rates. Forecast soundings depict elongated, mostly straight hodographs, suggesting transient, low-topped supercells would be the primary mode of convection. Some guidance also hints at relatively high amounts of low-level vertically oriented vorticity co-located with the better surface-based buoyancy. As such, low-level stretching with the more persistent supercells may support a brief tornado threat. The best chance for severe will be in the 21-01Z time frame. ..Squitieri.. 03/11/2023 .PREV DISCUSSION... /ISSUED 1030 AM CST Sat Mar 11 2023/ ...OK-TX into the lower MS Valley... Located to the south of a more pronounced mid-level low over the northern Great Plains, a low-amplitude disturbance embedded within strong westerly flow, will move from the central High Plains to the Ozarks/OH Valley during the period. Visible satellite imagery this morning shows an extensive stratus shield/moist sector over eastern OK/TX into AR/LA. As a warm front advances north during the day into eastern OK/AR, a low will develop east across the Red River Valley while a cold front progresses southeast across OK and a dryline sharpens over north TX. Steep 700-500 mb lapse rates were observed on 12z raobs over the southern Great Plains (7.9 deg C/km at Norman, OK). Gradual cooling temperatures in the mid-levels will overspread a destabilizing warm sector this afternoon. Forecast soundings show an initial capping inversion gradually weakening by late afternoon with temperatures warming into the 80s along the dryline portion of the overall risk area. Ample deep-layer shear will favor supercells with the initial storms. Model guidance continues to show scattered thunderstorms initially developing over eastern OK this evening and spreading east into AR during the evening and into the overnight. Some upscale growth into a mix of supercells and linear structures is indicated by the models. The predominant risk will be large to very large hail with the mostly elevated activity. A gradual weakening is expected as storms eventually move into northern MS late tonight as buoyancy lessens with east extent. Farther south along the dryline, convective initiation is still uncertain across north TX. Models continue to show a limited probability for storm initiation across this corridor. Nonetheless, if a storm or two were to develop and become sustained, a severe risk could materialize for a few hours. ...Southwest States and CA... A belt of strong/low-amplitude westerlies coupled with steep lapse rates and modest moisture could yield a couple of stronger storms late this afternoon/early evening across the California San Joaquin Valley and/or across southern Nevada into southern Utah/far northern Arizona. However, organized severe storms are not currently expected. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0117 PM CST Sat Mar 11 2023 Valid 121200Z - 131200Z ...NO CRITICAL AREAS... No changes are needed to the Day 2 Fire Weather Outlook. ..Thornton.. 03/11/2023 .PREV DISCUSSION... /ISSUED 0108 AM CST Sat Mar 11 2023/ ...Synopsis... Fire weather concerns will remain localized across the southern High Plains and perhaps the southern Florida Peninsula on Sunday. ...Southern High Plains... Zonal flow aloft is expected to persist across the southern Rockies through late Sunday; however, surface high pressure building into the central Plains in the wake of a cold frontal passage late Saturday/early Sunday will mute lee troughing. Nonetheless, breezy downslope winds appear likely in the immediate lee of the more prominent terrain features across the Trans Pecos region of southwest TX and across eastern NM. Localized elevated conditions are possible, but weak ensemble signals and only modestly dry fuels limit confidence in the fire weather threat. ...Southern Florida... Fuels remain dry across the southern half of the FL peninsula with 30-day precipitation amounts between 5-10% of normal. Drier model solutions hint at afternoon RH values falling into the 30-35% range with westerly winds near 10-15 mph. This may support pockets of elevated conditions, but a displacement of the strongest winds across northwest FL with drier conditions along the southeast coast limits confidence in the spatial extent of the threat. ...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 1118 AM CST Sat Mar 11 2023 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE GULF COASTAL STATES... ...SUMMARY... Scattered severe thunderstorms capable of producing large hail, damaging winds, and a couple tornadoes should occur Sunday across parts of the Southeast. Some of the hail could be very large (2+ inches in diameter). ...Synopsis... Strengthening westerly mid-level flow will overspread the Southeast tomorrow/Sunday as an upper trough amplifies across the eastern U.S. A cold front will continue to sag southeastward ahead of the upper trough, trailing a surface low poised to traverse the OH Valley/central Appalachians through the period. However, a weak impulse embedded within the strengthening mid-level westerly flow will aid in the development of a secondary surface low/lee trough near the southeastward-moving cold front over the Gulf Coastal states. The development of this surface low will aid in low-level warm-air/moisture advection across the Gulf Coast states, enhancing low-level lift, shear and buoyancy to support scattered strong to potentially severe storms during the morning and afternoon hours. ...Gulf Coast States... Thunderstorms (perhaps in an organized line) should be ongoing at the start of the period across portions of the TN Valley into the Southeast states. These storms will continue to drift southward, away from the surface cold front and the better deep-layer ascent, supporting weakening convective trends on at least a temporary basis. Sometime during the late morning to mid-afternoon hours though, the development of a secondary surface low will foster greater low-level lift/moisture advection, coincident with modest diurnal heating amid persistent cloud cover. A re-invigoration of convection is expected ahead of the cold front to support a potentially more organized severe threat. Point forecast soundings and high-resolution guidance-member-consensus depicts a warm sector of mid 60s F dewpoints, overspread by mid-level lapse rates (and resultant MLCAPE) of 6-7 C/km (1000 J/kg) from central AL eastward, and 8+ C/km (2000 J/kg) toward eastern LA/southern MS. Modest veering and strengthening winds with height will support elongated hodographs with mild low-level curvature across the warm sector. Transient supercells should be the initial storm mode before storms grow upscale into a line (since the cold front will be roughly aligned with deep-layer westerly flow). During the supercell stage, large hail is possible, with 2+ inch diameter stones possible from southern AL westward given the elongated hodographs, steep lapse rates and near-saturation in the hail-embryo bearing layer. Farther east, both supercells and linear bowing segments will pose both a damaging gust and hail threat. However, a couple of tornadoes are also possible wherever buoyancy can overlap areas of relatively more backed low-level flow ahead of the cold front. Storms should gradually weaken through the evening as they progress into northern FL given weakening ascent/buoyancy. ..Squitieri.. 03/11/2023 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1030 AM CST Sat Mar 11 2023 Valid 111630Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN OKLAHOMA AND FAR NORTHEAST TEXAS INTO CENTRAL/SOUTHERN ARKANSAS AND FAR NORTHWEST MISSISSIPPI... ...SUMMARY... Scattered severe thunderstorms capable of large to very large hail will be possible this evening and overnight especially across eastern Oklahoma and Arkansas. ...OK-TX into the lower MS Valley... Located to the south of a more pronounced mid-level low over the northern Great Plains, a low-amplitude disturbance embedded within strong westerly flow, will move from the central High Plains to the Ozarks/OH Valley during the period. Visible satellite imagery this morning shows an extensive stratus shield/moist sector over eastern OK/TX into AR/LA. As a warm front advances north during the day into eastern OK/AR, a low will develop east across the Red River Valley while a cold front progresses southeast across OK and a dryline sharpens over north TX. Steep 700-500 mb lapse rates were observed on 12z raobs over the southern Great Plains (7.9 deg C/km at Norman, OK). Gradual cooling temperatures in the mid-levels will overspread a destabilizing warm sector this afternoon. Forecast soundings show an initial capping inversion gradually weakening by late afternoon with temperatures warming into the 80s along the dryline portion of the overall risk area. Ample deep-layer shear will favor supercells with the initial storms. Model guidance continues to show scattered thunderstorms initially developing over eastern OK this evening and spreading east into AR during the evening and into the overnight. Some upscale growth into a mix of supercells and linear structures is indicated by the models. The predominant risk will be large to very large hail with the mostly elevated activity. A gradual weakening is expected as storms eventually move into northern MS late tonight as buoyancy lessens with east extent. Farther south along the dryline, convective initiation is still uncertain across north TX. Models continue to show a limited probability for storm initiation across this corridor. Nonetheless, if a storm or two were to develop and become sustained, a severe risk could materialize for a few hours. ...Southwest States and CA... A belt of strong/low-amplitude westerlies coupled with steep lapse rates and modest moisture could yield a couple of stronger storms late this afternoon/early evening across the California San Joaquin Valley and/or across southern Nevada into southern Utah/far northern Arizona. However, organized severe storms are not currently expected. ..Smith/Mosier.. 03/11/2023 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1032 AM CST Sat Mar 11 2023 Valid 111700Z - 121200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHEAST NEW MEXICO INTO SOUTHWEST TEXAS... Morning surface observations show strong southwesterly flow has begun across far western Texas and southeast New Mexico with winds sustained at 20-25 mph gusting 30-40 mph. Behind the dryline, relative humidity values are dropping quickly with daytime heating and mixing ongoing. The lowest values are located across southwestern Texas/southeast New Mexico, where critical fire weather will remain the most likely through the afternoon. A broad region of Elevated conditions will be possible across southwest Texas and eastern New Mexico. The current Elevated and Critical delineation are on track with no changes needed with this update. See previous discussion below. ..Thornton.. 03/11/2023 .PREV DISCUSSION... /ISSUED 1235 AM CST Sat Mar 11 2023/ ...Synopsis... Elevated to critical fire weather conditions remain likely this afternoon across the southern High Plains. Strengthening mid-level zonal flow is noted in water-vapor imagery across the central/southern Rockies with a notable lee cyclone deepening across southeast CO. Further intensification of the low is expected this afternoon as it shifts eastward into OK. An attendant trough/dryline is forecast to migrate east across TX, resulting in a breezy downslope flow regime across eastern NM and west TX by peak heating. Upstream surface observations and 00 UTC soundings across NM show limited boundary-layer moisture with overnight RH values in the teens and low 20s. This dry air mass will experience additional downslope warming/drying with minimum RH values near 15% likely by late afternoon as it spreads into eastern NM/west TX. Gradient winds near 15-25 mph will see frequent gusts up to 30-40 mph amid deep boundary-layer mixing. Confidence in sustained critical wind/RH criteria remains highest across southeast NM into portions of southwest TX; however, widespread elevated conditions appear likely across much of the region. Despite relatively high confidence in the wind/RH forecast, fuel conditions across the region remain marginal per latest fuel guidance with ERCs near seasonal normal values. Fine grasses will likely undergo sufficient drying by mid/late afternoon to support some fire weather concern, but the limited fuel status precludes substantial expansions at this time. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Fri Mar 10 20:31:01 UTC 2023.

MD 0266 CONCERNING SNOW SQUALL FOR PORTIONS OF SOUTHERN IDAHO
Mesoscale Discussion 0266 NWS Storm Prediction Center Norman OK 0134 PM CST Fri Mar 10 2023 Areas affected...portions of southern Idaho Concerning...Snow Squall Valid 101934Z - 102130Z SUMMARY...A snow squall is expected to continue across southern Idaho over the next couple of hours. Damaging to severe-equivalent wind gusts are the main threat with this line. Brief bouts of heavy snow and reduced visibility are also possible along with a 15-20 F drop in surface temperatures to near freezing. DISCUSSION...A snow squall has rapidly materialized across portions of southern ID to the NV border, with recent observations showing wind gusts exceeding 60 kts and a 15-20 F surface temperature plunge behind the snow-squall leading line. Preceding the snow squall is a plume of 7 C/km 0-3 km lapse rates. These lapse rates may promote a strong low-level vertical circulation which could sustain this intense, low-topped convective band for at least a couple more hours. The 15+ F surface temperature drop behind the leading line suggests that snow (perhaps in briefly heavy bouts) may occur behind the leading line. Furthermore, severe-equivalent wind gusts have been observed near or in association with this band of low-topped convection, and these winds appear to be the primary hazard. Nonetheless, reduced visibility will also be possible (regardless of precipitation loss) when considering the intense surface wind gusts. The convective line should eventually weaken after outpacing the steep low-level lapse rate plume. ..Squitieri.. 03/10/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...SLC...PIH...BOI...LKN... LAT...LON 42031460 42601383 42951305 43041243 42831169 42381159 41961193 41841322 41791429 42031460 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CST Fri Mar 10 2023 Valid 102000Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER FAR SOUTHERN GEORGIA INTO NORTHERN FLORIDA... ...SUMMARY... Isolated severe storms remain possible across parts of southern Georgia, southeast Alabama into northern Florida this afternoon. Locally strong winds and hail will be possible with some of these storms. Little change was made to the previous outlook except to remove risk area behind the front. A few reports of hail or strong gusts remain likely from northern FL into southern GA. ..Jewell.. 03/10/2023 .PREV DISCUSSION... /ISSUED 1027 AM CST Fri Mar 10 2023/ ...Synopsis... Late morning satellite imagery shows a mid-level shortwave trough amplifying over the upper OH Valley and Lower Great Lakes. A surface low over the OH/PA corridor this afternoon will weaken as the primary cyclone develops east of the Mid-Atlantic coast after dark. A cold front trailing southward through the southern Appalachians into the northeast Gulf Coast will push through the Southeast and much of FL through Saturday morning. A cluster of elevated thunderstorms ongoing late this morning will continue to move east near and north of an earlier outflow boundary draped from west to east across southern GA. The airmass south of the boundary in the warm sector is destabilizing with surface dewpoints rising into the low-mid 60s across north FL and southern GA as low-level moisture advects northeast. Strong westerly mid-level flow will support some storm organization potential as 1000-1500 J/kg MLCAPE develops by early afternoon across southern GA into the eastern FL Panhandle/north FL vicinity. Expecting additional storms to develop near the front as it pushes through adjacent parts of AL/GA/FL by early-mid afternoon. The lack of stronger large-scale forcing for ascent may limit the overall coverage/intensity of the storms this afternoon. Nonetheless, a few of the stronger storms may pose an isolated risk for large hail/damaging gusts before this activity weakens after sunset and moves east of the coast. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0151 PM CST Fri Mar 10 2023 Valid 111200Z - 121200Z ...CRITICAL FIRE WEATHER AREA FOR PARTS OF SOUTHEAST NM AND WEST TX... No changes are needed to the current Day 2 Fire Weather Outlook. See previous discussion below. ..Thornton.. 03/10/2023 .PREV DISCUSSION... /ISSUED 0224 AM CST Fri Mar 10 2023/ ...Synopsis... A strong mid-level jet will extend across the southwestern CONUS through the day on Saturday, and this should lead to a strong surface low over northwest Oklahoma around midday. This will lead to warm, dry, breezy conditions across the southern High Plains during the afternoon. Per latest model guidance, RH is expected to be near 10-15% across much of the southern High Plains with gusts to 40-50 mph. However the strongest gusts are expected to be across the Texas Panhandle and adjacent areas of New Mexico, while the lowest RH may be farther south across the Permian Basin and Texas Big Bend region. Fuels in the region are modestly dry, and given the strong winds expected, an Elevated area has been introduced in this outlook. A Critical area has also been added across the Permian basin where the best overlap between strong winds and low RH is expected to occur, though this may be expanded with subsequent outlooks. Additionally, there is some uncertainty as to the timing of a cold front moving southward through the Texas Panhandle on Saturday afternoon, which will determine the northern extent of the Elevated risk area. ...North Carolina... Some elevated conditions may also across parts of North Carolina, with gusts to 15-20 mph and RH near 30-35% in a post-frontal regime. However, marginally dry fuels should keep any elevated fire weather risk transient and localized. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 0265 CONCERNING HEAVY SNOW FOR PORTIONS OF FAR WESTERN NEW YORK
Mesoscale Discussion 0265 NWS Storm Prediction Center Norman OK 1243 PM CST Fri Mar 10 2023 Areas affected...portions of far western New York Concerning...Heavy snow Valid 101843Z - 102145Z SUMMARY...Brief periods of heavy snow, including 1 inch/hour rates, are possible over the next few hours in association with a broader precipitation band. DISCUSSION...Strong low-level warm-air/moisture advection is taking place ahead and to the north of a surface low, currently positioned over western Pennsylvania, which is poised to move east through the afternoon. A band of heavy snow is already underway across far western New York per latest surface observations. 850 mb frontogenesis is evident along the Lake Erie/Ontario shorelines and is serving as a source of convergence. As such, the enhanced lift of relatively rich low-level moisture into an already saturated dendritic growth zone should continue to support additional bouts of heavy snow (1 inch/hour) for at least a few more hours across western New York, as also suggested by 12Z HREF and the last few runs of the HRRR. ..Squitieri.. 03/10/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BGM...BUF... LAT...LON 42517933 43167892 43427791 43497672 43107623 42787624 42497680 42277729 42167777 42207819 42517933 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1117 AM CST Fri Mar 10 2023 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN OKLAHOMA ACROSS ARKANSAS AND INTO NORTHERN MISSISSIPPI... ...SUMMARY... Scattered severe thunderstorms producing primarily large damaging hail will be possible Saturday evening and overnight mainly from eastern Oklahoma, Arkansas and northern Mississippi. ...Synopsis... Height falls will occur across the Plains in response to an upper low over the northern Plains and a low-amplitude wave nosing into the southern Plains. Substantial cooling aloft will occur over the region, including the Ozarks and Arklatex region and toward the MS Valley late. At the surface, low pressure will develop into western OK and move toward the Red River as a cold front moves in from the north. A dryline will push east past I-35 in OK and TX during the afternoon as a warm front moves rapidly north across LA and into AR and eastern OK by 00Z. ...Eastern OK into AR and northern MS... Most of the day will be free of thunderstorms across the area as the air mass recovers with the passage of the warm front, and heating occurs just southwest of the area. Lift will increase substantially during the evening as the cooling aloft overspreads the area. Gradual deepening of the moist boundary layer will then lead to an eruption of thunderstorms centered over AR and possibly into eastern OK initially, and these will move rapidly east/southeastward toward northern MS overnight. Forecast soundings show large values of elevated instability and steep lapse rates, in addition to effective deep-layer shear in excess of 50 kt. The increasing speed shear with height will favor fast-moving, forward-tilted supercells which may produce damaging hail, some over 2" in diameter. Given the expectation of a few long-lived storms, damaging gusts cannot be ruled out as well with the hail-laden, cold downdrafts and despite a stable surface layer. ....Northeast TX into southern OK... A conditional risk of isolated supercells will exist along the dryline during the late afternoon and early evening as a heating erodes capping in a narrow zone from near or just east of I-35 from central OK into north TX. Overall, models indicate only low probabilities of thunderstorms, and this is likely due to the strongly veered 850 mb winds and subsequent drying of the low levels just above the surface. Most of the lift will be focused farther east near the warm front, but will maintain low severe probabilities for this conditional risk. ..Jewell.. 03/10/2023 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1049 AM CST Fri Mar 10 2023 Valid 101700Z - 111200Z Slight adjustments were made to the expand the current Elevated area further south and west into south-central New Mexico in agreement with the latest HREF probabilities of Elevated to near Critical fire weather conditions. Morning surface observations indicate relative humidity values behind the dryline across eastern and central New Mexico already around 15-20 percent with winds sustained around 10-12 mph gusting up to 25 mph. Diurnal mixing will continue through the afternoon with further relative humidity reductions and gusts as high as 30-35 mph. Fuels across New Mexico are marginal, precluding the need for any critical areas within the Elevated delineation. ..Thornton.. 03/10/2023 .PREV DISCUSSION... /ISSUED 0129 AM CST Fri Mar 10 2023/ ...Synopsis... Central CONUS will be near the apex of a mid-level ridge, and the resulting zonal flow aloft will result in the development of a lee trough over southeastern Colorado through the day today. Though the flow aloft is not particularly strong for this time of year, this will still lead to warm, dry, breezy conditions across the southern High Plain this afternoon. Diurnal mixing west of the dryline is expected to push RH to near 10-20% and gusts to 30-35 mph across eastern New Mexico and into southeastern Colorado. Fuels in this region are at least marginally receptive to fire spread, so an elevated area is maintained. Spotty elevated conditions may also occur across central and south Florida, with RH near 35-40% and gusts to 15-20 mph. Fuels are somewhat dry, however, cross-peninsula flow (i.e., off the warm Gulf of Mexico) is expected to keep any elevated conditions localized and transient. ...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 1027 AM CST Fri Mar 10 2023 Valid 101630Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR NORTH FLORIDA AND SOUTHERN GEORGIA WESTWARD INTO FAR SOUTHEAST ALABAMA... ...SUMMARY... Thunderstorms are expected to develop and intensify across parts of southern Georgia, southeast Alabama into northern Florida this afternoon. Locally strong winds and hail will be possible with some of these storms. ...Synopsis... Late morning satellite imagery shows a mid-level shortwave trough amplifying over the upper OH Valley and Lower Great Lakes. A surface low over the OH/PA corridor this afternoon will weaken as the primary cyclone develops east of the Mid-Atlantic coast after dark. A cold front trailing southward through the southern Appalachians into the northeast Gulf Coast will push through the Southeast and much of FL through Saturday morning. A cluster of elevated thunderstorms ongoing late this morning will continue to move east near and north of an earlier outflow boundary draped from west to east across southern GA. The airmass south of the boundary in the warm sector is destabilizing with surface dewpoints rising into the low-mid 60s across north FL and southern GA as low-level moisture advects northeast. Strong westerly mid-level flow will support some storm organization potential as 1000-1500 J/kg MLCAPE develops by early afternoon across southern GA into the eastern FL Panhandle/north FL vicinity. Expecting additional storms to develop near the front as it pushes through adjacent parts of AL/GA/FL by early-mid afternoon. The lack of stronger large-scale forcing for ascent may limit the overall coverage/intensity of the storms this afternoon. Nonetheless, a few of the stronger storms may pose an isolated risk for large hail/damaging gusts before this activity weakens after sunset and moves east of the coast. ..Smith/Squitieri.. 03/10/2023 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0145 PM CST Thu Mar 09 2023 Valid 092000Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO TONIGHT PARTS OF CENTRAL TO EAST TEXAS INTO WEST CENTRAL/SOUTHWEST ALABAMA... ...SUMMARY... Isolated strong to severe thunderstorm development remains possible late this afternoon into tonight from portions of central/east Texas to western Alabama. ...20Z Update... ...East of the Rockies... Only minor changes have been made, to the categorical (10 percent probability) thunderstorm line, generally to account for the continuing progression of the synoptic features. For further details, please refer to the 1630Z discussion, appended below. ...Pacific Coast states... A significant mid-level trough, and embedded low, will gradually turn eastward toward northern Pacific coastal areas later today through tonight. An associated deepening, and occluding surface cyclone is forecast to remains offshore of the Washington coast, but a trailing cold front will advance inland across western into central Oregon and northern California. It appears that the mid-level cold core of the system, including 500 mb temperatures of -30 to -35 C, may contribute to post-frontal boundary-layer destabilization near Oregon coastal areas by 09-12Z. Coupled with an increasing onshore low-level flow component, this is expected to support scattered deepening convection, some of which may become capable of producing lightning. Farther south, a plume of lower/mid tropospheric moisture return, emanating from the southern mid- and subtropical eastern Pacific, will spread inland ahead of the cold front, across the California coast and Sierra Nevada. Despite relatively warm mid-levels, forecast soundings indicate conditionally unstable profiles developing late this evening into the overnight hours, rooted mainly well above the surface, in the lower/mid troposphere. As winds at these elevations take on a strengthening westerly component, orographic forcing for ascent may contribute to convection occasional capable of producing lightning along the western slopes of the Sierra after 06Z. In lower elevations to the west, probabilities for weak thunderstorm potential are more uncertain. However, they might not be negligible across the Sacramento into San Francisco Bay areas overnight, where/when lift ahead of the inland advancing cold front may be enhanced by forcing for ascent near the southern periphery of the mid-level trough. ..Kerr.. 03/09/2023 .PREV DISCUSSION... /ISSUED 1030 AM CST Thu Mar 09 2023/ ...Central/east TX to western AL... Primary shortwave trough ejecting from the central Great Plains to the southern Great Lakes will yield a largely zonal regime across the southern states with minor mid-level perturbations embedded within the flow. A persistent baroclinic zone from TX to AL will strengthen by late afternoon as differential heating is underway with surface temperatures expected to rise into the 80s F across a large swath of the warm sector. Weak to moderate MLCAPE of 500-1500 J/kg is anticipated along and south of the Edwards Plateau in TX to the AR/LA border and west-central/southwest AL. Isolated to scattered showers and thunderstorms are most likely this afternoon from southeast OK and the Ark-La-Tex to central AL, on the cool side of the surface front. With generally weak MUCAPE, and a cool/stable boundary layer in place near and northeast of the front, storms should remain elevated with small hail as the primary threat. One exception may be along a confined portion of the front in the west-central/southwest AL vicinity, where weak low-level warm theta-e advection across this portion of the front might support a supercell or two. The spatiotemporal window for this conditional potential to be realized appears limited given the weak large-scale ascent. A swath of scattered thunderstorm development is expected this evening from the AR/LA border southwest into the Edwards Plateau of TX along and behind the surface cold front, yielding south/southeast acceleration of the front tonight. While isolated damaging winds are possible immediately along the front, the main threat should be isolated severe hail given the undercutting nature of the boundary. The greatest potential for supercells with mid-level rotation should be across the southwest portion of the outlook area in south-central TX. Here, steeper mid-level lapse rates and ample speed shear within the cloud-bearing layer could result in large hail tonight. Read more

No watches are valid as of Thu Mar 9 19:49:02 UTC 2023.

MD 0262 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR CENTRAL TO SOUTHERN AL AND PORTIONS OF EASTERN MS
Mesoscale Discussion 0262 NWS Storm Prediction Center Norman OK 0142 PM CST Thu Mar 09 2023 Areas affected...central to southern AL and portions of eastern MS Concerning...Severe potential...Watch unlikely Valid 091942Z - 092215Z Probability of Watch Issuance...5 percent SUMMARY...Thunderstorms are developing along a stationary front in central AL. These storms may pose a threat for localized small to marginally severe hail, but a WW is unlikely at this time. DISCUSSION...A couple of sustained, deep updrafts have formed in west-central AL along a stationary front during the last 30-60 min. Visible imagery suggests that a north-south convergence band -- evidenced by more congested localized Cu -- may be associated with this convection initiation. Nearby surface stations on the warm side of the front are observing lower 70s F temperatures and dewpoints in the low to mid 60s F. This would support MLCAPE values of around 500-1000 J/kg with the potential for surface-based convection. While minimal veering shear exists in the warm sector, current surface objective analysis and the KMXX VWP suggest local effective SRH values of up to 50-100 J/kg may be present. This low-level shear profile, along with larger cloud-layer shear around 60 kts, could support somewhat persistent updrafts along with a threat for marginally severe hail and wind gusts, but a WW is not expected. ..Flournoy/Grams.. 03/09/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BMX...MOB...JAN... LAT...LON 31448798 32038869 32818884 33278845 33278755 32878669 32258624 31608638 31338713 31448798 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook CORR 1 NWS Storm Prediction Center Norman OK 1137 AM CST Thu Mar 09 2023 Valid 101200Z - 111200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY ACROSS PARTS OF SOUTHERN GEORGIA...SOUTHEASTERN ALABAMA AND NORTHERN FLORIDA... CORRECTED FOR OUTLOOK GRAPHIC ...SUMMARY... A couple of strong thunderstorms are possible across parts of southern Georgia, adjacent southeastern Alabama and northern Florida Friday, accompanied by some risk for severe weather. ...Synopsis... Models suggest that flow in the mid- and higher latitudes of the eastern Pacific through western Atlantic will remain amplified, with generally weak westerlies, as blocking highs are generally maintained near the Aleutians and across the Canadian Arctic through this period. Lower amplitude flow will prevail in the southern mid- and subtropical latitudes, with broad mid-level troughing across the central Pacific transitioning to broad ridging across the eastern Pacific through the southern tier of the western into central U.S., and broad troughing farther downstream into the western Atlantic. Within this regime, one vigorous shortwave impulse is forecast to progress inland across the northern U.S. Pacific coast and northern Rockies by late Friday night. This will be accompanied by a weakening surface cyclone and inland advancing cold front across the interior Northwest and Rockies, and deepening surface troughing to the lee of the Rockies. It appears that a plume of higher moisture content air emanating from the subtropical Pacific, initially impinging on the Sierra Nevada, before spreading into the Great Basin, will gradually be suppressed southward, ahead of the front. East of the Rockies, a weak initial surface low is forecast to gradually migrate northeastward through the Allegheny Plateau vicinity, before much more substantive cyclogenesis takes place off the Mid Atlantic coast, in response to a significant short wave trough digging southeast of the Great Lakes region. As this occurs, low-level cooling and drying, in the wake of a trailing cold front, will overspread much of the Southeast through central Gulf coast. ...Pacific Northwest into northern Rockies... Models indicate that the inland migrating short wave will be accompanied by a compact mid-level cold core, including 500 mb temperatures of -30 to -35C. This will contribute to weak boundary-layer destabilization, which may become supportive of scattered low-topped convection capable of producing lightning near Oregon coastal areas at 12Z Friday, inland toward the Montana Rockies through the day. ...California coast through the Great Basin... Forecast soundings suggest that lower/mid-tropospheric moistening, coupled with weak mid-level cooling, will be sufficient to contribute to layers of weak conditional instability. It appears that this will mostly be rooted at higher altitudes, as cloud cover and precipitation hinder surface heating and boundary-layer destabilization at lower elevations, particularly to the west of the Sierra Nevada. Aided by 40 to 70 kt westerly flow in roughly the 4,000-10,000 foot layer, strong orographic forcing for ascent may contribute to convection capable of producing lightning across the western slopes of the Sierra and Wasatch. ...Southeast... Scattered thunderstorm activity is possible Friday near the southeastward advancing cold front. The general tendency may be for this activity to form to the cool side/above the front. However, near peak afternoon instability, a window of opportunity may develop for sustained thunderstorm activity rooted within the boundary-layer, just ahead of the front across parts of southern Georgia into northern Florida. Forecast soundings suggest that the environment might become conducive for a couple of strong storms posing at least some risk for severe hail and wind, before activity weakens by Friday evening. ..Kerr.. 03/09/2023 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1042 AM CST Thu Mar 09 2023 Valid 101200Z - 111200Z The previous forecast (see below) generally remains on track, and only minor adjustments were made with this update. In particular, the Elevated area was expanded slightly northward along the I-25 corridor in south-central CO. Here, the latest high-resolution guidance shows the potential for 20-25 mph sustained westerly surface winds (with higher gusts) and around 20 percent RH (especially in the wind-prone/gap-flow areas). ..Weinman.. 03/09/2023 .PREV DISCUSSION... /ISSUED 0156 AM CST Thu Mar 09 2023/ ...Synopsis... At the mid-levels, zonal flow is expected across the southern High Plains through the day on Friday, which will lead to the return of lee troughing. This should result in dry, breezy conditions to the west of a dryline across the area during the afternoon. RH may be near 10-20% with gusts near 25-30 mph across eastern New Mexico into southeast Colorado and the western Panhandles. Given at least marginally dry fuels in the region, this is enough to support the introduction of an Elevated risk area. Some uncertainty exists with regard to high-level cloud cover in the northern part of the Elevated area, which may limit surface heating, and therefore limit the fire weather risk. ...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 1042 AM CST Thu Mar 09 2023 Valid 091700Z - 101200Z Gradual cloud-clearing from west to east is evident from southeastern CO into far western KS -- aided by continued downslope flow and subsidence-induced drying on the backside of a departing midlevel shortwave trough. Farther east-southeast into portions of western KS and the OK Panhandle, deeper moisture (see 12Z DDC observed sounding) and related cloud coverage limit confidence in RH reductions. Therefore, the Elevated area has been trimmed over these areas. Along the I-25 corridor in south-central CO, locally critical conditions are possible (primarily in gap-flow areas) -- where 20-25 mph sustained westerly surface winds (with higher gusts) should overlap 10 percent RH. However, these conditions appear too localized for Critical highlights. For additional details on the Day 1 fire-weather risk, see the previous discussion below. ..Weinman.. 03/09/2023 .PREV DISCUSSION... /ISSUED 1259 AM CST Thu Mar 09 2023/ ...Synopsis... Mid-level shortwave ridging will build over the southern High Plains through the day today, and at the surface, a wind shift will pass the region during the morning hours. By afternoon, diurnal mixing is expected to drive RH to 5-15% from eastern New Mexico northward into southeastern Colorado and southwestern Kansas. Fuels in this region are at least marginally dry, and southeast Colorado and southwest Kansas are currently in exceptional drought. There are two areas with potential for stronger winds (gusts to 15-20 mph), one in eastern New Mexico, and another in southeastern Colorado, southwest Kansas, and into the northern Panhandles, For these reasons, the two separate Elevated risk areas are maintained. Across eastern Georgia and western South Carolina, expect some localized, transient elevated conditions with RH near 20% in the afternoon and marginally dry fuels. However, light winds preclude the introduction of any Elevated areas at this time. ...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 Thu Mar 09 2023 Valid 091630Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF CENTRAL TO EAST TX INTO WEST-CENTRAL/SOUTHWEST AL... ...SUMMARY... Isolated severe thunderstorms will be possible through tonight from portions of central/east Texas to western Alabama. ...Central/east TX to western AL... Primary shortwave trough ejecting from the central Great Plains to the southern Great Lakes will yield a largely zonal regime across the southern states with minor mid-level perturbations embedded within the flow. A persistent baroclinic zone from TX to AL will strengthen by late afternoon as differential heating is underway with surface temperatures expected to rise into the 80s F across a large swath of the warm sector. Weak to moderate MLCAPE of 500-1500 J/kg is anticipated along and south of the Edwards Plateau in TX to the AR/LA border and west-central/southwest AL. Isolated to scattered showers and thunderstorms are most likely this afternoon from southeast OK and the Ark-La-Tex to central AL, on the cool side of the surface front. With generally weak MUCAPE, and a cool/stable boundary layer in place near and northeast of the front, storms should remain elevated with small hail as the primary threat. One exception may be along a confined portion of the front in the west-central/southwest AL vicinity, where weak low-level warm theta-e advection across this portion of the front might support a supercell or two. The spatiotemporal window for this conditional potential to be realized appears limited given the weak large-scale ascent. A swath of scattered thunderstorm development is expected this evening from the AR/LA border southwest into the Edwards Plateau of TX along and behind the surface cold front, yielding south/southeast acceleration of the front tonight. While isolated damaging winds are possible immediately along the front, the main threat should be isolated severe hail given the undercutting nature of the boundary. The greatest potential for supercells with mid-level rotation should be across the southwest portion of the outlook area in south-central TX. Here, steeper mid-level lapse rates and ample speed shear within the cloud-bearing layer could result in large hail tonight. ..Grams/Flournoy.. 03/09/2023 Read more