Severe Storms

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Thu Sep 14 2023 Valid 142000Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN NM TO PARTS OF THE TX GULF COAST... ...SUMMARY... Isolated severe thunderstorm are possible along an axis from eastern New Mexico to the Texas Gulf Coast, mainly from late afternoon through this evening. ...20Z Update... The Marginal Risk has been expanded slightly northeastward along the upper TX Gulf Coast, in advance of a strong storm cluster near and northeast of Houston. These storms have developed within an environment characterized by rich low-level moisture and moderate buoyancy, but also weak midlevel lapse rates and warm temperatures aloft. Within this regime, effective shear of 25-30 kt will support modestly organized storms with a threat of locally damaging gusts until storms reach the coast. Deepening cumulus and recent storm development is ongoing across parts of the TX Hill Country, in the vicinity of a weak surface low/trough. It remains possible that a supercell or two will evolve out of this developing convection and move southeastward later this afternoon into this evening. Weak midlevel lapse rates may tend to limit storm severity, but any sustained supercell could pose a threat of localized severe gusts and hail approaching severe limits. Additional strong to isolated severe storm development will be possible across parts of eastern NM later this afternoon into this evening. See the previous discussion below for more details. ..Dean.. 09/14/2023 .PREV DISCUSSION... /ISSUED 1124 AM CDT Thu Sep 14 2023/ ...NM/TX... Current visible satellite imagery and surface analysis shows a boundary extending from southeast NM into central TX. A very moist and moderately unstable air mass is present along and south of this boundary, along with mostly clear skies and steepening low level lapse rates. Large scale forcing is weak across this region, but most 12z CAM solutions show isolated thunderstorms developing near the boundary by late afternoon and evening. Forecast soundings suggest sufficient mid/upper level westerly flow for organized multicell or occasional supercell structures capable of hail and gusty winds. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Thu Sep 14 2023 Valid 151200Z - 161200Z ...NO CRITICAL AREAS... No changes will be made to the currently valid outlook. Fire-weather concerns should remain localized with hot and dry conditions over parts of the Northwest. See the previous discussion for more information. ..Lyons.. 09/14/2023 .PREV DISCUSSION... /ISSUED 0114 AM CDT Thu Sep 14 2023/ ...Synopsis... Fire weather concerns are expected to remain low for Friday. Warm and very dry conditions (RH in the teens) are expected again Friday afternoon from northern CA and northwest NV through central OR and into southern WA. Locally breezy conditions will remain possible within the Cascades that may support localized elevated fire weather conditions; however, a weak signal in high-res ensemble guidance for sustained winds over 15 mph limits confidence in the overall fire weather threat and precludes highlights at this time. Locally dry/breezy conditions are also possible across the Dakotas within a post-frontal regime, but highlights are withheld due to a combination of low probability for elevated conditions and rain chances over the next 24 hours. ...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 1229 PM CDT Thu Sep 14 2023 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN HIGH PLAINS INTO CENTRAL TEXAS... ...SUMMARY... Isolated severe thunderstorms are possible over the southern High Plains eastward into central portions of Texas on Friday and Friday night. ...Synopsis... A mid/upper-level trough is forecast to move eastward across the upper Midwest/Great Lakes region on Friday, as a cold front moves through the northern Plains into parts of MN/WI. Generally zonal mid/upper-level flow will persist across much of the southern CONUS on Friday, in advance of a low-amplitude shortwave trough moving eastward near the Four Corners region. ...Southern High Plains into central TX... Isolated strong to potentially severe storms will be possible across a broad region from the southern High Plains into central TX on Friday, though confidence remains relatively low regarding the details and potential corridors of greater severe potential. Convection will likely be ongoing across parts of west-central/northwest TX Friday morning, though guidance varies regarding the location and intensity of any ongoing convection. If a more organized MCS can develop late in the D1/Thursday period, then it may spread southeastward across central TX during the day on Friday with an isolated severe-wind threat. However, with an already modest low-level jet expected to weaken through the day, confidence in this scenario remains low. Additional diurnal storm development will be possible Friday afternoon near an outflow-reinforced surface boundary that will likely be draped somewhere across central into southwest TX, and also across eastern NM within a favorably moist low-level flow regime in advance of the shortwave trough near the Four Corners region. Modest westerly midlevel flow will provide marginally sufficient effective shear for a few organized storms, including some potential for isolated supercells with initial more discrete development. Some severe hail threat will accompany the stronger discrete storms, especially from eastern NM into parts of the TX Panhandle/South Plains, where midlevel lapse rates will be steeper. With time, some southeastward-moving clusters may evolve and pose a risk of localized severe gusts and perhaps some hail spreading into parts of central and south TX during the evening/overnight. ...Eastern MN into northwest WI... In the wake of weak morning convection, isolated diurnal storm development will be possible along the cold front from eastern MN into northwest WI. While favorably cold temperatures aloft and steepening midlevel lapse rates will spread over the region, limited low-level moisture and buoyancy may tend to limit storm coverage and intensity. If confidence increases in more robust storm development, then hail probabilities may eventually be needed for the region. ..Dean.. 09/14/2023 Read more

No watches are valid as of Wed Sep 13 22:28:02 UTC 2023.

MD 2148 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR CENTRAL TO NORTHERN ARIZONA
Mesoscale Discussion 2148 NWS Storm Prediction Center Norman OK 0522 PM CDT Wed Sep 13 2023 Areas affected...central to northern Arizona Concerning...Severe potential...Watch unlikely Valid 132222Z - 140015Z Probability of Watch Issuance...5 percent SUMMARY...Instances of large hail will be possible for the next few hours as transient, but robust, thunderstorms continue to develop across central to northern Arizona. Watch issuance is not expected. DISCUSSION...Numerous robust, but short lived (30-60 minutes) thunderstorms continue to develop across central to northern AZ. Deep-layer flow over the region remains very weak (effective bulk shear values on the order of 15 knots), which is contributing to the short duration of most cells. However, MUCAPE over the region is near the 90th percentile for the Flagstaff, AZ region for mid-September. This, combined with mid-level lapse rates near 8 C/km, is likely supporting the robust, but transient updrafts noted in GOES IR and KFSX reflectivity imagery. Severe-hail signatures have been noted in MRMS products with these cells, suggesting that large hail is possible. This activity is largely being driven by a combination of weak low-level theta-e advection over the Mogollon Rim and lift along a composite outflow/weak dryline draped over the region. Both of these factors should continue to support thunderstorm development through sunset before the onset of nocturnal cooling. ..Moore/Edwards.. 09/13/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FGZ... LAT...LON 34151048 34381143 34551251 34791292 35231314 35721313 35881281 35791192 35591127 35301054 34981004 34690981 34510974 34250975 34121004 34151048 Read more

MD 2147 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR THE BIG BEND REGION OF TEXAS
Mesoscale Discussion 2147 NWS Storm Prediction Center Norman OK 0455 PM CDT Wed Sep 13 2023 Areas affected...The Big Bend region of Texas Concerning...Severe potential...Watch unlikely Valid 132155Z - 140000Z Probability of Watch Issuance...5 percent SUMMARY...Sporadic severe hail and wind will be possible over the next couple of hours as thunderstorms continue to mature. However, this threat will remain sufficiently limited to preclude watch issuance. DISCUSSION...Over the past 1-2 hours, GOES IR imagery has shown steadily cooling cloud top temperatures associated with a multicell cluster south of the Fort Stockton, TX area. Although individual cells within the cluster have demonstrated limited longevity and organization so far, the overall trend suggests that the potential for severe wind/hail is increasing for downstream areas. This cluster is expected to continue propagating east/southeast along a low-level theta-e gradient where buoyancy is maximized (MLCAPE up to 1500 J/kg). Furthermore, sufficient shear is present in the 0-5 km layer to support supercell structures, though the observed storm mode will likely continue to modulate this potential. While the severe threat is noted, these limitations will preclude the need for a watch. To the west, a cluster of storms across northern Mexico is undergoing similar intensification per GOES IR imagery, and should cross the TX/Mexico border within the next hour. These cells may intensify further as they move towards the regional buoyancy maximum, and could also pose a severe hail/wind threat along and just north of the Rio Grande. ..Moore/Edwards.. 09/13/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...EWX...MAF... LAT...LON 28990292 28890323 29440441 29720466 30190487 30420495 30610487 30650469 30670442 30520386 30500352 30620314 30760265 30760242 30660213 30410183 29850168 29700174 29750210 29630259 28990292 Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0449 PM CDT Wed Sep 13 2023 Valid 151200Z - 211200Z Mid-level ridging will remain in place over the Northwest through the first part of the extended forecast period. While winds will be weak, warm and dry conditions beneath the ridge may promote localized fire-weather concerns. Into the weekend and early next week, prominent troughing will likely develop over the Northwest, ushering in cooler and wetter conditions for the remainder of the forecast period. Overall fire-weather concerns remain low given the poor overlap of dry and windy conditions with receptive fuels. ...Northwest... As the upper ridge solidifies and shifts eastward late this week and into the weekend, low-level northerly flow is forecast to weaken over much of southern OR and northern CA. At the same time, the ridge aloft will promote dry and warm surface conditions across much of the Pacific Northwest. The warm and dry surface conditions, combined with only modest mid-level stability, may support some plume-dominated fire activity into the first part of the weekend. The strong heating and terrain effects may also support the development of a low-level thermal pressure trough, occasionally enhancing local winds to 10-15 mph across parts of the Columbia Basin and southern OR. However, given the lack of stronger synoptic flow, confidence in sustained fire-weather conditions is low. As the upper ridge shifts eastward, a weak, upper low will meander toward the CA coast from the eastern Pacific. At the same time, a broad upper trough and stronger flow aloft are forecast to move onshore across western BC. Ascent and weak mid-level moisture transport ahead of the upper-level systems may support isolated showers and thunderstorms across parts of southern OR and northern CA D4/D5 Sat/Sun. Modest storm speeds and a relatively dry sub-cloud layer could support a risk for a few dry lightning strikes over receptive fuels through the weekend. Considerable uncertainty exists regarding storm coverage and mode given the relatively modest forcing for ascent. Storm coverage appears greatest D5/Sun, but may shift eastward toward areas of less receptive fuels. Confidence lessens considerably heading into next week as various model solutions exist with the BC trough shifting eastward. ...Northern Rockies... Late in the weekend and into early next week, stronger westerly flow may emerge from the Northwest troughing into parts of the northern Rockies/Plains. There remains considerable model difference in the medium range. The GFS and some ensemble members are much stronger and more amplified with the overall upper air pattern. With the more amplified solutions, a strong cold front accompanying the upper trough may promote dry and breezy conditions over parts of Columbia Basin, eastern MT and western ND early next week. It remains uncertain if this will occur, but it may favor some potential for elevated fire-weather conditions next week. ..Lyons.. 09/13/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Wed Sep 13 2023 Valid 132000Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHERN NEW ENGLAND...PARTS OF THE SOUTHEAST...AND THE SOUTHWEST INTO WEST TEXAS... ...SUMMARY... Isolated severe thunderstorms remain possible across parts of southern New England, the Southwest into West Texas, and from Georgia to the South Atlantic coast this afternoon into this evening. ...20Z Update... A few thunderstorms have developed this afternoon across CT into Long Island Sound, in the wake of earlier morning convection. Wind profiles (as noted in VWPs from KOKX and KBOX) continue to be somewhat favorable for organized convection, and locally damaging gusts and/or a brief tornado remain possible through the remainder of the afternoon and potentially into the early evening. The Marginal Risk has been trimmed slightly from the west, but otherwise maintained across parts of southern New England. See MCD 2146 for more information. Elsewhere, the Marginal Risks across parts of the Southeast and Southwest/West TX remain unchanged. See the previous discussion below for more information. ..Dean.. 09/13/2023 .PREV DISCUSSION... /ISSUED 1144 AM CDT Wed Sep 13 2023/ ...Southern New England... A cluster of generally weakening thunderstorms is currently ongoing across the region and could still pose some continued strong/localized severe storm risk. For additional short-term information (through early afternoon), see Mesoscale Discussion 2145. Weak lapse rates and modest overall heating/buoyancy, along with marginal low-level shear, may keep the overall severe risk low. While uncertain, various short-term guidance is insistent that additional redevelopment could occur this afternoon in the wake of this morning's thunderstorm cluster, with renewed development potentially across southwest New England in proximity to the weak surface wave and eastward-advancing front. Should this happen, some severe risk could redevelop as diurnal destabilization occurs across a somewhat broader part of southern New England this afternoon. ...Arizona/New Mexico to West Texas... A low-amplitude mid-level disturbance over the southern Rockies will continue eastward toward west/north Texas through tonight. Conditionally, the most favorable area for a few supercells should be over the Permian Basin and Trans-Pecos of West Texas. Despite near moist-adiabatic mid-level lapse rates, including a lower hail risk than typical supercell situations, favorable speed shear will exist above 700 mb to support an elongated mid to upper hodograph. Nevertheless, timing of large-scale ascent attendant to the impulse appears to be early relative to peak heating, and boundary-layer warming will be the key driver to the degree of instability today. Accordingly, will continue to maintain a broad corridor of relatively low severe probabilities at this time, while still acknowledging some potential for storm clustering across west/southwest Texas later this afternoon/evening that could semi-focus a wind-related severe risk. Otherwise, isolated, marginal severe hail/wind will be possible from late afternoon to mid-evening over the southeast part of Arizona and southwest into east-central New Mexico. ...South Atlantic coast... Isolated to scattered thunderstorms should develop along the coastal sea breeze and across the Savannah Valley in association with a remnant MCV. While 0-3 km winds will be light, 20-25 kt 500-mb west-southwesterlies could support loose multicell clustering with locally strong gusts from 45-60 mph, with a peak threat in the late afternoon. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Wed Sep 13 2023 Valid 141200Z - 151200Z ...NO CRITICAL AREAS... The previous forecast remains valid with no changes. Localized dry and breezy conditions are possible over parts of the southern Cascades and northern Central valley of CA. Otherwise, fire-weather concerns over much of the CONUS are low. ..Lyons.. 09/13/2023 .PREV DISCUSSION... /ISSUED 0157 AM CDT Wed Sep 13 2023/ ...Synopsis... A mid-level trough will traverse the Northern Plains/international border while a cold front surges southward across eastern Montana into North Dakota tomorrow/Thursday. Behind this cold front, 15+ mph sustained northwesterly surface winds will coincide with 25-35 percent RH during the afternoon hours. Since RH and fuel receptiveness will be marginally supportive of widespread wildfire potential, fire weather highlights have been withheld. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Tue Sep 12 22:32:02 UTC 2023.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0439 PM CDT Tue Sep 12 2023 Valid 141200Z - 201200Z In the wake of earlier troughing, prominent mid-level ridging is forecast to remain over the Pacific Northwest through much of the extended forecast period. Beneath the ridge, dry and warm conditions are expected, albeit with weaker winds. To the east, persistent troughing and cooler than average temperatures are forecast for much of the central and eastern CONUS. Given the lack of overlap of strong winds with dry surface conditions, fire-weather concerns will be limited to localized areas. ...Northwest... Dry and breezy conditions are possible across southern OR and northern CA D3/Thur as the upper ridge builds over the eastern Pacific. Northerly flow of 10-20 mph and RH below 30% are possible through the afternoon. A few hours of dry and breezy conditions may overlap areas of dry fuels and ongoing fires, supporting locally elevated fire-weather concerns. However, widespread fire-weather conditions appear unlikely as gradient winds are forecast to weaken quickly into the evening. Through the remainder of the week and first part of next weekend, the building upper ridge will support continued warming and drying over much of the Pacific Northwest. A thermally induced surface pressure trough may support occasional gusty winds in proximity to the low RH, but the lack of stronger synoptic winds will keep fire-weather concerns localized. Through the weekend and end of the forecast period, a series of upper-level troughs will approach the West Coast. Broad ascent ahead of these systems may support isolated thunderstorms D5/D6 Sat/Sun across parts of far southern OR into northern CA. Exact storm coverage is highly uncertain given model timing differences. However, dry sub-cloud layers and modest PWAT values below 1 inch may support some risk for dry lightning strikes over receptive fuels. ..Lyons.. 09/12/2023 ...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 0439 PM CDT Tue Sep 12 2023 Valid 141200Z - 201200Z In the wake of earlier troughing, prominent mid-level ridging is forecast to remain over the Pacific Northwest through much of the extended forecast period. Beneath the ridge, dry and warm conditions are expected, albeit with weaker winds. To the east, persistent troughing and cooler than average temperatures are forecast for much of the central and eastern CONUS. Given the lack of overlap of strong winds with dry surface conditions, fire-weather concerns will be limited to localized areas. ...Northwest... Dry and breezy conditions are possible across southern OR and northern CA D3/Thur as the upper ridge builds over the eastern Pacific. Northerly flow of 10-20 mph and RH below 30% are possible through the afternoon. A few hours of dry and breezy conditions may overlap areas of dry fuels and ongoing fires, supporting locally elevated fire-weather concerns. However, widespread fire-weather conditions appear unlikely as gradient winds are forecast to weaken quickly into the evening. Through the remainder of the week and first part of next weekend, the building upper ridge will support continued warming and drying over much of the Pacific Northwest. A thermally induced surface pressure trough may support occasional gusty winds in proximity to the low RH, but the lack of stronger synoptic winds will keep fire-weather concerns localized. Through the weekend and end of the forecast period, a series of upper-level troughs will approach the West Coast. Broad ascent ahead of these systems may support isolated thunderstorms D5/D6 Sat/Sun across parts of far southern OR into northern CA. Exact storm coverage is highly uncertain given model timing differences. However, dry sub-cloud layers and modest PWAT values below 1 inch may support some risk for dry lightning strikes over receptive fuels. ..Lyons.. 09/12/2023 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2141 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF SOUTHERN ARIZONA AND SOUTHERN NEW MEXICO
Mesoscale Discussion 2141 NWS Storm Prediction Center Norman OK 0428 PM CDT Tue Sep 12 2023 Areas affected...portions of southern Arizona and southern New Mexico Concerning...Severe potential...Watch unlikely Valid 122128Z - 122300Z Probability of Watch Issuance...20 percent SUMMARY...Some uptick in severe potential may occur over the next few hours. Isolated bouts of severe hail/wind may accompany the strongest storms and a WW is not anticipated. DISCUSSION...Storms near the AZ/NM/international border area have been percolating in intensity over the last couple of hours, with MRMS mosaic radar imagery showing an increase in 1 inch MESH tracks with some of the strongest storms. Recently, robust convective initiation has taken place in far western Pinal County, AZ, where slightly elongated hodographs and 1000+ J/kg MLCAPE support supercell structures capable of severe hail. A severe gust or two also cannot be ruled out with the stronger storms. Overall, the severe threat should be isolated and a WW issuance is not expected. ..Squitieri.. 09/12/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABQ...EPZ...TWC...FGZ...PSR... LAT...LON 32921274 33661157 33930973 33380717 32890615 32430621 31990665 31810744 31560790 31270838 31340938 31361045 31541104 32111247 32921274 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Tue Sep 12 2023 Valid 131200Z - 141200Z ...NO CRITICAL AREAS... ...20z Update... Breezy northwest winds are forecast to develop over portions of the southern OR Cascades into the far northern Central Valley of CA. While occasional 15-25 mph gusts are possible, surface conditions are not expected to be overly dry with RH values generally above 30%. Occasional lower RH values may overlap locally with breezy conditions through the afternoon, but the limited coverage should keep fire-weather concerns localized. Thus, confidence remains too low to include elevated probabilities. ..Lyons.. 09/12/2023 .PREV DISCUSSION... /ISSUED 0121 AM CDT Tue Sep 12 2023/ ...Synopsis... Relatively zonal flow is expected across much of the central U.S. tomorrow/Wednesday. Nonetheless, some surface lee troughing is likely along the High Plains, which will encourage the northward transport of a moist low-level airmass. At the same time, more beneficial rainfall may occur across portions of the southern Plains (mainly Texas). As such, wildfire-spread concerns are relatively minimal, with no highlights introduced. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0300 PM CDT Tue Sep 12 2023 Valid 131200Z - 141200Z ...NO CRITICAL AREAS... ...20z Update... Breezy northwest winds are forecast to develop over portions of the southern OR Cascades into the far northern Central Valley of CA. While occasional 15-25 mph gusts are possible, surface conditions are not expected to be overly dry with RH values generally above 30%. Occasional lower RH values may overlap locally with breezy conditions through the afternoon, but the limited coverage should keep fire-weather concerns localized. Thus, confidence remains too low to include elevated probabilities. ..Lyons.. 09/12/2023 .PREV DISCUSSION... /ISSUED 0121 AM CDT Tue Sep 12 2023/ ...Synopsis... Relatively zonal flow is expected across much of the central U.S. tomorrow/Wednesday. Nonetheless, some surface lee troughing is likely along the High Plains, which will encourage the northward transport of a moist low-level airmass. At the same time, more beneficial rainfall may occur across portions of the southern Plains (mainly Texas). As such, wildfire-spread concerns are relatively minimal, with no highlights introduced. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Sep 12 2023 Valid 122000Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE EAST AND SOUTHWEST... ...SUMMARY... Isolated severe thunderstorms remain possible this afternoon into tonight, across parts of the southern Appalachians to Mid-Atlantic States, south Georgia to central Florida, and southern Arizona to southwest New Mexico. ...20Z Update... Some minor adjustments have been made to the general thunderstorm lines, but no changes have been made to the severe probabilities. See the previous discussion below for more information, and MCD 2140 regarding the short-term threat for northeast GA into parts of the Carolinas and southern VA. ..Dean.. 09/12/2023 .PREV DISCUSSION... /ISSUED 1129 AM CDT Tue Sep 12 2023/ ...Appalachians/Mid-Atlantic States... Broad height falls will occur regionally in advance of the upper trough centered near the Great Lakes/northern Ontario. Moderate differential diabatic heating will occur today ahead of a weak southwest/northeast-oriented baroclinic zone. This will aid the development of scattered thunderstorms through early/mid afternoon from the Tennessee Valley to the central Appalachians. Poor mid-level lapse rates will limit overall buoyancy and updraft vigor, but at least weak buoyancy coupled with 25-35 kt effective bulk shear should support multicell clusters and an attendant threat for sporadic damaging winds this afternoon through early evening. While a spatial decrease in the severe threat is expected after sunset, some uptick in severe risk may occur tonight as greater mid-level height falls overspread richer low-level moisture over the Chesapeake and Delmarva regions. With weak surface low development expected, low-level mass response and low-level shear/SRH may be adequate for a few transient supercells. These supercells should generally remain weak, but could potentially pose a low-probability brief tornado threat aside from localized wind damage. ...Florida/southern Georgia... A minor mid-level trough over the north-central Gulf will slowly progress east and remain well offshore through the period. Downstream of this feature, 500-mb west-southwesterly winds of 15-25 kt will persist and support short-duration/transient storm organization. As surface temperatures warm into the upper 80s to low 90s, isolated to scattered thunderstorms will develop along the sea breezes and collide inland. Ample buoyancy with MLCAPE of 2000-2500 J/kg will support vigorous downdrafts and sporadic wind gusts from 45-65 mph, along with the possibility of marginally severe hail from 0.75 to 1.25 inches. ...Southern Arizona/southwest New Mexico... A belt of confluent mid-level westerlies will yield a swath of 30-35 kt flow across the region, supporting potential for isolated severe thunderstorms from late afternoon through tonight. Mid-level lapse rates will be modest and timing/extent of large-scale ascent appears nebulous with multiple rounds of thunderstorm development from this morning through tonight. Although somewhat tempered by lingering early day clouds and precipitation, a plume of weak to moderate buoyancy should become established this afternoon south of the Mogollon Rim, with the strongest regional destabilization across parts of southwest into south-central Arizona. Scattered thunderstorms seem most likely during the late afternoon and evening within the buoyancy gradient and across the higher terrain. Sporadic occurrences of 50-60 mph wind gusts along with marginally severe hail around 1 inch will be possible through the period. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Tue Sep 12 2023 Valid 122000Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE EAST AND SOUTHWEST... ...SUMMARY... Isolated severe thunderstorms remain possible this afternoon into tonight, across parts of the southern Appalachians to Mid-Atlantic States, south Georgia to central Florida, and southern Arizona to southwest New Mexico. ...20Z Update... Some minor adjustments have been made to the general thunderstorm lines, but no changes have been made to the severe probabilities. See the previous discussion below for more information, and MCD 2140 regarding the short-term threat for northeast GA into parts of the Carolinas and southern VA. ..Dean.. 09/12/2023 .PREV DISCUSSION... /ISSUED 1129 AM CDT Tue Sep 12 2023/ ...Appalachians/Mid-Atlantic States... Broad height falls will occur regionally in advance of the upper trough centered near the Great Lakes/northern Ontario. Moderate differential diabatic heating will occur today ahead of a weak southwest/northeast-oriented baroclinic zone. This will aid the development of scattered thunderstorms through early/mid afternoon from the Tennessee Valley to the central Appalachians. Poor mid-level lapse rates will limit overall buoyancy and updraft vigor, but at least weak buoyancy coupled with 25-35 kt effective bulk shear should support multicell clusters and an attendant threat for sporadic damaging winds this afternoon through early evening. While a spatial decrease in the severe threat is expected after sunset, some uptick in severe risk may occur tonight as greater mid-level height falls overspread richer low-level moisture over the Chesapeake and Delmarva regions. With weak surface low development expected, low-level mass response and low-level shear/SRH may be adequate for a few transient supercells. These supercells should generally remain weak, but could potentially pose a low-probability brief tornado threat aside from localized wind damage. ...Florida/southern Georgia... A minor mid-level trough over the north-central Gulf will slowly progress east and remain well offshore through the period. Downstream of this feature, 500-mb west-southwesterly winds of 15-25 kt will persist and support short-duration/transient storm organization. As surface temperatures warm into the upper 80s to low 90s, isolated to scattered thunderstorms will develop along the sea breezes and collide inland. Ample buoyancy with MLCAPE of 2000-2500 J/kg will support vigorous downdrafts and sporadic wind gusts from 45-65 mph, along with the possibility of marginally severe hail from 0.75 to 1.25 inches. ...Southern Arizona/southwest New Mexico... A belt of confluent mid-level westerlies will yield a swath of 30-35 kt flow across the region, supporting potential for isolated severe thunderstorms from late afternoon through tonight. Mid-level lapse rates will be modest and timing/extent of large-scale ascent appears nebulous with multiple rounds of thunderstorm development from this morning through tonight. Although somewhat tempered by lingering early day clouds and precipitation, a plume of weak to moderate buoyancy should become established this afternoon south of the Mogollon Rim, with the strongest regional destabilization across parts of southwest into south-central Arizona. Scattered thunderstorms seem most likely during the late afternoon and evening within the buoyancy gradient and across the higher terrain. Sporadic occurrences of 50-60 mph wind gusts along with marginally severe hail around 1 inch will be possible through the period. Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1227 PM CDT Tue Sep 12 2023 Valid 131200Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF SOUTHERN NEW ENGLAND...COASTAL CAROLINAS...SOUTHERN HIGH PLAINS... ...SUMMARY... Marginally severe thunderstorms are possible in parts of the southern High Plains, southern New England, and the Carolinas on Wednesday. ...Synopsis... An upper-level trough will move from the Great Lakes/Ohio Valley toward New England on Wednesday. Multiple vorticity maxima will be embedded within the midlevel southwesterly flow ahead of this trough. At the surface, a cold front will move across parts of the Northeast and Mid Atlantic into the southern Appalachians, with a weak frontal wave potentially moving from the Mid Atlantic into New England through the day. Farther west, a broad upper-level trough will remain in place across parts of the western/central CONUS, with one notable shortwave trough expected to move eastward from the southern Rockies into the southern Plains. ...Northern NJ/Southeast NY into southern New England... A band of convection will likely be ongoing at the start of the forecast period somewhere across southeast NY/northern NJ into western parts of southern New England, aided by low-level warm advection and midlevel vorticity maxima ejecting northeastward ahead of the primary upper trough. Instability will generally remain weak, but moderate deep-layer shear, favorable moisture, and some enhancement of low-level shear/SRH within the warm-advection regime may support transient rotating cells capable of locally damaging gusts and/or a brief tornado. The primary threat may reside with the initial cluster of convection as it moves eastward across southern New England, though some redevelopment will be possible its wake, depending on timing of early convection and extent of destabilization in its wake. ...Coastal Carolina vicinity... In advance of the large-scale trough to the north, one or more weak midlevel vorticity maxima may move across parts of the Carolinas Wednesday. These may aid in scattered afternoon thunderstorm development within a warm, moist, and moderately unstable environment during the afternoon. Modest westerly midlevel flow will support effective shear of 25-30 kt, sufficient for some storm organization, and a few semi-organized cells/clusters will be possible. A Marginal Risk has been added for parts of near-coastal SC and southern NC, where the best overlap of instability, shear, and storm coverage is currently anticipated. ...Southern High Plains vicinity... Scattered thunderstorms are expected from the southern Rockies into the High Plains Wednesday afternoon/evening, as a midlevel shortwave trough traverses the region. Weak to moderate buoyancy and sufficient deep-layer shear will support a few organized cells/clusters capable of producing localized hail and severe gusts. ...Southeast AZ into southwest NM... Scattered thunderstorm development will again be possible across parts of southern AZ into southwest NM on Wednesday. Moisture/instability may be somewhat weaker than D1/Tuesday, though deep-layer shear will remain marginally sufficient for a few semi-organized storms. Depending on the extent of D1 convection across the region and its potential impact on D2 destabilization, severe probabilities may eventually be needed. ..Dean.. 09/12/2023 Read more

No Mesoscale Discussions are in effect as of Mon Sep 11 22:20:26 UTC 2023.

WW 0682 Status Updates
STATUS FOR WATCH 0682 HAS NOT BEEN ISSUED YET Read more