Severe Storms

WW 578 SEVERE TSTM MN MT ND 012050Z - 020500Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 578 NWS Storm Prediction Center Norman OK 350 PM CDT Tue Aug 1 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northwest Minnesota Extreme northeast Montana North Dakota * Effective this Tuesday afternoon from 350 PM until Midnight CDT. * Primary threats include... Scattered large hail and isolated very large hail events to 2 inches in diameter possible Scattered damaging wind gusts to 70 mph possible SUMMARY...Widely scattered thunderstorm development is expected this afternoon from northwest Minnesota westward across North Dakota, where the environment will favor splitting supercells capable of producing large hail and damaging winds. Additional storm development is expected near the Montana/North Dakota border, with the potential for these storms to grow into a cluster with damaging winds while moving east-southeastward through early tonight. The severe thunderstorm watch area is approximately along and 65 statute miles north and south of a line from 65 miles south southwest of Williston ND to 25 miles northeast of Detroit Lakes MN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU8). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 30020. ...Thompson Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Tue Aug 01 2023 Valid 021200Z - 031200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF CENTRAL TEXAS INTO SOUTHWEST OKLAHOMA... The Critical area was expanded slightly based on the latest high-resolution guidance. Farther west, locally elevated fire-weather conditions are possible in the Cascade gaps, though these conditions appear too localized for highlights. For additional details, see the previous discussion below. ..Weinman.. 08/01/2023 .PREV DISCUSSION... /ISSUED 1225 AM CDT Tue Aug 01 2023/ ...Synopsis... A surface cyclone will continue to slowly deepen across the central Plains on Wednesday as the upper-level ridge continues to deamplify. This will maintain a pressure gradient across the southern Plains, with a strengthening low-level jet late Wednesday afternoon and Wednesday evening. As a result, 15 to 20 mph winds are expected from central Texas into northern Oklahoma with relative humidity of 20 to 30 percent. While these conditions are well within the range of Elevated fire-weather criteria, they are borderline for a Critical area. However, fuels are very dry in the region and with temperatures over 100F, are expected to continue to dry further. Therefore, sustained Elevated conditions may be more capable of large-fire potential than typical Critical fire-weather conditions due to the fuel status. This warrants a Critical delineation for areas along and west of I-35 in central and northern Texas and into far southwest Oklahoma. ...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 0249 PM CDT Tue Aug 01 2023 Valid 012000Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON THROUGH EARLY TONIGHT FOR PARTS OF THE NORTHERN PLAINS AND CENTRAL HIGH PLAINS... ...SUMMARY... Severe-thunderstorm gusts are most probable over parts of the central High Plains and much of North Dakota to northwestern Minnesota, along with at least isolated large hail. ...20Z Update... Overall forecast remains on track with no changes needed to the existing outlook. Late afternoon thunderstorm development is still anticipated over ND, both along the front in north-central ND and in the MT/ND border vicinity. The environmental conditions still support supercells capable of large hail and damaging gusts. Additionally, ongoing thunderstorms across central CO as are still expected to grow upscale later this evening, with an attendant threat for severe outflow gusts and isolated large hail. ..Mosier.. 08/01/2023 .PREV DISCUSSION... /ISSUED 1119 AM CDT Tue Aug 01 2023/ ...Northern Plains through tonight... A midlevel shortwave trough is cresting the midlevel ridge and will continue east-southeastward over southern SK/AB toward ON, as an associated weak cold front moves southeastward into ND. Convection is ongoing in a few clusters near the ND/MT/SK border and northwest MN along the north edge of the unstable warm sector. Some form of these storms could persist through the afternoon, though the main severe threat is expected to be additional development along the front and/or outflow boundaries by mid-late afternoon. Steep midlevel lapse rates, boundary-layer dewpoints in the 65-70 F range and daytime heating will boost MLCAPE to 2000 J/kg or greater as convective inhibition weakens. Low-level flow will be weak beneath moderately strong mid-upper westerly flow, resulting in small low-level hodographs and longer hodographs above about 4 km AGL. This environment will support a mix of multicell clusters and some supercells capable of producing large hail and damaging winds as convection spreads southeastward late this afternoon into early tonight. ...Central High Plains this evening... Within the monsoonal moisture plume, convectively-enhanced waves will move slowly eastward from UT/WY/CO toward NE. Thunderstorms are expected to form later this afternoon near and just east of the Front Range in a weak upslope flow regime in CO, and convection will subsequently grow upscale into a cluster or two across northeast CO and vicinity this evening. Moderate buoyancy and relatively weak vertical shear will mainly favor multicell clusters capable of producing occasional severe outflow gusts and isolated large hail. ...MO area through tonight... Elevated convection persists late this morning over central MO in a low-level warm advection regime, though this convection is expected to diminish as warm advection weakens this afternoon. There will be a low chance for afternoon storm development on the west edge of the cloud debris and northeast edge of the hot surface temperatures/deeper mixing near the KS/MO border, with a conditional wind/hail threat. The more probable scenario will be for renewed thunderstorm development tonight as warm advection increases again on the nose of a southwesterly low-level jet. The overnight storms will be capable of producing isolated large hail and possibly a few strong outflow gusts. ...Carolinas to FL this afternoon... Surface heating with lingering low-level moisture, beneath midlevel drying, will result in moderate destabilization across the eastern Carolinas, where isolated thunderstorms are expected this afternoon along the sea breeze and subtle terrain influences inland. Buoyancy will be larger to the south (>2500 J/kg MLCAPE from southeast GA southward) where widely scattered afternoon thunderstorms are expected mainly inland from the west coast sea breeze. The moderate buoyancy, DCAPE near 1000 J/kg, and some modest enhancement to vertical shear from north FL northward will support a low-end threat for strong/damaging downburst winds. Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1226 PM CDT Tue Aug 01 2023 Valid 021200Z - 031200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL MISSOURI INTO SOUTHERN ILLINOIS... ...SUMMARY... Thunderstorms capable of damaging gusts are possible from central Missouri into southern Illinois Wednesday afternoon through evening. Isolated strong to severe thunderstorms capable of producing damaging gusts and hail are also possible across the Upper Great Lakes region and central High Plains. ...Synopsis... Upper ridging is forecast to remain in place over the southern Plains and Lower MS Valley, keeping that region hot and dry. Some modestly enhanced mid-level flow will exist from the northern Plains/Upper Midwest through the Mid-Atlantic, between the southern Plains ridge and an upper low over the Hudson Bay. A shortwave trough and associated surface low will likely move through this enhanced flow across Ontario. An attendant cold front is expected to move into the northern Plains, Upper Midwest, and Upper Great Lakes, with some thunderstorms possible along the front during afternoon and evening. Additionally, a convectively induced vorticity maximum will likely track eastward over the central Plains and into the Mid/Lower MO Valley. Some thunderstorms are possible from the Mid MO Valley into the Mid MS Valley as this vorticity maximum interacts with the moist and buoyant air mass over the region. ...Mid MO Valley into the Mid MS Valley... Numerous showers and thunderstorms will likely be ongoing Wednesday morning in an arc from far eastern NE to southeast MO/southern IL/far western KY, remnant from overnight storms from the Mid MO Valley into the Mid MS Valley. These storms will likely dissipate by late morning/early afternoon, but residual cloud cover and resulting differential heating will help induce a warm-front-like boundary across MO. Dewpoints are expected to be in the mid 70s in the vicinity of this boundary Wednesday afternoon, contributing to moderate/strong buoyancy. Even with strong daytime heating south/west of the boundary, some convective inhibition will likely persist, particularly with southwestward extent, where mixing will be greatest. However, convergence along this differential heating zone, combined with slightly higher dewpoints and less overall mixing, as well as ascent from the approaching vorticity maximum, is expected to result in convective initiation. Strong buoyancy will support a risk for hail within the first hour or so of development, before cell interactions and outflow-dominant structures influence a more linear storm mode. Additionally, given the presence of a surface boundary and some more southeasterly surface winds, a tornado or two cannot be entirely ruled out. However, a somewhat quick transition to a predominantly linear mode is anticipated, with at least some chance for cold pool organization into a coherent linear convective system. This system should then track southeastward along the buoyancy gradient into southeast MO, southern IL, and potentially even far western KY. ...Upper Midwest into the Upper Great Lakes... Moderate buoyancy is anticipated ahead of the approaching cold front mentioned in the synopsis. Convergence along the boundary will be modest, with higher storm coverage expected across Upper MI versus farther west across northern WI and northeast MN. Even so, expected moderate buoyancy will combine with 30-40 kt of effective bulk shear to support organized thunderstorms. Forecast soundings show modestly steep midlevel lapse rates and elongated/straight hodographs above around 1-2 km. This suggests isolated hail potential with the strongest storms. Where stronger heating occurs, steep low-level lapse rates will foster isolated strong/damaging gusts as well. ...Central High Plains... Afternoon thunderstorms across the higher terrain are forecast to progress eastward into the lower elevations of the central High Plains during the late afternoon/early evening. Steep low-level lapse rates and high cloud bases will likely support a few stronger gusts as this activity moves eastward into western KS. ..Mosier.. 08/01/2023 Read more

No watches are valid as of Mon Jul 31 22:16:01 UTC 2023.

MD 1800 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF CENTRAL/NORTH ND
Mesoscale Discussion 1800 NWS Storm Prediction Center Norman OK 0511 PM CDT Mon Jul 31 2023 Areas affected...Parts of central/north ND Concerning...Severe potential...Watch unlikely Valid 312211Z - 312345Z Probability of Watch Issuance...20 percent SUMMARY...Isolated severe storms will be possible this evening, with a threat of large hail and localized severe gusts. Watch issuance is currently considered unlikely, but will become possible if storm coverage becomes greater than expected. DISCUSSION...A small cluster of storms has recently developed over southwest Manitoba, with attempts at convective initiation noted across far northeast Bottineau County, ND, and increasing cumulus across north-central ND. Modest diurnal heating amid relatively rich low-level moisture is supporting moderate buoyancy (MLCAPE of 1500-3000 J/kg), while northwesterly midlevel flow is supporting effective shear of 35-45 kt across the region. As a result, the environment is conditionally favorable for supercell development. The primary uncertainty this evening is storm coverage. While multiple mid/upper-level shortwave troughs are moving across the Canadian Prairies, most of ND is under the influence of an upper ridge, and large-scale ascent will likely remain limited. However, a weak warm-advection regime may continue to support isolated storm development, with any mature storms tending to propagate southeastward along the primary instability gradient. As a result, a supercell or two may develop and move across parts of north and central ND this evening, with a threat of large hail and localized severe gusts. Watch issuance is currently considered unlikely due to the expectation for the threat to remain isolated, but will become possible if short-term trends support a greater coverage of storms than currently anticipated. ..Dean/Grams.. 07/31/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...FGF...BIS... LAT...LON 48990147 48989982 48299952 47629936 47379944 47120011 47250081 47710124 48100147 48660158 48990147 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Mon Jul 31 2023 Valid 011200Z - 021200Z There were two primary changes to the outlook with this update. 1) The Elevated highlights in central TX were expanded eastward to the I-35 corridor and northward into far southwest OK. Despite slightly weaker sustained southerly surface winds (around 10-15 mph) closer to the I-35 corridor, continued 100 deg surface temperatures, breezy/gusty afternoon winds, and critically dry fuels (above the 90th percentile ERCs) will still support elevated to spotty critical fire-weather conditions. Upon collaboration with TX Predictive Services, the western portion of the Elevated highlights were trimmed slightly -- as fine fuels (grasses) here will generally be less receptive to large-fire spread compared to the timber/brush fuels farther east owing to a lack of stronger sustained surface winds. 2) A small Elevated area was added over far northeast CA, northwest NV, and far southeast/south-central OR. A continuation of moderate southwesterly midlevel flow across the northern Sierra/southern Cascades will promote 15 mph sustained southwesterly surface winds and around 10 percent minimum RH over dry fuels. For additional details, see the previous discussion below. ..Weinman.. 07/31/2023 .PREV DISCUSSION... /ISSUED 0148 AM CDT Mon Jul 31 2023/ ...Synopsis... A weak lee cyclone is forecast to develop across Kansas on Tuesday as a mid-level shortwave trough crosses the central Plains. This will result in a tightening pressure gradient across the southern Plains with sustained winds around 15 mph. For now, the Elevated delineation covers portions of the Permian Basin into Northwest Texas where winds are expected to be 15 to 20 mph with relative humidity of 20 to 25 percent and critically dry fuels. Dry and breezy conditions may also exist northward into the TX/OK Panhandles, much of western Texas, and southern Kansas. However, fuels remain green across this region due to the significant rainfall in early July. Dry and breezy conditions are expected Tuesday across portions of northeast Montana. However, wetting rain across the region early this morning should moisten fuels in the region and alleviate significant fire weather concerns. Finally, some locally elevated fire weather conditions are possible across portions of northwest Nevada into southwest Idaho, but the threat appears too localized for an Elevated area at this time. ...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 0238 PM CDT Mon Jul 31 2023 Valid 312000Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS...LOWER/MID MISSISSIPPI VALLEY...COASTAL SOUTHEAST...AND ARIZONA... ...SUMMARY... Isolated severe thunderstorms remain possible over portions of the northern/central Plains, coastal Southeast, lower Missouri Valley to west-central Gulf Coast, and Arizona. ...20Z Update... No changes have been made to the prior outlook. ..Gleason.. 07/31/2023 .PREV DISCUSSION... /ISSUED 1121 AM CDT Mon Jul 31 2023/ ...MO to LA this afternoon into tonight... Multiple thunderstorm clusters occurred overnight, and the remnants of convection with outflow and debris clouds persist from southern AR into LA, and across northwest MO. The relatively widespread convective overturning/modification suggests the environment will not have sufficient time to recover by this afternoon. There will be some potential for additional development along the outflow boundary moving southward into southern LA this afternoon, where isolated downbursts may occur. Otherwise, the more probable scenario is for slightly elevated storms to form again tonight in the strengthening warm advection zone across MO. Lapse rates will not be as steep as prior days and midlevel temperatures will be relatively warm in proximity to the southern Plains ridge, so any hail/wind threat should remain marginal. ...Dakotas to northeast CO this afternoon into tonight... Lingering low-level moisture in a weak upslope flow regime will support scattered thunderstorm development this afternoon/evening from the Front Range in northeast CO northward into eastern WY. Midlevel lapse rates will not be as steep as prior days as a result of the monsoonal moisture plume spreading northeastward across UT/CO/WY, and flow aloft will also be relatively weak. Thus, primarily multicell clusters with isolated strong-severe outflow gusts will be the main threat as convection spreads eastward toward western NE and vicinity by tonight. Farther north into ND, the focus for storm development will be nebulous at best. There will be a small chance for diurnal storms in the differential heating zone across far southwest ND by late afternoon, and a storm or two could approach the international border from SK tonight. However, confidence in either scenario is low. ...Fl to Carolinas this afternoon/evening... A weak midlevel trough over the southeast Atlantic states and daytime heating in cloud breaks will drive diurnal convection this afternoon. The primary wind shift/front extends across north FL and off the coasts of the Carolinas, leaving terrain influences and a weak outflow boundary to focus thunderstorm development this afternoon. Lapse rates aloft are poor and buoyancy will be rather modest by summer standards - both of which suggest today is a low-end downburst day (at best) into the Carolinas. Stronger surface heating and destabilization will occur farther south into FL, where a few pulse severe storms with downburst winds will be possible this afternoon. ...AZ this afternoon/evening... With prior convection and the approach of a weak wave from northwest Mexico, there's been an increase in low-level moisture and a decrease in low-midlevel lapse rates since yesterday across southern AZ. Still, isolated strong outflow gusts will be possible with convection from southeast AZ northwestward in the vicinity of the Mogollon Rim, which is where the weaker convective inhibition is expected this afternoon/evening. Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Mon Jul 31 2023 Valid 011200Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTH DAKOTA AND NORTHWESTERN MINNESOTA... ...SUMMARY... Severe thunderstorms capable of producing large hail and damaging winds appear possible Tuesday across parts of North Dakota into northern Minnesota, and the central High Plains into the mid Missouri Valley. Thunderstorms capable of producing occasional damaging winds may also occur over parts of the coastal Southeast. ...Synopsis... An expansive upper ridge will remain anchored over the central CONUS on Tuesday. Multiple weak mid-level disturbances are forecast to rotate around the apex of the upper ridge across the northern/central Plains and Upper Midwest. Upper troughing is expected to persist across the eastern states. Between these features, a belt of modestly enhanced mid-level west-northwesterly flow will extend from the northern Plains and Upper Midwest to parts of the Southeast. ...Northern Plains/Upper Midwest... A weak mid-level shortwave trough should dampen the northern extent of upper ridging over central Canada and the northern Plains on Tuesday. At the surface, a cold front is forecast to move east-southeastward across these areas through the period. Rich low-level moisture, characterized by mid 60s to perhaps low 70s surface dewpoints, should be in place ahead of the front across ND into northern MN. Thunderstorms should develop along/ahead of the front by Tuesday afternoon in a moderately to strongly unstable airmass. The presence of steep mid-level lapse rates and around 30-40 kt of effective bulk shear should aid in some threat for supercells capable of producing large hail. Otherwise, one or more clusters may eventually develop along the length of the cold front and pose more of a severe wind threat as convection develops south-southeastward through Tuesday evening. Given a greater signal for supercells and multicells across this area, have introduced a Slight Risk. This activity should eventually weaken with eastward and southward extent into the northern Plains and Upper Midwest as it encounters a less unstable airmass. ...Central High Plains into the Mid Missouri Valley... Scattered to numerous thunderstorms should once again develop over the higher terrain of the central Rockies early Tuesday afternoon, and eventually spread eastward into the adjacent central High Plains through Tuesday evening. One or more weak mid-level vorticity maxima may aid in this convective development. While deep-layer shear appears fairly modest, generally 30 kt or less, convection should gradually strengthen as it encounters a more unstable airmass across eastern CO and vicinity. Most high-resolution guidance suggests that a small cluster will eventually consolidate and spread eastward across the central Plains Tuesday evening and possible continuing overnight. Isolated hail may occur with the initially more cellular convection, while severe/damaging winds appear more of a concern with eastward extent if a cluster does develop. Have therefore expanded the Marginal Risk eastward to account for this possibility. Farther east into the mid MO Valley, thunderstorms may be ongoing at the beginning of the period in a low-level warm advection regime. While most of this activity will probably remain sub-severe, some threat for hail and gusty winds may exist with the more robust cores through Tuesday morning. The potential for additional convective development Tuesday afternoon appears highly uncertain given weak large-scale forcing. But, there appears to be a signal for renewed thunderstorms in another low-level warm advection regime Tuesday night through early Wednesday morning. With ample MUCAPE and strong deep-layer shear forecast, any elevated supercells which can develop may pose an isolated threat for large hail and strong/gusty winds. ...Coastal Southeast... Isolated to scattered thunderstorms should develop Tuesday afternoon along and east of a weak lee surface trough, with additional convective development possible along the Atlantic sea breeze. Weak to locally moderate instability should develop with daytime heating of a moist low-level airmass. But, poor mid-level lapse rates will probably tend to limit updraft intensity to some extent. Still, around 20-30 kt of deep-layer shear should prove adequate for modest convective organization. An isolated threat for damaging winds may exist with the stronger clusters that form and spread eastward through Tuesday evening, before they eventually weaken and/or move offshore. ..Gleason.. 07/31/2023 Read more

MD 1790 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR CENTRAL AND EASTERN MONTANA
Mesoscale Discussion 1790 NWS Storm Prediction Center Norman OK 0442 PM CDT Sun Jul 30 2023 Areas affected...Central and Eastern Montana Concerning...Severe potential...Watch possible Valid 302142Z - 302315Z Probability of Watch Issuance...60 percent SUMMARY...A severe thunderstorm watch is possible this afternoon/evening across eastern Montana. DISCUSSION...Elevated thunderstorms are ongoing this afternoon across northeast Montana. 12Z CAM guidance was split whether this elevated convection would be strong/severe, however, current radar trends suggest a supercell or two, similar to the 12Z WRF-ARW/NSSL may be the most likely evolution. If this activity continues to intensify, it could eventually become surface based as heating and low-level moisture advection destabilizes the airmass ahead of it. Similarly, thunderstorms across southeast Montana are also likely somewhat elevated, but are moving into an airmass with increasing surface based instability and reducing inhibition. If one or both of these regions appear to "turn the corner", a watch may be needed in the next 1 to 2 hours. Regardless of this early activity across eastern Montana, a severe thunderstorm watch is more likely later this evening for supercells which are expected to form in central Montana and move east. At this time, inhibition appears to be limiting more robust convective development, but with a few more hours of heating and upslope flow, expect an uncapped airmass and a few mature supercells to develop and move off of the higher terrain. A strengthening southeasterly low-level jet later this evening and increasing moisture advection should maintain this threat into the early morning hours on Monday. ..Bentley/Grams.. 07/30/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BIS...UNR...BYZ...GGW...TFX... LAT...LON 47000977 48290987 48740966 49100794 49130567 49100434 48520378 46910360 45690350 44990401 44830531 44990688 45160811 47000977 Read more

MD 1789 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR EASTERN NEBRASKA...FAR WESTERN IOWA...FAR NORTHWEST MISSOURI...FAR NORTHEAST KANSAS
Mesoscale Discussion 1789 NWS Storm Prediction Center Norman OK 0326 PM CDT Sun Jul 30 2023 Areas affected...Eastern Nebraska...far western Iowa...far northwest Missouri...far northeast Kansas Concerning...Severe potential...Watch possible Valid 302026Z - 302230Z Probability of Watch Issuance...40 percent SUMMARY...Storms capable of occasional large hail are possible this afternoon. Overall coverage and intensify of storms is not certain. The necessity of a watch will depend on convective trends. DISCUSSION...Storms have continued to form in association with a subtle shortwave/weak warm-advection regime. These storms have occasionally produced large hail this afternoon in South Dakota. Additional thunderstorms have formed in eastern Nebraska, west of Omaha. MLCAPE of around 1500 J/kg and effective shear of 40-50 kts would support some continued risk of large hail. Storms, however, have not appeared overly organized on regional radar imagery and have tended to pulse intensity. The 12Z observed OAX and TOP soundings did show some dry air at low levels which appears to be reflected in objective MLCIN fields. That being said, these storms may be slightly elevated in nature. The need for a watch will be conditional on trends in storm coverage and intensity. ..Wendt/Thompson.. 07/30/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...EAX...FSD...OAX...TOP...GID... LAT...LON 41709808 42609822 43109821 43409758 42789655 41919585 40989503 40219511 39919562 39979641 41709808 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Sun Jul 30 2023 Valid 302000Z - 311200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NORTHEASTERN WYOMING AND WESTERN SOUTH DAKOTA... ...SUMMARY... Severe thunderstorms should be most organized over parts of the northern/central Plains through tonight, with the greatest threat for very large hail and severe outflow gusts centered near the Black Hills. ...20Z Update... No changes have been made to severe probabilities across the northern/central Plains. See Mesoscale Discussion 1786 and recently issued Severe Thunderstorm Watch 573 for more details on the potential for very large hail and severe wind gusts with developing thunderstorms over the Black Hills of SD. Wind probabilities have generally been adjusted southward across parts of the Southeast based on the progression of loosely organized clusters ongoing across AL/GA. Reference Mesoscale Discussion 1787 for additional information on the threat for strong to damaging winds associated with this convection. ..Gleason.. 07/30/2023 .PREV DISCUSSION... /ISSUED 1125 AM CDT Sun Jul 30 2023/ ...Northern Plains/MO Valley through tonight... Around the northern periphery of the central Rockies midlevel high, embedded speed maxima will continue to move eastward over MT and southeastward from the Dakotas to the upper MS Valley. Elevated convection is ongoing in a band of frontogenesis/warm advection from southern ND into northern SD, along the east edge of the steeper midlevel lapse rate plume. MUCAPE near 1500 J/kg and long hodographs with effective bulk shear in excess of 50 kt will continue to support the potential for elevated supercells capable of producing large hail and isolated strong outflow gusts as the storms spread southeastward through the afternoon. Farther west this afternoon/evening, additional storm development is likely across the northern High Plains in the zone of low-level upslope flow, and isolated storms may also form with daytime heating over the Black Hills. Very steep midlevel lapse rates noted in the 12z UNR sounding and relatively strong mid-upper flow/long hodographs will initially favor supercells capable of producing very large hail of 2-3 inches in diameter or greater. Some upscale growth is expected this evening as the storms move east of the higher terrain, with an increase in the potential for severe outflow gusts. The convection will likely persist overnight and develop southeastward toward middle/lower MO Valley as warm advection increases with a nocturnal low-level jet, with isolated large hail/damaging winds possible. ...Southeast this afternoon... A weak midlevel trough is moving slowly southeastward over northern MS/AL and the southern Appalachians. Isolated thunderstorms are ongoing along the wind shift across northern MS/AL, and this convection will likely increase through the afternoon as the low levels warm/destabilize to the south of the wind shift. Deep-layer flow/vertical shear will remain rather weak, so the primary threat will be downburst winds with multicell clusters through the afternoon. ...Southern AZ/southeast CA this afternoon/evening... Easterly flow aloft is established over AZ to the south of the Four Corners high, and on the northern periphery of a weak wave moving westward over northwest Mexico. Despite some moistening, 12z soundings still revealed steep lapse rates and the potential for deep inverted-V profiles across southern AZ this afternoon. Storms that form over the higher terrain will have the potential to spread westward over the lower deserts and produce isolated strong-severe outflow gusts. Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Sun Jul 30 2023 Valid 311200Z - 011200Z ...NO CRITICAL AREAS... The previous forecast (see below) remains on track, and no changes were made with this update. ..Weinman.. 07/30/2023 .PREV DISCUSSION... /ISSUED 0104 AM CDT Sun Jul 30 2023/ ...Synopsis... On Monday, the upper-level ridge centered over the western CONUS will amplify further. Meanwhile the mid-level trough across the Pacific Northwest will become less amplified as the main trough shifts into western Canada. As a result, the height gradient will weaken across the Northwest with weakening mid-level flow. Some localized, terrain favored locations in the Pacific Northwest may have some elevated fire weather conditions, but there is not a signal strong enough to warrant an Elevated delineation. Hot and dry conditions will continue to dry already critically dry fuels across central and western Texas. Winds will likely remain below 15 mph on Monday and alleviate any fire-weather concerns, but the continued hot, dry, and somewhat breezy conditions will continue to dry fuels in the region. Similar to Day 1/Sunday, thunderstorms are expected in southern California. Slow storm speeds and high PWAT values (1.7 to 1.9 in) should mitigate dry lightning concerns with this activity. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

WW 0573 Status Updates
STATUS FOR WATCH 0573 HAS NOT BEEN ISSUED YET Read more

WW 573 SEVERE TSTM SD WY 301950Z - 310400Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 573 NWS Storm Prediction Center Norman OK 150 PM MDT Sun Jul 30 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Western South Dakota Northeast Wyoming * Effective this Sunday afternoon and evening from 150 PM until 1000 PM MDT. * Primary threats include... Scattered large hail and isolated very large hail events to 3.5 inches in diameter likely Scattered damaging winds likely with isolated significant gusts to 75 mph possible A tornado or two possible SUMMARY...Scattered supercells are expected in the vicinity of the Black Hills through the afternoon, with the potential for isolated very large hail. Later this evening, additional storms will likely move into the watch area and grow upscale, with an attendant threat for severe outflow winds up to 75 mph. An isolated tornado will be possible with favorable storm interactions. The severe thunderstorm watch area is approximately along and 65 statute miles north and south of a line from 120 miles west of Rapid City SD to 20 miles east southeast of Philip SD. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU3). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && AVIATION...A few severe thunderstorms with hail surface and aloft to 3.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A few cumulonimbi with maximum tops to 600. Mean storm motion vector 31020. ...Thompson Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sun Jul 30 2023 Valid 311200Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS...LOWER/MID MISSISSIPPI VALLEY...COASTAL SOUTHEAST...AND SOUTHERN ARIZONA... ...SUMMARY... Isolated strong to severe thunderstorms capable of producing large hail and gusty winds appear possible Monday across parts of the northern/central Plains. Additional thunderstorms producing mainly strong to damaging winds may occur across parts of the lower/mid Mississippi Valley, coastal Southeast, and southern Arizona. ...Synopsis... An upper-level anticyclone will remain centered over the southern Plains Monday, with upper ridging extending northward over much of the Rockies and High Plains. Upper troughing will persist over much of eastern Canada and the Atlantic Coast states. A belt of enhanced mid-level northwesterly flow is forecast to persist from the northern Plains across the Midwest/OH Valley and parts of the Southeast. Surface high pressure will dominate over much of these regions as well, with a weak front forecast to be located along/near the central Gulf Coast northeastward to southeastern VA. Across the Plains, a surface trough should extend from eastern MT into eastern CO, with a reservoir of rich low-level moisture present to its east. ...Northern/Central Plains... Thunderstorms should form Monday afternoon over the higher terrain of the northern/central Rockies, and eventually develop eastward over the adjacent northern/central High Plains. One or more subtle mid-level vorticity maxima rotating around the upper ridge may aid this convective development. Greater low-level moisture and related instability is forecast to be present along/east of a weak surface trough across the High Plains. There will be some potential for initially high-based convection to gradually strengthen with eastward extent through Monday evening/night. Forecast deep-layer shear would support a mix of multicells and supercells with an associated threat for large hail and severe/damaging winds. However, considerable uncertainty remains regarding the number of supercells which may develop given weak/nebulous forcing aloft. Have therefore expanded the Marginal Risk to account for a range of possible solutions regarding convective evolution. ...Lower/Mid Mississippi Valley... Thunderstorms may be ongoing Monday morning across parts of MO and vicinity. This activity should be related to convection that is expected to develop during the Day 1 period across the northern/central High Plains, and subsequently spread southeastward overnight into early Monday morning. Modest low-level warm advection may also aid thunderstorm maintenance Monday morning. While details regarding convective evolution remain somewhat unclear, most guidance has come into general agreement that a small cluster will persist through the day as it moves south-southeastward across the lower/mid MS Valley. Moderate to strong instability should be in place ahead of this convection as daytime heating of a moist low-level airmass occurs. Although deep-layer shear should remain fairly modest, enough convective organization appears possible to support a cluster capable of producing mainly damaging winds through early Monday evening. ...Coastal Southeast... A rather moist low-level airmass should be in place ahead of a weak front across parts of the coastal Southeast states. Even though mid-level lapse rates will remain fairly poor, diurnal heating of this moist airmass will aid destabilization and steepening of low-level lapse rates by Monday afternoon. Thunderstorms that form across this region through the day may produce isolated damaging winds, with modest deep-layer shear aiding a mix of pulse and loosely organized multicell modes. This convection should diminish/move offshore Monday evening with the loss of daytime heating. ...Southern Arizona... Monsoonal moisture will likely remain across southern AZ on Monday. Convection should once again develop across the higher terrain of southeastern AZ during the afternoon. Modest easterly mid/upper-level flow should aid thunderstorms spreading eastward over the lower deserts through Monday evening. Isolated strong to severe wind gusts may occur with this activity, as very steep low/mid-level lapse rates aid efficient downdraft accelerations. ..Gleason.. 07/30/2023 Read more

MD 1779 CONCERNING SEVERE THUNDERSTORM WATCH 571... FOR EASTERN VIRGINIA INTO THE DELMARVA AND SOUTHERN NEW JERSEY
Mesoscale Discussion 1779 NWS Storm Prediction Center Norman OK 0520 PM CDT Sat Jul 29 2023 Areas affected...Eastern Virginia into the Delmarva and southern New Jersey Concerning...Severe Thunderstorm Watch 571... Valid 292220Z - 292345Z The severe weather threat for Severe Thunderstorm Watch 571 continues. SUMMARY...A damaging wind threat continues across eastern Virginia into the Delmarva and southern New Jersey. DISCUSSION...Storms developed across northern Virginia and central Maryland late this afternoon and quickly organized into a forward propagating squall line with numerous measured severe wind gusts over the past 1 to 2 hours. This line of storms has started to weaken with significant reduction in 9km MRMS CAPPI over the past hour. However, there is enough organization with this line of storms for continued damaging wind gusts and occasional severe wind gusts to the Atlantic Coast from southern New Jersey to southern Delaware. Farther southwest, additional convection has started to form along the front from near Blacksburg, Virginia to northeast Virginia. These storms are south of the better mid-level flow (~20 knots per RNK VWP vs 35-40 knots per LWX VWP) and therefore, storm organization may be a bit more transient. Nonetheless, significant instability (2000 to 2500 J/kg) and decent convergence along the cold front should be sufficient for a damaging wind threat as these storms move east through the evening. ..Bentley.. 07/29/2023 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...PHI...AKQ...LWX...RNK... LAT...LON 36628027 37227939 38357757 38777690 39077626 39527558 39807517 39767468 39487429 39017432 38307472 37417545 37117597 37017635 36727714 36628027 Read more

WW 0568 Status Updates
340- STATUS REPORT ON WW 568 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 25 ESE AVP TO 10 ESE MSV TO 35 WSW PSF TO 15 ENE PSF TO 15 WSW EEN TO 20 WSW CON. ..BENTLEY..07/29/23 ATTN...WFO...BOX...ALY...GYX...BGM... STATUS REPORT FOR WS 568 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS CTC003-005-013-015-292340- CT . CONNECTICUT COUNTIES INCLUDED ARE HARTFORD LITCHFIELD TOLLAND WINDHAM MAC001-003-005-007-009-011-013-015-017-019-021-023-025-027- 292340- MA . MASSACHUSETTS COUNTIES INCLUDED ARE BARNSTABLE BERKSHIRE BRISTOL DUKES ESSEX FRANKLIN HAMPDEN HAMPSHIRE MIDDLESEX NANTUCKET NORFOLK PLYMOUTH SUFFOLK WORCESTER NYC021-027-111-292340- Read more

WW 568 SEVERE TSTM CT MA ME NH NY PA RI VT CW 291730Z - 300100Z
0- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 568 NWS Storm Prediction Center Norman OK 130 PM EDT Sat Jul 29 2023 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northern Connecticut Massachusetts Extreme southern Maine Southern New Hampshire South central New York Northeast Pennsylvania Rhode Island Southern Vermont Coastal Waters * Effective this Saturday afternoon and evening from 130 PM until 900 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Isolated large hail events to 1 inch in diameter possible SUMMARY...Scattered thunderstorms are expected this afternoon from New York and northeast Pennsylvania eastward into parts of southern New England. The storm environment will favor a mix of multicell clusters and some supercells capable of producing damaging winds and isolated large hail through late evening. The severe thunderstorm watch area is approximately along and 55 statute miles north and south of a line from 50 miles north of Wilkesbarre PA to 30 miles east of Boston MA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU8). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 566...WW 567... AVIATION...A few severe thunderstorms with hail surface and aloft to 1 inch. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 27035. ...Thompson Read more

WW 0569 Status Updates
340- STATUS REPORT ON WW 569 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 15 W CHO TO 40 NE CHO TO 15 WNW BWI TO 40 ESE CXY TO 15 W ABE TO 15 NW MSV. ..BENTLEY..07/29/23 ATTN...WFO...OKX...LWX...PHI...CTP... STATUS REPORT FOR WS 569 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS CTC001-007-009-011-292340- CT . CONNECTICUT COUNTIES INCLUDED ARE FAIRFIELD MIDDLESEX NEW HAVEN NEW LONDON DEC001-003-005-292340- DE . DELAWARE COUNTIES INCLUDED ARE KENT NEW CASTLE SUSSEX DCC001-292340- DC . DISTRICT OF COLUMBIA COUNTIES INCLUDED ARE DISTRICT OF COLUMBIA Read more