Two Feathers Storm Dancers

Confirmed PDS tornado on the ground and doing damage south/southwest of Barnsdall OK.
Take shelter IMMEDIATELY!!!

I'm a bit behind on this, but as many of you may already know...
There is a very high probability of severe weather with the potential all modes of hazards (flooding/large hail/damaging winds/tornadoes), including the possibility of a tornado outbreak across the majority of OK/Southern Plains this late afternoon and into the evening hours.

Please be sure to stay weather alert and take any necessary precautions if you're in the hazard areas!!!

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SPC Day1 Otlk

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1102 AM CDT Mon May 06 2024

Valid 061630Z - 071200Z
..THERE IS A HIGH RISK OF SEVERE THUNDERSTORMS FROM CENTRAL AND NORTHERN OKLAHOMA INTO SOUTH-CENTRAL KANSAS...
..SUMMARY...
A regional outbreak of severe weather with multiple intense (EF3+), long-tracked tornadoes, as well as very large hail and severe thunderstorm gusts, is expected over parts of the south-central Plains from this afternoon through evening.
..NE/KS/OK to north TX...
Water-vapor imagery late this morning shows a potent mid- to upper-level trough/low over the central Rockies with a speed max moving through the base of the trough and into the southern and central High Plains. This negatively tilted mid level trough will continue northeast to near the Black Hills by this evening while its southern portion overspreads the KS/OK corridor. The 12z Amarillo, TX raob showed the leading edge of stronger 700-600 mb southwesterly flow nosing eastward into the High Plains. A cyclone near the NE Panhandle this morning will deepen as it moves north-northeast to the SD/ND border early Tuesday morning. An associated Pacific front will push east into the High Plains and overtake the northern portion of the dryline across parts of the central High Plains this afternoon into this evening. Farther south, a dryline will mix east into western OK by late this afternoon with a broad moist/unstable warm sector across the southern Great Plains and becoming increasingly pinched in spatial width farther north into the north-central Great Plains. An attendant warm front will advance northward from OK into the lower MO Valley by early evening and later into the mid MS Valley.

Visible satellite imagery shows considerable low stratus and stratocumulus from north TX into the central Great Plains. The 12z Fort Worth, TX raob sampled the richer low-level moisture (15 g/kg lowest 100mb mean mixing ratio) compared to areas farther north. Surface analysis late this morning shows rapid northward transport of moisture into OK with 65-70 deg F dewpoints advecting northward through OK to the KS border. This plume of richer moisture will continue northward today beneath an EML and lead to moderate destabilization over NE with a very to extremely unstable airmass forecast to develop farther south over the southern half of KS into OK and adjacent north TX.

Initial thunderstorm development is likely as the upper forcing impinges on the northwestern periphery of the moist/unstable sector across the central High Plains (western KS/NE) and northward into SD with time. Steep 700-500 mb lapse rates and strengthening flow becoming more meridional with time will favor organized storms, including supercells and bands of storms with an associated isolated to scattered risk for hail/wind and perhaps a few tornadoes. Farther south, the erosion of the cap is expected initially over the KS portion of the dryline and perhaps into northwest OK by the mid afternoon. Strengthening flow through the column combined with strong to extreme buoyancy (2500-4500 J/kg MLCAPE) --from I-70 in central KS to I-40 in central OK-- will strongly favor supercell development. Strong upper-level diffluence across the central Great Plains and intensifying southwesterly to westerly 250-mb flow, which will result in very long hodographs, will strongly favor discrete storm modes, at least initially. Large to giant hail (3-4 inches in diameter) is possible with the more robust supercells. The LLJ is forecast to be strongest over KS northward into the north-central Plains through 21z. During the 21-00z timeframe, the flow associated with the LLJ will strengthen over OK acting to enlarge hodographs. Climatologically large combinations of deep-layer shear, buoyancy, and SRH will result in extreme values of composite indices (STP 6-12) during the 22z-06z timeframe across the Moderate to High Risks. Several discrete supercells are expected to traverse across a large portion of the Moderate and High-Risk equivalent tornado probabilities. Tornadoes, some of which can be intense (EF3+), are forecast late this afternoon and well into the evening. Some model guidance shows regenerative supercell development across central OK this evening. Have extended the High Risk slightly farther south to account for this possibility.
..Lower MO Valley/Ozarks/mid MS Valley late...
As greater storm coverage and merging occurs this evening across KS into northern OK, large-scale ascent will further promote upscale growth into a severe squall line across eastern KS and moving into the lower MO Valley and western part of the Ozarks. Have upgraded severe-wind probabilities and this resulted in a slight spatial extension of the Moderate Risk to the east across southeast KS/northeast OK. A severe risk will probably continue east to the MS River overnight with an attendant wind risk and perhaps an isolated risk for a tornado.
..Northern Plains...
No appreciable change from previous forecast thinking for severe potential across the northern Plains. A prefrontal corridor of favorable moisture and diurnal destabilization will become quite narrow with north and northwestward extent. Nonetheless, it should support scattered thunderstorms in northward-shifting plume, curving from the western Dakotas (and perhaps parts of extreme northeastern WY and southeastern MT) southeastward to central NE, and connecting to the northern part of the central Plains severe threat. With strong large-scale lift, cooling aloft, rapidly weakening MLCINH, and robust low-level mass response/shear expected ahead of the ejecting shortwave trough, confidence is growing that an arc of strong-severe thunderstorms will develop, offering large hail, severe gusts and at least marginal tornado potential. Even with 50s to low 60s F surface dewpoints and limited time for substantial diabatic heating, the net steepening of low/middle level lapse rates should support peak MLCAPE near or slightly above 1000 J/kg. Deep shear may not be particularly intense in a regime of strongly difluent flow aloft, but still should be adequate for supercell potential given large lowest-km hodographs possible, and effective SRH in the 150-300 J/kg range. Severe potential should diminish after about 00Z.
..West-central/southwest TX...
Model guidance continues to indicate isolated thunderstorms are possible in mid/late afternoon along/ ahead of the dryline over northwest to southwest TX. Although large-scale/mid-upper forcing will be negligible (displaced to the north), any pockets of relatively persistent/maximized low-level lift may aid in local erosion of the cap and convective initiation. Mid/upper 60s to low 70s F surface dewpoints and steep low/middle-level lapse rates will contribute to 3000-4000 J/kg MLCAPE amidst enough deep shear for supercells. A conditional significant-hail and marginal tornado threat exists with sustained supercell(s) -- if any can form. Coverage concerns preclude more than marginal categorical outlook at this time.
..Mid South/TN Valley into the southern Appalachians...
A mid-level shortwave trough over TN this morning will continue to move east into the southern Appalachians today. An enhanced belt of westerly mid-level flow accompanying this impulse will overspread this general region. In wake of decaying morning convection over the southern Appalachians, ample heating of a moist boundary layer will result in moderate destabilization by early-mid afternoon. Storm redevelopment is forecast this afternoon along and north of a trailing/diffuse convective boundary over the TN Valley. Scattered thunderstorms will probably develop by early to mid afternoon. Effective shear magnitudes 25-30 kt will support some organization in the form of clusters and perhaps transient supercells. Marginal Risk equivalent severe probabilities have been added to highlight this isolated severe threat.

There is a significant risk for severe storms across central/eastern Oklahoma, with an elevated risk for all modes of severe potential (damaging hail/wind/tornadoes)... Though I feel that hail will be the more widespread risk.

A Tornado Watch has been issued for much of central Oklahoma and into north-central TX, and is in effect until 9pm CST.

As always during the potential for severe weather, please remain weather aware and take any necessary precautions!!

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Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Mon Apr 01 2024

Valid 011630Z - 021200Z
..THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM EXTREME NORTH TX INTO CENTRAL/EASTERN OK...
..SUMMARY...
Severe thunderstorms with very large hail (2-3 inch diameter or greater), damaging gusts (60-80 mph) and a few tornadoes (potentially up to EF2) are expected this afternoon into tonight from north Texas and Oklahoma into the lower Ohio River Valley.
..Synopsis...
Embedded speed maxima (90-100+ kt 500 mb) from southern NM/far west TX to northwest Mexico will eject northeastward to OK this evening and MO overnight. An associated lee cyclone will deepen this afternoon across the TX South Plains and then progress into northwest OK this evening and the mid MS Valley by the end of the period. A broad/moist warm sector is in place from the southern Plains to the mid MS/lower OH Valleys, beneath a warm elevated mixed layer with 8-9 C/km midlevel lapse rates. The cap will weaken through the afternoon from the west, with thunderstorm initiation becoming likely by mid afternoon along a surface front from KS into MO/IL, and mid-late afternoon along the dryline from western/central OK into northwest TX.
..KS/MO/IL/IN through tonight...
Scattered thunderstorm development is likely starting mid afternoon along the baroclinic zone from KS into MO, and storms will subsequently spread eastward along the warm front from MO into IL/IN. The environment will favor supercells capable of producing very large hail (2-3 inches in diameter) and a few tornadoes, with an isolated strong tornado possible. Storm mode will become messier into the overnight hours with upscale growth into clusters/line segments, with an increase in the threat for damaging winds (60-80 mph), and a continued threat for tornadoes (possibly up to EF2) with embedded/QLCS circulations.
..OK/TX this afternoon into early tonight...
The elevated mixed layer and associated cap, along with widespread clouds, will tend to delay surface-based storm development until mid-late afternoon, when forcing for ascent increases from the southwest with the approach of the mid-upper jet streak. By about 21z, scattered thunderstorm development is expected along the dryline from northwest TX into western OK, and storms will spread quickly northeastward into central/eastern OK through this evening/early tonight. Steep midlevel lapse rates and boundary-layer dewpoints in the mid-upper 60s will contribute to MLCAPE of 2000-3000 J/kg, in an environment with very strong deep-layer shear/long hodographs favorable for multiple supercells with very large hail (3 inches in diameter or greater). The magnitude of the tornado threat is a bit less certain, given a weakness in the low-level shear until a more consolidated low-level jet response begins by late evening, when storm mergers and upscale growth become more probable into eastern OK/northwest AR/southwest MO early tonight. However, given the very strong flow and seasonably rich low-level moisture, there will be the potential for a couple of strong (roughly EF2) tornadoes late this afternoon into tonight.

Seasonal climatology forecasts are showing the potential for a very active storm season across the plains, central US, and Dixie.
While currently in an active ENSO (El Niño Southern Oscillation) weather pattern, it is expected to shift to an ENSO neutral pattern in late spring/early summer, before shifting to a La Niña pattern later into the summer.
This along with the confluence of colder ocean water in the south Pacific and a pocket of isolated warm water in the northern Pacific, could be cause for an abundance of severe weather across the aforementioned regions this spring.

I will be active in both forecast modeling to keep ahead of any potential, as well as chasing severe storms when able... So, stay tuned!!!



***Seasonal Forecast Discussion***
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FXUS05 KWBC 151332 PMD90D Prognostic Discussion for Long-Lead Seasonal Outlooks NWS Climate Prediction Center College Park MD 830 AM EST Thu Feb 15 2024

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

While El Niño conditions continue with equatorial sea surface temperatures (SSTs) above average across the central and eastern equatorial Pacific Ocean, the total subsurface ocean heat content anomaly across the equatorial Pacific has dropped to near zero, signaling an imminent transition to ENSO-neutral conditions. The atmospheric circulation across the global tropics is consistent with the ongoing El Niño though, and El Niño is forecast to impact the circulation for the March-April-May season with a transition to ENSO-neutral conditions later in the spring and early summer. La Niña conditions are forecast to likely develop later in summer or by autumn.



The March-April-May (MAM) 2024 temperature outlook favors above-normal temperatures across the northwestern Contiguous United States (CONUS), including the Pacific Northwest, northern to central California, parts of the Great Basin, and the northern Rockies. Above-normal temperatures are favored across the northern CONUS, including the northern Great Plains, Great Lakes region, and Northeast. The highest forecast confidence for above-normal temperatures is for the Pacific Northwest, where the probabilities of above-normal temperatures exceed 60 percent. Above-normal temperatures are favored across Alaska. Equal chances (EC) of above-, near- or below-normal seasonal mean temperatures are indicated across the southern CONUS, where El Niño impacts increase the chances of below- and near-normal temperatures, while decadal time scale trends increase the likelihood of above-normal temperatures.

The MAM 2024 precipitation outlook favors below-normal precipitation for parts of the Pacific Northwest and northern Rockies, while above-normal precipitation is favored from the eastern Central Plains across the middle and lower Mississippi Valley into the mid-Atlantic and Southeast, associated with lingering impacts due to El Niño. Above-normal precipitation is also favored for parts of northwestern and southern Mainland Alaska. Below-normal precipitation is favored for much of the Rio Grande Valley. EC of below-, near- and above-normal total seasonal precipitation are depicted by remaining areas in white.

BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS Note: For Graphical Displays of the Forecast Tools Discussed Below See: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

Above-average SSTs persist across the equatorial central and eastern Pacific Ocean, with a slight weakening of positive anomalies over the east-central Pacific in recent weeks. The most recent weekly SST anomaly for the Niño 3.4 region is at +1.7 degrees Celsius. Equatorial subsurface temperature anomalies (averaged over 180-100W longitude and 0-300 meters depth) are near zero degrees Celsius after a decrease from a peak of +1.5 degrees Celsius in late November. Negative subsurface temperature anomalies at depths greater than 50 meters have spread from the Western Pacific eastward across the east-central Pacific in recent weeks. In the latest four-week period, outgoing longwave radiation (OLR) anomalies at the top of the atmosphere are negative to the west of the Date Line near the equator and extend over the Eastern Pacific to the north of the equator. Low-level (850-hPa) wind anomalies were near long-term averages over most of the equatorial Pacific in recent weeks. Upper-level (200-hPa) wind anomalies were easterly over the eastern equatorial Pacific. These atmospheric and oceanic conditions reflect a continuation of El Niño into the current month. The Madden-Julian Oscillation (MJO) continues to propagate with active convection across the Western Pacific ocean, constructively interfering with El Niño. However, dynamical model forecasts indicate large uncertainties in the Realtime Multivariate MJO (RMM) index and a likely decrease in the amplitude of the MJO in the coming weeks.

PROGNOSTIC DISCUSSION OF SST FORECASTS

The CPC SST consolidation forecast for the Niño 3.4 region predicts rapidly decreasing positive anomalies in spring with a near zero median anomaly by the April-May-June (AMJ) season. Dynamical and statistical models are in good agreement that a transition to ENSO-neutral conditions is likely to occur either in spring or by early summer. The CPC ENSO Outlook indicates that the probability of ENSO-neutral during AMJ is nearly 80 percent. The probability of a La Niña increases to greater than 50 percent beginning in the June-July-August (JJA) summer season. By the August-September-October (A*O) three-month period and later into autumn, there is more than a 70 percent chance of La Niña.

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

The seasonal temperature and precipitation outlooks for MAM 2024 through MAM 2025 were based on dynamical model guidance through the first five leads, including the North American Multi-Model Ensemble (NMME). Statistical models, such as the ENSO-OCN tool that combines the probable temperature and precipitation impacts of the predicted median Nino 3.4 SST anomaly, as forecast by the CPC SST consolidation, with the decadal temperature and precipitation trends, were used at all leads. A skill-weighted consolidation of NMME dynamical models, a consolidation of statistical models, as well as a full consolidation of all available models were primary tools in the seasonal temperature and precipitation outlooks. El Niño impacts were considered explicitly, using regression of the Niño 3.4 index on temperature and precipitation, for only the MAM 2024 outlook. Beginning in A*O 2024 through the final lead outlook for MAM 2025, the impacts of La Niña were considered, using temperature and precipitation signals from regression to negative values of the Niño 3.4 index.

PROGNOSTIC DISCUSSION OF OUTLOOKS - MAM 2024 TO MAM 2025

TEMPERATURE

The MAM 2024 temperature outlook predicts elevated probabilities of above-normal temperatures for Alaska and across the northern tier of the CONUS, supported by NMME forecasts, forecast tool consolidations, and typical impacts due to El Niño. The highest probabilities for above-normal cover northwestern parts of Oregon and much of Washington, where the teleconnection to El Niño has its strongest correlation. Weaker probabilities still favoring above-normal temperatures are forecast over the Northern Plains, due to uncertainty in the Arctic Oscillation (AO) phase. A persistent negative phase of the AO would lead to near- or below-normal temperatures in this region. Above-normal temperatures are likely for much of the Great Lakes region and Northeast with probabilities exceeding 50 percent, where the Great Lake surface temperatures are anomalously warm and decadal trends in the Northeast are strongly positive. As a rapid transition to a neutral ENSO state is predicted, the seasonal temperature outlooks for AMJ through JJA 2024 rely primarily on signals related to decadal trends. The outlooks are supported by the NMME forecasts through July-August-September (JAS) 2024 and by the consolidation of available tools through A*O 2024. Uncertainty for the northern and central Great Plains increases through spring into summer where decadal trends are weaker, while higher probabilities for likely above-normal temperatures expand across the western CONUS. Above-normal temperatures are favored across most of Alaska through MJJ 2024, and primarily eastern Mainland Alaska in the summer seasons. By the autumn and the September-October-November (SON) 2024 outlook, probabilities for above-normal temperatures decrease for the northwestern and north-central CONUS, while elevated probabilities for above-normal temperatures increase for northern Mainland Alaska and decrease for southern Mainland Alaska, related to potential impacts of a developing La Niña. For the CONUS, areas forecast to have EC of below-, near- and above-normal temperatures expand from the Northwest in October-November-December (OND) 2024 down the west coast by December-January-February (DJF) 2024/25. Below-normal temperatures are slightly favored for parts of the Pacific Northwest for the DJF 2024/25 season through MAM 2025, due to the more likely impacts of La Niña. Forecasted areas of EC expand into the Central Plains, Central Mississippi Valley, and Ohio Valley in the winter season and later leads through MAM 2025. These longer lead forecasts are supported largely by the ENSO-OCN forecast tool and the statistical model consolidation.

PRECIPITATION

The MAM 2024 precipitation outlook favors below-normal precipitation for the Pacific Northwest, consistent with possible impacts of El Niño during the first half of the season. Below-normal precipitation is favored for much of the Rio Grande Valley, while above-normal precipitation is favored for much of the eastern CONUS, supported by the consolidation of available forecast tools. Above-normal precipitation is favored for northwestern and southern Mainland Alaska, consistent with the NMME consolidation forecast. Through spring into summer, an area of favored above-normal precipitation expands across most of Mainland Alaska, largely supported by the NMME and the consolidation of precipitation forecast tools. Below-normal precipitation is slightly favored across much of the western half of the CONUS (excluding most of California and western areas of the Great Basin and Southwest) through JJA 2024, supported by the NMME and the consolidation. The areas where above-normal precipitation is favored over the eastern CONUS shift eastward towards the Atlantic coast by MJJ 2024, and then are confined to parts of the northeastern CONUS by summer, largely consistent with signals related to decadal precipitation trends. Below-normal precipitation is favored for parts of the Southwest from A*O 2024 through MAM 2025, and for parts of the Southeast from OND 2024 through MAM 2025. Above-normal precipitation is favored for parts of northern Alaska in the autumn seasons and for northern and eastern interior Alaska in the winter through MAM 2025, consistent with the statistical model consolidation. Above-normal precipitation is favored over parts of the Midwest during the winter seasons. The precipitation outlooks for autumn through winter are largely related to potential impacts due to likely development of La Niña.

FORECASTER: Dan Collins

The Climatic normals are based on conditions between 1991 and 2020, following the World Meterological Organization convention of using the most recent 3 complete decades as the climatic reference period. The probability anomalies for temperature and precipitation based on these new normals better represent shorter term climatic anomalies than the forecasts based on older normals.

For a description of of the standard forecast tools - their skill- and the forecast format please see our web page at http://www.cpc.ncep.noaa.gov/products/predictions/long_range/tools.html (Use Lower Case Letters) Information on the formation of skill of the CAS forecasts may be found at: http://www.cpc.ncep.noaa.gov/products/Soilmst_Monitoring/US/Outlook/outlook.shtm l (use lowercase letters) Notes - These climate outlooks are intended for use prior to the start of their valid period. Within any given valid period observations and short and medium range forecasts should be consulted.

This set of outlooks will be superseded by the issuance of the new set next month on Mar 21 2024

1991-2020 base period means were implemented effective with the May 20, 2021 forecast release.

Watching for a potential severe weather outbreak across central/northeastern Oklahoma/northwestern Arkansas and up through central Missouri, into portions of Illinois on Tuesday (02/27/24).
So far, tornado risks are looking low to moderate, and might be more of a damaging wind and/or hail risk system.
I will keep my eye on this and will advise of any changes.

A Freeze Warning will be in effect for the majority of Eastern OK (including OKC) from midnight tonight (Mon 11/30) until 9am tomorrow morning (Mon 11/30), along with another potential and more widespread Freeze Warning for overnight Tuesday (11/31).
Temperatures will reach below the freezing point.
Please take any necessary precautions as wet roads could lead to icing, as well as potential damage to plants outdoors and water lines, and risk to any outdoors pets!!

Much of central/northeastern OK is now under a Severe Thunderstorm Watch with a Mesoscale Discussion in association with probable storm development.
Storm cells have already begun forming over central OK, with one cell under a Severe Storm Warning with a Special Weather Statement associated.
Main threats of these storms may be localized wind gusts in excess of 80mph, and 1"+ diameter hail.
As always, stay weather aware and take any necessary precautions in the path of these storms!!!

(Cell in photo is forming over Skiatook)

Strong to severe storms have sprung up across central/east-central OK.
Main threats are strong winds and potential for moderately sized hail.
Please stay weather aware and take any necessary precautions on the paths of these storms!!!

Severe Storm warnings are now being issued in association with the storms moving across east-central OK, along with downstream severe storm watches and discussions.
Storms at this time are now capable of 70mph winds and quarter sized hail.
Please remain weather aware and take any necessary precautions if you're in the path of these storms!!!

Storm activity is expected to increase through the day and into the evening for much of northern OK/southern KS.
Main threats at this time are anticipated to be high winds and large hail, especially for northwestern portions of OK/southwestern portions of KS, with the possibility of a tornado within a small corridor in that region.
Please remain weather aware throughout the day, and take any necessary precautions if you should find yourself in the path of any of these storms!!!

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Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0751 AM CDT Tue Jun 27 2023

Valid 271300Z - 281200Z
..THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO TONIGHT FROM SOUTHWEST KS AND THE OK PANHANDLE ACROSS NORTHERN OK/SOUTHERN KS...
..THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO TONIGHT ACROSS WESTERN/NORTHERN NE INTO SOUTHERN SD...
..SUMMARY...
Storms producing severe winds of 60-85 mph and very large hail of 2-3 inches in diameter are probable in a corridor from southwest Kansas and the Oklahoma Panhandle across northern Oklahoma and southern Kansas this afternoon into tonight. More isolated large hail and damaging winds will be possible across parts of Nebraska and southern South Dakota.
..KS/OK to the Ozarks through tonight...
A midlevel high will shift slowly eastward across TX, as a shortwave trough ejects east-northeastward from the central Rockies to the central Plains through tonight. This pattern will support lee cyclogenesis across eastern CO and the north/northwestward return of the richer low-level moisture (68-72 F dewpoints) from southern OK and the TX South Plains toward KS through the afternoon. The ongoing storms in central OK (and southwest AR) may persist through the day while moving eastward/southeastward along the moisture/buoyancy gradient and the edge of the stronger cap. In the wake of this morning convection, large buoyancy is expected (MLCAPE near 4000 J/kg) in a corridor from central/northern OK into southwest KS, as a result of 9 C/km midlevel lapse rates atop the moist axis, and along the north edge of the hottest surface temperatures. This same corridor will lie beneath the southern fringe of the stronger mid-upper west-southwesterly flow (40-50+ kt).

Thunderstorm development is expected by mid afternoon immediately downstream from the Raton Mesa area in southeast CO, and storms will subsequently spread into southwest KS and possibly the OK Panhandle this evening. The initial storms will likely be supercells capable of producing very large hail of 2-3 inches in diameter. Temperature-dewpoint spreads will be higher in CO, but an increase in low-level shear this evening and increasing moisture with eastward extent could result in a window of opportunity for a tornado or two with the more discrete supercells. Thereafter, upscale growth into an MCS appears likely, due to storm interactions/mergers in the steep lapse rate environment with intense downdraft potential. Swaths of severe gusts of 60-85 mph will be possible into tonight across southern KS/northern OK, and the threat for at least isolated damaging winds could persist into northern AR overnight.
..Northwest KS/NE/southern SD through tonight...
In the wake of elevated morning storms associated with warm advection near 700 mb, moisture advection and surface heating will contribute to destabilization through the afternoon from northwest KS across NE into southern SD. Lee cyclogenesis across northeast CO will help sharpen a dryline by afternoon close to the longitude of the CO/KS border, which should focus widely scattered thunderstorm development later this afternoon into NE and possibly northwest KS. Moderate-strong buoyancy and relatively long/straight hodographs will favor supercells capable of producing isolated very large hail (2 to 2.75 inches in diameter) and isolated damaging winds. Though a relative gap is possible somewhere near northwest KS, confidence in the details is low, and the entire zone conditionally favors supercells. Otherwise, storms will be possible from northeast WY into western SD, and some elevated convection may persist while spreading eastward toward northeast NE overnight. Isolated large hail and strong-damaging gusts will be possible.
..Mid-Atlantic into eastern NY this afternoon/evening...
A midlevel trough with embedded perturbations and an associated surface cold front will move slowly eastward across NY/PA and toward the Mid-Atlantic coast. Lapse rates, buoyancy and vertical have all been reduced compared to yesterday, in the wake of prior widespread convection and as the primary jet moves offshore. Still, slightly cooler midlevel temperatures and surface heating with residual moisture in cloud breaks could support isolated storms with gusty winds.