Severe Storm Outlook Narrative (AC)
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Issued by NWS
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828 ACUS01 KWNS 061629 SWODY1 SPC AC 061627 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CDT Thu Jun 06 2024 Valid 061630Z - 071200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PARTS OF THE MID-ATLANTIC STATES...EASTERN HALF OF THE FLORIDA PENINSULA...AND WESTERN OKLAHOMA AND THE TEXAS PANHANDLE... ...SUMMARY... Scattered severe thunderstorms are possible this afternoon into the early evening for parts of the Mid-Atlantic states due to 50-65 mph damaging gusts. Scattered severe thunderstorms are also possible over the eastern half of the Florida Peninsula and parts of western Oklahoma and the Texas Panhandle. Large hail (1 to 1.75 inches in diameter) and severe gusts (60-70 mph) will be the hazards with the stronger thunderstorms. ...NY into the Carolinas this afternoon/evening... Radar/satellite imagery late this morning shows a mid-level vorticity maximum moving east along the NY/PA border ahead of a mid-level trough over the Great Lakes. The larger-scale trough will move into NY/PA by this evening. A surface cold front and pre-frontal lee trough will push east during the day and into the Mid-Atlantic states this afternoon/evening. Visible-satellite imagery shows considerable mid- to high-level cloud cover delaying heating from northern VA into NY. However, very moist low levels (upper 60s to lower 70s surface dewpoints) and breaks in the cloud cover will yield moderate buoyancy by early to mid afternoon. Some enhancement in 700-mb flow was noted on area WSR-88D VADs (more recently at KLWX (Sterling, VA) where westerly flow has increased from 35 to 45 kt in the 2-4 km layer. Scattered thunderstorms will preferentially develop on the aforementioned surface boundaries and spread east into the destabilizing airmass. Several bands of multicells are forecast from NC into the Chesapeake/Delaware Bay vicinity. It is here where slightly greater coverage of 50-65 mph gusts capable of wind damage are forecast. Farther north, more isolated strong to locally severe/damaging storms are expected over NY where less instability is forecast. Farther south, some modest enhancement in 850-700 mb flow will overspread the Carolina Piedmont into the coastal plain, but lower expected storm coverage and less confidence in storm intensity precludes higher severe probabilities at this time. ...Eastern half of the FL Peninsula this afternoon... Water-vapor imagery shows an upper low centered near Daytona Beach slowly migrating east into the adjacent Gulf Stream waters, as a positively tilted mid-level trough extends from the central Gulf Coast into the GA/SC vicinity. Model guidance indicates the East Coast sea breeze will preferentially focus thunderstorm development this afternoon. Strong heating underway over the interior part of the Peninsula will result in very steep 0-3 km lapse rates (around 9 deg C/km). Surface temperatures warming into the mid 90s away from the coast and dewpoints in the lower 70s will contribute to 3000 J/kg MLCAPE. Seasonally cool midlevel temperatures (-8 to -10 C at 500 mb) and the large buoyancy will support some threat for isolated large hail (1-1.75 inch diameter) where vertical shear is slightly enhanced by the sea breeze. The large buoyancy will also result in substantial water-loaded downdrafts with the potential for isolated wind damage (55-65 mph gusts). ...TX Panhandle/western OK this afternoon/evening... A weak surface cold front will drift southward from KS into northern OK and the TX/OK Panhandles by later this afternoon/evening. Weak lee cyclogenesis across eastern NM will induce southerly low-level flow and northward moisture advection across TX/OK to the south of the front. Strong surface heating and the increase in low-level moisture will contribute to moderate buoyancy by mid-late afternoon (MLCAPE >1500 J/kg), in an environment of steep low-level lapse rates/deep mixing. Low-level convergence/ascent along the front should focus thunderstorm development by mid-late afternoon from northwest OK into the TX Panhandle, and storms will subsequently spread southward through the evening. Moderate buoyancy, inverted-V profiles and northwesterly effective bulk shear of 35-40 kt will favor a mix of multicell clusters and high-based supercells capable of producing severe outflow gusts (mainly 60-70 mph) and isolated large hail (1-1.5 inch diameter). ..Smith/Squitieri.. 06/06/2024 $$