SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0735 AM CDT Mon Jun 14 2021 Valid 141300Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO EARLY TONIGHT FROM EASTERN OH AND SOUTHERN PA INTO THE MID-ATLANTIC... ...SUMMARY... Thunderstorms associated with damaging wind gusts and hail will be possible across Pennsylvania into parts of the Mid Atlantic this afternoon through early tonight. Isolated large hail and damaging gusts may also occur across the Piedmont of the Carolinas, as well as the central and northern High Plains this afternoon/evening. ...Appalachians/Mid-Atlantic through tonight... A midlevel shortwave trough over the upper Great Lakes will dig southeastward toward NY and the central Appalachians through tonight. The midlevel trough will be preceded by a weak surface cold front that will move across OH/PA/western NY this afternoon, and reach the Mid-Atlantic coast overnight. Surface heating today will boost temperatures into the mid 70s to lower 80s from southern/eastern OH into PA ahead of the front, where boundary-layer dewpoints will range from the mid 50s to lower 60s. This will support moderate buoyancy (MLCAPE around 1000 J/kg), with steep low-level lapse rates in response to surface heating/mixing. Storm initiation will likely occur by early afternoon near the PA/OH border as the band of weak convection now over Lower MI (representative of forcing for ascent) intersects the destabilizing warm sector. Effective bulk shear will increase to near 50 kt with the approach of the exit region of the mid-upper jet, and combine with the moderate buoyancy to support a mix of supercells and organized multicell clusters capable of producing damaging winds and isolated large hail. The convection will spread east-southeastward across PA through the afternoon/evening, and reach the Mid-Atlantic coast overnight, while gradually diminishing buoyancy and vertical shear with northward extent into NY will diminish the severe threat. The threat for damaging winds may persist until 03-06z with the primary band of convection as a result of residual buoyancy with upper 60s boundary-layer dewpoints into NJ and the northern Chesapeake region. ...Central/northern High Plains this afternoon/evening... A midlevel high will develop north-northeastward from western NM toward CO, with height rises to its north across the central/northern High Plains. Forcing for ascent will be weak, but terrain circulations and an upslope low-level flow component should support isolated, high-based thunderstorm development to the east of the higher terrain from northeast CO to eastern WY and southeast MT with daytime heating and deep mixing. Isolated storms may also form along a slow-moving front across northern NE. MLCAPE of 2000-2500 J/kg and effective bulk shear of 35-45 kt with mid-upper westerlies atop low-level southeasterly flow supports a conditional severe hail/wind threat. ...Southwest TX this afternoon... A remnant MCV over northwest TX will move southwestward toward the Pecos Valley by late afternoon. On the southern and eastern fringes of early convection, strong surface heating/mixing will result in moderate buoyancy and inverted-v profiles. New storm development during the afternoon withe MCV could pose a threat for isolated strong/damaging downbursts. ..Thompson/Leitman.. 06/14/2021 Read more LIVE: spc.noaa.gov
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