SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0141 PM CST Mon Feb 22 2021 Valid 222000Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN NORTH CAROLINA INTO SOUTHEAST VIRGINIA... ...SUMMARY... Isolated strong wind gusts remain possible with a narrow band of showers/thunderstorms this afternoon across eastern North Carolina and southeast Virginia. ...Eastern North Carolina through southeast Virginia... Only minor changes have been made to previous forecast which remains on track. A forced band of low-topped convection extends from southeast VA through eastern NC. Some increase in reflectivity along the leading band has been noted. This convective band is embedded within deep forcing for ascent and strong wind profiles accompanying a progressive shortwave trough. Some of this momentum might remain capable of reaching the surface due to precipitation loading and modest evaporative cooling within the heavier bands as evidenced by the 41 kt gust at Wakefield VA. However, overall severe threat will remain limited due to the very marginal thermodynamic environment. ..Dial.. 02/22/2021 .PREV DISCUSSION... /ISSUED 1021 AM CST Mon Feb 22 2021/ ...Eastern NC/southeastern VA this afternoon... A midlevel trough and associated surface cold front/trough now crossing the Appalachians will continue eastward to the Mid-Atlantic and southeast Atlantic coasts late this afternoon into early tonight. Strong forcing for ascent along the front (represented by the current band of precipitation across the Piedmont), and modest low-level warming/destabilization to its east, will support a band of low-topped convection this afternoon from southeast VA into eastern NC. There should be enough cloud breaks to allow surface temperatures to warm into the upper 50s across southeastern VA to lower 60s across eastern NC, as boundary-layer dewpoints increase to the 50-55 F range within a modifying air mass off the western Atlantic. This will result in weak surface-based buoyancy (SBCAPE of 100-250 J/kg), and convection may become deep enough for charge separation and isolated lightning flash potential. Regardless of the presence of lightning, very strong low-midlevel winds could be transported to the surface in the shallow convective band. Otherwise, the cold front will move southeastward into south GA/north FL later this afternoon and continue southward into central FL by early Tuesday. Air mass modification will continue through the day and into tonight ahead of the front, but the depth of buoyancy and lightning potential are somewhat in question across FL given the warm temperature profiles in the 800-650 mb layer, and the stronger forcing for ascent passing well to the north of FL.
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