SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0700 AM CST Mon Feb 22 2021 Valid 221300Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST VIRGINIA/EASTERN NORTH CAROLINA... ...SUMMARY... A couple of strong to locally severe thunderstorms with gusty winds may occur this afternoon across eastern North Carolina and/or southeast Virginia. ...Synopsis... A progressive upper trough and associated 150 kt 300 mb jet streak will overspread the eastern CONUS through the day. Very strong deep-layer wind fields are expected to precede the upper trough axis and an approaching surface cold front during the afternoon hours across portions of the Mid-Atlantic southward to Carolina coastal areas. This is where a modified marine layer may promote very modest low-level buoyancy, potentially supporting deep enough moist convection to foster a few lightning flashes. Farther south across southern Georgia into Florida, forcing for ascent will be weaker as the upper trough is expected to remain mainly north of the area. However, more appreciable instability will be in place, with isolated thunderstorm development possible along a weak but broad confluence zone ahead of a southward sagging cold front. ...Eastern North Carolina/southeast Virginia and vicinity... Convective potential across the region is still not fully certain given the initially cold/stable boundary layer across the region and the influence of scattered showers upstream across the Appalachians in vicinity of an eastward-moving cold front. However, early morning RAP/HRRR runs appear to have trended a bit more conducive with depictions of thermodynamic profiles potentially capable of a few lightning strikes with low-topped convection this afternoon, coincident with limited but non-zero surface-rooted buoyancy. Furthermore, various convection-allowing models are plausibly indicating the potential for an increasingly organized low-topped convective line this afternoon centered across southeast Virginia and eastern North Carolina (roughly 1-5 pm EST). Even if just minimal near-surface-based buoyancy can become established coincident with low/middle 50s F surface dewpoints, there seems to be some potential for some convectively enhanced wind gusts given the magnitude (50+ kt) of southwesterly winds within the lowest 3 km AGL. ..Guyer.. 02/22/2021
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