*** THREAT FOR SEVERE THUNDERSTORMS SUNDAY CONTINUES...BUT UNCERTAINTIES REMAIN *** The threat for a significant outbreak of severe thunderstorms across the region continues for Sunday...but there are definitely some uncertainties regarding location and timing, which could significantly impact the amount and degree of severe weather. Facts: * Complexes of thunderstorms will develop in advance of a deepening upper trough and associated cold front across the Great Lakes. * The air mass across the Midwest/Ohio Valley is extremely unstable. * The air mass across our region, particularly Virginia, is much more stable. * One or more thunderstorm complexes across the OH Valley will spread southeast overnight and move into West Virginia after midnight and toward daybreak. Possibilities: * The thunderstorm complex moving into West Virginia late tonight/early Sunday could be severe with widespread damaging wind as it moves into the western part of the state...decreasing intensity as it spreads toward the mountains in the eastern part of the state around daybreak. * Numerous outflow boundaries will be left over from the morning convection allowing for thunderstorms to redevelop during the afternoon and evening across the region along the southward moving frontal boundary. * Most significant threat for severe thunderstorms during the afternoon appears to be across northern Virginia and perhaps extreme western Virginia and eastern Tennessee...but thunderstorm development across much of the region will be possible. * Afternoon thunderstorms will be scattered and severe threat will be more limited to localized areas and not expected to be as widespread. * Strong downslope westerly winds could limit redevelopment of thunderstorms east of the Alleghany Front and Blue Ridge Sunday Afternoon...allowing thunderstorms redeveloping during the afternoon to focus more on northern VA and far southwest VA...say toward Abingdon and Bristol...then backbuilding into eastern TN. As you can see from the rainfall graphic available here: hpc.ncep.noaa.gov/qpf/d13_fill.gif rainfall east of the Alleghany Front will be substantially less than that expected to the west. As you can see there are many uncertainties...so please keep abreast of our latest forecasts and any watches, warnings, and advisories that may be issued during the next 24-36 hours. Once we get past Sunday evening...we are expecting an extended period of much below normal temperatures and little if any thunderstorm activity across the region for several days...in fact much of the upcoming week.
Posted on: Sat, 26 Jul 2014 22:58:51 +0000
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