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Heavy Snow And Hazardous Travel Conditions Expected Over The Rockies, Locally Heavy Rainfall Over The South

Heavy snow and hazardous travel conditions will persist over portions of the central and southern Rockies into Friday before diminishing. A cold front will track eastward bringing the potential for locally heavy rainfall from the south central U.S. to the Appalachians into Saturday. Localized flooding will be possible. Read More >

Overview

A deep, positively tilted upper trough was positioned from south-central Canada to the eastern Rockies on the morning of October 30th. The trough moved northeastward into the Upper Midwest by the morning of the 31st (and started to become neutral, then negatively tilted). At the same time, surface low pressure in the Southern Plains was rapidly deepening as it tracked into the Ohio Valley. A trailing cold front was positioned from KY to the north-central Gulf of Mexico during the morning of the 31st. Ahead of the front, temperatures (and dew points) were already in the 60s across our CWA, with 70 degree dew points in the Carolinas. The airmass behind the cold front was anomalously cold for the end of October (several inches of snow fell over parts of the Midwest). A line of showers (with gusty winds) was located along the cold front. Rapid cyclogenesis continued as the low tracked northeastward toward New England. This allowed for the cold front to rapidly move to the east (reaching the mountains of VA by early evening on 10/31). Temperatures were in the mid 70s-low 80s across the area, with dew points around 70°. By this time, a line of thunderstorms had developed across the western Carolinas (in a warm, moisture rich airmass with moderate instability). These thunderstorms developed slightly ahead of the cold front/aforementioned line of showers. 

By 7 PM on the evening of the 31st, the pre-frontal line of thunderstorms had tracked to the northeast, and was now positioned from the southern VA Piedmont (just W of our CWA) to the central Carolinas. With a strengthening low to our N and a strong cold front approaching from the W, it is not a surprise that the low-mid level kinematics were favorable for damaging winds and a few tornadoes. While surface winds were largely out of the south, a strong (50 kt) south-southwesterly 925 mb jet was positioned over our area. This resulted in 300-500 m2/s2 of 0-1 km SRH. Deep layer shear was present from the surface to the mid levels (500 mb winds were SW at 70-90 kt). Marginal-moderate instability (500-1500 J/kg of MLCAPE...highest south) was present over our CWA during the evening. As the line crossed our western CWA boundary (just before 8 PM), one of the cells produced an EF-1 tornado in the southwestern part of Mecklenburg County, VA. The pre-frontal line slowly weakened as it approached central VA (likely due to slowly waning instability) and had nearly fallen apart by 10 PM. Meanwhile, the actual cold front (and line of showers along it) was tracking eastward across the VA Piedmont by 10 PM. Widespread gusts of 35-45 mph were measured at AWOS sites across the VA Piedmont as the line tracked through. The line increased in intensity as it tracked through central VA, with gusts up to 50 mph measured (with a 51 mph gust at RIC). Additional strengthening occurred as the line tracked through the Lower MD Eastern Shore/eastern VA/NE NC, with some bowing segments noted. This may have been due to a strengthening south-southwesterly 925 mb jet (65-70 kt by midnight across coastal areas). In addition to widespread 50-60 mph (measured) wind gusts, a tornado (EF-1) briefly touched down in the southern part of the City of Chesapeake. A few gusts of 65-70 mph were measured at two near-surface marine sites (Dominion Terminal on the Lower James River and Ocean City).

The widespread wind resulted in areas of downed trees and power lines (especially across SE VA and the Lower MD Eastern Shore). In addition, there were a few reports of minor structural damage due to the intense straight line winds.

 

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