SPC MD 164

By Newsroom America Feeds at 20 Mar 2018

Mesoscale Discussion 0164 NWS Storm Prediction Center Norman OK 0855 PM CDT Tue Mar 20 2018 Areas affected...Portions of WV and western/central VA Concerning...Heavy snow Valid 210155Z - 210800Z SUMMARY...A band of moderate to heavy snow will develop northeastward across WV and western/central Virginia this evening and overnight. Snowfall rates around 1 inch per hour are likely, especially in the higher terrain. DISCUSSION...A shortwave trough will pivot northeastward across the Mid-Atlantic this evening/overnight, while a large-scale upper trough over the OH/TN Valley transitions to a closed low. Forcing for ascent preceding the shortwave trough will encourage development and deepening of a surface low off the NC/VA coast through the early overnight hours. A separate area of weak low pressure will remain over WV/far southwestern VA. A front will extend between these two lows, with a cold low-level airmass in place across much of the Mid-Atlantic to the north of the front. Moderate to heavy precipitation is ongoing this evening across southwestern VA into parts of WV in association with the previously mentioned shortwave trough. The 00Z sounding from Roanoke, VA shows a modest (around 3.7 degrees C) low-level warm nose centered around 820 mb. As mid-level temperatures cool with the shortwave trough passage, the low-level thermal profile is likewise forecast to quickly fall below freezing across WV and parts of western/central VA. Indeed, recent surface observations and mPING reports across southwestern VA are indicating a fast transition from rain to snow, with some sleet mixed in at the leading of the precipitation shield. Continued east-northeasterly winds in the surface-850 mb layer will enhanced uplift along the Blue Ridge and Appalachian Mountains this evening and overnight. Snowfall rates of 1 inch per hour appear likely across much of the discussion area, especially in the higher terrain where this low-level uplift will be maximized. Most recent high-resolution guidance is in reasonable agreement in the placement of this moderate to heavy snowfall axis through about 08Z. Precipitation may lessen/shift farther eastward after this time as the coastal low develops northeastward over the western Atlantic and the shortwave trough moves away from this region. ..Gleason.. 03/21/2018 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...AKQ...LWX...RNK...PBZ...RLX... LAT...LON 36998146 37498166 37918170 38398135 38708084 38878036 38907998 39057954 39317912 39457873 39457833 39327795 38877784 37997819 37257893 36777983 36608045 36658104 36998146 Read more



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