Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 100826 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 326 AM EST Sat Dec 10 2016 .SYNOPSIS... High pressure will build east across the Mid-Atlantic region today before sliding to the coast tonight and then offshore on Sunday. The associated cold airmass will remain over the area through early Sunday before moderating. A cold front will approach the region late Sunday night before working east through the area later Monday into Monday night. && .NEAR TERM /THROUGH TONIGHT/... As of 245 AM EST Saturday... Overall mainly a temperature forecast today into tonight as surface high pressure slides overhead this afternoon and to the coast overnight. Lingering upper trough along with passing weak shortwave energy may act to keep upslope low clouds/flurries across the far west this morning before drying and weakening westerly flow helps diminish clouds this afternoon. However 850 temperatures will be slow to warm in the wake of another impulse aloft, with most guidance now giving only 20s to lower 30s mountains, with somewhat warmer upper 30s/low 40s east per weak downslope. Some high clouds could also mix in and with the low sun angle suspect the colder side of guidance best. Thus lowered highs a little espcly west closer to the latest Euro Mos. Otherwise mainly sunny but still cold under diminishing winds. Warm advection aloft will develop behind the exiting ridge overnight with the main axis of lift taking shape to the northwest along a weak warm front aloft and within strong upper zonal flow. Appears most of this deep moisture will stay to the north with the upper jet helping to shear an axis of mid/high clouds eastward across mainly the northern half of the region through daybreak per most model humidity fields. However southward extent and thickness of the canopy to likely play into how low temps could go given residual very dry dewpoints in place. Think also likely to see some spots plummet early on before steadying out under the clouds and at elevation where return southwest flow will start to mix down late. Therefore running on the colder side of Mos valleys and southern sections per better radiational cooling while leaning a bit warmer north but still teens to low/mid 20s under intervals of clouds at this point. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 300 PM EST Friday... The upper flow is low amplitude and progressive will not add much in the way of dynamic lift, but a plume of moisture surging up through the piedmont late Sunday/Sunday night may help generate some showers ahead of the main body of precipitation associated with the approaching cold front. While temperatures will be steady to rising Sunday night, temperature profiles support the possibility of some freezing rain at the higher elevations from western Greenbrier through the Alleghany Highlands with a light glaze possible before going over to all rain Monday morning. Winds may also become gusty along the ridges Sunday night into Monday but the warm air advection pattern will inhibit downward momentum transfer of higher winds to lower elevations. The bulk of precipitation will arrive in the west toward daybreak Monday and move across the region from west to east into Monday afternoon. Lingering upslope precipitation west of the Ridge will transition to some wet snow across western Greenbrier with no accumulation expected. With the progressive pattern and transitory nature of weather systems into early next week, expect temperatures to be variable. Readings will be below normal Sunday followed by a warming trend as the high shifts to our east and winds become southerly with above normal readings on Monday. However, temperatures Monday will be falling behind the cold front as it moves through from west to east. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 300 PM EST Friday... The upper pattern will remain progressive as a large closed low digs into eastern Canada and keeps the Appalachians and central mid Atlantic region in essentially zonal flow. So after a brief period of relatively quiet weather under high pressure on Tuesday, the next weather system will begin to affect our area very late Tuesday night. Strong isentropic lift will develop over an in-situ wedge as a complex low approaches from the southwest. There may be some p-type issues at the higher elevations with the initial surge of warm air advection late Tuesday night through the first part of Wednesday. However, a significant surge of cold air will start moving in during the day Wednesday behind the departing low and transition precipitation to snow, especially in upslope areas west of the Blue Ridge. There may also be some freezing issues as the cold air arrives on blustery winds and interacts with wet surfaces Wednesday night. Lingering snow showers west of the Ridge will dissipate as cold high pressure builds in through the end of the workweek. Temperatures will generally exhibit a cooling trend for most of next week with highs on Tuesday well above normal, falling to well below normal by Thursday. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... As of 1132 PM EST Friday... Upslope cloudiness still keeping BLF/LWB in MVFR territory. Will see a slow erosion of the clouds through the night but expect these two sites to be VFR by 12z. Otherwise VFR through the period with high pressure building in from the west. Extended aviation discussion... Next weather system to follow will be a cold front, models suggesting a Sunday Night arrival which will likely produce sub- VFR conditions at times, and possibly wintry mix in the mountains. The cold front crosses the area Monday with continued threat of showers and sub-VFR at times, then somewhat of a break Monday night and maybe Tuesday, with another system arriving midweek with more precip, and more than likely sub-VFR at times. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...MBS LONG TERM...MBS AVIATION...KK/PM/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.