Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 161405 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 905 AM EST Mon Dec 16 2019 .SYNOPSIS... Low pressure passes to our north along the Ohio Valley Monday into Tuesday, with its associated cold front coming through our region on Tuesday. High pressure will settle in behind the front by Wednesday and provide dry weather into Friday. This weekend will bring the next chance of active weather. && .NEAR TERM /THROUGH TONIGHT/... As of 900 AM EST Monday... Dropped the winter wx advisory as temps have warmed above freezing and no reports of ice/sleet have been received. Expect periods of rain from the Clinch River Valley to the Alleghanys this morning with less chances south and east of I-81. Previous discussion from early this morning... Low pressure currently in the Tennessee Valley approaches our area, with an associated east-west warm front splitting the region around the Highway 460 corridor. Southerly flow will enhance milder temperatures and advect Gulf moisture towards the front throughout the day today. The front then lifts away to the north tonight. No major changes in this update in regards to precipitation coverage today or the winter weather in Greenbrier and Bath counties this morning. Lows this morning will be in the 30s for most of the CWA, with lower 30s across the mountains and the southside staying in the upper 30s. South of the warm front boundary, highs reach into the upper 50s. North of the boundary cloud cover and precipitation will keep high temperatures relegated to the mid-upper 40s. && .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... As of 330 AM EST Monday... A cold front should cross overhead on Tuesday and provide a line of moderate rain across the Mid Atlantic. Although the latest GFS still pushes the cold front eastward toward the coast faster than the other models, the timing consistency between the models is getting better. A non-diurnal temperature pattern will take place as temperatures should fall behind the frontal boundary, which will occur during the morning hours west of the Blue Ridge and later in the afternoon across the Piedmont. As temperatures fall below freezing, the rain will change to snow showers across the higher elevations west of the Blue Ridge. Snow accumulations up to an inch are anticipated for western Greenbrier County with maybe a dusting to a half an inch west of a line from Bluefield to Boone. Behind the cold front, winds will increase from the northwest. Model soundings indicate 850 mb winds increasing to near 45 knots by midday Tuesday and persisting into Wednesday. These wind gusts may let up a little during Tuesday night as a nocturnal inversion forms, but boundary layer mixing on Wednesday should eliminate this inversion and allow more gusts to occur. The highest ridgetops could possibly see up to wind advisory criteria, so this threat has been highlighted in the HWO for Tuesday afternoon through Wednesday. With good cold air advection expected due to the aforementioned northwest flow, low temperatures for Wednesday morning and Thursday morning were dropped a few more degrees. High pressure should arrive over the Appalachian Mountains by Wednesday night and keep conditions dry through Thursday night. The upper air pattern will flatten and become more zonal by Thursday as an upper level trough in the northern stream heads offshore. Some ridging appears to take place overhead on Thursday night ahead of an approaching shortwave trough in the southern stream that crosses over the Plains. && .LONG TERM /FRIDAY THROUGH SUNDAY/... As of 350 PM EST Sunday... High pressure will move over the area Thursday into Friday providing dry conditions with seasonably cool to cold temperatures overall. Temperatures will be a bit below normal with lows in the teens west to 20s east and highs in the 30s west to 40s east. The weekend remains very questionable with regard to precipitation chances and type. GFS and ECMWF continue to flip- flop on the track of a strong southern stream system. As such, have not made any significant changes to this period leaving in slight chance pops for a rain/snow mixture. The latest GFS has trended toward the ECMWF, keeping the threat for any more significant amounts of precipitation well south/southeast of our area. This is far from being resolved at this point and conditions for the weekend should be monitored closely during the next few days to address the potential for any winter weather over the weekend. Solutions continue to range from a significant snow event to a zero event. However, it should be noted that the preponderance of evidence at this time is toward a non-snow event and litte precipitation overall. There is also a question with regard to the temperatures in place at that time as models show a warming with the northern stream lifting out of the area. It should also be noted that WPC favors the the northern and southern streams remaining out of phase with regard to this event, which would also support the southern solution. Stay tuned! /Confidence in Forecast Parameters/ Temperatures - Moderate, Precipitation Probabilities - Low Winds - Moderate. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... As of 1201 AM EST Monday... Cloud bases will gradually lower overnight with transition to MVFR/IFR overnight into Monday morning. Clouds and precipitation will increase, spreading across the area from north to south. Between roughly 06Z/1AM and 12Z/7AM Monday, ceilings across the area will range from IFR to MVFR with light rain expected south to roughly a KBLF-KROA-KFVX line. Some of the higher locations between roughly KLWB-KHSP may see a light wintry mix from late tonight until mid-morning Monday. The precipitation will slowly expand southward Monday morning with IFR ceilings becoming more commonplace along with sub-VFR visibilities for the precipitation and some light fog. A strong southwest low level jet is expected to develop overnight above relatively weaker surface winds. Low level wind shear looks promising for parts of the region during the 06Z/1AM through 18Z/1PM Monday portion of the current valid TAF forecast period. Some improvement is expected Monday afternoon as warmer air moves up from the south. This improvement will be brief, with lowering conditions again after sunset Monday. Confidence in the above aviation forecast is moderate. Extended Aviation Discussion... Sub-VFR conditions will continue across the region through Tuesday ahead and immediately behind the passage of a cold front. Winds will also become very gusty behind the cold front. A return to VFR is expected Wednesday and Thursday but with winds remaining gusty. VFR conditions and light winds are expected Friday. Some moisture may try and return Saturday from the south with Sub- VFR conditions possible. Confidence in the above aviation forecast is moderate to high. The biggest question is the timing, and for some locations precipitation type, with Monday/Tuesday system. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/VFJ NEAR TERM...AMS/VFJ/WP SHORT TERM...PW LONG TERM...PW/RAB AVIATION...AMS/PM

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