Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 091848 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 148 PM EST Fri Dec 9 2016 .SYNOPSIS...
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High pressure will build across the Mid-Atlantic region today through Saturday. The associated cold airmass will remain over the area through early Sunday before beginning to moderate. A cold front will approach the area late Sunday night in Monday.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 1000 AM EST Friday... Adjusted pops for snow showers and snow flurries for this morning into the afternoon. A heavier snow band could produce up to an inch. Made changes to temperatures for late morning into this afternoon. more later changes this morning. As of 500 AM EST Friday... Forecast area is now entirely under the influence of an arctic airmass. We are still much better off than our neighboring states to the northwest where combination of single digit temperatures and lake effect snow is ongoing. For our region, just flurries for the mountains and temperatures in the teens and 20s, but still bone chilling enough to wear a heavier layer or two and add a little heavier BTU producing wood to the fire. Will continue to advertise an inch or two of snow for the mountains of WVA...mainly northwest of Lewisburg, otherwise mainly trace amounts elsewhere, and no activity east of the Blue Ridge where skies will remain clear. Temperatures today will struggle to get much above freezing east of the Blue Ridge, and remain below freezing in the west. Highest ridges, above 3500 feet are progged to remain in the teens... I think we have 15 degrees forecast for the high temperature on Mount Rogers today, after a low of 8 or 9 last night. Wind chills at these respectively colder higher elevations will also dip into the minus 5-10 degree range. Elsewhere winds will still be a factor with apparent temperatures in the single digits and teens. Blustery northwest winds today will gradually subside tonight. This in combination with mostly clear skies will allow for ideal radiational cooling conditions, promoting temperatures in the teens for most of the CWA, and upper single digits for the highest elevations, such as Mount Rogers and similar elevation. && .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... As of 500 AM EST Friday... Large, sprawling anticyclone associated with moderating Arctic- origin cold airmass will be centered over the Appalachians on Saturday before shifting eastward later in the day. As that occurs, southwesterly return flow begins overnight Saturday with initially light/variable winds becoming more southeasterly with time. Sky conditions trend mostly clear and dry with highs ranging from the upper 20s in western Greenbrier County to the upper 30s to lower 40s east of the Blue Ridge and northwest North Carolina mountains. Evening lows in the upper teens for the Alleghany Highlands and far southwest Virginia to the lower 20s from the New River, Roanoke Valleys east. For Sunday, clouds begin to increase as high pressure builds off the Chesapeake with lingering ridging building back into the foothills of Virginia and North Carolina. 850 mb temperatures continue to climb back to values a couple degrees either side of 0C through Sunday; however limited insolational effects should keep highs only in the upper 30s to mid 40s. Moving into Sunday night, pressure gradient begins to increase particularly in western sections in advance of a developing surface low over northern IL. Both GFS and ECMWF begin to overspread some light precip eastward into what appears to be an in-situ or hybrid cold air damming type setup. Given that the airmass is still dry I opted to confine the highest PoPs through midnight across the Alleghany Highlands and into far southwest Virginia. Effect of clouds and increasing winds should allow for only a slow fall in temperatures, which stand to fall to lows in the low to mid 30s. Cold front then pushes eastward across the region during the day on Monday with PoPs increased into the Likely range. There`s still some question as it pertains to the low-level thermal structure on precipitation type and have therefore maintained cold rain or snow as weather types for now. The forecast calls for any frozen precip to change to rain by the mid/late morning. However, given the cold airmass now in place over our area, it`s possible road surfaces are marginally cold enough to produce some slippery travel even in cold rain, if for a short period of time. Something to keep in mind. Front clears our area later Monday with skies trending partly to mostly cloudy by evening. Shown highs in the 40s west of the Blue Ridge (except upper 40s/low 50s in southwest flow in Smyth county), to the lower 50s east of the Blue Ridge...with evening lows in the 30s. && .LONG TERM /TUESDAY THROUGH THURSDAY/... As of 500 AM EST Friday... No sooner does this system exit our region do we turn our eyes southwest again with the approach of yet another potentially wintry system starting either late in the day Tuesday or late Tuesday night. There are notable differences on timing, storm path, precipitation coverage and amount between the GFS and ECMWF. Given the differences, our forecast will favor more of a persistence forecast with the model blend. A wintry mix will again be possible during this onset window of opportunity. However, for now given the uncertainties, a snow versus rain forecast is more practical. By Wednesday afternoon, the associated trough axis, regardless of model, is expected to be east of the area and we switch again to a gusty northwest flow regime. Our precipitation will transition to rain or snow showers, with the best coverage of snow showers across the mountains, winding down Wednesday night. Thursday looks to be drier with less cloud cover. Temperatures during this portion of the forecast will start the period around ten degrees above normal, and cool to reading around normal by the end of the period. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... As of 1242 PM EST Friday... MVFR SCT to BKN clouds will continue with the northwest flow into the mountains this afternoon into tonight. This will continue MVFR ceilings at KLWB and KBLF for this afternoon into tonight with scattered flurries. The heaviest snow showers will be tapering off during the next couple of hours. Cold temperatures will persist through the forecast period, remaining below freezing west of the Blue Ridge. Winds will gradually subside over the next 24 hours as high pressure finally builds overhead for Saturday. High pressure will pass overhead Saturday promoting light winds and clear skies. VFR conditions will prevail Saturday into Saturday night. High confidence in ceilings, visibilities and winds during the taf period. 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, with possibly more precip Tuesday, a pattern that will promote sub-VFR conditions attms. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM NEAR TERM...KK/PM SHORT TERM...AL LONG TERM...AL/DS AVIATION...KK/PM

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