Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 170423 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1123 PM EST Thu Feb 16 2017 .SYNOPSIS... High pressure will remain in control through Friday night. After some early morning cloud cover, temperatures moderate back up to above normal levels Friday and remain above normal for much of the weekend. The next chance for precipitation is not until later Saturday into Saturday evening as a disturbance brings a period of showers to the region. && .NEAR TERM /THROUGH FRIDAY/...
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As of 1116 PM EST Thursday... Seeing differences in temperatures this evening per lack of cloud cover and less wind and those areas with clouds and/or wind. Earlier this evening, Danville had already dipped to 32, while it was still in the upper 30s to lower 40s further north toward Roanoke and Lynchburg. Satellite and model trends showing altocu hanging around from the Alleghanys over to southside VA and the NC piedmont early overnight while another batch of mid/high clouds arrives during this time in the west. Kept forecast lows close to the previous set ranging from the mid 20s in some of the mountains and high mountain valleys of the west, with most in the upper 20s to lower 30s. Previous discussion from early evening... Increased cloud cover a bit over our southwest mountains of VA into NC per latest Satellite loops. Appears will see this dissipate some this evening but more upstream warm advection cloud cover arrives by midnight. The previous forecast has this well in hand. No other major changes were made to this update. Previous afternoon discussion... A brisk, cool Thursday afternoon across VA, southeast WV into northwestern NC today due to surface ridging and an associated dry low-level air mass. Our area remains in cyclonic flow in mid-levels; however, a line of low to mid-level cloud cover evident in afternoon visible imagery from near Tazewell County VA up into the Great Lakes separates colder air to our northeast and milder temperatures aloft over the central/southern Plains and the South. For Tonight: While mid-level cyclonic flow aloft is maintained early this evening, the 500 mb low begins to pull away from New England later tonight. Northwesterly wind gusts should continue to abate through early evening as boundary layer stabilizes with nightfall and lingering pressure gradient diminishes. Aforementioned NW-SE oriented low-/mid-level cloud shield then begins to return northeastward as a warm front aloft. 12z model consensus depicts a weak vort max that ripples south-southeastward along the 500 mb height gradient during the latter half of the overnight (06-12z Friday) as the warm front propagates northeastward. Some of the higher-resolution CAM output generates some weak reflectivity in simulated reflectivity progs, but I`ve generally downplayed chances for snow showers given how dry the low-level air mass is. Even flurries may be hard to come by. Because of the cloud shield, I`ve opted to raise low temperatures up by a few degrees over MOS; should winds drop off sooner and the cloud shield advance slower than presently anticipated (i.e. leading to better radiational cooling) lows may be several degrees lower than forecast, mainly in the northeastern tier of counties. Shown lows from the mid 20s/upper 20s north, upper 20s/near 30 for the NC mountains, New River Valley into far southwest VA and a couple degrees above freezing for the foothills and VA Southside/NC Piedmont. For Friday: Expect there to be at least some morning cloud cover that will shift to the northeast, with clearing skies then taking place for the afternoon. Initially light/variable winds trend light southwesterly and 850 mb temperatures should run in the +4 to +7 degree C range by the afternoon. While there should be some improvement in dewpoints Friday, they may be slower to rise in the afternoon as dry air aloft is mixed down. All in all though, after the morning cloud cover burns off it turns out to be a pleasant, mild February afternoon with highs well into the 50s to middle 60s.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 310 PM EST Thursday... We will be in the southern stream of a progressive split flow regime through the weekend. This will keep our temperatures well above normal through Sunday. A closed low over Texas will slowly start to open up as it moves in our direction Saturday, spreading a chance of showers into locations west of the Blue Ridge late in the day. As the upper low transitions to an open wave and moves through the southeast, the chance of showers will spread across most of the area west of I-77 and north of Route 460 Saturday night and linger into Sunday in the west before ridging builds in and we return to fair weather through Sunday night. Expect temperatures to be running at least 10 to 15 degrees above normal through the weekend, with highs in the mid/upper 60s east of the Blue Ridge and upper 50s/lower 60s west. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 310 PM EST Thursday... The upper ridge over the eastern US will flatten as the pattern transitions to more of a zonal flow, with a closed low slowly weakening as it moves eastward along the Gulf coast. This will continue our fair weather and warm conditions into the start of next week. However, high pressure will wedge in behind a backdoor cold front late Monday into Monday night. While a sprinkle may accompany the front Monday night, the main effect will be for a bit of a cool down on Tuesday though readings will still be above normal. Differences in guidance bring increasing uncertainty to the forecast heading into midweek as the upper trof flattens. The most likely scenario will be for an increasing chance of scattered showers Tuesday night and Wednesday thanks to some short wave energy and an approaching frontal boundary. However, overall dynamic support appears limited with little isentropic lift so overall extent and magnitude of any precipitation will not be great. The track of the closed low over the Gulf appears to be trending further south, creating a drier solution for the Appalachians and central mid Atlantic region with just a slight chance of a shower. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/...
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As of 1116 PM EST Thursday... Staying VFR this period though not without some bkn/ovc cigs in the 5-10kft range into early Friday morning. Afterwards should be mainly skc-sct. Winds have died down and expect this trend to continue into Friday with high pressure in place. Extended Aviation Discussion... VFR conditions remain the rule through Saturday. Next potential for sub- VFR conditions is late Saturday into Sunday as a disturbance moves into the area from the Deep South. Warmer temperatures will accompany this system, so any precipitation should be in the form of rain showers. Lower ceilings associated with these showers may linger into Sunday before clearing and return to VFR Sunday night through Monday. Dry weather will prevail Monday night into Tuesday.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AL/WP NEAR TERM...AL/WP SHORT TERM...MBS LONG TERM...MBS AVIATION...AL/PM/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.