Area Forecast Discussion
Issued by NWS Blacksburg, VA

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207 FXUS61 KRNK 141937 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 237 PM EST Sun Jan 14 2018 .SYNOPSIS...
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Cold high pressure will extend south across the region tonight before weakening Monday into Monday night. A second surge of Arctic air comes in behind a cold front that passes through the area later Tuesday into Tuesday night. Arctic high pressure follows the front with very cold air for the middle of next week.
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&& .NEAR TERM /THROUGH MONDAY/...
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As of 237 PM EST Sunday... Cold surface high pressure to our north will control our weather tonight into Monday. A shortwave approaches around the mean upper trough to the north late tonight into Monday morning. This feature combined with weak warm advection aloft will bring some increase in mid and high clouds overnight. The low temperatures are tricky tonight depending on the timing and opaqueness of the cloud cover. Blended Conshort and coop mos for low temperatures overnight with readings from around 7 degrees in the mountains to the mid teens along the southern Blue Ridge mountains. A clipper over the Great Lakes will travel east Monday and a trailing cold front will approach our region from the west. Decreased pops on Monday with dry airmass in placed. High temperatures on Monday will vary from the mid 20s in the mountains to the the upper 30s in the piedmont.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
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As of 237 PM EST Sunday... The item of interest during this portion of the forecast will be a cold front, and potential waves along it, that are looking more promising in helping to produce at least some measurable snow across the entire forecast area in the Tuesday/Wednesday time period. The latest runs of the various model guidance are consistent with a slower arrival time of precipitation associated with the approaching cold front. While earlier editions placed light snow into western sections of the area by Monday afternoon, the latest various are more conservative, and suggest more of the wee hours of Tuesday morning. During the day Tuesday, the GFS solution continues to be the most progressive with the system and has a quick burst of light snow, primarily confined to western and northern sections of the area. The European and NAM solutions are not as progressive thanks to two factors. The first the propagation of a shortwave trough northward along the front Tuesday night into Wednesday. This feature would help slow the progression of the front and add a burst of moisture and lift across eastern sections of the area. Secondly, each of these solutions hint at the formation of a coastal off off the VA/NC coast during this same time period, yet another element that would cause the forward progression of the advancing front to lag, and thus allow for more time to snow across the area, especially the east. Given the models are trending towards the reinforcing wave along the front impacting the region, and the folks at WPC are also leaning towards this higher total scenario based upon their discussions, our forecast will follow suit. If the latest numbers come to fruition, areas roughly west of Interstate-81 and also north of route 460, so there is some overlap in these regions, may be candidates for a Winter Weather Advisory, 2 to 4 inches, as we get closer in time to the event. No area currently would be a candidate for a Winter Storm Watch/Warning at this time. Areas southeast of this region are more likely to receive 1 to 2 inches. Another potential hazard during the late Tuesday night/early Wednesday morning time frame will be the wind chill. Some of the higher elevations may see readings reach five below zero or lower. We will need to continue monitor this as as approach these dates for any need Wind Chill Advisories, or wording to the same incorporated in any Winter Weather Advisories.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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As of 1000 AM EST Sunday... Wednesday night, a few lingering upslope snow showers will still be possible across western Greenbrier County, WV within the brisk northwest flow on the backside of the departing upper trough. The remainder of the region is expected to be mostly clear to clear, with the entire region continuing to trend colder as compared to 24 hour prior. Have trended a little colder than guidance in the west given the anticipation of at least some coverage of snow on the ground across that part of the forecast area. The combination of the falling temperatures and still brisk winds, may yield some wind chill values at or below the five below zero range late Wednesday night into early Thursday morning, especially across portions of the area west of the crest of the Blue Ridge. On Thursday a shortwave ridge is expected to build across the region allowing for dry weather and the start of moderating temperatures. On Friday, a shortwave trough is expected to track eastward from the Great Lakes region into New England. Any associated weather is expected to remain north of our region. However, the proximity of this feature should help tighten the pressure gradient and yield an increase in wind speeds and gusts across the region. The Friday feature will be shortlived with the area resuming a transition to greater ridging across the eastern third of the country. Look for dry weather and temperatures continuing to moderate heading into the weekend. By Sunday, a deepening upper low is progged to be positioned over, or just west of, the Upper Mississippi Valley, with its associated cold front approaching our region. The WV/VA/NC area will remain within a strong southwest warm air advection flow ahead of the cold front. Some light patchy rain will be possible during the day within a region of insentropic lift. Temperatures will continue to trend milder. Through this period of the forecast, gradual warming is forecast. On Thursday, look for temperatures to average five to ten degrees below normal. However, but Sunday, temperatures are expected to average ten degrees above average.
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&& .AVIATION /20Z SUNDAY THROUGH FRIDAY/... As of 1236 PM EST Sunday... VFR conditions are expected across the region as cold dry high pressure moves out of the Ohio Valley and into New England. This should finally bring the Appalachians and central Mid Atlantic region fair weather and good flight conditions tonight into Monday. Winds will be light and variable tonight into Monday. A weak disturbance approaching from the west will bring increasing mid/high clouds overnight but bases are expected to remain at or above 5k feet over the west with mainly high clouds across the east. High confidence in ceilings, visibilities and winds during the taf period. Extended Discussion... VFR will prevail Monday afternoon into Monday night under high pressure. Sub-VFR cigs/vsbys in light snow or snow showers are possible late Tuesday into Wednesday from a clipper system. This will lead to another surge of Arctic air with corresponding drier air anticipated for Thursday and Friday. Drier weather will continue Saturday, before moisture returns on Sunday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...KK NEAR TERM...KK SHORT TERM...DS LONG TERM...DS AVIATION...JH/KK

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