Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 211808 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 108 PM EST Tue Nov 21 2017 .SYNOPSIS... Three cold fronts cross through the Mid Atlantic region this week. One passes through tonight, the next on Thanksgiving Day, and the third on Saturday. && .NEAR TERM /THROUGH TONIGHT/... As of 1250 PM EST Tuesday... The advancement of low level clouds into the area has been slower than expected. This has allowed for filtered sunshine to impact a greater extent of the region. Therefore, high temperatures across manly locations across the southern and western sections of the region are being increase by a few degrees. Also, the patchy light precipitation that was expected along and just east of the crest of the Blue Ridge roughly south of Hill City, VA has as also been delayed, but still anticipated to develop by early this evening. As of 955 AM EST Tuesday... Cloud cover will continue to spread north across the area this afternoon. Shallow low level moisture will advect into and pool along the lee of the Blue Ridge from roughly near Floyd, VA southwest into the Northern Mountains of North Carolina. While not a lot is expected, some patchy light rain is still possible along this region this afternoon. Have made some small adjustments downward on forecast high temperatures today, especially in the north, based upon the latest observations and expected arrival of the thicker cloud cover. As of 210 AM EST Tuesday... Ridge of high pressure will be well off the East Coast today with a cold front moving into the central United States. Will have southwest winds through a deep layer today as an upper trough approaches in the northern stream. Air mass will saturate from the top down with increasing cloud cover throughout the day. Will be starting with some high clouds and warm air advection in the morning. Only minor changes to forecast maximum temperatures. Some weak upslope and isentropic lift along the southern Blue Ridge and foothills this afternoon. Will maintain a low probability of precipitation. Cold front arrives overnight and will be crossing through southeast West Virginia, northwest North Carolina and southwest Virginia between 06Z/1AM and 12Z/7AM. This will turn the wind to the northwest and begin to bring in drier air aloft behind the front. Precipitable water values along and ahead of the front increase to near 0.75 inches, especially in central and eastern Virginia and North Carolina. Will keep a low probability of precipitation tonight in the piedmont, especially east of Danville and Lynchburg. Best cold air advection is in the mountains tonight. Clouds and mixing will limit temperature drop in the east. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... As of 145 PM EST Tuesday... A weak cold front will pass over the region Wednesday morning. Behind the front, a tight pressure gradient will form over the mountains, bringing breezy conditions to the area during the morning. High pressure will began to edge into the region during the afternoon, allowing winds to slowly subside into the evening. The weather pattern becomes quasi-static going into Friday. An elongated surface ridge will remain stationary from Texas to West Virginia. Meanwhile, an upper level trough will slowly advance east across the deep south. This trough will guide a weak tropical disturbance across the panhandle of Florida late Wednesday night to off the Carolina coast Friday. Influences from the surface ridge and dry air entraining into the tropical disturbance from the north will keep the region dry Thursday and Friday. Temperatures will warm to near seasonal levels Wednesday, but become cool on Thursday with a blanket of high clouds over the region. Temperatures will rebound back towards normal on Friday. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... As of 130 PM EST Monday... Mean upper troffiness to prevail through the period with reinforcing energy arriving late in the weekend that looks to carve out an even deeper 500 mb cold pool into Monday. Otherwise should see mainly dry weather under weak high pressure and slightly below seasonal temperatures until a strong cold front arrives later Saturday. This front will again be followed by colder temperatures Sunday with cooler air lingering into early next week under chilly high pressure. Appears a few rain showers will be possible northwest ahead of the front Saturday afternoon, followed by western snow showers early Sunday, but little more than continued very low pops for now. Highs mostly 50s Saturday, cooling to mainly 40s Sunday- Monday, with perhaps 30s in spots across the mountains behind the front similar to this past Sunday. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 1240 PM EST Tuesday... Primarily VFR conditions prevailed across the region. Only parts of the Northern Mountains of North Carolina and neighboring Blue Ridge sections of southwest Virginia were experiencing MVFR ceilings. Visibilities all were VFR across the area. As we progress through the afternoon and evening hours, MVFR ceilings should gradually work there way into more of the region, and some patch light rain will also arrive in the area currently experiencing MVFR ceilings. Overnight, a cold front will approach and sweep across the area. Concurrently, an area of low pressure will head north along the U.S. east coast with the western edge of its associated precipitation skirting the eastern sections of the forecast area. MVFR/IFR ceilings will become more common as the night progresses. Rapid improvement to VFR is expected east of the crest of the Blue Ridge by Wednesday morning behind the front. Sub-VFR ceilings will continue through at least mid-day along and near a KBLF-KLWB line given the influence of lingering low level moisture and a northwest flow regime. Extended Discussion... High pressure will provide for primarily VFR conditions Wednesday afternoon through Friday. A cold front will cross the area over the weekend. While primarily VFR conditions are still expected, some brief sub-VFR conditions are expected in the vicinity of the front. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/DS SHORT TERM...RCS LONG TERM...JH AVIATION...DS

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