Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 211503 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1003 AM 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/...
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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.
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&& .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 /15Z TUESDAY THROUGH SATURDAY/... As of 645 AM EST Tuesday... High pressure was well off the East Coast this morning and a cold front extended from Wisconsin to Nebraska. Between these two systems there was a deep layer of southwest winds over the Mid Atlantic region into the Carolinas. High clouds covered much of the region this morning. MVFR clouds were spreading north into western North Carolina and theses are expected to reach southwest Virginia before noon. Ceilings will continua to lower along the southern Blue Ridge and across the foothills this afternoon and evening. IFR to LIFR clouds are likely at higher elevations overnight. The cold front will cross through the area late tonight into Wednesday morning. Winds will shift to the northwest behind the front. High confidence on this timing which brings the front through KLWB and KBLF after 07Z/2AM. There is a low probability of rain across central North Carolina and into eastern Virginia tonight, mainly south and east of KDAN and KLYH. Extended Discussion... High pressure then establishes itself for Wednesday through Friday with VFR conditions. The next chance for sub-VFR conditions is with a cold front on Saturday. Dry weather is anticipated for Sunday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/DS SHORT TERM...RCS LONG TERM...JH AVIATION...AMS/RAB is the U.S. government's official web portal to all federal, state and local government web resources and services.