Area Forecast Discussion
Issued by NWS Blacksburg, VA

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023 FXUS61 KRNK 210738 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 238 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/... As of 210 AM EDT 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 /07Z TUESDAY THROUGH SATURDAY/... As of 1220 AM EST Tuesday... Broad surface high pressure will slide eastward tonight into Tuesday. Scattered cirrus, especially southern areas tonight, will support a decoupled boundary layer and light or calm surface winds. The air mass is too dry to support any fog overnight or early Tuesday morning. Expect more variable cloudiness into Tuesday, with the greatest cloudiness to the south and east from low-level warm advection. After 18z Tuesday, MVFR ceilings in the 020-030 range will likely begin to evolve from TNB northeast toward ROA, spreading across the remainder of the CWA west of the Blue Ridge after 00Z. Southwest winds increase Tuesday to around 6-8 kts and may gust up to 20 kts by late afternoon across southeast WV and southwest VA. Ceilings will continue to lower along Tuesday night in advance of a new cold front approaching from the west, with upslope clouds increasing in its wake west of the Blue Ridge. Medium to high confidence in ceilings through the TAF valid period. High confidence in VFR visibilities through the TAF valid period. Medium to high confidence in wind speed and direction through the TAF valid period. Extended Discussion... Another mainly dry cold front will move through Tuesday night into Wednesday morning. A few rain showers will be possible south and east of the Blue Ridge as a southern stream system tracks across the southeast states. High pressure then establishes itself for the Wednesday through Friday, including Thanksgiving, with an expectation of good flying conditions for Thanksgiving travel in the RNK airspace. 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 SHORT TERM...RCS LONG TERM...JH AVIATION...RAB

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