Area Forecast Discussion
Issued by NWS Blacksburg, VA

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282 FXUS61 KRNK 221331 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 931 AM EDT Fri Sep 22 2017 .SYNOPSIS... High pressure will cover the region into the weekend. A cold front will approach the Mid Atlantic region the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... As of 930 AM EDT Friday... Any lingering fog/low clouds will dissipate shorty, leaving us with a good deal of mid/high clouds streaming over the region from the northeast. Expect short wave energy pushing south through the region to combine with orographic effects and diurnal instability to generate some scattered afternoon showers/thunder from the Grayson Highlands south through the NC mountains. Otherwise, a dry forecast. Highs today will be quite similar to readings yesterday with middle 80s east of the Blue Ridge and upper 70s/lower 80s to the west. Previous discussion... 500MB ridge will be centered over Michigan today with the surface high over Pennsylvania. Weak upper trof extends from eastern North Carolina to the Florida panhandle. Models also indicating some subtle low level convergence over North Carolina this afternoon. Will have highest probability of precipitation over the northwest North Carolina mountains, where the instability and CAPES are most supportive of showers and thunderstorms this afternoon. Drier air coming in tonight from the northeast. This should limit areal extent of fog. MET/MAV guidance has been running cool for maximum temperatures the past few days. Will be making only slight adjustments to follow bias corrected guidance and persistence for both highs and lows. && .SHORT TERM /SATURDAY THROUGH MONDAY/... As of 240 AM EDT Friday... Very quiet weather-wise this period as weather across the central Appalachians, Blue Ridge and VA/NC Piedmont region is dominated by deep-layer ridge centered over the Great Lakes. Related subsidence will lead to dry weather and keep even fair weather cumulus to a minimum as PWAT values are commonly at or below 1" this weekend. Summerlike temperatures, running some 10 degrees milder than late- September climatology project to continue with little change in air mass. 850 mb temperatures are on the order of +15 to +18C. Given the stable and persistent pattern, I`ve heavily utilized bias-corrected max/min temperature fields versus guidance consensus. This produces highs in the upper 70s to mid 80s and lows mid 50s to mid 60s. Those looking for more Fall-like temperatures may need to look toward the middle of next week at the earliest. With good mixing anticipated, dewpoints should follow a diurnal trend - falling in aftn while recovering at night. While dewpoints are a bit higher than typical conditions for late September they`re not by any means uncomfortable. All in all, a great stretch of weather for any outdoor plans. We`ll continue to keep an eye on developments in the western Atlantic pertaining to Maria, but it does look like its effects will remain over coastal waters with high surf over the eastern coastal mid-Atlantic before a recurve into the northern Atlantic. Interests are encouraged to monitor the latest forecast and advisories on Maria from the National Hurricane Center. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... As of 142 PM EDT Wednesday... Models showed good large-scale agreement across CONUS through medium range. The amplified weather pattern continues across the country with an active tropics in the western Atlantic ocean. Model ensembles and consensus from NHC keep Maria east of the mainland. See latest NHC advisory for position and track. The trough across the central U.S. and associated cold front will slowly travel eastward. The strong upper level ridge should hold across our area. Operational models showed the potential for some clouds and possible showers to flirt with our piedmont counties Tuesday afternoon with Maria interacting with coastal front and trough. Hard to tell how far west any moisture really pushes. 12z run looked less impressive with moisture and qpf. Interesting to note the weak shortwave rotating around the upper ridge across southeast portions of forecast area. A cold front will weaken as it moves east and travel through the eastern U.S. Thursday into Friday. Temperatures remain above normal during extended period with lows generally in the upper 50s to around 60 in the west, to lower to mid 60s in the east. High temperatures will range from the mid 70s to around 80 in the west, to lower to mid 80s in the east. The strength of the subsidence with Maria and amounts of cloud cover will greatly impact the temperatures. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... As of 720 AM EDT Friday... Just like the last several mornings, patchy dense fog has developed in mountain river valleys. KBCB was down to LIFR and KBLF visibility was dropping and may occasionally lower to IFR through 13Z/9AM. Mid levels clouds were approaching KLWB so fog at that site is much less likely this morning. All the fog/stratus will lift by 14Z/10AM making for mainly VFR under light east to northeast wind as high pressure starts to build in. A weak upper level trough over North Carolina should push farther south limiting any isolated showers and thunderstorms to the mountains of northwest North Carolina. Extended Aviation Discussion... Overall persistence forecast to prevail this weekend into early next week as strong high pressure aloft builds in from the northwest keeping tropical moisture offshore. This should also maintain good flying conditions along with mostly dry weather, outside of any late night/early morning fog from Saturday through Tuesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/MBS SHORT TERM...AL LONG TERM...KK AVIATION...AMS/JH is the U.S. government's official web portal to all federal, state and local government web resources and services.