Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 300744 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 344 AM EDT Fri Sep 30 2016 .SYNOPSIS... A strong upper level area of low pressure will remain just west of the mountains today before slowly lifting to the north later tonight into Saturday. This system will combine with a residual stationary front across the region to produce periods of showers and thunderstorms into late tonight. The low will move northeast, away from the region, resulting in drier weather this weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 245 AM EDT Friday... Broken bands of heavy rain producing showers continue across the west under the tail of a passing speed max and over the northeast third with added low level convergence early this morning. Expect this trend to persist through daybreak with main coverage likely shifting into the northwest sections as multiple short band type features merge. Then questions with added coverage through the day as the upper low begins to shift back north while the jet aloft remains strong over continued low level convergence espcly north and east this afternoon. Will also have to watch for another band to work north along the southern Blue Ridge this morning as several solutions including the latest HRRR and 00z ECMWF paint quite a bit of QPF extending north from the North Carolina foothills into the west between 12-16z. This along a residual convergence axis well to the south and eventually along the eastward moving occluded front that will swing across the Blue Ridge this afternoon. This along with some breaks and decent instability southeast may allow one final heavier band of shra/tsra to evolve across the north/east this afternoon given strong veering with height and moist PWATS. However with uncertainty wont hoist another watch at this point while allowing the ongoing FFA to end with this package given only current scattered nature to shra attm. Otherwise again running with likely/cat pops today, except tapering to chance heading into the southwest zones where will likely remain in the dry slot aloft with limited added showers. Lowered high temps a little under easterly flow and more clouds as expecting a range from near 80 southeast to only the 60s far west. Upper low should continue to trudge north toward the Ohio Valley overnight allowing drier air aloft to gradually win out from southwest to northeast behind the passing surface occluded boundary. Think still decent coverage in the north/east during the evening before showers fade late tonight with little focus remaining. May even see some clearing work in from the southwest after midnight so mostly chance pops tapering to spotty showers northeast sections by dawn. Expect more clearing west to allow temps to fall into the cool 40s in spots with overall low/mid 50s elsewhere, except low 60s far east. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 305 AM EDT Friday... Drying trend will continue over the weekend as the upper low finally lifts farther north and weak high pressure slides in from the west. May still have an isolated shower around early Saturday over the north, otherwise cutting pops with more sunshine on tap by the afternoon. Another spoke of energy looks to rotate around the upper low Saturday night with this feature reaching the western mountains later Sunday. Moisture quite limited with the weak associated front but cant totally rule out an isolated shower western slopes late Sunday into Sunday night. Otherwise expecting mainly clear skies Saturday night and mainly sunny Sunday before clouds invade the west late. High temps to remain mild under west/southwest flow aloft with mostly 70s both Saturday and Sunday and lows mostly 50s Saturday night given good radiational cooling conditions. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 330 PM EDT Thursday... The upper low will give way to ridging in the eastern US through the early part of next week. This stall the approaching front and allow a large area of high pressure to settle over New England and wedge down the east side of the Appalachians. The big variable lies with the potential track of TS Matthew as it is expected to turn north and move up the Atlantic coast. The exact track of Matthew will determine how much, if any, precipitation it can push into the region from the east and how much overrunning precipitation will develop as it interacts with the wedge. Right now, the most likely scenario is for some light overrunning precipitation to develop by Tuesday and increase a bit into Wednesday especially in the east, with any significant effects form Matthew remaining to our east. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... As of 1250 AM EDT Friday... Variable but overall sub-VFR conditions will prevail overnight with cigs fluctuating between MVFR and low end IFR at times. Best coverage of showers resulting in vsby restrictions look to occur along the KLYH-KHSP corridor for the rest of the night. However another narrow band of showers and storms may affect areas from KBLF to KBCB/KROA into the early morning hours. Thus will include either a vicinity or tempo mention with perhaps a brief prevailing group of lower cigs/vsbys. Should finally see convection wane before daybreak but still enough to keep thunder in a few western sites over the next few hours. Uncertainty continues with the degree of added convective coverage on Friday with the upper low starting to retrograde while the occluded boundary to the west shifts east and starts to cutoff deeper moisture late. Models continue to focus showers and storms across the northwest corridor Friday morning, then along and north of a KLWB- KDAN line. Should see any IFR conditions slowly improve to MVFR/VFR by midday/early afternoon though think places like ROA/LYH/LWB will keep MVFR to the end of this taf period. Will include more showers and storms given decent probability during the afternoon in most locations with tapering of showers by the evening as the main corridor of deeper lift slides north. Extended aviation discussion... A deep upper low will finally shift farther to the north by Saturday and away from the region on Sunday. This should allow for a gradual improvement in cigs after early sub-VFR Saturday with widespread VFR Sunday as weak high pressure builds in. Looks like overall VFR to then prevail into early next week outside of some upslope low clouds Monday and perhaps along the Blue Ridge Tuesday as another weak wedge develops under high pressure to the north. && .HYDROLOGY... As of 330 AM EDT Friday... Overall convective bands have decreased in both coverage and intensity early this morning so letting the watch go across the north for now. Otherwise main concern again with the redevelopment of heavier bands from the south/southeast through the day as multiple areas of convergence pivot around the upper low to the west. Likely looking at another inch or so of rainfall on average across the north with locally higher amounts where deeper convection mixes in. Also some concern along the Blue Ridge through midday with possible very early morning redevelopment and training as seen a few models. Given now saturated soil conditions and elevated stream/creek levels will be easier for flooding or flash flooding to develop while still appears most mainstem rivers will stay below flood levels for now. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/JH NEAR TERM...JH SHORT TERM...JH LONG TERM...MBS AVIATION...AMS/JH/WP HYDROLOGY...JH is the U.S. government's official web portal to all federal, state and local government web resources and services.