Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 260739 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 339 AM EDT Sun Mar 26 2017 .SYNOPSIS... A series of low pressure systems will bring unsettled weather with a good chance for showers and thunderstorms, mainly west of the Blue Ridge, through Tuesday. Temperatures will remain well above normal with a gradual warming trend bringing high temperatures well into the 70s through the first part of next week. && .NEAR TERM /THROUGH TONIGHT/... As of 315 AM EDT Sunday... Satellite imagery and surface obs indicate mostly mid/high clouds over the region. However, radar shows precipitation associated with an approaching low pressure system is not far off to our west. This stacked low will move from the Mississippi valley into the Great Lakes region and push a frontal system into the area from the west. The aforementioned precipitation will spread across locations west of the Blue Ridge this morning with just a chance of showers spreading east of the Ridge by later this afternoon. Instability is largely absent but modestly steep mid/upper lapse rates may be able to support some rumbles of thunder. As the closed low opens and slides by to our northwest we will get into some shallow upper ridging that will lessen any dynamic forcing to support widespread showers. However fairly deep moisture will remain across the region and allow orographic affects in the southerly flow to continue a chance of showers mainly along and west of the Ridge through Sunday night. Highs today will be a good 5 to 10 degrees above normal with lower 70s in the east to upper 50s/middle 60s in the west. && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... As of 315 AM EDT Sunday... Both the 00z GFS/ECMWF seem to be in fairly good agreement with the 5h pattern with some minor differences with the surface and precip output. Monday still looks like to be cloudier with some low level convergence working across the mountains, so will still see some showers and isolated thunderstorms developing namely in the mountains. Temperatures despite the cloud cover rise to the mid to upper 60s mountains to lower to mid 70s foothills/piedmont. Surface front and upper shortwave enter the mountains by 12z Tuesday so increasing threat of showers and some thunderstorms late Monday night in the mountains, with coverage increasing along and east of the Blue Ridge after 8am Tuesday. Some forecast differences shaping up Tuesday afternoon, since both 00z models showing a faster drying solution starting to move in from the southwest. Will leave high chance to low likely pops mainly along and north of a Bluefield- Pulaski-Chatham line, but will see less coverage over the NC mountains/foothills/piedmont after 2-4pm. Sfc low somewhat weak, but as the low moves across, the 8h jet of 30- 35kts with some westerly flow along/behind the front should bring some gust to 20-25 mph. High temperatures dependent on sunshine and showers, thinking the piedmont will see potential for some sunshine more than the mountains, with even better chance of more sun arriving in the NC foothills in the afternoon. Warm temperatures overall with highs in the mid to upper 70s east of the Blue Ridge, with upper 60s to around 70 in the mountains. Brief period of residual showers across the Appalachians Tuesday night with drying elsewhere. Frontal boundary will shifts to the coast by 12z Wednesday, but extends west into the Gulf Coast States. Meanwhile, high pressure over Ontario will build southward into the TN valley. This high shifts east Wednesday into Wednesday night, with a battle between drier/cooler air north and more moist air south. Will start to see lower dewpoints work in Wednesday afternoon on a north to northeast wind. Not out of the question to keep some clouds around, especially across the NC mountains/foothills with sprinkles possible. Wednesday night, the flow in the low levels should turn more southeast, and cannot rule out the chance for showers to develop along the southern Blue Ridge and adjacent foothills from Floyd to Boone. High temps Wednesday will mild, though if there is more clouds we could be cooler. For now going with lower to mid 60s mountains, to lower to mid 70s foothills/piedmont. && .LONG TERM /THURSDAY THROUGH SATURDAY/... As of 400 PM EDT Saturday... Mainly dry Thursday outside some showers over the southern Blue Ridge in the morning, with some increasing moisture after 00z Friday in the southwest Virginia area. By Friday, the next, and fairly potent, upper low tracks toward the area. However, there is considerable discrepancy between the GFS and the ECMWF in the configuration and timing of this system into the eastern U.S. The GFS depicts more of an open wave reaching the CWA as early as Thursday night moving east of the area by Friday afternoon. Meanwhile, the ECMWF is much slower, deeper, and further south with a cutoff upper low lifting it slowly north-northeast into the Ohio Valley by late Friday. The difference between the two models can be accounted for in noting the strength and blocking of an upstream ridge across the Atlantic. This upstream ridge is much stronger per ECMWF, which also depicts a notable wedge down the east side of the Appalachians as the closed low lifts north into the Ohio Valley. The ECMWF would result in a much wetter and stormier pattern for the CWA, although it would not arrive until Friday as opposed to Thu night per GFS. For now, have generally broad brushed the area with high chance to likely pops beginning Thu night and continuing into Friday. In addition to the differences noted above, there are also massive differences between the two models regarding instability and the potential for severe, with the ECMWF much more noteworthy in this category. For now, have included a chance for thunder without any further details. It will likely take several runs for the models to resolve their differences on this system. Another system is slated to follow by the end of the weekend or the beginning of the next week, so the active pattern is expected to continue into the next week. Temperatures will be closer to normal Wed-Thu, then begin to trend back to above normal levels Fri-Sat. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... As of 235 AM EDT Sunday... A slow moving stacked low pressure system will move from the Mississippi valley into the Great Lakes region and push a frontal system into the area from the west. This will allow us to start Sunday with VFR at TAF sites, followed by precipitation spreading westward across the area and a trend for lowering cigs to MVFR by the afternoon along and west of the Blue Ridge. The downward trend will continue as we head into Sunday evening with MVFR spreading east of the Ridge and IFR setting in to the west, but any significant obvis looks to hold off until after this TAF period. Instability is largely absent but modestly steep mid/upper lapse rates may be able to support some rumbles of thunder. However, believe the expected chances and coverage of thunder is quite low so will not include any mention in the TAFs. The low level wind field will be amplifying west of the Blue Ridge as the low approaches and this will create some gusty conditions but wind speeds do not appear as if they will pose any significant issues for aircraft. Extended Aviation Discussion... An active weather period with a series of vigorous upper-level low pressure areas tracking from west to east across the U.S. during the week. Monday the area will be between systems, but a moist/unstable air mass will remain in place and widely scattered showers and isolated thunderstorms are possible. Areas of sub-VFR cigs/vsbys are also possible, especially during the morning hours, in low clouds and fog. The next upper-level low will arrive Tuesday with another chance for showers and thunderstorms along with periods of sub-VFR conditions. Wednesday-Thursday may bring a period of improved aviation conditions as a weak cold front temporarily pushes the deeper moisture south of the area. However, by Friday the next in the series of upper-level systems arrives with another chance for showers, thunderstorms, and sub-VFR conditions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS SHORT TERM...WP LONG TERM...PM/RAB AVIATION...AL/MBS is the U.S. government's official web portal to all federal, state and local government web resources and services.