Area Forecast Discussion
Issued by NWS Blacksburg, VA

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010 FXUS61 KRNK 250729 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 329 AM EDT Fri May 25 2018 .SYNOPSIS...
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High pressure moves offshore this afternoon. A tropical low moving into the Gulf of Mexico Saturday will move ashore and wobble over the lower Mississippi by Memorial Day. Tropical moisture will stream northward into the region with a return of shower and storms especially during the afternoons and evenings.
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&& .NEAR TERM /THROUGH TONIGHT/...
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s of 300 AM EDT Friday... Very light returns noted on radar this morning along the Blue Ridge, but overall just lower stratocu. Fog somewhat limited at the moment and think the stratocu will maintain patchy nature to fog through the morning rush, with visibilities mainly above a mile. For today, not too much change from previous forecast as southeast flow continues to advect higher pwats our way, reaching 1.5" in the afternoon. Overall models favor more along and west of the Blue Ridge threat for better coverage of showers/storms today, but not too impressed with overall threat, so keeping it mainly in the scattered/chance range, with maybe 50-60 pops across the NC High county. In the east, with high pressure and weak subsidence keeping things fairly dry, with isolated to no coverage east of Roanoke to Martinsville. Having more moisture in the air will allow for more buildup of cumulus. Model sky cover forecast are showing more sunshine but think skies will become more broken in coverage, but still enough of sun today to get temps into the upper 70s to lower 80s most locations, with cooler/cloudier expected in the NC mountains north to the Grayson Highlands with upper 60s to lower 70s. Tonight, not seeing a dry forecast as models confident in showing more moisture advecting along backside of the high offshore, while tropical low moves northward toward the Gulf of Mexico near Cuba. The flow in the low levels becomes more southerly and should see scattered showers/storms stick around mainly in the mountains through the night, though thunder threat diminishes by midnight. Not enough coverage yet to have any flood watches, but not out of the question to have some localized issues in the NC mountains late today into this evening. Low temperatures will be stickier/muggy as dewpoints climb into the 60s, which will lead to lows in the 60s.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
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As of 300 AM EDT Friday... A shallow northern stream trof will swing through New England this weekend as a tropical low slowly moves up the eastern Gulf and into the southeastern US. This will establish a flow of deep moisture into the Appalachians and central mid Atlantic region for the next several days. A series of weak short waves will move up from the south and bring good coverage of diurnally biased showers and thunderstorms for the weekend. While instability will be substantial, hodographs/deep shear are not impressive but precipitable water values are expected to be in the top percentiles. These factors will generate stout updrafts that will support heavy rainfall and set up the possibility of flooding with training convection, along with some degree of severe threat with the most vigorous storms. The threat appears to be across the entire area on Saturday but Sunday may be more confined to locations west of the Blue Ridge. By Sunday night the tropical low will start to retrograde along the Gulf coast as the upper trof over the northeast pulls out. This will stretch dynamic forcing out and may help suppress heavy precipitation to the lower half of the area, perhaps from route 460 southward, but confidence in specifics is not high in this pattern. We have had a few days with little rainfall to allow the ground to dry out but it will not take much to recharge. While there is considerable spread in ensemble guidance, there is enough clustering of hefty multiday QPF totals to warrant concern. Will start to highlight the region for potential hydro issues in the HWO and wait for a more specific region to declare itself in time before considering any watches.
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&& .LONG TERM /TUESDAY THROUGH THURSDAY/...
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As of 115 PM EDT Thursday Tuesday will have upslope southeast wind and precipitable water values around 1.5 inches so all that moisture will mean the potential for heavy rain. Potential tropical system will remain near the Gulf Coast Monday through Wednesday between upper ridge over the southwest then central United States and the off the southeast coast. Thursday the low opens and fills and moves northeast. Models have come into better agreement taking this feature into the Tennessee Valley by Thursday morning. ECMWF has the deeper moisture over Virginia and North Carolina again Wednesday and Thursday.
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&& .AVIATION /08Z FRIDAY THROUGH TUESDAY/... As of 125 AM EDT Friday... Not too much change in the forecast as will see some scattered to broken mainly VFR cigs along/south of a BLF-ROA-LYH line this morning, but cannot rule out some lower cigs approaching BCB toward dawn. Fog still possible as dewpoint depressions are zero to 2 degrees and winds are light, plus wet ground, but confidence is low to medium on how low vsbys could go. Leaning toward fog at all sites, except ROA/BLF for now. Any fog and lower cigs will scatter out to a scatter to broken deck of VFR cigs after 14z. Isolated to scattered showers/few tsra in the afternoon, but coverage so low that no mention in tafs at this point, but models indicate best threat would be LWB-BLF-TRI corridor. .Extended Aviation Discussion... VFR Friday night. Fairy active over the weekend into next week with tropical moisture streaming back in. Not a complete washout, but periods of sub-VFR likely with heavier showers/storms at times, with worse conditions heading south to the Gulf Coast states. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RCS/WP NEAR TERM... SHORT TERM...MBS LONG TERM...AMS AVIATION...JR/RCS/WP

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