Area Forecast Discussion
Issued by NWS Blacksburg, VA-- Remove Highlighting --
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FXUS61 KRNK 272315
Area Forecast Discussion
National Weather Service Blacksburg VA
715 PM EDT Thu Apr 27 2017
A cold front will early tonight. High pressure will then build
off the Atlantic coast and begin a trend for warmer and more
humid conditions, with a slight chance for a shower or
thunderstorm, through the weekend. Another cold front will move
through on Monday and bring a good chance for thunderstorms,
followed by some cooler temperatures through the first part of
.NEAR TERM /THROUGH FRIDAY/...
As of 700 PM EDT Thursday...
Updated forecast to account for radar coverage of showers and a
few storms over the mountains, moving northeast at 40 mph.
Mesoanalysis shows a more stable environment lee of the
Appalachians so severe threat looks to be diminished and thunder
chances should wind down as well after 8pm, with a few cloud to
ground strikes still possible in the piedmont until late
evening. Trended temps a few degrees cooler than previous due to
shower cooled air. Short term models show best coverage of
showers after 8pm in the piedmont then drying after midnight.
Previous afternoon discussion...
The latest models continue to slow the arrival of showers and
thunderstorms from the Tennessee River Valley toward our forecast
area. Throughout the day, surface heating has been trying to
overcome increasing cloud cover from the west and an impressive cap
as depicted in the 12Z RNK sounding. An old outflow boundary will
approach the Appalachian Mountains this evening, which should
provide enough lift to spark scattered showers and thunderstorms.
The Storm Prediction Center still maintains a marginal risk of
severe weather, but whether anything happens or not will depend on
if the aforementioned cap can be broken. Strong wind gusts would be
the primary threat due to a 40 knot low level jet ahead of a cold
front in the Ohio River Valley.
Any shower and thunderstorm activity that develops this evening will
cross over the Blue Ridge early tonight before fading over the
Piedmont by midnight. As the surface front crosses overhead later in
the night, the models dissipate this front due to strong upper level
ridging over the Southeast. Skies should clear toward early Friday
morning, but it may allow patchy morning fog to develop in the river
valleys. The fog should vanish quickly and give way to mostly sunny
skies through the day. With less cloud cover and drier conditions
for Friday, expect high temperatures to be a few degrees warmer than
Thursday and about 10 to 15 degrees above normal for late April.
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 345 PM EDT Thursday...
Region remains under large upper southeast ridge. Broad subsidence
and 850MB temperatures peaking around +20 will result in maximum
temperatures as much as 10 degrees above normal. However, on Sunday
high clouds blowing off from showers and thunderstorms well upstream
may limit full potential of heating. Will be cutting back of
probability of precipitation for Sunday. Bufkit soundings on Sunday
showed a cap just above 5000 feet and not much of any lift.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 345 PM EDT Thursday...
Progressive pattern as closed upper low continues northeast into the
Great Lakes on Monday and Tuesday. Models keep the long wave trof
over the east with another low closing off somewhere around the
Tennessee Valley on Thursday. WPC was leaning more towards the ECMWF
with split flow and a southern stream not as deep as the GFS by
The system on Monday and Tuesday brings a surface cold front through
the Mid Atlantic states on Monday and Monday night. Once a short
wave goes by on Tuesday night, the front sinks south and high
pressure builds in keeping deeper moisture south of Virginia and
.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
As of 712 PM EDT Thursday...
Showery conditions near ROA/LWB/BCB and moving into LYH/DAN this
evening with mainly VFR outside heavier downpours. Downpours
should drop vsbys to IFR with MVFR cigs, so will have tempo
groups in to account for this. Thunder threat should subside by
TAF start time with mesoanalysis showing little to no
Appears threat of showers will exit the piedmont after 05z,
then overnight will deal with fog potential given wet ground and
clearing skies. At the moment seems BCB/LWB will have best
chance of IFR or worse vsbys but could see MVFR at the other
sites as well.
All TAF sites should return to VFR after 12Z Friday with light
south winds expected.
Extended Aviation Discussion...
High pressure should build off the Southeast coast during this
weekend. Other than the potential for MVFR/IFR morning fog at
the usual river valley locations, VFR conditions should prevail
through Saturday. As a low pressure system approaches from the
west on Sunday and Monday, the potential for afternoon showers
and thunderstorms will increase. The cold front associated with
this system should reach the Appalachian Mountains by Monday
afternoon and depart offshore on Tuesday morning, so expect the
best chance of MVFR conditions during the frontal passage.
Potential for high temperature records to be broken Saturday,
Roanoke 89/1915 89
Lynchburg 88/1974 89
Danville 91/1981 88
Bluefield 83/1996 85
Blacksburg 83/1974 84