Scientific Forecaster Discussion
fxus61 krnk 182248
Area forecast discussion
National Weather Service Blacksburg Virginia
648 PM EDT Tue Jun 18 2019
the mid Atlantic remains in a stagnant weather pattern with a
stationary front overhead through Wednesday night. By Thursday,
low pressure will arrive to shove the stationary front offshore.
High pressure should return to provide drier weather for Friday
Near term /through Wednesday/...
as of 200 PM EDT Tuesday...
A stationary front remains draped over the mid Atlantic.
Meanwhile, a shortwave upper level trough over Kentucky and
Tennessee will aid in synoptic lift to providing strong
thunderstorms this afternoon. The air mass is again warm,
moist, and unstable with somewhat weak shear and considerably
high freezing levels. In addition to this air mass, a jet streak
associated with this shortwave upper level trough will provide
some upper diffluence. Precipitable water values should climb
again to over 1.5 inches to provide high efficiency of rainfall.
Earlier showers and cloud cover have restricted activity north
of Route 460, but storms are beginning to fire over the
Piedmont and the southern Blue Ridge.
A threat for severe weather due most likely to damaging winds
exists if the convection becomes deep enough. Wpc also has a
slight risk of excessive rainfall due to the significant amount
of rain from yesterday, especially in northwest North Carolina
close to Mount Airy. Consequently, a Flash Flood Watch is in
effect to cover for the heavy rainfall expected in the showers
and thunderstorms later today and tonight. While the convection
should subside by midnight, lingering showers may persist
through the night and into Wednesday morning. More showers and
thunderstorms are likely by Wednesday afternoon, but synoptic
lift will not be as robust due to the shortwave upper level
trough passing offshore. Nevertheless, localized flooding and
severe weather is not out of the question for Wednesday.
Short term /Wednesday night through Friday night/...
as of 300 PM EDT Tuesday...
Loss of daytime heating will bring an end to shower/storm
threat Wednesday night, little or no upper support for lingering
precip. Coverage is expected to increase Thursday as another
short wave trough traverses the forecast area from the west.
This trough is expected to spin up a surface low across the Ohio
Valley with an associated cold front that is progged to cross
the mid-Atlantic Thursday night. Depending on how much debris
cloudiness is around early Thursday, day as a whole could turn
out to be rather busy with potential for organized deep
convection that would promote both severe and Hydro issues.
Much of the thunderstorm activity is expected to pass east of
our area Thursday evening as the cold front passes through.
Frontal passage will bring a drying northwest wind shift, with
perhaps a few residual showers lingering overnight across the
higher terrain of southeast West Virginia, in addition to areas
north of 460 in Virginia closer to the surface low that will be
moving across the northern mid-Atlantic. Friday looks to remain
dry, with slightly cooler temperatures and a noticable drop in
humidity. Models are hinting at upper level energy returning
late Friday night to bring more shower activity from the west,
however confidence is too low at this point to mention in the
forecast, with better chances for this on Saturday.
Long term /Saturday through Tuesday/...
as of 300 am EDT Tuesday...
Drying is expected to be short-lived as moisture returns
Saturday via southwest wind flow and return of frontal
boundary...a warm front. Passage of this feature is expected to
bring clouds in addition to scattered showers and storms
Saturday, followed by a restoration of the heat and humidity for
Sunday and Monday. Return of deeper moisture will result in
another multi-day period of showers and storms with the
potential of both isolated severe and Hydro concerns.
Aviation /00z Wednesday through Sunday/...
as of 645 PM EDT Tuesday...
Showers and thunderstorms will continue into this evening,
mainly affecting klyh/kdan to kmtv before the heavier rainfall
moves to the east. This likely to result in periods of MVFR/IFR
through about 01z/9pm. Outside of any convective activity,
conditions will mainly be VFR with just lighter showers and
higher cloud bases, but ceilings should lower overnight due to
increasing low-level moisture. Confidence is increasing for
MVFR ceilings to occur after midnight and hold until Tuesday
morning. Even IFR ceilings are possible at kblf/klwb/kbcb.
Conditions should slowly improve to VFR by the afternoon, but
more showers and thunderstorms will occur. Although confidence
not as high for widespread showers/storms on Wednesday, appears
still enough coverage around to include either a prevailing or
vicinity mention Wednesday afternoon/evening.
Extended aviation discussion...
A stationary front over the mid Atlantic along with waves of low
pressure tracking eastward along this boundary should keep an
active weather trend going on Thursday. Showers and
thunderstorms will likely develop Thursday afternoon and
evening, which will produce areas of MVFR and heavy rainfall.
MVFR or IFR conditions from fog or low clouds may also occur
during the late night hours due to increasing moisture. By
Friday, a cold front will move through the mid Atlantic to
provide drier weather with VFR conditions through Saturday. A
warm front should arrive on Sunday to spark another chance of
showers and thunderstorms.
as of 300 PM EDT Tuesday...
Flash Flood Watch is in effect from much of the forecast area
along and south of Highway 460. This is an area that received
widespread heavier rainfall yesterday with the potential to
repeat similar rainfall pattern this evening and into the
Virginia...Flash Flood Watch until 6 am EDT Wednesday for vaz007-009>018-
NC...Flash Flood Watch until 6 am EDT Wednesday for ncz001>005-
WV...Flash Flood Watch until 6 am EDT Wednesday for wvz042.
near term...precipitable water