Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
619 am EDT sun Jul 5 2015
closed middle/upper level low approaches today. Opens into trough
tonight or Monday as it passes over. Cold front approaches
from Midwest late Tuesday...could stall/weaken in vicinity Wednesday.
Near term /through tonight/...
main weather maker for the near term is the closed 500mb trough that is
currently spinning over Tennessee. Models all in good agreement slowly drifting
the low to the NE across Kentucky today. They also agree on it gradually
opening into the mean trough as it crosses County Warning Area late tonight into
Monday. The new 06z NAM is a bit farther west with the low track
into tonight...so will need to watch for this trend in other models
as well. Best chance of showers will be to the east of the upper low
track...so for today thinking the highest rain amounts should be in
the Coal fields of SW Virginia and S WV...northward into the central
mountains. Some uncertainty on if heavier showers will also begin to
wrap around the northern side of the low...which could bring heavier
showers into the tri-state region as well. The hrrr is trying to
show hints of this in its final few hours this afternoon...while the
NAM keeps things more in southern and eastern County Warning Area. Will go with a
Flash Flood Watch for generally the southern third of the County Warning Area for
today and tonight.
With abundance of clouds east of the Ohio River...trended toward
cooler guidance. The exception will be far northwest County Warning Area where the thicker
clouds will arrive last...so bumped up temperatures there a degree or two.
Short term /Monday through Tuesday night/...
the weakening middle level low should be lifting northeast Monday with
the trough axis near the Ohio River. Along that western trough
axis...hard to determine the coverage of the showers and thus probability of precipitation
along on the western periphery of this system. Did expand
likely probability of precipitation in much of West Virginia lowlands Monday...but did not
go to the Ohio River and westward.
Still picturing a lull in showers/lowering probability of precipitation from southwest to
northeast late Monday into Monday night.
00z NAM tries to form early morning convection Tuesday in the Ohio
Valley...forcing appears to the increasing low level flow and warm
air advection. Will not jump on that specific solution now. Did
try to increase probability of precipitation a bit faster Tuesday afternoon and Tuesday
evening ahead of the approaching midwestern front. With more
instability and taller storms possible...will mention a water/flood
concern in the hazardous weather potential for Tuesday night into
Wednesday for northern and central counties...not the southeast.
Long term /Wednesday through Saturday/...
operational models all have a front waffling around the forecast
area for Wednesday into the weekend. Big differences however with
the timing of the front slipping south of the region on either late
Wednesday or Thursday...before returning back northward. Due to low
confidence on timing of features...will use a blend of the European model (ecmwf) and
gefs ensemble means but not be too specific with timing.
Aviation /10z Sunday through Thursday/...
upper level low spinning over Tennessee currently will gradually drive
showers into the forecast area from the SW. Isolated to scattered
thunder also possible. Expect VFR with an isolated shower possible across
the west...with MVFR to IFR in the heavier showers across the
south and east. Fog formation is tricky at end of taf period
tonight with some showers and clouds around...but still very moist
Forecast confidence and alternate scenarios through 12z Monday...
Forecast confidence: medium.
Alternate scenarios: timing of showers may vary...could get lower
flight categories in heaviest showers/storms. Fog timing and
density may vary tonight.
After 12z Monday...brief IFR possible in thunderstorms late
Tuesday through Thursday.
WV...Flash Flood Watch from 11 am EDT this morning through late
tonight for wvz005-013-015-024>027-033>037.
Kentucky...Flash Flood Watch from 11 am EDT this morning through late
tonight for kyz105.
Virginia...Flash Flood Watch from 11 am EDT this morning through late
tonight for vaz003-004.