Scientific Forecaster Discussion
fxus61 krlx 231043
Area forecast discussion
National Weather Service Charleston WV
643 am EDT Mon Sep 23 2019
cold front late today, followed by high pressure mid week. Weak
front Thursday, followed by high pressure building surface and
aloft through next weekend.
Near term /through tonight/...
as of 635 am Monday...
Forecast in good shape and if anything the front may be an hour
slower than currently progged late today. Otherwise, strong llvl
inversion near the surface will become eradicated in the next
couple of hours. This will allow temperatures to respond as well
as wind in the protected hollows/valleys. Light showers across
southeast Ohio will try to make inroads into WV this morning but
will likely weaken considerably as the prefrontal trof crosses.
As of 215 am Monday...
Transient upper trof will progress thru the Great Lakes today
as the associated elongated baroclinic zone Ushers in a welcome
but brief reprieve from the heat of late. Hi res models are
keying on some light showers with a prefrontal surface trof this
morning across southeast Ohio with a tendency to weaken as it
progresses further east late morning. Upstream regional radar
mosaic would support this idea as well.
The actual cold front will lag several hours behind this
feature and with some breaks in clouds expected, some
instability may be realized as models are hinting around 500
j/kg MLCAPE. This combined with some respectable shear across
the north, I elected to add some thunder in the grids later this
afternoon east of the Ohio River. I'm not expecting any severe as
lapse rates remain meager and stronger upper level forcing
remains north of the area. Still, there could be some decent
gusts in any thunderstorm given the Stout dry layer beneath 850 mb.
Timing of frontal passage continues to slow with models now indicating
passage late in the afternoon across the west and during the
evening closer to the mountains.
Low level moisture is progged to pool against the mountains
tonight which should yield decent Post frontal low stratus.
Elsewhere, clouds will scatter behind the front. However, with boundary
layer winds staying up, fog should be confined to the more
protected river valleys/hollows.
Short term /Tuesday through Thursday night/...
as of 435 am Monday...
The first full day of autumn brings, appropriately enough,
cooler weather, as high pressure builds into the area in the
wake of a cold front. This breaks the heat, but not for long.
Low level moisture in the wake of the front will lead to
stratocu on morning mixing, mainly across northern WV and the WV
mountains, but these clouds should mix through to allow for
afternoon sunshine as the mixing layer deepens.
The high will cross the area Tuesday night, allowing for a
clear, calm and cool night. This will allow for lows in the 40s
for the cooler valley locations away from rivers, for the first
time since last Spring in some cases. Even upper 30s are
possible in better sheltered northern mountain valleys.
The high will exit Wednesday, allowing for a warmer afternoon
in light south to southwest flow on its backside. This also
allows for the approach of the next cold front Wednesday night,
which then crosses on Thursday, driven by a quick moving upper
level short wave trough. Rainfall amounts and the thunderstorm
threat Thursday look minimal with this quick moving early autumn
High pressure moves in for another clear, calm and cool night
Thursday night, although not quite as cool as Tuesday night.
Lowered lows in the valleys per met guidance in radiative
cooling Tuesday night. Otherwise central guidance generally
followed, which reflects temperatures closer to normal,
compared with recent days.
Long term /Friday through Sunday/...
as of 435 am Monday...
The long term period will bring more dry, very warm weather, as
upper level high pressure gradually builds in from the south.
The details of the forecast Friday into the weekend will depend
upon how quickly that upper level high builds.
Surface high pressure exits Friday, and a warm front moves up
through the area Friday night into Saturday, ahead of another
cold front approaching from the northwest. That front, driven by
a quick moving upper level short wave trough that lifts through
the Great Lakes Friday, and then scoots up into eastern Canada
on Saturday, makes its closest approach Saturday and Saturday
night, before lifting back north Sunday into Monday. How slowly
or quickly this process occurs will be tied to how slowly or
quickly the upper level high builds in from the south.
The various fronts Friday into the weekend will bring clouds,
but the chance for any precipitation, which would be light, is
low, and the current forecast is dry. Dry, hot weather should be
in full force to close the weekend, or at least by the start
the next work week.
Central guidance continues the previous forecast of well above
normal temperatures throughout the period.
Aviation /12z Monday through Friday/...
as of 640 am Monday...
Prefrontal band of weakening showers will cross this morning
with little to no impact for aviation. Otherwise, VFR
conditions should prevail with developing gusts to 20kts out of
the west-southwest. Cold front crosses west to east after 18z with
scattered -shra. Prob30 groups were coded up for the potential
for brief reductions in visibility along with MVFR bases. -Tsra was
substituted in the prob30 groups at pkb/ckb where weak
instability resides. Front looks to exit the mountains this
evening with some Post frontal low stratus developing at
mountain terminals, lowering into IFR at bkw overnight.
Forecast confidence and alternate scenarios through 12z Tuesday...
Forecast confidence: high.
Alternate scenarios: timing of showers with the cold front could
vary by an hour or two.
Experimental table of flight category objectively shows consistency
of weather forecast office forecast to available model information:
h = high: taf consistent with all models or all but one model.
M = medium: taf has varying level of consistency with models.
L = low: taf inconsistent with all models or all but one model.
UTC 1hrly 10 11 12 13 14 15 16 17 18 19 20 21
EDT 1hrly 06 07 08 09 10 11 12 13 14 15 16 17
crw consistency h h h h h h h h h h h h
heights consistency h h h h h h h h h l h l
bkw consistency h h h h h h h h h h h h
ekn consistency l l l h h h h h h h h h
pkb consistency h h h h h h h h h h h h
ckb consistency h h h h h h l h h h h h
After 12z Tuesday...
IFR or worse along the mountains Tuesday morning, in stratus
and Ridgetop fog, in the wake of cold front.