Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
258 PM EST Tuesday Nov 25 2014
low pressure moving up the East Coast Wednesday brings snow to
the Appalachians. Weaker systems until early Friday.
Near term /through Wednesday/...
attention turns to fast moving system slated to move in overnight
and exit tomorrow afternoon. Looks as if most of our concern will
come with sharp short wave trough rotating through as opposed to developing
surface low along the East Coast. While the west extent of the precipitation is
by and large similar amongst the NAM and global models...amount
and thermal profiles differ. This makes for a challenging forecast
regarding winter weather. The mesoscale NAM is wetter and colder in
the lower portions of the bl.../below 3 kft/ than GFS. The new
European model (ecmwf) along with sref tend to side with NAM for thermal profiles
but with less quantitative precipitation forecast. After coordination with wpc...went more toward
the GFS and NAM 4 km for thermal profiles with little in the way
off cold air advection to work off. As for quantitative precipitation forecast a blend of GFS and sref was used.
All of this resulted in precipitation quickly overspreading SW Virginia
and east half of WV after midnight. Expect this to initially take the
form of rain in The Lowlands and for elevations below 2500 feet in
the mountains. As the bl cools expect a switch to snow across the
lower elevations of the mountainous counties first...followed by
lowlands east of US 119 in the S and along and east of i79 in the north
toward morning. The short wave trough quickly moves through with surface low
racing NE just off the East Coast. As such...quickly bring probability of precipitation down
from SW to NE...so that by early afternoon the County Warning Area should be dry
by and large.
As for accumulations...have a general 4 to 8 for Randolph and
Pocahontas where the watch was upgraded to a warning. Hoisted an
advisory for the remainder of the WV mountains down into SW Virginia for
1 to 3 inches with 2 to 4 for the central mountains. Also put
adjacent lowland counties of the north mountains in an advection for 1 to 3
inches. There will be a sharp cutoff to precipitation with areas of southeast Ohio
staying mainly dry perhaps. Have little to no accumulations in the
west lowlands including the crw/pkb/hts metropolitan areas. Should the
colder and wetter NAM trends continue...then a little more in the way
of accumulations may make it into the Kanawha valley.
Short term /Wednesday night through Friday/...
large storm moving up the East Coast will spread snow over the
mountain counties on Wednesday where a Winter Storm Watch remains
in effect for up to 6 to 8 inches of snow at the highest elevations.
In this package...lowered temperatures a bit to bring snow to lower
elevations and increased westward extent of snow to near
Huntington per 00z guidance moving the moisture slug further west.
Still not confident enough for a warning...but it is looking more
After the large storm moves off to the north another clipper will
impact the area on Thanksgiving day giving a light dusting of snow
to most places then we dry out for the remainder of the period.
Long term /Friday night through Tuesday/...
used a blend of the European model (ecmwf) and European model (ecmwf) ensemble mean for the forecast.
High pressure slides eastward Friday night and Saturday...providing
warm air advection. Next frontal boundary pushes into the region on
Sunday or Sunday night. The front then hangs near the area on Monday
as a wave moves along the front...pushing it southward Monday night.
The front will return back northward Tuesday as a warm front.
Aviation /20z Tuesday through Sunday/...
expect VFR conditions at all sites through this evening...under
light west southwest flow.
A low pressure system is expected to develop and track north along
the eastern sea board Wednesday. Precipitation will quickly
overspread much of the area after midnight with mainly rain in the
lower elevations with developing MVFR conditions and IFR or worse snow
in the mountains to include kbkw and kekn by 09z. The rain may
change to snow across the lowland terminals before ending
Wednesday morning...with the greatest chance at IFR conditions at
kckb and kcrw. This system quickly exits off to the NE by early
afternoon with improving conditions from SW to NE. Some MVFR
stratus may linger though.
Forecast confidence and alternate scenarios through 18z Wednesday...
Forecast confidence: high.
Alternate scenarios: timing precipitation and associated conditions may
vary late tonight and early Wednesday.
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 20 21 22 23 00 01 02 03 04 05 06 07
EST 1hrly 15 16 17 18 19 20 21 22 23 00 01 02
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 h h h
bkw consistency h h h h h h h h h h h h
ekn consistency h h h 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 h h h h h h
After 18z Wednesday...
IFR conditions in snow is possible over the mountains on
Wednesday night and Thursday.
WV...Winter Weather Advisory from 1 am to 4 PM EST Wednesday for
Winter Storm Warning from 1 am to 4 PM EST Wednesday for
Winter Weather Advisory from midnight tonight to 1 PM EST
Wednesday for wvz033>036.
Virginia...Winter Weather Advisory from midnight tonight to 1 PM EST
Wednesday for vaz003-004.