Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
706 PM EST sun Feb 7 2016
high pressure exits tonight. Cold front Monday. Unsettled/colder
Tuesday and Wednesday under large middle/upper level low...with
rounds of snow showers that linger through much of the week.
Near term /through Monday/...
700pm update...opted to keep a more predominately rain mixture on
Monday morning...based on latest guidance which keeps a fairly
deep warm layer below 850mb.
Upper low digs down from the upper Midwest tonight with an
associated surface low and trailing cold front. Cold front passes
the region tomorrow bringing rain and snow showers with it.
Precipitation will enter the Ohio Valley around daybreak and
spread eastward from there. Forecast confidence is fairly high on
the timing of frontal passage but still some uncertainty with regard to
p-types. Current thinking is that before the front arrives most of
the region should be above freezing...however as heaviest precipitation
moves overhead wet-bulbing in area of greatest forcing could drop
surface temperatures enough for a quick burst of wet snow to occur
in The Lowlands. This will likely only be with the heaviest band
of precipitation and after the best forcing moves
through...expecting just plain rain showers outside of the higher
terrain. As far as accumulation GOES through 00z Tuesday...it
looks like 1 to 2 inches will be possible in the mountains and
generally a half inch or less in The Lowlands.
Due to the uncertainty with boundary layers temperatures...on-
coming shifts will just have to monitor how the event unfolds and
an Special Weather Statement for a brief period of heavy snow tomorrow morning could be
Short term /Monday night through Wednesday/...
deep l/west trough over the eastern U.S. This entire period spells below
normal temperatures and snow showers.
The party begins right at the start of the period Monday nt...with
cold advection overspreading the area from SW to NE...behind a northwest
to southeast oriented surface low pressure trough extending from the eastern
Great Lakes to the Delaware-Maryland-Virginia peninsula by 12z Tuesday. Outside
widespread upslope snow showers...models depict a Lake Michigan
trajectory coming across the northern tier of the forecast area Monday nt into
Tuesday...enhancing lowland snow amounts there vs. Areas farther S.
Beyond that...tough to time the smaller scale features rotating
around the evolving upper low nearby to the north...but it looks like
the general trajectories may not change much. With 850 mb
temperatures dropping into the teens below zero c Tuesday and slowly
dropping further beyond that...dendritic Crystal growth is
favored...resulting in high snow to liquid ratios.
For starters...snow totals for Monday nt through Tuesday are close to 12
hour advisory criteria but 3-5 inches short of warning criteria on
a County average basis throughout the forecast area. Thus not
introducing any headlines at this time although it is plausible
advisories will be needed for that period...and then Tuesday nt into
Wednesday look to be nearly as snowy with the upper level low and l/west
trough axis still over the upper and middle Ohio valleys. The Lake
Michigan trajectory into northern portions of the forecast area may still be
there or may be becoming reestablished Wednesday afternoon.
Temperatures were lower than guidance but generally stayed close
to previous package and raw guidance in this anomalous pna
pattern...perhaps just slowing down the cooling a bit Monday nt.
Long term /Wednesday night through Sunday/...
still expecting scattered snow showers over the area Wednesday night.
Streamline analysis and hysplit backwards trajectory parcels along
with Omega/relative humidity in the dendritic growth zone do indicate some
enhancement from Lake Michigan for a time in the evening...affecting
southeast Ohio and especially north WV. This is enhanced further with a subtle
vorticity maximum rounding the base of the upper trough.
So...have kept some fairly healthy probability of precipitation over the north during the night.
However...expect this to be a low quantitative precipitation forecast/high pop scenario with
greatest accumulations Wednesday night over the north WV mountains where
an inch or two of additional snow may fall. Thursday morning will
feature some lingering snow showers and flurries...primarily within
any Lake Michigan plume as shown on GFS. 850 mb thermal trough lingers in
the vicinity so hard to see much in the way of improvement with the
erosion of the stratocu and any temperature moderation.
We finally get some warm air advection going Thursday night which should be enough
for some clearing areawide. At the surface high pressure will be
building in which will make for a very cold night should we indeed
lose the clouds amid a fresh snow pack. Some below zero readings are
possible in the in the typical cold spots of the mountain valleys.
Confidence begins to decrease heading into the weekend. The global
models are having some issues resolving features and the overall
mean trough over the eastern Continental U.S.. thus have stayed close to wpc
which favored a colder European model (ecmwf) solution for the weekend amid another
Arctic hammer drop. No big system is envisioned over the weekend
Aviation /00z Monday through Friday/...
clouds will be on the increase tonight as cold front approaches
the area from the west. Rain or snow showers will enter the Ohio
Valley by daybreak and spread eastward through the day. MVFR with
increasing chances of IFR. All terminals will likely stay below
VFR conditions through the remainder of the period.
Forecast confidence and alternate scenarios through 00z Tuesday...
Alternate scenarios: temperatures may be cool enough to have IFR
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 00 01 02 03 04 05 06 07 08 09 10 11
EST 1hrly 19 20 21 22 23 00 01 02 03 04 05 06
crw consistency h h h h h h h h h h h M
heights consistency h h h h h h h h h h M M
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 M
ckb consistency h h h h h h h h h h h h
After 00z Tuesday...
MVFR to periods of IFR conditions possible in rain/snow showers
all the way into Wednesday...with the worst conditions expected
Tuesday morning through Wednesday morning.