Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
1237 am EST Monday Feb 8 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 today/...
1230 am update...
nothing Earth shattering in terms of changes yet...but still in
the middle of the forecast package.
Previous discussion... 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 /tonight 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 /06z Monday through Friday/...
expecting overall deteriorating aviation conditions through the
taf period...with a strong cold front passing through
today...bringing rain changing to snow...lowering ceiling...and
visibilities that will likely bounce in and out of precipitation.
For the ceilings...introduce MVFR near the onset...but have IFR at
some locations as the lowest levels saturate in the Post frontal
environment. With the visibilities...generally use MVFR with the
onset and in rain...but IFR likely after several hours of light
rain...and especially once the transition to light snow occurs.
Forecast confidence and alternate scenarios through 06z Tuesday...
Forecast confidence...high in the deteriorating trends...and medium
in the details and timing.
Alternate scenarios: timing of IFR will vary. Low level saturation
may require earlier onset of IFR once the cold front passes.
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.
Date Monday 02/08/16
UTC 1hrly 03 04 05 06 07 08 09 10 11 12 13 14
EST 1hrly 22 23 00 01 02 03 04 05 06 07 08 09
crw consistency h h h h h h h h M M M l
heights consistency h h h h h h h M M l l M
bkw consistency h h h h h h h h h M M M
ekn consistency h h h h h h h h h h h h
pkb consistency h h h h h h h h M l l l
ckb consistency h h h h h h h h h h h h
After 06z Tuesday...
periods of IFR conditions possible in rain/snow showers all the
way through Wednesday night...with the worst conditions expected
Tuesday morning through Wednesday morning.
WV...Winter Weather Advisory from noon today to 1 am EST Tuesday