Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
550 am EST Sat Feb 13 2016
bitterly cold weather this weekend. A complex system is likely to
bring significant mixed precipitation early next week.
Near term /through tonight/...
545 am update...
Bumped up snow totals a hair over the southeast WV plateau/SW Virginia through
early this morning given the persistent snow bands over those
Previous discussion below...
Arctic air will continue to settle into the area today. 850 mb
thermal trough looks to cross later this afternoon...with 850 mb temperatures
bottoming out around -22c. Thinking scattered to broken stratocu will be
the rule today with some passing flurries and shsn over the high
terrain. Temperatures today top out in the middle to upper teens over The
Lowlands with single digits in the mountains and staying below
zero on the highest ridges. Winds will continue to be gusty today
resulting in low wind chill values. Definitely a day to stay
Clearing tonight with high pressure building directly overhead
late will result in temperatures dipping below 0 not just in the high
terrain but many sheltered lowland locations as well. There will
be some middle/hi clouds trying to work in from the SW very late
which may cap the fall over NE Kentucky and S WV.
Short term /Sunday through Tuesday/...
complex system this period looks just a little colder. The
Lowlands look to get most of their snow from warm advection sun nt
into Monday with high end advisory amounts possible. The northern
mountains also receive a pounding Monday nt which would warrant
warnings if current model output holds up. The central and southern
mountains could get advisory criteria ice amounts. Given
differences among the models and from run to run...it was agreed
among neighboring offices to hold off on coding this up at this
point...especially with ongoing advisories in the near term. Will
update the severe weather potential statement to better reflect these possibilities.
The high pressure system representing the center of the Arctic air
mass overtaking the area at this time...will exit the area on
Sunday...and a warm advection / overrunning pattern sets up late
Sunday through Monday...in deep layer S to SW flow veering with
height...ahead of upper level short wave troughs approaching from the west.
The first one moves through the Great Lakes and upper Ohio valleys
sun nt...with increasing moisture...cloud and precipitation
overrunning the area as a result. With the antecedent Arctic
air...the column remains prognosticated to remain cold enough for snow
throughout the area sun nt...leading to initial accumulations of
generally 1 to 3 inches late Sun afternoon through sun nt...the
highest amounts S.
Ongoing warm advection Monday eventually brings the column above
freezing from 850 mb down sometime Monday afternoon throughout much of
The Lowlands. This limits snowfall accumulations to an inch or
less across The Lowlands...while another 1 to 3 inches are
possible over the northern mountains. A cold layer is prognosticated to linger
between 850 mb and the surface for a time Monday...leading to a period of
sleet and / or freezing rain in the transition.
The second short wave trough tracks farther S than the first...as a l/west
trough over the eastern U.S becomes reestablished. One difference from
previous runs is that surface low pressure center generated by this
short wave appears to be more of a flat wave and farther S. Amidst the
establishment of the l/west trough in the east...this amounts to a
colder solution compared with previous runs...a trend that may be
interesting to follow. The short wave approaches Monday and crosses Monday
nt...as the surface wave rides northeastward just east of the central Appalachians
One limiting factor in a transition back to snow across The
Lowlands Monday nt is the lack of fresh cold air arriving behind the
system. However...it may not take too much further a trend toward
colder to impact the precipitation type forecast for Monday nt given the
marginal nature of the column temperatures currently prognosticated. As
is...the track of the system and the return of the cold air aloft
could result in the higher elevations in the mountains of northern WV
getting clocked with significant snowfall Monday nt.
Another factor in this complex event is the cold air damming in
the typical east of the mountains wedge area...which could result in
at least advisory criteria ice across the central and southern
mountains of WV and down into SW Virginia...mainly the eastern slopes or
eastern portions of the eastern flank counties of the forecast area.
The precipitation winds down late Monday nt into Tuesday as the system
pulls out...ending as rain or drizzle across The Lowlands Tuesday as
we lose the upper level moisture and with it the Crystal growth
Used a NAM and consensus blend for surface temperatures and the NAM
for temperatures aloft...and a NAM/GFS/ECMWF/wpc blend for quantitative precipitation forecast.
Long term /Tuesday night through Friday/...
still lots of uncertainty concerning early next week storm...and
thus...low confidence in the forecast. GFS and NAM seems to be
trending colder/more easterly with the low early next week...while
the European model (ecmwf) continues to show a warmer/more westerly track with the
system. The uncertainty in the path...of course...creates conundrums
in the precipitation type and amount forecast. Regardless of which
model...good 40+kt low level jet will aid in high moisture transport into the
region. One thing that does look fairly certain...is mountainous
counties should get decent accumulations...with lowlands less
certain...as may transition to a rain snow mix or even all rain
Monday afternoon and night...before transitioning to all snow...then
possibly back to a mix or all rain Tuesday afternoon. Southeast Ohio
zones are also quite uncertain...as depending on the path of the
system...there may be a sharp gradient...with the possibility that
southeast Ohio zones could see little to no precipitation. In
addition...if the storm takes a more westerly track...may even see
periods of a wintry mix including periods of sleet across the area
particularly Monday night. So all in all...still lots of
uncertainty...but will start highlighting this system in the severe weather potential statement. In
addition...any snow that occurs...will be a heavy wet snow.
In addition to the wintry precipitation...expecting quantitative precipitation forecast of over an
inch across the mountains...and up to an inch across The Lowlands.
This...particularly if quite a bit of it falls as rain...could lead
to rises on area streams and creeks...and potentially lead to strong
rises on the main Stem rivers next week. This will need to be
Stay tuned to the latest forecast.
Aviation /12z Saturday through Wednesday/...
Arctic front now crossing the mountains as of 06z with a band of
squalls...temporarily dropping mountain terminals into IFR
visibility/MVFR along with gusty winds to 35 kts. Behind
this...generally VFR conditions with occasional drops into MVFR
with any passing shsn with mainly MVFR shsn continuing through 12z.
Gusty winds 20 to 30 kts will continue...with the highest gusts
for the mountain terminals.
After 12z...mainly scattered/broken VFR stratocu with occasional mountain
flurries. Winds will gradually diminish...but still looking at 15
to 20 kts. High pressure will build in tonight which will allow
winds to finally subside.
Forecast confidence and alternate scenarios through 12z Sunday...
Forecast confidence: medium
Alternate scenarios: upslope snow showers this morning may linger
a bit longer in the mountains.
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 Sat 02/13/16
UTC 1hrly 10 11 12 13 14 15 16 17 18 19 20 21
EST 1hrly 05 06 07 08 09 10 11 12 13 14 15 16
crw consistency M M M M M h h h h h h h
heights consistency M M M M h h h h h h h h
bkw consistency M M M M M M M M M M M M
ekn consistency M M M M M M M M M M M M
pkb consistency h h h h h h h h h h h h
ckb consistency M M M M M M M h h h h h
After 12z Sunday...
IFR conditions possible in light snow Sunday night and
Monday...transitioning to a mixed precipitation event for Tuesday.
WV...Wind Chill Advisory until 9 am EST Sunday for wvz032-035>040-