Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
1246 PM EST Monday Jan 26 2015
low pressure system moves off to the east today. Colder air moves in
late today into Tuesday. High pressure Wednesday. Low pressure
Near term /through tonight/...
snow band has crossed the Ohio River into West Virginia. Reworking
the temperatures based on current trends...and largely using the
rap for the next few hours through 00z. Will be working on some
forecast snow totals as well as this transitions to an upslope
event later today.
models showing cold air gradually moving into the region today
changing the precipitation from rain to snow. Models are also
showing some good lift in an eastward propagating band behind the
change over to snow...allowing for some light snow accumulations
today...especially over central and northern portions of the
forecast area. Will continue the Winter Weather Advisory for Perry
County as that area has already changed to snow and should receive
the most accumulations this morning.
Low level cold air moves in late today and tonight...causing over
turning in the lower atmosphere. This combined with upslope should
create some light snow for much of the area. Will increase probability of precipitation
some. The coldest of this air is in a layer that the GFS seems to
not be able to capture. Will rely on the mes NAM for low
Short term /Tuesday through Thursday night/...
snow showers will continue across the north lowlands and north mountains
Tuesday with a fetch off Lake Erie and continued cold air advection. There appears
to be a subtle spoke of energy diving on the back side of the trough
which may enhance the snow showers and expand coverage into the c
lowlands and remainder of the mountains. Have a few inches coded up
in the high terrain with perhaps a dusting into S mountains and
parts of The Lowlands Tuesday evening.
Surface high builds in Wednesday to shut off the snow showers. Tried
to hold onto some stratus across WV for at least first half of the
day with subsidence inversion developing atop lingering low level
moisture. Warm air advection should scatter this out later in the afternoon.
A quick moving clipper type system will cross Thursday...with good
amount of warm air advection ahead of it for Wednesday night. This will likely
result in a non diurnal trace...especially across the ridges where a
Good Ridge/valley split will exist. Right now it appears this system
will track just north of the area resulting in rain outside of the
mountains. There could be a brief wintry mix at the onset across southeast
Ohio and north WV. Precipitation will change to snow showers everywhere Thursday
For temperatures...stayed close to the NAM/met guidance early on to account
for the better resolution in the low level cold air. This results in
Tuesday being rather cold with many places struggling to make it to
30 in The Lowlands. Cold Tuesday night with teens lowlands/single
digits high elevations. Temperatures rebound on Wednesday into the low to
middle 30s. With aforementioned warm air advection Wednesday night...have temperatures rising
overnight after a quick fall Wednesday evening. Thursday should make
it into the 40s with some middle 40s S zones and up into favored
downsloping areas. The mountains should stay in the 30s.
Long term /Friday through Sunday/...
period starts with high pressure overhead...that almost immediately
gives way to a low pressure system approaching from the west. Models
are generally a bit faster with this system...so precipitation could
reach western portions of the forecast area around dawn Thursday. This then
spreads east across the area Thursday...followed by upslope precipitation in
the wake of the system Thursday nt into Friday.
With the low center tracking of the area...enough warm air should
arrive for a mainly wet...not white or icy...Thu. However...mixed
precipitation including freezing rain could occur at the beginning
if precipitation is able to rush in before surface temperatures climb
above freezing Thursday morning. However...given most of the area will
be in the warm sector ahead of a cold front that does not arrive
until evening...most of the precipitation should occur in the
afternoon and therefore be of the wet variety.
Colder air coming in behind the system changes the rain to snow
showers but then quickly cuts off the precipitation from the west as
the drier air moves in. Upslope snow showers diminish on Friday...as
high pressure builds in from the west...cutting off the moisture and
upslope flow. This should lead to good radiative cooling Friday nt.
Another system affects the area next weekend. The models remain
diverse on the nature and evolution of this system...but none
advertise anything major...and all show that the overall cold theme
in a positive pna continues. Thus have the chance for light snow
At or very close to wpc values for temperatures...they looked like a
very reasonable compromise between the inordinately cold and dry
European model (ecmwf) hires...and the GFS based guidance...which seemed too high
given its mass field solutions.
Aviation /17z Monday through Friday/...
feeling that the best course of action in the aviation forecast
today is pessimistic with prevailing IFR or worse conditions. Band
of snow is now pushing east and will be east of the Ohio River in
the next hour or two.
As this system moves east...flow turns to the northwest and the
northeast mountains get into an upslope regime. Ekn and ckb will
be most affected by this...as bkw will be too far south this time
around. Continue with the IFR at these locations the
longest...although the flow itself without snow will keep bkw
Have improving conditions when snow ends at terminals...but to
MVFR ceilings only.
Forecast confidence and alternate scenarios through 18z Tuesday...
Forecast confidence: low to medium.
Alternate scenario: observation may bounce. Timing issues will exist.
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 18 19 20 21 22 23 00 01 02 03 04 05
EST 1hrly 13 14 15 16 17 18 19 20 21 22 23 00
crw consistency h h h h h M h M M M M M
heights consistency h M l l h h h h h M l l
bkw consistency h h h h h h h h M M M M
ekn consistency M h h h M h M M M h M M
pkb consistency h h h h h M M M M M l M
ckb consistency h h h h h h h h h h h h
After 18z Tuesday...
IFR possible in snow Tuesday in the northern and central WV