Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
232 PM EST Monday Dec 22 2014
warm front tonight into Tuesday. Low pressure moves west of the
area but brings rain Tuesday night into Wednesday. Cold front
Wednesday night. High pressure late Christmas day.
Near term /through Tuesday/...
with the very light precipitation over mainly the northern mountains moving
out with an upper disturbance this afternoon...and temperatures
getting to just above freezing...the Freezing Rain Advisory is
expired. There will be a lull in the precipitation for the remainder of the
afternoon with even some breaks in the clouds...especially west of
the mountains where southeast downsloping winds are in effect.
For tonight...models show a warm front lifting north through the area.
Latest NAM/GFS models are somewhat generous with the probability of precipitation and with
quantitative precipitation forecast with the warm front tonight...but the most recent hi res
models are downplaying the prospects for precipitation tonight. The newest
hi res models of the hrrr/rap seem to recognize a typical shadow zone
in the precipitation between the Ohio River and the mountains...and also even
downplay the prospects for precipitation tonight. Have basically chosen a
compromise here. While downplaying the aggressive models...there is
an upper disturbance generating scattered light rain over the
eastern Tennessee Valley this afternoon. This feature will lift
north with the warm front. So we will introduce some probability of precipitation all areas
tonight. Will have the greater probability of precipitation west of the Ohio River and in
the mountains...while only a slight chance between the Ohio River
and the mountains. In any event...quantitative precipitation forecast will be light and all rain as
temperatures not expected to fall below freezing...even in the
northern mountains...with increasing warm advection and the clouds.
Look for lows mainly in the 30s to near 40.
For Tuesday...look for a brief precipitation break in the warm sector in
the morning before the next upper disturbance approaches from the
west with scattered showers working from west to east mainly in the
afternoon. No thunder yet. With a brisk southerly breeze...look for
temperatures to soar well above normal...in the lower 60s in some
Short term /Tuesday night through Thursday night/...
still looks like an interesting system will impact the region during
this period. But it appears the chance for a white Christmas is
quite small across most of the area. Current thinking is that even
the highest elevations may only see a few tenths of snow Wednesday
night into Christmas day.
NAM/GFS/ECMWF/Canadian models all indicate an area of low pressure
will lift north from the Gulf Coast into the Great Lakes region.
The GFS and Canadian are the fastest moving the low northeast...
followed by the European model (ecmwf) and NAM. End result will be a good chance of
precipitation beginning Tuesday night.
Have generally gone closer to the GFS/Canadian solution...bringing
an associated cold front eastward through the area on Christmas
evening. The rain should mix with...and/or change to snow across most
locations by 12z Christmas day.
Precipitation should decrease from the west on Christmas day with
most locations dry by late Christmas.
Models indicate high temperatures Christmas day will be in the low
40s across The Lowlands...and only remain below freezing across the
highest elevations. So any remaining precipitation should change
back to rain across much of the area during the day.
However...the region will experience windy conditions Wednesday
night and continuing through Christmas day.
Long term /Friday through Monday/...
Christmas evening will continue to be windy behind the front. The
sun will likely make a welcome return with dry air moving in for
By Sunday 00z...models diverge with little agreement. Leaned more
towards the GFS for probability of precipitation as that solution appears to be more
realistic than the European model (ecmwf). Some waviness around the trough moving
east will create a slight chance for some precipitation. With
warmer temperatures...the majority of this will fall as rain with a
chance for some wintry mix and snow overnight. A slight chance of
rain...and snow at higher elevations...may continue through Monday
Generally followed HPC guidance for temperatures with a few tweaks.
Aviation /20z Monday through Saturday/...
18z Monday through 18z Tuesday...
MVFR ceilings will hold along the east slopes of the mountains this
afternoon with southeast upslope flow...affecting bkw. Elsewhere
generally 4000-6000 ceilings with breaks especially western slopes
of the mountains.
After 00z...warm front will lift north through the area tonight. Models
are very generous with rain...as temperatures will stay above
freezing. Not real confident with the widespread rain...but have
introduced at least low probability of precipitation tonight. Otherwise...look for MVFR
ceilings to hold east facing slopes of the mountains...and VFR
ceilings to lower to MVFR after 06z mainly west of the Ohio River
and over northern West Virginia.
After 12z Tuesday...warm front and associated light rain shifts
north of the area early. Generally becoming VFR ceilings area wide
by 15z as we get into the warm sector...with threat of scattered
showers well ahead of a cold front increases by around 18z.
S to southeast flow will continue...with higher elevations gusting 20 to 25
kts at times through the taf period.
Forecast confidence and alternate scenarios through 18z Tuesday...
Forecast confidence: low to medium.
Alternate scenarios: MVFR ceilings and light rain chances may be
more widespread with the warm front tonight.
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 M h h l l M M l l l l l
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 Tuesday...
IFR possible in rain Tuesday nt into Wednesday...changing to snow showers
Wednesday nt...as an intense low pressure center passes.