Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
151 PM EDT Thursday Oct 30 2014
high pressure today. Low pressure with rain Friday evening. Colder
air and the low should result in accumulating snow in the mountain
counties overnight Friday night into Saturday.
Near term /through tonight/...
high pressure will move across to our east by later tonight. As
the high pressure traverses the area...winds will be light to calm
overnight. This could aid the formation of some fog...but with the
building cloud cover...not expecting any fog to be dense.
Clouds will continue to fill in overnight ahead of an approaching
low and associated cold front leading to mostly cloudy skies. Probability of precipitation
will continue to increase through the day Friday.
Temperatures tonight continue to appear to be cool...however...did not go
quite as low as some guidance as the cloud cover should limit
Short term /Friday through Sunday night/...
first meaningful snow of the season anticipated for the WV and Virginia
mountainous counties...and perhaps hilltops in the southern WV Coal
fields...overnight Friday night and Saturday morning...
Whatever the winter of 2014/15 will bring...it begins early and
loudly...as major East Coast l/west trough amplification takes place early
A northern upper level low drops almost due S...down the backside of the
amplifying l/west and into the base...or from the Great Lakes to the
smokies...12z Friday-12z Sat. A lead southern stream short wave trough already in
the base of the l/west over the southeastern states as of 12z Friday...moves up
the east side of the l/W...along the East Coast...generating an initial
surface wave along an offshore baroclinic zone.
Friday finds the forecast area already in in relatively dry...chilly air
nearly capable of supporting snow with key values near
thresholds...like 0c at 800 mb.5 and 540 km between 500 mb and h10...along
with prognosticated precipitable water values of only two thirds of an inch. As such...the
northern stream upper level low will not have much moisture or
baroclinicity to work with as it digs through or just west of the forecast
area...with associated frontogenetic forcing not really cranking up
until the low approaches the southeast coast.
Showers will break out Friday as the surface cold front associated with the
northern stream feature...approaches and then moves through from the west.
Precipitation will likely become more widespread Friday nt into
Sat...as the negative tilt feature digging S of the area places the
area in strong forcing including q vector convergence. The
aforementioned factors will keep quantitative precipitation forecast values mainly below a half an
inch / 6 hours.
The cold core slides southeastward across SW portions of the forecast area Friday nt
into Sat...while the warmer air gets hung up over northestern portions of
the forecast area Friday into Friday nt...until the primary surface low just to
the north fills by Sat morning. The warm boundary layer air does not
get completely eradicated...keeping accumulating snow levels above
2500 or even 3000 feet...with levels perhaps getting below 2500 feet
over SW portions of the forecast area...closer to the upper low track.
All of this sort of balances snow amts in the mountains the coldest
air over the smaller southern mountains. Generally looking at County
averages in the advisory range at best...with peak amounts near 4
inches for the southern mountains and as high as 6 inches at Snowshoe.
Will thus maintain severe weather potential statement mention for the mountainous counties.
As the l/west shifts east...the system scoots up the East
Coast...offshore...it make take until Sun morning for the upslope
snows showers to wane and the clouds to break up. High pressure
sails across sun nt...proving ideal radiative cooling most of the nt,
Have temperatures nearer lower side of guidance with bias corrected
guidance not a good fit in this highly anomalous pattern.
Long term /Monday through Wednesday/...
models rapidly lift the upper low off the Atlantic coast Saturday
night...which will end the lingering mountain snow showers...with
only additional minor high elevation accumulations before dawn
Sunday. Strong dry Canadian high pressure will then be the dominant
feature through Monday. The high pressure center will settle over
the area Sunday night...then shift off the Atlantic coast early next
week. This will bring a dramatic turnaround in temperatures this
period. Well below normal temperatures this weekend with widespread
sub freezing temperatures Sunday night under the center of high
pressure...will warm up to near normal values by Tuesday as the high
shifts off the Atlantic coast.
While all this above is happening...models show another upper trough
digging into the Mississippi Valley and driving it east to affect
our area later Tuesday and Wednesday. By this time...temperatures
will be well above freezing for a rain event.
Aviation /18z Thursday through Tuesday/...
cloud cover will continue to build in through the afternoon with
most sites still maintaining VFR conditions...however...ceilings
will drop to MVFR conditions for some sites as the evening progresses.
Some fog is possible overnight...though the cloud cover should
limit the fog to MVFR conditions overnight for most...if not
Winds should be light through the period.
Forecast confidence and alternate scenarios through 18z Friday...
Forecast confidence: medium.
Alternate scenarios: timing and density of morning fog. Cloud
cover could vary overnight.
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
EDT 1hrly 14 15 16 17 18 19 20 21 22 23 00 01
crw consistency h h h h h h M M M M M M
heights consistency h h h h h h M M M M M M
bkw consistency h h h h h h M M M 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 M M M M M M
ckb consistency h h h h h h h h h h h h
After 18z Friday...
IFR developing Friday evening in rain...changing to mostly snow over
Southern Mountain counties including bkw 06z to 12z Saturday...with
a rain and snow mixture in The Lowlands Saturday.