Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
516 PM EST Thursday Mar 5 2015
Arctic high pressure cuts off the snow and brings record cold
tonight. High pressure dominates...with weak systems to the north
and...eventually...weak systems to the south...through the period.
Near term /through Friday/...
5 PM update...tweaked the pop and sky grids. Some clearing
starting to occur across parts of southeast Ohio already. Added in
probability of precipitation across parts of West Virginia as previous forecast was
clearing light band moving through the area a little too quickly.
In addition...hourly temperatures are slightly colder than was
predicted...making for a very tough low temperature forecast for
tonight...however...think current min T forecast looks decent.
Previous discussion follows...
while snow intensities continue to lessen this afternoon...we will
wait for a northern stream short wave to race across the area late
this afternoon into this evening before the snow totally cuts off.
However...most of the snow outside the mountains the remainder of
this afternoon will lend little to no additional accumulation...with
maybe an additional inch or two in the mountains. Expect we will
expire the remaining winter storm warnings...if not canceling them
before hand...the last batch expiring at 7 PM over West Virginia and
southwest Virginia. Models in good agreement in rapidly building the
Arctic high over the area tonight. This will effectively clear skies
from west to east later tonight and the winds will go very light.
This brings up the main forecast challenge tonight for the minimum
temperatures given the deep snow pack. Models try to hang the low
clouds into a good portion of the night east of the Ohio
River...which would try to hold temperatures from falling well below
the guidance per snow pack effect. In general...will go below temperature
guidance tonight...especially in the west where clear skies are more
likely to occur faster. However...at this point...will not go wild
on this. Look for temperatures to drop into the single digits...to below
zero especially in the west. With winds dropping off...no Wind Chill
For Friday...there may be some diurnal stratocu development and
possibly a flurry late in the morning...but they will mix out with
drier air aloft in the afternoon and will not mention. With the high
shifting east of the area and light southwest flow developing...look
for temperatures to rebound somewhat Friday...but still remaining below
freezing with compliments of the snow pack.
A record shattering nt is on tap...
Site bkw crw ekn heights pkb
record 16-2001+ 10-1917 0-1901 8-1902 6-1960
forecast 5 6 - 3 1 - 1
Short term /Friday night through Sunday/...
high pressure settles S of the area this period...allowing weak
disturbances to the north to graze by. An upper level short wave trough
crossing late Friday Sans moisture given the dry Arctic high will still
be close by...so expect nothing more than middle cloud with it. The
next disturbance is prognosticated to be flatter...but with the high
farther away...there is the small chance something reaches the
ground as it skirts across the north.
Stout low level moisture is prognosticated beneath an inversion as warm
advection takes place aloft this weekend....prompting a cloudier
Blended in mostly bias correct guidance for lows...lower east and
higher west Friday nt as low and middle level moisture results in increasing
clouds west. Lows Sat nt are higher given the cloudier forecast. Did
raise highs slightly over the weekend given latest guidance but
still stayed lower than guidance all around given the slowly eroding
Long term /Sunday night through Thursday/...
west-northwest flow aloft nearest southern edge of northern stream this period...although
there is model disagreement as to whether highs rise much. This
effects how far north southern stream systems get Tuesday and again late in the
period. This also affects how much temperatures moderate. Still do
show some moderation given no significant replenishment of cold air
and the March sun. Blended in wpc and...in some cases the mex as
well...which were not far apart...and the forecast is close to or
slightly above the previous forecast.
Aviation /22z Thursday through Tuesday/...
18z Thursday through 18z Friday...
at 18z mostly VFR ceilings west of the Ohio River. Widespread
IFR/LIFR conditions in snow...mainly along and east of the Ohio
River at 18z...will continue improving from west to east this
afternoon...to MVFR ceilings as the snow ends.
For this afternoon. Expect VFR conditions west of the Ohio
River...MVFR ceilings by 21z reaching a crw-ckb line and into the
mountains by 00z. Clearing then spreads southeastward...becoming
mostly clear by 00z west of the Ohio River...by 06z reaching a
crw-ckb line...and into the mountains by 09z.
Snows will mainly be confined to the mountains by 22z..and end there
by 05z. After 09z...mainly VFR with scattered stratocu after 14z.
Northwest winds on the order of 5 to 10 kts with a few gusts to 20 kts
ridgetops...will become light by 06z.
Forecast confidence and alternate scenarios through 00z Saturday...
Forecast confidence: medium.
Alternate scenarios: snow may end faster this afternoon...an
clearing may be faster 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 M M h h h h h h h h h
heights consistency M M h h h h h h h h h h
bkw consistency h h h h h h h h h h h h
ekn consistency M h h h h h h h h h h h
pkb consistency M h h h h h h h h h h h
ckb consistency h M M h h h h h M M h h
After 00z Saturday...
no widespread IFR conditions are expected at this time.
WV...Winter Storm Warning until 7 PM EST this evening for
Kentucky...Winter Storm Warning until 7 PM EST this evening for kyz105.
Virginia...Winter Storm Warning until 7 PM EST this evening for vaz003-