Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
457 am EDT Sat Sep 5 2015
southeast flow brings a subtle decrease in heat...humidity and
thunderstorm coverage today. Weakening middle level disturbances
gradually give way to high pressure during this Labor Day weekend.
Near term /through tonight/...
surface high pressure builds down the East Coast behind a back door
cold front...bringing a slight lowering of temperatures and dew
points for the near term. Upper level forcing will be weak...in
light flow in a coll area between upper level highs to the east and
SW...and upper level lows to the S and north. As such...expect
afternoon thunderstorms to be fewer and farther between compared
with Friday...and they should dissipate promptly upon loss of heating
The southeast flow around the back side of the East Coast high will provide
upslope flow on the eastern fringes of the forecast area. This may
result in a light shower there this morning...and then may be
enough to help initiate storms over the mountains this afternoon
especially if we could get differential heating between the east and
west slopes. These storms may then drift westward out of the
mountains...in the light mean layer Erly flow.
Another tranquil nt is upcoming with valley fog forming..as surface
high pressure ridging noses southwestward over the area.
MOS guidance is well converged and looks good in this benign
pattern...leaned toward bias corrected values for lows tonight.
Short term /Sunday through Monday night/...
upper ridge holds across eastern U.S. During the period...with a
continuation of above normal temperatures for this time of year.
Weak disturbances...combined with a southeasterly flow as surface
high pressure remains centered off the coast...will keep chances of
showers and storms in the forecast...mainly across the
mountains...and mainly during peak heating hours. Could see an
isolated storm sneak down into The Lowlands...but for now will
maintain a dry forecast. Ridge will start to flatten out across the
area late in the period...with the approach of a cold front.
Long term /Tuesday through Friday/...
more of the same through Wednesday...hot and muggy conditions with
just an isolated shra/tsra. Pattern finally begins to break toward
Thursday with falling heights amid a transition more into a east
Continental U.S. Trough. The cold front that will mark this transition looks to
cross long about Thursday with a good shot a much needed rain
over the area.
Aviation /08z Saturday through Wednesday/...
convection had died off for the nt...and dense valley was forming
beneath a canopy of only high thin cloud. This cirrus may be just
enough to prevent a persistent LIFR dense fog at most airports.
Bkw had experienced IFR fog in the wake of a thunderstorm that
affected that Airport 00-02z. It was lifting out around 06z and it
was unclear whether a light southeast puff there would be enough to keep
the fog from returning there overnight. Amendments are likely
The overall very warm and humid weather pattern
continues...although a southeast flow of slightly drier air will bring
the humidity down a bit on Sat. Scattered convection Sat
afternoon may not amount to as much as was the case Friday
afternoon. This convection should die own more promptly upon
sunset Sat evening...and dense valley fog will start forming by
06z although it is not likely to directly impact airports until
after 06z Sunday. However...at least a period of dense fog is
likely after dark where it rains Sat afternoon and evening.
Surface flow will be light S to southeast while east to NE flow aloft overnight
becomes light southeast on Sat.
Forecast confidence and alternate scenarios through 06z Sunday...
Forecast confidence: medium.
Alternate scenarios: timing and coverage of fog overnight tonight
may vary from forecast. Convection Sat afternoon is expected to be
scattered and thus not explicitly coded up in the tafs...but
amendments may be needed as the afternoon convection develops and
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 09/05/15
UTC 1hrly 06 07 08 09 10 11 12 13 14 15 16 17
EDT 1hrly 02 03 04 05 06 07 08 09 10 11 12 13
crw consistency h h h M M M h h h h h h
heights consistency M M l l l l l M h h h h
bkw consistency M h h h h h M M M M M M
ekn consistency M l l l l l l l h h h h
pkb consistency h h h h M M M h h h h h
ckb consistency h h h h h M M h h h h h
After 06z Sunday...
IFR possible in valley fog overnight into the morning next several