Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston WV
1007 am EDT Friday Sep 4 2015
ever present weak upper level disturbances and a very warm and
humid air mass spell mainly afternoon and evening convection.
Southeast flow increases tonight into Saturday.
Near term /through tonight/...
1000 am update...
minor adjustments this morning to the probability of precipitation...having toned down the
slights for the expected lull this morning. This lull should be
brief and expect mountain storms to fire with the heating...and
over the Ohio Valley as well.
a thunderstorm complex over lower Michigan and eastern Ohio was
located right in the diffluent zone southeast of an upper level low over
lower Michigan. However...the flow regime is a little too light
for models to resolve details...with time...of this and other weak
upper level features...placed in an axis roughly northwest to southeast...from
the Great Lakes...to the U.S. Southeast coast...and beyond...between
upper level highs located over the northestern U.S..and the deep S.
The complex itself was having trouble making in roads southward into the
forecast area early this morning...consistent with the virtually none
corfidi vectors. What is left of it should fall apart on Post-
sunrise cloud top warming. The forecast area remaining in the upper
level weakness between the two upper level highs spells scattered
afternoon convection that...in the moisture rich air...only slowly
diminishes tonight. The slow moving storms will result in heavy
but manageable rainfall. The atmosphere will resolve the upper
level details via where the last of the storms persist tonight.
Meanwhile...a surface high builds southward behind a back door cold front
pushing southward along the East Coast. This will introduce low level
moisture into the eastern slopes by Sat morning...as the low level
flow veers to east to southeast.
Blended in met/mav for highs today and bias corrected met for
lows tonight. Not much of a baroclinic zone involved so the
temperature variations will mainly be a function of convection.
Short term /Saturday through Sunday night/...
no significant changes were necessary to the short term forecast
period. Area remains in a warm humid pattern...with upper ridge
holding across the eastern u... temperatures above normal for
this time of year. Weak disturbances in the flow...will keep a
mention of showers and thunderstorms in the forecast...particularly
during peak heating hours. With the high moisture content of the
air...storms will contain heavy downpours...and with the weak
flow...will be slow to move. Thus...the pattern of any storm that
develops could produce a good inch or more of rain over a particular
For temperatures...continued to hug the warm side of guidance with
building ridge across the area over weekend...and kept overnight
lows on the warm side with humid air mass in place.
Long term /Monday through Thursday/...
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. It is looking like a wave will develop
along the front with a good shot a much needed rain over the
area...particularly along the Ohio River.
Aviation /14z Friday through Tuesday/...
anvil cloud from thunderstorm complex in Ohio had already
dissipated much of the fog along the Ohio River early this
morning. The fog should dissipate by 14z elsewhere. Question is
how far S and east the thunderstorms will get before dissipating
later this morning...there is the chance some get as far southeast as
Otherwise...scattered afternoon convection will fire up again Friday
afternoon...as an upper level disturbance over Ohio early this
morning...drifts over WV today.
Tonight will be another tough call. On the one hand...afternoon
and evening rainfall greatly increases the chance of and hastens
the timing of the formation of overnight fog. On the other
hand...overnight convection and associated cloudiness interfere with
Light and variable surface flow...mainly north...today...becomes light east
to southeast tonight. Light north to NE flow aloft today will become light
southeast to east tonight.
Forecast confidence and alternate scenarios through 12z Saturday...
Forecast confidence: medium.
Alternate scenarios: may need amendments and tempos if storms
form/move towards terminals at anytime. Timing and coverage of
fog overnight tonight may vary from forecast.
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 12 13 14 15 16 17 18 19 20 21 22 23
EDT 1hrly 08 09 10 11 12 13 14 15 16 17 18 19
crw consistency l h h h h h h h h h h h
heights consistency M h h h h h h h h h h h
bkw consistency h M M M M h h h h h h h
ekn consistency l M h h h h h h h h h h
pkb consistency M M h h h h h h h h h h
ckb consistency l h h h h h h h h h h h
After 12z Saturday...
IFR possible in valley fog overnight into the morning next several