Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1140 am EDT Wednesday Sep 2 2015
above normal temperatures for early September will continue into
next week with gradually decreasing humidity levels. Opportunities
for rainfall will remain limited as high pressure dominates the
regional weather pattern.
Near term /through tonight/...
did cut back probability of precipitation some...main area that may see a shower
or storm will be southern PA.
Earlier discussion below.
Early morning fog/haze will burn off by 14-15z. The fog may be
locally dense with visibility at or below 1/2sm especially in the north where infrared
satellite shows clear skies. Will continue to monitor observation/webcams for
possible Special Weather Statement issuance for commute impacts later this morning.
A low amplitude shortwave impulse will track across WV today.
Hires ensembles show isolated non-severe convection developing in
the warm/humid airmass over western PA /near The Spine of the
alleghenies/Laurel Highlands southward into the WV-Maryland panhandles/
particularly as instability increases this afternoon. Highest probability of precipitation
are over southern Bedford/Fulton counties per multi-model consensus.
Any precipitation should remain largely disorganized and wane/dissipate
into tonight with the loss of heating.
Started with persistence as background grid for day 1 maximum/min
temperatures and blended with the latest guidance. The result is another
very warm and humid day by early September standards. More fog
likely overnight with nighttime mins a degree or two warmer on the
Short term /Thursday through Friday night/...
surface cold front pushing southward from New York into PA on Thursday
should initiate widely scattered convection per model consensus as
it encounters an unseasonably warm/humid and moderately unstable
airmass from the Great Lakes/Ohio Valley into the northern middle Atlantic.
Confidence in the details however is low as there is still some
spread noted in quantitative precipitation forecast details which appear to be associated with
convectively augmented vorticity maxima located upstream. Will
continue to advertise 20-30 probability of precipitation during the day and drop mention
overnight. We are in the climatology favored fog season /Aug-sept/ so
with light/vrb winds...clearing and relatively high blyr moisture would
anticipate another period of fog Thursday night into early Friday
The cold front becomes quasi-stationary just south of the PA/Maryland
Line on Friday. Isolated to scattered convection will again be
possible in vicinity of the central Appalachians into S-centrl PA based on
a blend of short term model data. High pressure over Quebec will
sink southward through northern New England later Friday and take control of
the weather pattern into the upcoming Holiday weekend. Temperatures will cool
down some to end the week but still above normal for this time of
Long term /Saturday through Tuesday/...
high pressure at the surface and aloft will dominate the regional weather
pattern over the Labor Day weekend and into early next week. A
continuation of warmer-than-avg temperatures is expected with
lower humidity and no rainfall.
It looks as though the stable ridging pattern in the east may
break down during the middle to second half of next week. The
operational GFS/European model (ecmwf) show a lead cold front weakening as it
crosses the Great Lakes next Tuesday. A more significant cold
front may approach by the end of the week.
Aviation /16z Wednesday through Sunday/...
did adjust tafs for fog late tonight on the update.
Will adjust more if needed on the 18z package.
Earlier discussion below.
The early morning patchy fog is slowly lifting/dissipating. With
ipt...lns and aoo as the IFR and lower holdouts. Conditions should
improve over the next few hours with conditions improving by 14z.
Expect mainly VFR conditions today with the only chance for
showers and thunderstorms and rain south of jst. With the probability to intersect
any taf sites low have left any mention out.
More clear nights with am valley fog and mostly sunny days are
expected for the next several days.
Thu-sun...patchy am fog poss...mainly kipt/kbfd. Otherwise VFR.