Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
153 PM EDT Sat Aug 29 2015
high pressure overhead will slowly drift to the east over the
weekend. Much warmer weather will move into region. Very warm and
increasingly humid weather will continue into the middle of next
Near term /until 11 PM this evening/...
scattered/broken cumulus over the hills will most likely be suppressed this
evening without any gaining enough strength/height to attain
shower status. Dewpoints now in the l60s over the southeastern half of the
region. But they have also dried/mixed out to the l50s in the northwestern
mountains none probability of precipitation still good...as any small echo which shows up on
radar may not even reach the ground. The cumulus will dissipate this
Short term /11 PM this evening through 6 PM Sunday/...
some early morning fog in the valleys - which should be of lesser
coverage than Sat morning. Then...the temperatures rise even
better...adding another 3-4f onto Sat/S maxes.
Ridge at the surface and aloft is starting to get pressed a little to
the east by an advancing upper trough and slight feed of Gulf
moisture. Thus...support in the forms of instability and moisture
will be available on Sunday. Will increase probability of precipitation slightly but keep
them mainly over the northwestern half of the area as axis of the dying
trough. Sref probability of precipitation way too ambitious. Probability of precipitation from MOS are closer to
but still a little higher than what the expected coverage will
allow for. Will keep them 50 or less northwest and close to or below 20
in the southeast half.
Long term /Sunday night through Saturday/...
after that...the long term looks to be dominated by an anomalous
upper-level ridge across the eastern United States. The 12z gefs
shows 850hpa temperatures running +1sd across through next week...which
will translate to above-normal surface temperatures. This warmth and
increasing humidity should allow for at least a slight chance for
diurnal convection each day...but the probability of widespread
rainfall is low.
There are a couple of interesting features that bear watching for
late in the long term period. The first is the remnants of
Erika...which are forecast to be in the vicinity of the Florida/Georgia coast by
the middle of next week. It remains to be seen whether moisture
from this system will eventually try to work its way northward
into PA. The other interesting feature is a backdoor cold front that
some models bring into the Middle-Atlantic States next thurs/Fri. This
feature could have an impact on temperatures late next week.
Aviation /17z Saturday through Wednesday/...
diurnal cumulus around the region should dissipate this evening. The
high pressure ridge overhead moves only slightly to the east
tonight and Sunday. So the wind should still be light through the
night. Expect some fog to form in the valleys much as it did Sat
a.M. Since dewpoints stay in the u50s to l60s...and mainly clear
sky overhead. The lone place where there could be a passing shower
overnight would be kbfd. However...the chance is so low that only a
vcsh is necessary.
Upper trough sliding across the upper Great Lakes today will try
to weaken The Big Ridge overhead on Sunday. With slightly better
dynamics and higher temperatures...there should widely scattered rain showers/thunderstorms and rain form
over the higher elevations Sunday afternoon. With the time of highest
probability/coverage not until after the end of the taf valid
period...while just beyond the forecast period...will then hint at the
scattered thunderstorms and rain expected Sunday afternoon with a prob30 at kbfd for the far
end of the forecast period. All but kmdt/klns do have a 20-30pct chance of a
rain showers Sunday afternoon. The convection will be fueled mainly by daytime
heat and should dwindle through the evening. Monday will be very
similar to Sunday. Then the large ridge translating eastward will
join up with the ridge on the East Coast/western Atlantic...pinching
off any trace of the trough. Thus...mainly hot...humid weather
with little to no chance of showers will last for much of the new
Monday...mainly PM rain showers/thunderstorms and rain poss.
Tue-Thu...no sig weather expected.