Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
655 am EST Monday Nov 30 2015
high pressure over New England will slip to the east today. Clouds
will increase quickly from south to north through the day. An
upper low over the plains states will slide across the Great Lakes
through midweek. A period of rain will result from Monday night
into Wednesday when a cold front will push through. Temperatures
will be at or slightly above seasonal normals all week long...but
moderate slightly for the upcoming weekend.
Near term /until 7 PM this evening/...
645 am update...
high clouds are really thin...so mostly sunny should handle it for
the morning. Only low clouds are in Somerset...but should be
moving north across the Mason-Dixon line later this morning.
Overall...just tweaks to sky/near-term temperatures.
it is fairly clear over the north and high clouds cover the rest
of the area. Temperatures hanging in the l30s in the south but 20s
elsewhere. High pressure centered to the northeast will slide to
the east and the surface winds will veer from NE to east/southeast today. The
925-850mb winds are already starting to turn and pushing low
clouds in New York away from PA. Upslope flow into the southern mountains will
bring the high relative humidity air in and condensation will allow a stratus
layer to form and move rapidly to the north today. The low clouds
will near State College at 18z...and be almost to the New York border by
sunset. The clouds may produce some patchy light rain in the
afternoon over the S. Maxes will be pretty uniform throughout the
region with the clouds over the south severely limiting the
diurnal range. The sunshine in the morning/early afternoon will
allow the temperatures to get into the l40s over most of the area. The
coolest readings will be in the dammed-up/cloudy SC mountains
Short term /7 PM this evening through Wednesday/...
patchy light rain will continue to press northward through the
night. Upper ridge axis then moves to the east. A very strong
upper low closed up over the High Plains will bring a plume of
moisture up from the southwest. A more-constant rain will then
spread over the region from the SW. Clouds and high dewpoints will
restrict the temperature fall. Widespread M-u30s will be seen for lows
tonight. There is a challenging aspect to the forecast tonight.
The temperatures will likely wetbulb at first as the precipitation
begins...but the initial temperatures will be in the m30s over The
Laurels/SC mountains this could make a very brief period of freezing
temperatures while the light rain is falling. However...temperatures are
marginal at best and the warm ground will likely not allow
any ice to accrete onto the surface. Will keep out mentions of
fzdz/freezing rain at this point.
Rain is expected to be off and on through the subsequent 36
hours. The upper low deepens as it moves into the upper Great
Lakes. The moisture plume is not all that deep/impressive...with
precipitable waters only around an inch. While that is above normal...it is not
all that unusual. The cold/occluded front arrives on Wednesday
morning. Some spread in the timing of the front is still seen.
European model (ecmwf) is slower with the frontal passage. It develops a weak low
along the front over the Gulf Coast states and brings it up the
eastern side of the Appalachians on Wednesday. Ensemble quantitative precipitation forecast spread
is more narrow now...with a general inch for the entire period.
Less in the north/northwest and more over the southeastern third/half of the area.
Rather highs in the 40s on Tuesday will be about normal in the southeast
but 10f above normal in the northwest. Maxes Wednesday ahead of the front
and after 36 hours of S/southeast flow will be about 5-10f above normal
over the entire area.
Long term /Wednesday night through Sunday/...
expansive upper low now over The Rockies is forecast to track
through the Great Lakes/Ohio Valley and into New England by the
end of the week. A resurgence of the eastern U.S. Upper ridge then
appears probably as more troffing develops over the western
Behind the front which will be passing at the start of the period
expect brisk winds and scattered showers changing over to
-shsn/flurries in the higher elevations and Northwest. Lake effect
-snsh/flurries in the northwest will diminish into Thursday as
another short-wave ridge pushes in Thursday and Thursday night.
Chances for precipitation look minimal for the remainder of the period.
Aviation /12z Monday through Friday/...
thin high clouds over much of the area as of 630 am.
Clouds did thin some...as the first cluter of cold top
clouds is now mainly east of Virginia.
12z tafs sent.
Earlier discussion below.
Rain as far north as central Virginia...will be into the area later
this after and evening. VFR conditions will give way to MVFR and IFR
conditions late today into Tuesday.
An increasingly moist southeasterly flow will develop today...as high
pressure moves off the new eng coast and warm front approaches from
the south. Model soundings indicate MVFR ceilings are likely to
overspread the state from the south during the afternoon. IFR ceilings are
likely by evening over the central mountains there is a just slight
chance of -fzra at kjst...as precipitation arrives Monday evening. Bulk of
model data indicates only rain as precipitation overspreads the area
Tuesday...rain/low ceilings likely.
Wednesday...rain/low ceilings poss. Evening shsn/visible reductions poss kbfd.
Thursday...am shsn/visible reductions poss kbfd.
Friday...no sig weather expected.