Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
649 am EST sun Nov 29 2015
a front lying south of the state will sag southward today and
light rain along the southern tier will gradually taper off. Cool
air will slide in from the northeast as high pressure builds into
the region. An upper low over the plains states will then slide
across the Great Lakes through midweek. A period of rain will
result from Monday night into Tuesday night or Wednesday.
Temperatures will be seasonably cool all week long.
Near term /until 6 PM this evening/...
6 am update...
higher returns on radar along rte 22 right now. Some look bright
enough that they may contain sleet. Mrms p-type and dual-pole
p-type algorithms agree. Surface has been and still is warm enough
that if there is some sleet mixed in with the rain there that
nothing will stick on the roads. With some certainty that the
precipitation will continue to move to the east/southeast - have bumped probability of precipitation up
and timed precipitation in more detail/specificity than previous forecast had.
Temperatures and winds all on track.
radar shows light rain over the S/southeast moving to the east. Lots of
clouds around and they should hang all day in the south. The flow
aloft is just a little bit from the north of west...so the
moisture plume will likely not waggle to the north.
However...current trajectories of the plume over the Midwest seem
to be drawing it toward the state. Thus...clouds will likely stay
around all day in the south. Dry air will be brought in from the
northeast as high pressure moves eastward from the upper Great
Lakes. Breaks in the clouds should develop over the I-80 corridor
today but the lowering subsidence inversion will try to make some
clearing in the north. However...the low clouds are pretty
extensive in the north and upstream in New York state. Will hold onto some
low clouds in the northern tier. Maxes will be held down as the shallow
cold air bleeds in from the NE and the clouds hang on over much of
Short term /6 PM this evening through Tuesday night/...
clearing will try to spread over much of the area tonight. Temperatures
will drop into the 20s over much of the area. Perhaps only the
higher terrain of the south will stay above 30f. On Monday...the
925-850mb winds turn to the south/east. This will bring moisture
back into the SC mountains before sunset on Monday. The moisture will
get thicker through the night as it spreads north/west upslope. There
will probably be some dz...and the temperatures will be marginally cold
enough for it to freeze Monday night if sufficiently cold air can
seep into the south. Maxes Monday will be only 40-45f. With the
increasing clouds...the diurnal change from Monday to Monday night will
be little more than 5-8f.
The upper low over the plains will deepen and slide to the east
into the upper Great Lakes. Deep southwesterly flow will bring
rain as a cold/occluded front moves through the Ohio Valley.
Thiming fairly similar on the U.S. Guidance members that drying
should occur from west-east by Wednesday morning. However...the European model (ecmwf)
takes up to 24 more hours to push that moisture off to the east.
Long term /Wednesday through Saturday/...
the associated front will then sweep east across PA on Wednesday.
Behind the front 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. After the middle week system...the operational
models...and the ensembles diverge in their solutions. This lends
itself to more uncertainty and less confidence in any timing of
the pattern. However a ridge should build...bringing drier and
fair weather. This should keep any tumultuous weather to the south
through the rest of the period.
Aviation /12z Sunday through Thursday/...
most areas still cloudy with IFR and MVFR conditions.
One has to get to the north side of the lower lakes
to see much in the way of clearing.
Seg and ipt seeing some clearing as of 630 am.
For the 12z tafs...did slow improvement down some.
This especially the case for bfd.
Still expect partial clearing from north to south today...as
high pressure over eastern Canada sags southward.
Model output suggests stubborn low ceilings may hold on most of
the day at kaoo/kjst.
Monday...evening low ceilings poss central mountains
Tuesday...rain/low ceilings likely.
Wednesday...early rain/low ceilings poss east. PM shsn/visible reductions poss kbfd.
Thursday...am shsn/visible reductions poss kbfd.