Scientific Forecaster Discussion
fxus61 kctp 221103
Area forecast discussion
National Weather Service State College PA
703 am EDT Tue Oct 22 2019
a cold front will push east across the region today.
Pennsylvania will remain under a broad west southwest flow aloft
for the rest of the forecast period with weak cold fronts likely
coming through late this week and early next week.
Near term /until 6 PM this evening/...
low level confluence and plume of tropical moisture along
approaching low level jet is producing a band rain from
eastern lk Erie through eastern Tennessee early this morning.
Confidence remains very high that this band of rain will move
steadily east across forecast area today with passage of
anomalous low level jet/plume of tropical moisture preceding an
approaching cold/occluded front.
Model timing indicates this slow moving band of rain will last
close to 6 hours in most places with the heaviest falling during
mid to late morning over the western counties, during early
afternoon across the central counties, and during late
afternoon/early evening over the eastern part of the forecast
Latest hrefv2 supports a widespread rainfall of around a half
inch, with totals around an inch quite likely where the moist
southerly flow ascends the higher ridges of north central PA and
the Poconos. Elevated instability appears to be negligible, so
no mention of thunder.
Short term /6 PM this evening through 6 PM Wednesday/...
a developing wave on approaching cold front over the Delmarva
will slow the exit of rain across the eastern edge of the
forecast area this evening, but all rain should be east of the
area by around 03z. Clearing skies, wet ground and light wind
will likely result in patchy fog across the eastern half of the
state tonight, while a more active breeze precludes fog
formation over the western counties.
High pressure and low pwat air mass is progged to build into the
area Wednesday, accompanied by fair and breezy conditions.
Strong subsidence in wake of mid level shortwave will help mix
down some fairly gusty west winds. BUFKIT soundings support
occasional gusts in the 20-25kt range. Mixing down 850mb temps
supports seasonable Max temps Wednesday, ranging from the 50s
over much of central PA to the low 60s across the susq valley.
Long term /Wednesday night through Monday/...
fair and milder conditions appear likely Thursday, as high
pressure passes off the mid Atlantic coast and a return
southwest flow develops. Medium range guidance indicates a
cold front passage is likely Friday. Despite a fairly decent
mid level shortwave, moisture will be lacking with this system,
so have kept the pops fairly low.
The operational GFS and its slow moving upper trough over PA
appears to be an outlier this weekend. The gefs and operational
ec/CMC all indicate upper ridging and fair weather for
Saturday. However, Med range model consensus supports an
increasing chance of showers Sunday into early Monday associated
with a surface low tracking west of the area through the grt
lks. A deep southerly flow ahead of this feature will draw Gulf
of Mexico moisture northward into the Ohio Valley with rain
possible across at least the northwest half of PA.
Aviation /12z Tuesday through Saturday/...
reduced flying conditions will affect all of central PA
airspace today. IFR conds at several taf sites will spread to
all sites by later this morning as cigs lower and drizzle and
rain overspread the region ahead of an approaching cold front.
The rain will pull east of the area late Tuesday into early
Tuesday night. After that, building high pressure will provide
relatively quiet weather Wed into thurs.
Wed and Thu...no sig wx expected.
Fri...some showers possible, especially west late.
Sat...areas of low cigs early, otherwise mainly VFR.