Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 240934
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
534 AM EDT Mon Apr 24 2017

.SYNOPSIS...
A storm system over the southeastern states will begin to make
slow progress northward along the coast over the next several
days.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Rain is advancing from the south on scheduled. Have tried to
refine the timing and northward extent of the rain and opaque
cloud cover for the near term. Overall, the timing is similar
between all the guidance. QPF will be light today, on the order
of a tenth of an inch or less south of I-80 and a tenth to
quarter of an inch south of the turnpike. Maxes should be above
normals in the north but below normal in the south. It may be
tough to get to the m50s in the south. Have nudged the temps
down there just slightly.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
The guidance is very consistent with timing and placement of the
major mass features. Deep easterly flow will slide up the coast
into PA through the short term period. So, confidence continues
to be high that rainfall will occur through the period.
However, the details on when and how heavy the rain will be is
something very difficult to pin down. Will leave POPs generally
under likelies in the north and far west tonight, but spread
them gradually to the north and west.

The confidence in occurrence of the decent rain is highest on
Tuesday, and mainly to the east of UNV. However, the tilt of the
trough which the upper low is associated with is a little fuzzy.
With a more-negative tilt it may move a little faster, and bands
of rain may move more quickly. This would probably keep the rain
lighter at any one location. But, there is a wide and rather
even spread seen in the SREF and GEFS precip total/accumulation
plumes between a low-end of 0.10" at UNV to a max of 1.20". Most
of this rain should be out of stable profiles, so thunder and
big totals are not likely. A middle-of-the-road QPF forecast is
on order. Temps will be seasonably mild overnight tonight. Maxes
on Tues will be homogeneous in the u50s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The upper low is progged to take a right turn as or even before
it gets to our latitude. As it pulls away to the east, the
chance of rain drops off Tuesday night. It will get warm fast.
It should feel like summer through the second half of the week.

As the 500 hPa low fills and the attendant low moves to our
northeast the chance of rain should fall off Wednesday into
Wednesday evening. Our 850 hPa temperatures will rise rapidly
Wednesday and it should be noticeably warmer Wednesday relative
to Monday and Tuesday.

Thursday into Saturday the 850 hPa temperatures will be well
above normal, mainly in the 14 to 16C range and we will be on
the western edge of a rather impressive early season subtropical
ridge.

Thursday through at least Saturday should be very warm and
humid. We should have several days with high temperatures around
80. Thursday into Friday will see the passage of large upper
level trough. Have left broad POPS as this trough will move a
corresponding front through.

&&

.AVIATION /09Z MONDAY THROUGH FRIDAY/...
High pressure and associated dry air mass over Pennsylvania will
ensure widespread VFR conditions and light winds through
tonight. Latest LAMP/downscaled NAM and SREF suggest there
could be some patchy fog in vicinity of LNS early Monday
morning. However, given the expected amount of mid and high
level cloudiness, feel significant fog formation is unlikely.

Low pressure lifting up the east coast will spread lowering
clouds and spotty light rain into southern Pa Monday. Initially,
dry air in the low levels should keep conditions VFR. However,
model soundings and SREF prob charts suggest MVFR conditions
will become likely by Monday evening across southern Pa, with
IFR even possible at AOO/JST.

Outlook...

Tue...Rain/low CIGs likely.

Wed...AM rain/low CIGs possible.

Thu...AM fog possible. PM tsra impacts possible.

Fri...PM tsra impacts possible.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Dangelo/Ceru
AVIATION...Fitzgerald



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