Area Forecast Discussion
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FXUS61 KCTP 242233
Area Forecast Discussion
National Weather Service State College PA
633 PM EDT Mon Apr 24 2017
A storm system over the southeastern states will begin to make
slow progress northward along the coast over the next several
.NEAR TERM /THROUGH TUESDAY/...
Rain continues to advance from the south. Showers remain
scattered as lower atmosphere is fairly dry. 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. Temps
through southern and central PA are in low 60s where the mainly
sunny Northern portion of PA has reached the 70s.
.SHORT TERM /TUESDAY NIGHT THROUGH 6 PM TUESDAY/...
The guidance is very consistent with timing and placement of the
major features. Deep easterly flow will slide up the coast into
PA through the short term period. Moisture will slowly
infiltrate the lower levels and rainfall will become more
widespread overnight into Tuesday morning. The confidence in
occurrence of the decent rain is highest tomorrow afternoon,
especially through the eastern half of the region. 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. Looking at
latest plumes keep precip total/accumulation around 0.5 through
the period. Most of this rain should be out of stable profiles,
so thunder and big totals are not likely. Temps will be
seasonably mild overnight tonight. Maxes on Tues will be
homogeneous in the u50s to low 60s in the far northwest where
skies will see some sun.
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Moist and anomalously strong (approx -3 sigma) southeasterly
flow off the Atlantic will bring occasional rain/showers to the
eastern 1/2 to 2/3rds of the CWA Tuesday night with QPF likely
averaging just another 1-2 tenths in most places across the Susq
Valley and Western Poconos (less across the central and western
mtns). Min temps will be on the mild side - in the upper 40s
across the western mtns and lower 50s elsewhere.
The slowly weakening (1004-1006mb) sfc low, and filling upper
low will be moving NE twd Cape Cod late Wed/Wed night.
Bkn-Ovc cloud cover on the western fringe of the departing low
will bring a slight chc for showers across the eastern part of
our CWA (mainly Wednesday morning), while increasing sunshine
greets residents over the western half of the state.
A fairly sharp and slightly anomalous upper ridge will slide
across the Appalachian Chain and Mid Atlantic Piedmont Wednesday
night and Thursday bringing dry conditions and well above
normal temps min and max temps Wed night and Thu will be at
least 12-15F above normal with even greater departures over
nearly 20 deg F above normal across the northern and western
Late this week and over the upcoming weekend persistent
and quite strong southwesterly flow aloft will be accompanied by
a few embedded shortwaves and associated sfc warm/weak cold
frontal boundaries. This will bring periods of unsettled weather
with uncertain timing with respect to exact onset/ending timing
of the showers. The best chcs for rain appear to be Thursday
night and again later Sunday into Monday as the broad lift from
the RE region of an upper level jet (140-150 kt) and quite
potent sfc cold front slides east from the Ohio Valley.
Well above normal max/min temps (though probably not
record level temps) will persist Friday through Sunday, before
a gradual cool off begins Monday. Main forecast concern for the
Fri-Sat period, when medium range models indicate a peak in
temps (with maxes in the 70s to around 80) will be the location
of a warm/stationary frontal boundary across northern and
western PA. Clouds and some showers could lead to a temp bust by
several deg or more on the high side (with observed temps
possibly holding in the 60s across the northern mtns).
.AVIATION /22Z MONDAY THROUGH SATURDAY/...
Low pressure lifting up the east coast will spread lowering
clouds and spotty light rain into central Pa overnight. Model
soundings and SREF prob charts suggest MVFR conditions will
become likely this evening across southern Pa and after midnight
across the northern half of the state. As the storm system moves
closer, expect a steadier rain to develop Tuesday. With the
exception of BFD/IPT, model soundings support IFR CIGs across
central Pa Tuesday.
Tue...Rain/low CIGs likely.
Wed...AM rain/low CIGs possible.
Thu...AM fog possible. PM tsra impacts possible.
Fri...PM tsra impacts possible.