Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 261114
Area Forecast Discussion
National Weather Service State College PA
714 AM EDT Wed Apr 26 2017
A moist east-northeast inflow from the Atlantic Ocean will
provide a cloudy and misty start today, followed by clearing
through the afternoon. A few strong to severe storms are
possible across the Northwest Alleghenies Thursday afternoon and
evening. Warmer temperatures are expected through the end of the
.NEAR TERM /THROUGH TONIGHT/...
Low pressure off the Delmarva/NJ coast this morning will track
north-northeast today to a consensus position located southeast
of Cape Cod by the end of the period. Moist east-northeast flow
and residual low level moisture will provide a cloudy and misty
start to the day with even some light rain at times into mid
morning across the Susquehanna Valley where current radar and
HRRR shows rain band wrapping NWWD - but the overall trend by
later today should be toward improving conditions with
increasing sunshine especially over western areas as the system
moves slowly away from the area. It will be warmer than
yesterday with highs ranging from the low 70s west to mid 60s
east. Cloud trends will be key with the potential for cooler
readings if clearing is slower to evolve. Low clouds may
redevelop over the southeast overnight into AM Thursday with
mild readings in the 50s.
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Lead shortwave trough will pivot through the Great Lakes with
an attending surface low occluding into Ontario, while its
trailing front pushes eastward through the OH Valley. Latest
model data shows at least marginal instability (MLCAPE >500
J/kg) developing within a strongly sheared pre-frontal
environment from the upper OH Valley into western PA. The
SPC D2 outlook expanded the marginal risk into NW PA and this
area is being monitored for possible increase in thunderstorm
risk level to SLGT (2/5) in later updates. Utilized a multi-
model blend for this period which remained consistent in
placing the highest POPS over the NW Alleghenies Thursday
afternoon/evening, shifting EWD into north-central PA early
Thursday night. Lingering showers should push east or dissipate
as the front becomes quasi-stationary and oriented more west-
east over CPA into Friday. The precip potential increases into
Friday night based on NBM/ECENS blend as SW flow aloft directs
higher moisture/PWs along the frontal zone.
Temperatures will average well-above late April climatology with
Thursday most likely the warmest day when many locations could
reach 80F. The placement of the frontal boundary suggests the
warmest temperatures on Friday will be across southern PA with
another run at 80F.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
Model and ensemble guidance remained in good agreement with
large scale pattern amplification this period with a vigorous
closed H5 low ejecting northeast from the southern Rockies into
the upper Great Lakes/Canada and deep surface cyclone expected
to lift out of the MS Valley. Meanwhile, an anomalous upper
ridge centered over the Southeast U.S./western Atlantic will
gradually weaken and shift east.
The details of weekend forecast are still uncertain with rain
risk likely focusing along/north of quasi-stationary frontal
zone progged to shift south of PA by early Sunday before lifting
back to the north as warm front. Therefore continued to utilize
a NBM/ECENS/WPC blend for max/min temps and POPS which
maintained good continuity with previous fcst. While unsettled
with a period of rain likely at some point, the fcst does not
look like a washout. Temperatures should remain above late-
April climo but could be too warm/cool depending what side of
the boundary you are on.
Max POPS remain centered on Monday/May 1st as the aforementioned
cold front crosses the Appalachians and continues toward the
Atlantic seaboard. A severe weather threat may evolve downstream
from the OH Valley into the Mid Atlantic, but at this time it is
unclear whether instability will be sufficient to support severe
Temperatures will decline to near normal behind the cold front by
next Tuesday May 2nd.
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --The focus of moist and rather deep east to northeasterly flow
off the Atlantic, in conjunction with low pressure lifting
north from the Delaware coast, will maintain IFR to LIFR cigs
into the late morning hours today (based on SREF Prob charts)
with areas of MVFR to IFR Vsbys in -DZ and BR (especially over
the east facing slopes and crests of the ridges).
The early low CIGs/area of light rain and drizzle across the
Susq Valley and points east will give way to gradually
improving conditions during the late morning and afternoon hours
today, as the storm system weakens and moves northeast twd Cape
Model RH profile support VFR conditions at BFD/JST by midday,
while more gradual clearing takes place across the eastern half
of the state during the afternoon. Poorest flying conditions
will likely hang on the longest (perhaps until 16-17Z) across
the Lower Susq Valley invof KMDT, KLNS and KMUI.
Thu...AM fog possible. Isolated PM tsra impacts possible west.
Fri...No sig wx expected.
Sat...Rain/low CIGs possible NW Mtns. Isolated tsra impacts
Sun...Low CIGs possible east. Isolated PM tsra impacts possible
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