Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 200225

Area Forecast Discussion
National Weather Service State College PA
1025 PM EDT Tue Jun 19 2018

The front stalled to our south will be brought northward again
as a wave of low pressure rides along it and over southern PA
on Wed. A brief break in rainy days should occur on Thursday,
but the pattern remains active with additional low pressure
waves moving through over the weekend.


Still seeing the radar returns to our north as no threat to make
anything more than a sprinkle with the mid clouds moving over
the dry air. Latest NAM keeps timing right with RAP/HRRR/GFS in
keeping the meas precip off to the west of the CWA until right
at 12Z.

Mid clouds advancing from the NW should not make any precip (at
least that reaches the sfc). All really is on track.

Surface cold front was pushing south of the the PA/MD border at
1930Z but will stall out over the next 6 hours or so before
buckling across WVA and the Ohio valley and returning back to
the NE as a warm front late tonight and Wed.

Prior to this, notably more comfortable/drier dewpoint air and
cooler temps will continue to advect south into the region late
this afternoon on a 8-12kt North to NNE wind with gusts into
the teens. Sky cover will be minimal through 06z Wednesday
before clouds quickly spread in afterward.

POPs will increase across the far western zones during the mid
to late morning hours Wednesday ahead of the next wave
approaching from the OH Valley, accompanied by increasing large
scale UVVEL developing beneath the Right Entrance Region of an
anomalous westerly upper jet (that will be stretched from the
Upper Glakes to New England).

Max/min temps will be about 10-15 degrees lower than yesterday
with less humidity.

Followed close to LAV guidance for Mins tonight ranging from the
upper 40s in the perennial cold spots up north, to the lower 60s
along the southern border of PA to the west of I-81 where cloud
cover will linger within the higher theta-e air.


After the mainly clear and cold night across our central and
eastern zones, the timing of thickening cloud cover, and
eventual rain later Wed morning and Wed afternoon will be
optimal for well below normal high temps as a 10-20 kt
Ageostrophic flow at the sfc maintains shallow cool air beneath
the thermally direct cell of a potent upper level jet just to
our north.

Short term/hires models, HREF and additional EFS guidance indicates
that a general moderate to heavy rainfall event of 0.75-1.25
inches will occur across the southern half of PA with some
concern that locally heavier amounts could fall in bands of
training TSRA near and south of the PA turnpike where some low-
mdt cape develops within PWAT air of 1.5-1.75 inches.

Further north, near and to the north of Interstate 80, a more
general moderate stratiform rain will occur and keep temps quite
cool (and only in the 60s) as noted above.

WPC MRGL/SLGT ERO covers the southern 1/2 of the area and is
mentioned in HWO. However, 6-12 hour FFG values are 2-3 inches
over much of Scent PA and the Lower Susq Region, which is
approx twice our current rainfall forecast.


The latest mid range models continue to have deep moisture and
QPF Wednesday night into Thursday. The GEFS M climate shows best
anomalous QPF in the 18Z to 00Z Thursday however based on
operational EC and GFS it could linger so have adjusted QPF and
POPS accordingly.

As the trough continues to trek eastward Thursday. This will
advect dry northwesterly flow as a weak ridge builds over the
Ohio/Michigan/IN border. The models are in fair agreement on
the movement and timing of the deep upper level low and a
surface low pressure that is fcst to track north from the
Midwest through the Great Lakes into southeastern Canada Fri-
Sun. Rounds of showers and thunderstorms appear probable during
this time. High pressure should return dry weather early next


Widespread VFR conditions with excellent vsbys expected to
continue through at least the first half of tonight before
lower and thickening cloud covers spreads in from the west along
and ahead of a warm front and wave of low pressure that will
move from the Ohio Valley east along the Mason-Dixon line during
the day Wednesday.

Conditions will gradually deteriorate into the MVFR category late
Wed morning and Wed afternoon, with areas of IFR Cigs and
in rain of varying intensity.


Thu...Early AM rain/cig and vsby reductions possible - mainly
across the SE half of Pa.

Fri...PM showers/cig reductions possible central mountains.

Sat...AM showers/cig reductions possible. Sct PM tsra impacts


Astronomical summer begins Thursday, June 21st at 607 AM.




NEAR TERM...Dangelo/Lambert
LONG TERM...Ceru/Steinbugl
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