Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 240354

Area Forecast Discussion
National Weather Service State College PA
1154 PM EDT Fri Jun 23 2017

The combination of an approaching frontal system and the
remnants of Tropical Storm Cindy will funnel a plume of deep
tropical moisture bringing a steady rain to southern
Pennsylvania tonight. Occasional lighter showers are expected
across the northwest half of the state through the first half of
tonight. The cold front will push east across the region during
the morning Saturday, followed by drier and cooler air with
comfortable humidity that will last through much of next week.


Showers are becoming more numerous once again as the leading
edge of the deep plume of tropical moisture begins to drift
across southwestern and south-central PA.

Moderate surface and ML instability persists across the Lower
Susq Valley this evening, and a few brief, strong TSRA should
race quickly ENE across that region within the strongly sheared
llvl environment.

Temps are still in the mid to upper 70s across the Lower and
Middle Susq Valley, while reading across the Central, Northern
and Western mtns are in the mid 60s to low 70s.

Analysis shows PWATs exceeding 2" (2-4 sigma) in a wide plume
from the Louisiana Gulf Coast up into central PA, and moisture
transport vectors indicate a continued advection of this
tropical airmass into our region.

After a few to several more tenths of an inch of rainfall across
the Central and Nrn Mtns, with up to an additional 0.50-1.00
inch over the southern tier counties of PA, there could be some
minor flooding problems across the Laurels and southern tier
counties. However, large scale outflow boundary(s) (seen on
satellite animation and regional 88D mosaic) were driving the
stronger/heavier rain producing convection to the south of the
state tonight.

With the steadiest and heaviest tropical rains (and embedded
taller convection) impacting the SW counties of the state attm,
and the Cfront just making its way inland of Lake Erie`s SE
shore, will maintain high pops throughout the first half of

The most vulnerable area for heavy to possibly excessive rain
amounts, it looks to be the Laurels where instability will
combine with terrain bringing enhanced lift causing localized
heavier amounts. As a result we will continue the Flash Flood
Watch through 09Z Sat for our SWRN 4 counties.


Conditions will improve rapidly Saturday morning as the deep
moisture speeds eastward. NHC expects whatever is left of Cindy
to be on the MD coast by 8AM so the best of the rain will be
over with drier air sweeping in behind the departing low and
cold front.


Models have trended toward much better agreement with the
evolution of the seasonably strong large scale upper trough over
the Eastern U.S. A couple of shortwave impulses reflecting weak
surface fronts or troughs will provide a limited/mainly diurnal
opportunity for widely scattered showers/isolated low- topped
thunderstorms Sunday-Tuesday. However, much of the this period
will be pleasant and dry with below normal PW supporting low
humidity and below normal temperatures relative to late June

The trough is fcst to lift out and leave a more zonal pattern by
the middle of the week, followed by a resurgence of the
Southeast U.S. upper ridge. Models and ensembles show the ridge
breaking down in the west as a trough shifts east across the
Rockies into the Plains. Southerly flow increasing ahead of its
attendant frontal system should result in an upward/warmer trend
in temperatures accompanied by low level moisture/humidity.
Expect max/min temps to get back to seasonal levels around
midweek and likely reaching above normal levels by next Friday.


Wide range of flying conditions continue to prevail across
Central Pennsylvania this evening /04z/. Much better than
previously forecast, with VFR conditions existing at most TAF
locations, with the exception being KBFD.

One last surge of rain and embedded convection will make a run
at southern tier and southeastern counties before rapidly
winding down after 08z/09z time frame. HRRR would lead us to
believe that last of any significant rain will be exiting
eastern portions of Central Pennsylvania around 10z.

Moist low levels and upward flow will likely bring or keep
western airfields under low ceiling restrictions until the
14z time frame, but elsewhere, conditions could be VFR by 10z-

With rain moving off quickly Saturday morning, a brisk west-
northwest wind and a quick return to VFR conditions is


Sat...Scattered restrictions in AM showers...otherwise becoming
Sun...Mainly VFR.
Mon-Tue...Mainly VFR, but with a chance of SHRA/TSRA.


KCCX radar will be offline for approximately 4 days starting
Saturday, June 24th for technicians to install the first of 4
major service-life extension upgrades. The work on the radar has
been scheduled to minimize potential impacts to operations and
will be delayed if hazardous weather is forecast.


Flash Flood Watch until 5 AM EDT Saturday for PAZ024-025-033-


SYNOPSIS...La Corte/Lambert
NEAR TERM...La Corte/Lambert
LONG TERM...Steinbugl
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