Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 230348
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1148 PM EDT Thu Jun 22 2017

.SYNOPSIS...
A deep southerly flow of high PWAT air will overspread
Pennsylvania tonight and Friday ahead of a deepening trough
over the Plains states. A cold front will push east across the
region during the morning or early afternoon hours Saturday,
followed by drier and cooler air with comfortable humidity that
will last through much of next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
Dwindling batch of convection over the Lower Susq Valley should
push east of the forecast area by around 04Z. In it`s wake,
cooling/stabilizing boundary layer and weak large scale forcing
argue for a period of quiet weather late this evening. Batch of
rain over the Ohio Valley should lift northeast across the
forecast area between 08Z-15Z, as anomalous southwesterly low
level jet arrives. Latest model data continues to indicate the
western half of Pa will get the heaviest rain from this feature.
GEFS 850hpa mflux values approach +5SD across the Laurel
Highlands, where up to an additional inch of rain could fall
Friday morning.

Batch of stratiform rain in the morning should give way to
scattered afternoon convection, as nose of low level jet lifts
past the area and model soundings support a bit of
brightening/increasing instability by the PM hours. High PWATs
and will support locally heavy rainfall from any showers/storms
that form during Friday afternoon and make those locations more
prone to flooding as remnants of TS Cindy track across the area
Friday night. Superblend/NationalBlend high temps ranging from
the low 70s over the northwest mountains, where overcast skies
are expected, to the mid 80s over the Lower Susq Valley, where
model RH profiles support partly sunny skies by afternoon.

Any decision on Flood Watches for remnants of TS Cindy Friday
night will be made by later shifts.

&&

.SHORT TERM /FRIDAY NIGHT/...
*Heavy rain and short-term flooding risk Friday-Friday night.

A significant influx of deep tropical moisture (PW 1.50-2"+)
associated with the remnants of TS Cindy will combine with an
approaching northern stream trough and cold front to bring an
elevated risk of heavy rainfall and potential flooding to
portions of central PA. The deep moisture will focus along/ahead
of an emerging frontal zone and interact with the westerlies
aloft and weak instability to support the heavy rain/FF risk.
The area that appears to be most susceptible/at greatest risk
would be over SW PA (southwest Alleghenies/Laurel Highlands)
where a multi-model blend incorporating HIRES models/CAMs has
been fairly consistent with location of max QPF. Enhanced
terrain lift will also be a factor over a region that has the
lowest short-term FFG in the CWA. Updated WPC D2 ERO shows a
MDT risk for excessive rain over SW PA clipping Somerset Co. with
SLGT risk encompassing the rest of the area. We will continue
to highlight +RA/FF risk via HWO at this time - later shifts
will likely consider a FF watch at shorter ranges with increasing
confidence. Expect some consolidation of pcpn along the frontal
boundary as it pushes southeast across the area Friday night
with max POPs generally shifting from west to east by the 06-12z
Saturday period.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
From a large scale perspective, the medium range forecast will
feature a seasonably strong/amplified upper trough settling over
the Northeast U.S into next week. The theme continues to be
above avg confidence in the pattern but low confidence in the
details.

Expect moisture/rainfall associated with the remnants of TS
Cindy to exit the area by Saturday afternoon. Drier, low PW
air arrives behind the cold front with decreasing clouds and
lowering humidity providing a nice start to the weekend. An
extended period of comfortable, low-humidity conditions with
temperatures near to below late June climatology are expected
to last through the early part of next week. A few cool nights
early next week with min temps 40-55F.

Precipitation opportunities will be modulated by shortwave
impulses reflecting weak surface fronts/troughs which have low
predictability at this range. Any pcpn would be generally
scattered in nature and on the light side given below normal
moisture levels for late June. The 22/12z GEFS shows PW values
remaining below average through midweek which would tend to
favor mainly dry wx.

Temperatures should stay on the cooler side of climo through
midweek as the upper level trough shifts east of the area.
Differences continue with the trough evolution later in the
week with the GFS initially more amplified before building SE
U.S. ridge. The EC generally maintains a mean trough over the
Northeast CONUS into the second half of next week.

&&

.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Only some isolated showers across the north remain across
Central Pennsylvania as of 03z. While mainly VFR conditions
exist, some isolated fog is beginning to develop in areas that
say early rainfall.

Short term guidance suggests that mainly rain free conditions
will persist for several more hours, before another wave of
rain approaches from the Ohio Valley. This will rapidly
overspread western and central portions of the region prior to
12z, and the rest of the area shortly after sunrise. It appears
that the most concentrated and heavier rain will be confined to
western areas, with more showery activity to the east during
Friday.

Rain from the remnants of Cindy then overspread the area later
Friday and overnight Friday Night. This should bring widespread
rain, embedded thunder, and low ceilings to the entire region.

Rapid improvement Saturday as the front and remnant tropical
moisture slide off to the east. VFR conditions should return
for the most part by morning, but some lingering showers could
keep spotty restrictions in place in some areas.

.OUTLOOK...

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

&&

.EQUIPMENT...
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.

&&

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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...Fitzgerald
SHORT TERM...Steinbugl
LONG TERM...Steinbugl
AVIATION...Jung
EQUIPMENT...



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