Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 300310
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1110 PM EDT Mon May 29 2017

.SYNOPSIS...
A cold front over eastern PA will weaken and dissipate
overnight. Another cold front will push toward the region
Tuesday. Low pressure at the surface and aloft will stay
centered near James Bay Canada through the rest of the week
providing a period of slightly cooler than normal temperatures
along with several chances for scattered showers and
thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
10PM update...

The meso anal shows the a weak front remaining stalled over my
eastern zones extending from just west of IPT south to around
Camp David MD. The low clouds and cooler marine air remain
entrenched over the eastern zones. The HRRR suggests this
boundary could even slide a bit to the west over the next few
hours before washing out altogether in the strengthening SW
flow after midnight.

Upstream convection embedded in the broad cyclonic flow aloft
could sneak a few showers/isolated thunderstorms into my western
and northern zones overnight, but the majority of the region
will remain dry and mild. Lows will average about 5-10 deg above
normal.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
Brief ridging will allow any popcorn sprinkles and light showers
to clear over the western two-thirds of the CWA this evening,
and residual moisture may lead to areas of fog, especially in
the central valleys. The low level moisture and low stratus deck
AOB 1000 ft AGL will push gradually westward across the Central
Mtns and West Br Susq Valley and stay intact through early
Tuesday. Mins tonight will dip into the 50s for most, as the
dewpoints will be the bottom limit.

A separate, weak sfc trough will be pushed into the area from
the northwest tonight. 8H temps fall a bit over the NW. Heights
fall just a little, too, so some precip is possible before
sunrise Tuesday over the northwestern third of the area, but it
should be light.

The trough begins to catch the stalled trough over the eastern
counties. The southerly or southeasterly wind will yield good
convergence and will crank up some showers and thunderstorms.
Have painted high POPs for the area, but the amount/severity of
destabilization is in question with the clouds in the NE early
in the day. NAM cranks out 1500joules of CAPE and LI drops to -2
or so in the mid-day and aftn on Tues. SPC marginal Risk of svr
wx for Day 2 (Tues) is painted across our eastern half, focused
on the peak heating time. Will continue to mention this in the
HWO.

Max temps across the region will range through the 70s, with the
warmest readings once again in the scent mtns where 78-80F
readings should occur.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
The long term period begins with a good consensus on the
location and shape of the large upper level low over southern
Canada. That low will dominate the weather pattern this week
into next. As the low rotates it will bring successive short and
long wave troughs through the Mid Atlantic region. These
troughs will bring the possibility of precipitation, mainly
Wednesday and Friday afternoon. This upper level low will also
bring cooler northwesterly flow into central PA. That flow
should keep temperatures around, to slightly below, normal.

The next chance for significant precipitation will be Friday night
into Saturday as that upper level low progresses eastward. The
models begin to diverge on the position, timing and strength of
the system. This decreases confidence. However, all models show
a boundary that should set up through the keystone state. The
main question is when will it progress through and how much
moisture will be available for QPF when the corresponding cold
front moves through Saturday.

Current GFS brings precipitation through Saturday where the EC
brings largest QPF Sunday.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Some minor adjustments to 03Z TAFS.

Activity to the southeast is south of our area, and showers
to the west are weakening. Left shower out of BFD, that area
north of PA now.

For 00Z TAF package, did add brief tempo group for fog
at UNV, AOO, and BFD, given wet ground. I did not make it
too long, given short nights.

Far eastern areas will likely see MVFR and IFR conditions
tonight into Tuesday, given easterly flow.

For Tuesday, expect most of the area to be VFR. For now,
went with VCSH instead of any significant time or point
with showers and storms. Dewpoints not real high, much
lower than yesterday, and low level flow not real strong,
hard to see much in the way of widespread storms with low
CIGS etc.

Best chance for a dry day will be Thursday.

.OUTLOOK...

Wed...Chance of showers.

Thu...No sig wx expected.

Fri...Chance of showers and thunderstorms.

Sat...Still a chance of showers and thunderstorms.

&&

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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Lambert
LONG TERM...Ceru/Martin
AVIATION...Martin


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