-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 212002
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
402 PM EDT Wed Jun 21 2017

.SYNOPSIS...
An upper air disturbance will will push southeast across the
region this afternoon. A deep upper level trough will approach
the region bringing increasing humidity along with the chance
for showers and thunderstorms late Thursday into Saturday. Drier
and cooler conditions will return later in the weekend into
next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Radar shows a broken line of showers and thunderstorm from
around SEG west to around JST. The HRRR keeps the activity
mainly south of I-80 for the remainder of the day.

While moisture is not abundant, moderate instability and shear
are in place ahead of an approaching shortwave and upper jet
streak. Forecast model soundings show a nice inverted V
signature for this afternoon. SPC has painted much of the CWA
with a Marginal Risk for severe storms. While the updrafts thus
far have not been especially robust, this looks reasonable given
the instability/shear and expected lift under the left exit
region of the upper level jet.

Relatively high convective LCLs/cloud bases will help to
produce isolated and brief, strong downburst winds through late
afternoon. Basin average rainfall today should stay under 0.20
of an inch.

A push of lower PWAT air in the wake of this sfc/upper level
disturbance should result in drying over NW PA and the remainder
of the forecast area as we get into the overnight. Temperatures
will fall into the 40s over the north and range to around 60
over the SE. This expected cooling down near the dewpoint in
most areas should equate to areas of fog late at night,
especially in the valleys and areas where it rains over the next
few hours.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
Thursday will start out partly cloudy and comfortable with the
patchy early fog as a bubble of high pressure slides SE and
over us for late morning.

The low level flow will strengthen from the SW during the
afternoon bringing in noticeably more humid air along with an
increasing chance of an afternoon or evening shower or
thunderstorm.

PWATs will increase from below normal (only 15-20 mm this
morning) to over 40 mm (or 1-2 sigma) by 00Z Friday just to the
west of the approaching warm front.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
-- Changed Discussion --
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. Expect moisture/rainfall
associated with the remnants of TS Cindy to exit the area by
the start of the weekend. Confidence is low with details
(timing) with multiple shortwaves reflecting surface
fronts/troughs inducing risk for isolated to scattered showers
and Tstorms Mon-Wed.

By Friday the tropical airmass will have re-established itself
with dewpoints well up into the 60s and lower 70s over the
entire region making for a sticky end of the work week. Model
consensus continues to signal rain on Friday/Friday night
corresponding with a peak in H85 moisture flux and PW. The
heaviest rain is fcst to stay to the south of PA.

Drier, low PW air arrives by early Saturday and lasts through
the weekend. This should translate into comfortable, low-
humidity conditions with temperatures near to slightly below
late June climatology. Precipitation opportunities will be
modulated by several shortwave impulses which have low
predictability at this range. Any rains would be generally
scattered and on the lighter side given overall lack of deep
layer moisture. 21/12z GEFS shows PW values remaining below
average into midweek.

Temperatures should stay on the cooler side of climo through
midweek as the upper level trough shifts east of the area. FWIW
the GFS is more bullish vs. EC on heights rebounding/building SE
U.S. upper ridging into the second half of next week. That
said, there is general agreement in a modest warming trend later
next week as the trough moves out and heights return to normal.
-- End Changed Discussion --


&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
VFR conditions will continue into the evening hours.

An approaching upper level disturbance is triggering scattered
showers and thunderstorms. Some of the stronger storms will
cause brief localized sub VFR conditions, and could also cause
strong wind gusts, mainly this afternoon.

The wind will become SW picking up to around 10 mph gusting to
15-20 mph.

Any convection will down pretty quickly by early evening, and
initially mainly clear skies and quickly diminishing wind will
likely lead to areas of valley fog during the overnight hours
(mainly where rain falls today).

A warm front will approach the region Thursday triggering
showers and scattered thunderstorms, mainly over the west and NW
during the afternoon.

.OUTLOOK...

Fri...Widespread sub VFR likely with rain and embedded
thunderstorms.

Sat-Sun...Mainly VFR

Mon...Mainly VFR. Chc SHRA/TSRA.

&&

.EQUIPMENT...
-- Changed Discussion --
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.
-- End Changed Discussion --

&&

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

&&

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