769
FXUS61 KCTP 101928
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
328 PM EDT Fri May 10 2024

.SYNOPSIS...
Upper level troughing will remain over Pennsylvania through
this weekend with shortwaves tracking over the state and
focusing rainfall today and Saturday night into early Sunday.

The upper trough will lift out early next week, then a cold
front will likely push through Tuesday. A wave of low pressure
is likely to track south of Pennsylvania next Wednesday.

&&

.NEAR TERM /UNTIL 11 PM THIS EVENING/...
Regional radar mosaic this mid afternoon shows a well-defined
low to mid level inverted trough and zone of enhanced FGEN
forcing and quasi-stnry area of rain over the Central and Nrn
Mtns of PA. This area of mainly MDT rain was embedded with a
broader and very slowly dissipating area of lighter rain being
supported by the nose of a -2 to -3 sigma easterly LLJ
(deviation from the normal u-component of the wind at this time
of year).

This moisture laden llvl easterly flow will persist for the
next 2-4 hours before the sfc-850 mb low slides off the Mid
Atlantic Coast and causes the aforementioned N/S inverted trough
to weaken and winds to back around to the north then northwest.
This will help to accelerate the diminishing trend of the
rain coverage and intensity, though we expect some lingering
periods of light rain/drizzle through early tonight.

Narrow ridging at the sfc and aloft will slide east across the
region later tonight. Any clearing with this feature will be
quite fleeting as the light wind, cool/moist air and wet ground
quickly leads to patchy dense fog and reformation of stratus for
5-8 through the mid morning Saturday.

Chilly temps for mid may with a tight range of only 5-6 deg F
(ranging from the mid and upper 40s across the higher terrain
of the North and West, to the low 50s in the Central and
Southern Valleys of the state) will dip about 8-10 deg F for
lows tonight between 40-45F.

Additional rainfall amounts late this afternoon and evening
will likely range from several hundredths of an inch in most
places to locally around one quarter of an inch in some spots,
especially across the Western Poconos where the aforementioned
nose of the LLJ will linger the longest.

&&

.SHORT TERM /11 PM THIS EVENING THROUGH SATURDAY NIGHT/...
After the break from the rain tonight into early Saturday,
expect a return of showers Saturday PM associated with height
falls ahead of a potent upper level shortwave diving across the
Grt Lks. Strong large scale forcing, in combination with some
minimal model cape, supports high POPs with a tsra possible in
spots during the afternoon. Moderate PWAT values indicate that
rainfall Sat PM should not be significant, generally between
0.1 and 0.2 inches based on ensemble mean qpf.

The upper trough is progged to cut off and track along the
PA/NY border Sat night into Sunday morning. Low level
instability associated with this feature should result in
plenty of cloud cover and at least scattered showers lasting
into early Sunday. Brightening skies and diminishing showers
look likely by Sunday afternoon, as the upper trough exits the
state and surface surface ridging builds in from the west.
Mixing down progged 850mb temps of around 4C translates to
expected highs in the low to mid 60s over much of the forecast
area, with upper 50s over the higher terrain of Eastern PA.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Tendency to have a large scale upper level ridge over the west
this weekend, will result in much below normal 500 mb heights
over the east into next week.

While some milder and drier conditions will be possible Monday
into Tuesday, much of the time it will be cooler than normal
and wet from time to time for much of the upcoming week. Sunday
will be one day that will feature gusty winds and cold temperatures.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Widespread rain across central Pennsylvania will continue to
impact cigs and vsbys, keeping them mainly in the upper IFR to
MVFR range through early tonight.

As the llvl wind backs from the east through the north and to
the northwest, cigs will ocnly dip into the LIFR range with
ocnl IFR vsbys at KJST and KBFD.

We`ll likely get a small break from the rain after 00Z Saturday
before the next trough is progged to swing through Saturday
afternoon.

The break in the cloud cover, very light wind and moist ground
will lead to at least patchy dense fog with LIFR to VLIFR
possible at all central PA airfields late tonight through about
12 or 13Z Sat.

Outlook...

Sat...PM showers/low cigs possible, mainly W Mtns.

Sun...AM low cigs possible W Mtns. Sct afternoon showers/brief
vis reductions possible.

Mon...AM dry and mainly VFR. Showers return PM.

Tue...Showers and tstms.

&&

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

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Steinbugl
AVIATION...Lambert