-- Discussion containing changed information from previous version are highlighted. --
029
FXUS61 KCTP 102334
AFDCTP

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

.SYNOPSIS...
Upper level troughing will remain over Pennsylvania this
weekend. A strong shortwave moving through the broader flow will
generate numerous rain showers and a couple of thunderstorms on
Saturday afternoon and night.

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 7 AM SATURDAY MORNING/...
Showers starting to shrivel up and slide to the east as the
forcing moves away to the east. Breaks in the clouds over the
western highlands will probably get bigger, allowing for
cooling to the dewpoints. The wind goes calm, too. So, a
widespread fog is expected tonight. The locations that do not
fog up will probably be the ones holding onto the clouds and
patchy drizzle.

Prev...
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 /7 AM SATURDAY MORNING 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/...
Closed 500mb low moves across PA/NY border early Sunday followed
by rising heights into early next week. This will translate into
a seasonably cool and showery Mother`s Day followed by a warmer
and mainly dry start to next week. QPF will remain light given
lack of deep moisture. Forecast daytime high temps on Sunday in
the 55-65F range are 5-10F below early May climo. Max temps
should rebound +10-20F on Monday aided by a milder SW flow.

A cold front trailing low pressure in eastern Canada is fcst to
stall out over the lower Great Lakes Monday and could trigger a
shower or t-storm over the far NW mtns. Most of CPA should start
the week rain-free. A southern stream wave and accompanying
higher pwats are projected to link-up to bring rain Tue-Wed.

Model and ensemble consensus favors another ridge building in
behind this system into the second half of next week. The
overall upper level pattern heading into next weekend looks
rather blocky - which is typical for this time of year - but
also results in much lower confidence/predictability. Some data
suggest a cut-off low pressure system could bring a slight risk
of heavy rainfall on 5/18 per the latest CPC 8-14 day hazards
outlook.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
Widespread MVFR to low-end VFR cigs were found over Central PA
at 00z, with light rain across the area beginning to dissipate.
The clouds are beginning to break up over the western
highlands.

Lingering light rain will continue to dissipate late this
evening. Diminishing winds and ample low-level moisture will
likely result in the development of fog and/or low clouds
overnight, with IFR/LIFR conds possible at all central PA
airfields outside of perhaps the Lower Susq Valley.

Cigs and vsbys should improve to VFR areawide by midday on
Saturday, before another round of rain showers pushes from west
to east across the area Saturday aftn/eve.

Outlook...

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

Mon...AM dry and mainly VFR. Showers return across the north by
aftn.

Tue...Showers/tstms and reductions developing.

Wed...Showery weather and reductions continue.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert/Dangelo
SHORT TERM...Lambert
LONG TERM...Steinbugl
AVIATION...Evanego