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000
FXUS61 KCTP 191918
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
318 PM EDT Fri Apr 19 2024

.SYNOPSIS...
A weak front will push east across the region late today and
early tonight, accompanied by a narrow band of rain showers.


Expect cooler conditions for the weekend with a gusty west to
West-northwest breeze on Saturday.

Frost is possible Sunday and Monday mornings as high pressure
moves overhead.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Shallow cool air and stratus continues to blanket practically
the entire CWA this mid afternoon hour, with the exception of
the Laurel Highlands, where some earlier breaks in the cloud
cover (within a narrow warm sector) created several hundred J/KG
of CAPE and deeper mixing/higher cloud bases in the 2.5-3.0 kft
agl range.

This limited CAPE along the Cold/Occluded front was leading to
the development of a second line (roughly 30NM wide) of light
to MDT showers, currently near and just to the east of the
length of the RT 219 corridor in PA.

As this line of showers drifts over the cooler and much more
stable air over Central PA and the Susq Valley, they should
slowly diminish through the late afternoon/early evening.

QPF will be 0.10" or less in most places with the lowest
amounts across the Susq Valley and points east.

Temps will hold in the upper 40s to mid 50s across Central and
Eastern PA, while the narrow warm wedge poking north just west
of the Allegheny Front will bring a brief period of temps in the
low 60s for afternoon maxes.

Partial clearing will move into the Western Mtns late this
evening, and after midnight throughout the Central Mtns and Susq
Valley.

Min temps at Sunrise Sat will vary from the mid and upper 30s
over the higher terrain of the north and west, to the upper 40s
in Lancaster County where the clouds will hang on the longest.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
We`ll see partly to mostly sunny skies and milder temps in most
of the ridge and valley region (given the cloudy and cool
conditions there today (Friday), while somewhat cooler air will
advect into the Western Mtn with some periods of shallow, BKN-
OVC upslope stratocu.

The colder air aloft and wrap moisture around will keep clouds
over the nrn tier and perhaps into the central mountains, esp
during the peak heating. There could be a sprinkle or two out
of any of the deeper cu that form across the nrn half of the
CWA, but not enough to warrant anything higher than a 20 PoP.
Maxes in the 50s and l/m60s are pretty close to norms for this
time of year.

Deep vertical mixing up through 7-8 KFT AGL will tap some 35-40
KT winds, but taking an average of about 70 percent of the max
in the layer yields peak WNW wind gusts of 25 to 30 kts during
the late morning and afternoon hours.

The setup for frost Saturday night is uncertain, depending on
the timing and coverage of low clouds that may develop in a thin
layer of upslope moisture beneath the low level inversion. If
more clouds develop earlier in the night, Saturday night could
be more of an advective marginal cold freeze setup (vs. more
favorable radiational/decoupling frost pattern.) But for now,
models suggest there could be at least a few hours of mostly
clear skies and light winds before the clouds develop, during
which frost can form. Low temps are fcst in the 30-35F range
over the northwest half of the CWA which could impact counties
activating the growing season April 21 along the US220/I99/I80
corridor.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
The bulk of model guidance supports dry conditions Sunday
through through Tuesday morning as high pressure builds into the
area. Upper-level troughing does support below-average
temperatures for the majority of the period.

The combination of light winds, dry air, and mostly clear skies
associated with the surface ridge is likely to result in more
widespread frost Sunday night into Monday morning. The greatest
risk of frost is over the northern mountains where the growing
season is not active, but areas in the growing season further
south could also be affected.

Temperatures are expected to warm Monday into Tuesday with the
surface high pressure shifting eastward off the east coast and
an approaching shortwave bringing the next chance of showers.
Ensemble plumes indicate the best chance for precipitation will
come Tuesday night into Wednesday morning, with scattered
showers lingering into Wednesday afternoon. Another shot of
cold air will follow for Wed night into Thu morning, with
temperatures taking another dip below the freezing mark across
the northern tier. Those with agricultural interests should keep
an eye on the forecast through the end of next week as
frost and/or freeze conditions are possible Thursday and Friday
mornings.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
The brief period of LLWS across the Western Mtns of PA will end
early this afternoon.

Widespread IFR to low-end MVFR cigs will persist across
practically all of Central PA and the Susq Valley airfields
through the rest of the daylight hours today, before gradually
improvement to MVFR occurs early tonight with areas of VFR
developing throughout the Central Ridge and Valley region of the
state after midnight as a light west-northwest downslope/drying
breeze develops in the wake of a cold front.

Prior to the passage of this cold/occluded front will be a 20-30
mile wide band of showers that will march across the Western and
Central Mtns of PA between 19-22Z, and impact the Susq Valley
and locations to the east between 22Z and Midnight (04Z Sat).

Low clouds and spotty showers could linger in the KMDT and KLNS
areas until 10-12Z Sat with quick improvement expected during
mid to late morning hours and a gusty WNW wind (up to 25-30 KTS
at times) developing for the late morning and afternoon hours.


Outlook...

Sat...Pre-dawn low cigs/showers possible Eastern PA.

Sun-Mon...No sig wx expected.

Tue...Slight chance of evening showers/cig reductions NW Mtns.

&&

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

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Banghoff/Colbert
AVIATION...Lambert