National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS61 KCTP 181828
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
228 PM EDT Thu Apr 18 2024

.SYNOPSIS...
-Mostly cloudy this afternoon with a shower in a couple of
 spots
-Band of frontal rain showers moves through on Friday
-Weekend cool down; frost/freeze risk Sunday & Monday A.M.

&&

.NEAR TERM /THROUGH TONIGHT/...
North-south oriented occluded front stalls over the Susquehanna
Valley for the rest of today where hires ensemble guidance
project the best odds for a couple of rain showers. Otherwise,
expect considerable cloud cover with dry conditions prevailing
most of the time especially to the west of the front along the
Allegheny Plateau. A moist southeast upslope flow will yield low
clouds and areas of fog/drizzle over the Endless Mtns north of
KIPT and the southwest Poconos/Coal Region around Schuylkill
County. Highs will range from around 65-70 degrees in the south
central valleys north of the WV/MD panhandle to 50-55 in the
higher terrain along the border with WFOs BGM/PHI.

Low clouds and areas of fog/drizzle migrate westward into the
central ridge and valley region overnight. Showers associated
with an approaching cold front could reach the extreme western
part of the CWA by daybreak Friday, but most likely hold off
until after 12Z. Lows will range from around 40F on the ridgetops
in Schuylkill & Sullivan County to 50F over southwest Somerset
County.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
A band of light to briefly moderate rain showers will accompany
a cold front through CPA on Friday. PWs peak around 1" ahead of
the front over far south central PA where some mdt to briefly
heavy downpours/embedded t-storm cannot be ruled out - but
overall lack of CAPE will allow the front to pass through with
very light QPF <0.25 inch.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Cooler and drier air will arrive in CPA behind the cold front
to start the weekend, directed by a west wind gusting 25-35 mph.
A shortwave trough crossing the eastern Great Lakes may touch
of an isolated shower over north central PA late Sat morning
into the afternoon. Sfc ridging will ensure dry weather Saturday
night as focus shifts to frost and freeze risk.

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.

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 PM, with scattered showers lingering into
Wednesday. 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.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
A north-south quasi-stationary front down the Susq Valley
separated shallow, cloudy, cool and moist air to the east from
drier air with increasing breaks in the cloud cover to the west.

Expect a high probability for IFR to low end MVFR to persist
through tonight near and to the east of the Susq Valley, while
a transition to mainly VFR will occur across Central and
Western PA airfields late this afternoon and will continue
through at least the first half of tonight.

After 05Z Friday, a llvl east to southeast flow will develop and
push a deck of stratus/stratocu westward across the
aforementioned, initially VFR leading to a fairly quick change
back to IFR CIGS. Included a 6-8 hour period of LLWS late
tonight through the mid morning hours Friday, though wind speeds
aloft will be borderline for mention of the LLWS.

A few showers will move into the region from the west later
Friday morning as a weak cold front approaches, and should
create enough vertical mixing to bump CIGS back up into the MVFR
category.

Outlook...

Fri...CFROPA. IFR to start the day, then mainly MVFR with ocnl
dips to IFR.

Sat...Light SHRA N, no sig wx elsewhere.

Sun-Mon...No sig wx.

&&

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

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Fitzgerald/Colbert/NPB
AVIATION...Lambert