Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 191607
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1207 PM EDT Fri Apr 19 2024

.SYNOPSIS...
A weak front will cross the area today and cause spotty light
rain showers. Expect cooler conditions for the weekend with a
gusty west breeze on Saturday. Frost is possible Sunday and
Monday mornings as high pressure moves overhead.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
Shallow cool air and stratus continues to cover practically the
entire CWA this midday hour, with the exception of the Laurel
Highlands west of RT 219 where some breaks were developing as a
warm front and narrow warm sector were entering that area.

A moderate south to south-southwesterly LLJ of 35-45 kts was
supporting a fairly narrow band of -shra near the Allegheny
Front in west-central PA. As the warm front, followed closely by
the cold front (near and just to the west of the PA/OH border at
1530Z) moves east into the CWA this afternoon, expect some
breaks in the clouds and limited CAPE to help form another band
of light-mdt showers, with just a slight chc of a low-topped
TSRA INVOF the Laurel Highlands.

The --SHRA are starting to get into Warren Co at 11Z. Stratus
is just about covering all of the CWA. The high/mid clouds
pretty much cover the rest. All is going as planned, so no
changes planned in the near term.

QPF is expected to be only a quarter of an inch at most (SW)
with many places just getting 0.10" or less. The temps may fall
some behind the front, but more so after dark when the CAA gets
going better. Morning 8H temps in the +10-14C range will drop
into the single digits (+) by the end of the day, but most of
the cooling happens after 21Z. BFD will be around 50F at sunset.
The low clouds in advance of the front and the SHRA should
allow temp rises of only 8-10F west and 10-15F east, and those
are rather optimistic numbers - bust potential on maxes is
higher than normal today.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH 6 PM SATURDAY/...
The front and last of the SHRA will be about halfway through the
CWA at 00Z, and could take until 06z to push past HAR and
another several hrs to get all the way out of Lanc Co. Again,
these will be very light showers. Clearing occurs for most of
the western half of the CWA, but wrap around clouds will move
into the NW before sunrise. 8H temps dip to around +4C SE and
-4C far NW by sunrise Sat. Mins will dip into the m30s in the NW
(BFD), but still be in the 40s for most of the area. The west
wind may make it feel more uncomfortable, but these numbers are
still 10F above normal mins.

Saturday doesn`t look like the best of days with a gusty W wind,
and a slow bleed of colder air. But, the colder air aloft and
wrap around will keep clouds over the nrn tier and perhaps into
the central mountains, esp in the peak heating. There could be a
sprinkle or two out of any of the chunkier cu across the nrn
half of the area, 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.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
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 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 /16Z FRIDAY THROUGH TUESDAY/...
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.

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

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/Dangelo
NEAR TERM...Lambert/Dangelo
SHORT TERM...Dangelo
LONG TERM...Banghoff/Colbert
AVIATION...Lambert/Fitzgerald/Gartner


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