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000
FXUS61 KCTP 190816
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
416 AM 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 6 PM THIS EVENING/...
Low stratus is making headway into the western mtns at 07Z, and
should make it to the western border of the CWA just before SHRA
arrive from the west. A cold front is moving into western OH at
07Z and should arrive around mid-day in the west. There is still
some ltg with the showers as they move across OH, with some as
close as KZZV. However, the moisture ribbon will likely become
thinner as the SHRA get here. PWAT gets just barely over 1".
Thus, while a few volleys of light SHRA should pass through,
the 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 /6 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 6 to push past HAR and another 4-5
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 /08Z FRIDAY THROUGH TUESDAY/...
A moistening southeast flow will cause stratus over Eastern PA
to expand westward overnight. Latest model RH time sections
and ensemble prob charts support predominantly MVFR cigs across
the lower elevations of the Susq Valley overnight. Farther
west, expect a fairly rapid transition from VFR to IFR cigs
between 06Z-10Z, as the increasing moisture is forced to ascend
the higher terrain of the Appalachians. Upon examination of the
latest model soundings have removed earlier mention of LLWS for
the overnight. However, a brief period of LLWS does look
possible over the NW Mtns (KBFD) between 12Z-16Z associated with
increasing winds aloft ahead of a cold front approaching from
the Grt Lks.

Very little improvement is expected Friday, as a moist
southeast flow off of the Atlantic remains in place. Diurnal
heating is likely to result in a very modest increase in cigs,
with VFR possible across the Lower Susq Valley (MDT/LNS) by
afternoon but borderline IFR/MVFR cigs likely holding on along
the spine of the Appalachians. In addition to the low cigs, a
few showers will move into the region during the late AM and
afternoon hours in advance of the approaching front.

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