-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KCTP 232348
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
748 PM EDT Tue Apr 23 2024

.SYNOPSIS...
-Periods of rain showers tonight through Wednesday afternoon
 (mainly across the NW Mtns tonight)
-Rain-free late this week with a renewed frost/freeze risk early
 Thursday and Friday mornings

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Dry air under the advancing rain is eating it up before it hits
the ground in many places. Have tweaked PoPs slightly. Wind
gusts continue in the 20s and even a little higher to the west
as the rain-cooled air drops to the ground. The thin line on
the radar (bug front?) which was up over the Alleghenies
parallel to the ridges close to the radar is getting pushed to
the east, now, too.

Prev...
High clouds will thicken up from the west late this afternoon
and cloud bases will lower headed through this evening with rain
showers following for the overnight hours.

PWAT values are 0.8 of an inch or less which will support
rainfall amounts generally less than one tenth of an inch across
the SE half of the CWA through 12Z Wed, with 1-2 tenths acrs the
NW half of the region and mainly before 08Z Wed.

Prior to the showers, low humidity and breezy conditions (wind
gusts 20-30 mph from the south/southwest), will occur for the
rest of the daylight hours.

The gusty wind+low RH combo does raise some fire wx concerns
(see fire wx section, SPS and HWOCTP for details).

Temps are closing in on their forecast highs of the low to mid
60s across the higher terrain of the north and west and around
70F in the Central and Southern Valleys.

Low temps tonight in the low 40s/50s are +10-15 degrees warmer
than the last two nights (no frost) thanks to an active
southwest to westerly breeze along with clouds/rain showers.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
The main upper level shortwave trough swings through the area
early Wednesday, followed by a secondary cold frontal passage
during the afternoon leading the way for a pool of slightly
anomalously cold air aloft (about -25C at 500 mb or about -1
sigma).

Latest hires model guidance shows scattered low-topped diurnal
convective showers developing during the late morning (Mainly
over the NW Mtns) and through the afternoon across the Central
and SE zones with the potential to produce locally gusty winds.
SPC continues to indicate non- severe t-storm probs over the
southeastern portion of the CWA for Day 2 where HREF shows a few
hundred J/kg of CAPE. Highs on Wednesday will trend cooler and
range from the upper 40s in the northern tier to mid 60s in the
southeast. Expect rain shower activity to fade quickly toward
sunset/into early Wednesday night or shortly after 00Z Thu.

1030+mb Canadian high pressure building over the region
Wednesday night below normal pwats will bring dry wx/rain free
conditions into late week. The main focus will return to
potential for frost/freeze conditions which remain highlighted
in the HWO.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
A chilly but tranquil start to the extended period Thursday
morning with widespread freeze/frosts expected from sprawling
Canadian sfc high pressure. Plenty of sunshine is expected
throughout the day to help rebound temps through the 50s to
lower 60s.

The sfc high drifts off of the eastern seaboard by Friday
morning, with another chilly night expected (especially over
eastern areas) as moderating return flow begins Friday morning.
As a result, milder temps are expected by Friday afternoon
along with a gradual increase in mid to high clouds, leading
to the next chance of rain Friday night into Saturday.

The weekend appears somewhat unsettled with the warm sector
struggling to overspread central PA. It won`t be raining all the
time, but a shower cannot be ruled out from the Friday night
through Sunday afternoon period. Upper ridging may eventually
win out by Sunday night and Monday for drier and warmer
conditions during that time, and highs could surge through the
70s and perhaps exceed 80F over the south on Monday afternoon.

Both the EPS and GEFS indicate the warm front will lift north
of the region by Sunday and Monday, resulting in markedly warmer
and more humid conditions with scattered PM convection
possible. Mean progged 850mb temps south of the warm front are
around 12C, supportive of highs in the 75-80F range.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
High and mid-level clouds continue to thicken over central PA
this evening. There are some light radar returns moving in from
western PA, but the low-levels remain quite dry so precip is
having trouble reaching the ground. The south to southwesterly
breeze has diminished a bit, but we continue to see occasional
gusts of 15-20 kts in some locations.

Cigs will continue to lower through the overnight hours, with
the western highlands (BFD, JST) dropping to MVFR, if not IFR,
by daybreak on Wed. The central mtns will likely drop to
borderline MVFR/VFR by daybreak, with the Lower Susq Valley
remaining VFR.

We should eventually see light rain showers make it to the
ground across the western highlands, but this activity is likely
to diminish as it progresses eastward overnight. There could
also be some LLWS with a 35-45 kt southwesterly wind a couple
thousand feet above the sfc.

Surface winds will become northwesterly late tonight into Wed
morning, and become gusty again by afternoon. Spotty showers
remain possible on Wed as well.

Outlook...

Wed...Spotty -SHRA with MVFR cigs west and predominantly VFR
east.

Thu-Fri...Predominantly VFR conds under high pressure.

Fri night-Sat...Patchy rain developing from west to east.

Sun...Scattered SHRA/TSRA possible.
-- End Changed Discussion --

&&

.FIRE WEATHER...
Low humidity (20-30% minRH) and breezy conditions (20-30 mph wind
gusts from the south/southwest) will result in an elevated risk
of wildfire spread late this afternoon. However, dead fuel
moisture values per latest PABOF/DCNR sitrep and ongoing Spring
green-up are both limiting factors offsetting the wind+RH fire
wx risk to a large extent in CPA.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Freeze Watch from late Wednesday night through Thursday
morning for PAZ019-025>027-045-046-049>053.

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert/Fitzgerald/Dangelo
SHORT TERM...Lambert
LONG TERM...DeVoir/Fitzgerald
AVIATION...Evanego
FIRE WEATHER...Lambert