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821
FXUS61 KCTP 040823
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
423 AM EDT Sat May 4 2024

.SYNOPSIS...
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-Noticeable cool down for the first weekend of May with cloudy
 skies and periods of rain
-Remaining unsettled next week with a gradual warming trend
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&&

.NEAR TERM /THROUGH TONIGHT/...
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MRMS radar at 08Z shows ~100mi wide band of light to moderate
rain along a SW to NE oriented 500mb vorticity axis extending
from the southwest corner of PA into the Endless Mtns north of
KIPT. Expect this corridor of rain to remain in-place through
daybreak with more rain on the way to start the first weekend in
May.

The latest hires model guidance supports periods of rain
throughout today and into tonight ahead of an upper level
shortwave lifting out of the Tennessee Valley. The associated
southerly low level jet and plume of higher pwats will
overrun a dome of cool/stable air (entrenched within a CAD
pattern configuration) to bring 0.25-0.75" of rain to the area.
This pattern will also ensure a significant cool down from
recent days with fcst max temps in the 50-60F range or 10 to 25
degrees cooler vs. yesterday depending on location. Not much
change in sensible wx overnight with periods of rain continuing
with lows in the 45-50F range or +5-10F above early May climo.
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&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Sunday looks to be another relatively cool day for early May
due to a persistent southeast flow off of the Atlantic. However,
a slight rebound in warmth is expected over the western and
southwestern periphery of the CWA as steadier rain tapers off.
Fcst highs range from 55F in the Endless mtns and southern
Poconos to ~70F in the far southwest corner of the CWA (near
Confluence in Somerset County).

Scattered diurnal convection appears likely to the west of the
Alleghenies Sunday afternoon which could spill into central PA
late in the day. THe SPC MRGL risk SWO clips a portion of
Warren County.

The CAD pattern loses its grip Sunday night into Monday as a
weak cold front presses southeast from Lake Erie. Guidance has
been bullish on fog development and will continue mention in
the wx grids. Fcst lows Sunday night are +10-20F above climo
for early May in the low 50s to near 60F.

Temperatures are forecast to bounce on Monday with fcst maxes
getting back into the 70-80F range. High pressure and low pwat
air should dry out the northern tier, but nearly stationary
frontal zone will maintain a chance of showers/t-storms over
south central PA through Monday night.
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&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
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Upper level ridging over PA indicates warm and generally dry
conditions are likely Tuesday. However, a warm front lifting out
of the Ohio Valley could result in increasing clouds with a PM
shower/tsra, primarily across the southwest counties. The bulk
of medium range guidance supports a very warm Wednesday with
scattered convection, as the area briefly breaks into the warm
sector ahead of a cold front pushing in from the Grt Lks.

Model consensus supports a better chance for a more widespread
rainfall Thursday, associated with a deepening upstream trough
and wave of low pressure riding along the stalled cold front
just south of PA. The surface low and deepest moisture is
progged to shift east of the area by Thursday night. However,
falling heights ahead of the upper trough will likely support
scattered, diurnally-driven convection Friday, along with a
downward trend in temperatures.
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&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
As of 0630 UTC Sat, MVFR cigs have moved into the Laurels (JST
and AOO) as well as portions of south central PA (CXY and THV).
The low cigs will continue to expand over the next several
hours, with the remaining TAF sites likely dropping to MVFR or
lower by daybreak. Confidence in MVFR cigs after 11z is lowest
at LNS, where much of the hires guidance shows LNS on the
eastern periphery of the MVFR cloud deck.

IFR conds are likely to develop first across the western
airfields (BFD, JST, and AOO between 10z and 15z Sat) and then
expand eastward through the day. Confidence is low in the exact
timing of the low cigs. Periods of light rain will continue
through the day.

Southeast winds of 5-15 kts will continue through the TAF
period, with gusts up to 25 kts. LLWS may become a concern from
00z-18z Sun as a southerly LLJ develops with 2kft winds 35-45
kts, strongest through north central PA. The LLJ will also
produce the most widespread and heaviest rainfall during this
period.

Outlook...

Sun...Widespread restrictions due to low cigs. SHRA likely with
a slight chance of TSRA. Areas of fog poss Sun night.

Mon-Wed...AM fog/clouds poss. PM -SHRA possible areawide.

&&

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

&&

$$

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