-- Discussion containing changed information from previous version are highlighted. --
541
FXUS61 KCTP 041724
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
124 PM EDT Sat May 4 2024

.SYNOPSIS...
-Noticeable cool down for the first weekend of May with cloudy
 skies and periods of rain
-Morning ridgetop patchy fog is possible for Sunday and Monday
-Remaining unsettled next week with a gradual warming trend

&&

.NEAR TERM /THROUGH TONIGHT/...
Light rain continues to move across central Pennsylvania from
SW to NE. Current MRMS shows precipitation bands across the mid-
atlantic region from central Ohio to the coast of Maryland.
Additional rain will likely develop across southern tier of the
commonwealth near the Mason-Dixon line in the early afternoon
hours.

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.
Patchy fog will be possible overnight in the higher elevations
with low dewpoint departures and relatively stable air near the
surface.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
-- Changed Discussion --
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 as CAPE values increase. The SPC MRGL risk SWO
clips a portion of Warren County. Everywhere else remains under
general thunder.

The CAD pattern loses its grip Sunday night into Monday as a
weak cold front presses southeast from Lake Erie. This will
allow for the possibility of night time convection along the
cold front. Guidance has been bullish on fog development and the
mention of it has increased in coverage 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.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
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.

&&

.AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
The low cigs will continue to expand over the next several
hours, with the remaining TAF sites likely dropping to MVFR or
lower by mid morning. Confidence in MVFR cigs after 12z is
lowest at LNS, where much of the hires guidance shows LNS on the
eastern periphery of the MVFR cloud deck through much of the
day.

IFR/LIFR conds have already developed across the western
airfields (BFD, JST, and AOO) and will expand eastward towards
UNV by 14-18z. However, it may take until evening for IFR cigs
to reach the Susq valley. Confidence is low in the timing of
the lower 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/Bowen
NEAR TERM...Steinbugl/Bowen
SHORT TERM...Steinbugl/Bowen
LONG TERM...Fitzgerald
AVIATION...Colbert/NPB