-- Discussion containing changed information from previous version are highlighted. --
357
FXUS61 KCTP 041824
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
224 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/...
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.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
-- Changed Discussion --
Unsettled weather is expected for the long term period with
multiple chances for showers and thunderstorms. The first chance
will come on Tuesday as a warm front lifts north of the area and
moisture advection increases. The best chance for any showers
or storms on Tuesday will be across the southwestern counties.
Wednesday will be the warmest day of the period with highs in
the upper 70s and 80s as the region will be in the warm sector
of an approaching low pressure system. Most model guidance shows
a weak wave of low pressure tracking to our north during the day
on Wednesday along the warm front ahead of the primary low.
This will bring more showers and storms to the area.

The best chance for widespread showers and thunderstorms
appears to be on Thursday as a cold front moves through. Locally
heavy rainfall will be possible with ensembles showing PWATs
approaching 1.3 inches across the southern tier along with
surface CAPE of 500-1000 J/kg. A few stronger thunderstorms
appear possible as well, as deep layer shear begins to increase
as the upper level trough moves in.

Temperatures will be on a downward trend behind the cold front
and into the weekend. Highs on Saturday will range from the
upper 50s across the northern and western mountains to the mid
to upper 60s for the southeast. There is some disagreement in
the models with respect to rain chances through the end of the
period, but scattered showers appear likely as a couple of
shortwaves ride through the southern edge of an upper low
positioned to our north.
-- End Changed Discussion --

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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Low ceilings across the northern and western mountains will
continue to spread eastward through the rest of the afternoon
and IFR ceilings are expected areawide by early this evening.
Confidence is low in the timing of the lower ceilings. Periods
of light rain will continue through the day.

Southeast winds of 5-15 kts will continue through the TAF
period, with a few gusts up to 20 kts possible. A strengthening
LLJ will move in this evening and will lead to a period of LLWS
at western sites as winds 2000 feet above the ground increase to
35-40 kts. The LLJ will also lead to an increase in rain
coverage and intensity. As the rainfall intensity increases
overnight, expect visibilities to drop into the IFR range. Rain
will continue into the afternoon on Sunday and ceilings will
remain IFR/LIFR through at least 18Z.

Outlook...

Sun Night...Areas of fog possible.

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

Thu...Restrictions possible in TSRA.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...Steinbugl/Bowen
NEAR TERM...Steinbugl/Bowen
SHORT TERM...Steinbugl/Bowen
LONG TERM...Bauco
AVIATION...Colbert/Bauco