739
FXUS61 KCTP 050703
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
303 AM EDT Sun May 5 2024

.SYNOPSIS...
Cloudy skies with areas of light rain, drizzle and fog will
persist throughout the weekend. High pressure slowly building
eastward from the central Great Lakes will bring some drying and
brightening to northern and central Pennsylvania by Monday and
Tuesday, but the south will remain on the cloudy side with some
showers. The pattern remains unsettled mid to late week with
weather systems bringing rain chances Tuesday night into
Wednesday, and Wednesday night into Thursday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Boundary layer convergence continues to ramp up this evening
over central PA as 850 mb jet amplifies in rich deep layer
moisture environment combined with easterly llvl maritime flow.
This will continue to support widespread light rain and drizzle
throughout central PA through the overnight and keep
temperatures within a few degrees of current readings through
12z Sunday morning.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/...
Sunday will be unseasonably cool with slowly decreasing easterly
flow from off of the western Atlantic, as we start to see an
increasing southerly component in time. This will lead to a
slight rebound in warmth over especially western/southwestern
periphery of the CWA as steadier precip tapers off. Fcst highs
should 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).

Even with the advancing warm sector, 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 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 western counties. The bulk of
medium range guidance supports a very warm Wednesday with
scattered convection, as the area briefly breaks into the warm
sector south of a weak low tracking across upstate NY. A round
of convection may accompany the trailing cold front. Ensemble
mean pre-frontal 850mb temps around 16C suggests max temps as
high as the mid to upper 80s are possible over the Lower Susq
Valley.

The best chance for widespread showers and thunderstorms
appears to be on 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 and Saturday,
along with a downward trend in temperatures. EPS mean 850mb
temps by Saturday are only around 3C, which is supportive of
highs ranging from just the mid 50s to mid 60s.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
A moist southeast flow preceding a slow-moving warm front in the
Ohio Valley will produce low cigs and rain across the forecast
area through at least Sunday morning. Guidance points to
deteriorating conditions overnight with widespread IFR/LIFR cigs
by early Sunday morning. LIFR cigs are most likely where the
southeast flow is forced to ascend the higher terrain of Central
PA. Strengthening south-southwest winds aloft will result in
marginal LLWS overnight into Sunday morning, with the best
chance of LLWS criteria being met across the northern tier of
the state.

Little improvement in flying conditions is expected over most
of Central PA Sunday, as a moist southeast flow off of the
Atlantic persists. However, model soundings indicate some modest
improvement is possible late in the day along and west of the
spine of the Alleghenies, prior to the development of scattered
convection during the evening hours. The highest chance for TSRA
is at JST and BFD, mainly between 22z Sun and 03z Mon.

Areas of fog are likely Sunday night into early Monday as drier
air works in aloft, but ample moisture remains trapped at the
sfc beneath a thermal inversion. Most if not all airfields will
trend VFR by Mon afternoon after any early fog dissipates.

Outlook...

Mon...AM low cigs/fog likely. Stray shower late.

Tue...Patchy AM valley fog possible, mainly Southern PA. Isold
PM tsra impacts possible Western PA.

Wed...AM low cigs possible NW Mtns.

Thu...Rain/low cigs possible. PM tsra impacts possible
southwest PA.

&&

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

&&

$$

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