872
FXUS61 KCTP 172229
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
629 PM EDT Fri May 17 2024

.SYNOPSIS...
A weakening frontal system from the Ohio Valley
will spread showers over western and central portions of
central Pennsylvania tonight. Low pressure passing well to the
south of Pennsylvania will bring additional showers to central
Pennsylvania into Saturday afternoon, followed by high pressure
and dry weather arriving for Sunday. Mainly dry conditions are
expected through the middle of next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
Decaying frontal system has maintained scattered to numerous
showers and isolated storms over western PA late this afternoon
into this evening. It remains quite stable along and east of the
Alleghenies, and earlier activity in PBZ`s area is weakening as
it approaches the Laurel Highlands.

PW up to 1.5" and mean flow <20kts in the lower half of the atm
(sfc-500mb) can still bring some local heavy downpours over far
southwest PA, but concern is limited for the Laurels given
stable stratification.

Shortwave tracking ENE from WV will help expand rainfall to the
east late tonight into early Saturday morning. Moist southeast
upslope flow will enhance rainfall in some of the favored
terrain while also supporting low clouds/cigs and fog. Lows
in the 55-60F range are +5-15F above mid May climo with the
larger departures across the western and northern Alleghenies.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
Another wet start to the weekend with plenty of clouds, periods
of light rain/showers, and areas of fog. Hires model data
focuses the bulk of the rain early in the day, becoming more
scattered through the afternoon into the evening. Cool air
damming (CAD) pattern with moist east southeast flow will
result in highs ranging from 70-75F in the far NW mtns (5F above
climo) to 60-65F across the southeast half of the CWA (5-10F
below climo). Continued to temper NBM with blend of raw hires
model data given typical downside risk for cooler temps in this
type of CAD pattern setup.

We remain increasingly optimistic that Sunday will turn out to
be a much nicer day vs. Saturday. With the arrival of lower pwat
air and more northerly wind component along with ridging at the
sfc and aloft, odds favor a mainly dry and warmer end to the
weekend with some breaks of sun especially across the northern
tier. Latest model data indicates highs recover +5-10F across
the board with max temps around 80F fcst in the NW Alleghenies.

Look for areas of fog both Saturday night and Sunday night.

Temps continue to trend warmer into early next week with highs
on Monday reaching the upper 70s to mid 80s. High pressure
continues to build over CPA promoting rain-free conditions to
start next week.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
A dry start to the extended period will be likely with high
pressure ridging building over the mid-atlantic region and a
deep surface low parked over the central plains. High pressure
and dry air will stay in place through Tuesday before the upper
level trough pushes them both out by Wednesday afternoon. 850mb
temps of near 16C along with surface warm air advection suggest
high temperatures could reach the mid 80s on Tuesday and
Wednesday.

By the middle of next week, upper troughing will move across
Pennsylvania and support a better chance for showers and
thunderstorms. At the surface, there remains plenty of model
uncertainty about the timing of a cold front. The mean timing is
Wednesday afternoon, but individual models bring precipitation
as early as Tuesday evening and as a late as Thursday morning.
If the front moves through Wednesday afternoon or evening, it
could produce the first threat for severe weather in some time
given the aforementioned WAA bringing greater instability.

After the front moves through, considerable uncertainty exists
in terms of how much and how frequent rain will be. A chance of
showers remains in place through the end of the week despite
zonal flow aloft providing little in the way of synoptic
forcing. The next chance for a widespread soaking rain will come
during the weekend with a center of low pressure developing
across the Ohio Valley by Friday afternoon.

&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
Most sites are holding onto borderline MVFR conditions this
afternoon with lower clouds refusing to let up. An approaching
warm front will spread showers (and perhaps some thunder) and
lowering cigs into the western half of PA during the afternoon
and evening hours. Latest ensemble prob charts indicate an
increasing probability of IFR cigs (50-70% chc) by late evening
over the western highlands (JST, BFD). Some of these rain
showers could also be heavy at times. Expected reductions to
visby as these showers cross over sites.

IFR conds will continue into the overnight across the western
highlands, with cigs expected to drop to borderline IFR late
this evening into the overnight across the central mtns. The
Susq Valley should see cigs drop to IFR overnight as well.
Periods of rain will continue into the overnight hours with some
drizzle possible in the early morning. Fog is also likely to
develop across much of central PA by daybreak Saturday. Fog
will lift by the early afternoon Saturday, but lower clouds will
keep cigs in MVFR with no improvement to VFR likely.

Outlook...

Sat...Restrictive lower ceilings and periods of rain
continuing.

Sun...Morning low cigs/fog possible. Becoming VFR by afternoon.

Mon...Patchy AM fog possible. Otherwise, becoming VFR.

Tue...Predominantly VFR, w/ no sig wx expected.

Wed...Sct to widespread shra/tsra will return.

&&

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

&&

$$

SYNOPSIS...DeVoir
NEAR TERM...DeVoir/Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Bowen
AVIATION...Bowen