214
FXUS61 KCTP 261815
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
215 PM EDT Thu Sep 26 2024

.SYNOPSIS...
*Mostly cloudy with periods of rain and mild nights through
 the early to middle part of next week
*The heaviest rain over the next 5-7 days is expected over parts
 of south central PA which should provide relief in abnormally
 dry to moderate/severe drought conditions
*A shift toward drier weather is possible by the end of next
 week/first weekend of October

&&

.NEAR TERM /THROUGH TONIGHT/...
1045AM/1445UTC: Mid morning update coincided with radar trends
and ramped POPs along fgen precip frontal zone extending from
just north of Pittsburgh through State College to near
KAVP/Scranton-WB. Otherwise, not much change for the last
Thursday of September with cloudy skies and noticeable uptick
in humidity.

Previous Discussion Issued: 628 AM EDT Thu Sep 26 2024

Temperatures have trended up overnight, deviating from a typical
diurnal pattern. It is amazing the difference a southerly wind
can make after what has felt like an unending stretch of
easterly flow. Quite mild at daybreak with temperatures in the
60s, which is +15 to +20 compared to average for this time of
year. Heaviest rain showers are southeast of I-81 this morning,
downstream of a corridor of 2-4" extending southwest to
northeast in northern Virginia into Maryland. Rainfall rates
have tapered with northeastward extent thanks to lower
instability and PWATs, but a quick half inch to inch of rain is
possible through 8 or 9AM there.

Persistence is a good forecast as overcast skies and periods of
showers continue to buffet Central Pennsylvania. An upper trough
over Quebec and a closed low over the Ohio Valley are keeping
our pattern fairly steady-state. Mid-level vort max traversing
the region this morning will help focus showers across northern
half of PA later this morning before drifting northeast into
the afternoon. At the surface, a weak front will drift eastward
and eventually stall out across the Mason-Dixon Line later
tonight. Rainfall totals will approach half an inch toward the
Poconos with only light amounts farther west and south.

Ahead of the front, southerly winds rotating around broad high
pressure over the Atlantic should help moderate temperatures
today compared to the last few. Highs in the 70s areawide are
+10 to +15 F higher than yesterday. Overnight, a welcome lull in
the precipitation will occur as the aforementioned front settles
over southern PA. Another mild night on tap with lows near 70 in
the southern tier, although slightly drier air will filter in
north of US-6 allowing temperatures to drop into the middle 50s.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
Little in the way of changes for Days 2 through 4 as the upper-
level trough over New England moves off the the Atlantic Coast
Thurs night into Friday, while the moisture remnants of Helene
become wrapped up in the upper low over the Lower Ohio Valley.

At the sfc, a stationary front will become draped across
southern Pennsylvania. This will keep the best PWATs associated
with the tropical airmass south of the region, with easterly
winds in control in our neck of the woods. That will mean more
clouds and occasional showers with upslope flow. As Helene moves
north through the Mississippi Valley on Friday, outer rainbands
are progged to drift northward through PA. Showers will be
efficient rainfall producers, and will have to monitor for
spin, but rainfall amounts should not be too significant.
Temperature- wise, the days will see temperatures fairly close
to average, while clouds will keep nighttime temperatures well
above average for early fall.

Latest guidance indicates the potential for a period of heavier
rain later Saturday night into Sunday, prompting WPC to hoist a
Marginal Risk of Excessive Rainfall for that period. Still
enough uncertainty in model guidance & overlap with the driest
part of the CWA to hold off on getting too concerned. Most
likely to be a continuation of beneficial rainfall through
Saturday night, but will continue to monitor as hi-res guidance
comes into range.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
An upper-level low over the Ohio Valley will drift east across
the Commonwealth into the beginning of next week, keeping rain
chances around through at least Tuesday. Uncertainty begins to
increase towards the middle of the week as a northern stream
shortwave tracks near the region, bringing a cold front along
with it. The timing of this feature is a little unclear with
some ensemble members showing the front tracking through early
Wednesday morning while others show a later frontal passage.
Moisture appears to be limited ahead of the front and the best
forcing looks to remain to our north, so widespread rainfall
does not appear likely at this point.

High pressure building in behind the front will bring drier
weather and cooler temperatures for the end of the week. Highs
will generally be in the 60s with overnight lows in the 40s.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Scattered showers will continue through the rest of the
afternoon and may cause brief periods of IFR visibilities if
they move directly over any airfields. The general trend
through the day though has been towards higher ceilings with
many sites reporting VFR ceilings as of 18Z.

By later this evening (01-05z), the expectation is that cloud
bases will lower again to categorical IFR reductions, especially
over the southern half of Central Pennsylvania where the HREF
shows a 80-90% chance of ceilings below 1000 feet. Surface
winds of 5-8 kt from the E-SE can be anticipated this afternoon,
with otherwise light and variable winds less than 5 kt.

These low clouds will slowly rise to MVFR across the western
half of the region during the late morning and early afternoon
on Friday, though model soundings suggest that IFR ceilings
remain likely across the southeast through at least 18Z.

Outlook...

Fri...Lower ceilings are likely area-wide in the morning, then
during the afternoon the best chance of showers/low ceilings
will be across southern PA.

Sat-Mon...The highest probabilities for low ceilings and
showers should again be across southern PA.

Tue...Scattered showers with restrictions possible.

&&

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

&&

$$

SYNOPSIS...Steinbugl/Banghoff
NEAR TERM...Steinbugl/Banghoff
SHORT TERM...Banghoff
LONG TERM...Dangelo/Bauco
AVIATION...Jurewicz/Bauco