969
FXUS61 KCTP 210538
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
138 AM EDT Mon Sep 21 2026

.WHAT HAS CHANGED...
* Tweaks to near term based on radar/sat trends
* Flood watch considered, rejected for now

&&

.KEY MESSAGES...
1) Rain moves to the south early tonight, but returns for
Monday. Flood watch still possible with the support of later
model guidance.

2) Rain potential continues for much of this week, although
uncertainty remains in the details due to offshore low
development possibilities. On the cool side as well.

&&

.DISCUSSION...
KEY MESSAGE 1: Rain moves to the south early tonight, but returns
for Monday. Flood watch still possible with the support of
later model guidance.

The vast majority of the stronger convection moving through
Central and Southern Ohio this evening is aimed SW of our SW
Laurel Highland zones overnight per the latest HREF and its high
res members.

-------------------------------------------------------------

KEY MESSAGE 2: Rain potential continues for much of this week,
although uncertainty remains in the details due to offshore low
development possibilities. On the cool side as well.

A fairly strong short wave trough currently over rolls in from
the midwest late tonight. That should yield a renewal of
rainfall in the Laurels. The system will still be working with
1.5-2.0" PWATs. But, it will arriving at an even more- stable
time of day. The steady east and slightly northward spread of
precip will only reinforce the stability (and keep temps chilly)
Monday. Again, thunder cannot be ruled out, but would likely be
elevated. It may remain dry (or just patchy drizzle) across the
northern tier for much of the day. Models funnel the best
moisture into the eastern half of PA Monday night, easing the
flooding potential somewhat for the Laurels.

24 hour QPF ENS LPMM in the 12Z Mon-00Z Tue period shows at most
1-1.5 inches across southern Somerset County with less than 0.25
of an inch NE of the RT 322 corridor in Central PA and the Lower
Susq Valley. Another period of slightly more expansive 1-1.5
inch amounts is expected for Monday night through Tuesday
morning, and could enhance the flooding threat across the SW
third of the CWA. But with little instability/ heavy rainfall
rates likely, there`s plenty of time at this point to fine tune
the area to message for this potential moderately impactful
event.

Extremely blocky pattern aloft yields very low confidence in
sfc features and precip potential/placement beyond Tuesday. Low
pressure tries to develop off shore (along the Gulf Stream) Wed,
but may be shunted eastward through the second half of the
week. The sure bet this week is for below normal max temps.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
N/NE`erly surface winds will guide drier/continental air
southward across much of the Commonwealth through Monday
morning, with dewpoints trending down into the 50s areawide.
Although conditions will trend drier near the surface, lingering
moisture aloft will blanket much of the area in mid/high clouds
(VFR), with sub-VFR ceilings favored throughout the day along
the Allegheny Ridge terrain (mainly MVFR for KJST/KAOO, and
perhaps IFR at KJST). Moreover, periodic MVFR is possible
through Monday morning at KMDT/KLNS downwind of the Atlantic
Ocean.

Another round of rain will gradually overspread the southern
2/3rds of the Commonwealth throughout the day on Monday as a low
pressure drifts across the Mid-Atlantic, with a stout 1030-1040
mb high pressure over southern Canada looking to keep the
Northern Tier (KBFD) mainly dry. Surface winds will trend
E/NE`erly at the surface Monday night and bring marine air back
into much of our area, with mid-level (850 mb) SE`erly flow also
helping to slowly bring moisture back north. This looks to
favor a trend towards MVFR-IFR across all terminals Monday night
as moisture rebounds.


Outlook...

Tue-Thu...Restrictions possible from -SHRA/BR and low ceilings,
mainly S.

Fri...VFR favored as a developing coastal low looks to bring subsidence
overhead, though -RA and lower cloud ceilings associated with this
system may reach our eastern terminals.

&&

.CLIMATE...
As of 5 PM, 1.05 inches of rain fell at AOO (Altoona) PA today.
This broke the old record of 0.73 inches set in 1957.

&&

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

&&

$$

WHAT HAS CHANGED...Lambert/Dangelo
KEY MESSAGES...Lambert/Dangelo
DISCUSSION...Lambert/Dangelo/Colbert
AVIATION...Teare
CLIMATE...Martin