465
FXUS61 KCTP 202319
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
719 PM EDT Sun Sep 20 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 considered.

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 considered.

Nebulous/broad sfc low pressure over the CWA at 18Z, seemingly
centered somewhere within 40 miles of UNV. Several short wave
troughs continue to roll into and over the Mid-Atlantic, but
none have instability to work with north of the Mason-Dixon Line.
PWATs remain high, touching the 2" mark in York/Lanc Cos. Flow
is westerly and constant, but slightly confluent aloft. The
closest thunder at 18Z is in ern OH and dropping steadily south
enough that it will likely miss our CWA. But, occasional
showers/rain continue to move in from upstream. QPF still looks
low enough (<0.75") through midnight in the Laurels where the
FFG is lowest (just under an inch in some places). That should
be low enough in intensity/duration to keep any hydo problems
minor and isolated. After collaboration with neighboring
offices, we had low enough confidence in flooding-intensity
rainfall to stay away from a Flood Watch at this point in time.
But, the Laurels (particiularly Somerset Co) would be the place
most-susceptible to any flooding into late this evening.
Conditions are too dry farther east, and the bulk of the rain
should stay south of I-80 for the rest of the day.

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

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
lower LM 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.

Extremely blocky pattern aloft yeilds 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 /00Z MONDAY THROUGH FRIDAY/...
Cold front will continue to sag southward overnight, taking
most of the showers with it. Expect widespread IFR and MVFR
conditions with a lot of variation.

For Monday, main change was to back off on improvement being
quie as good as what the 18Z TAF package had. Low level
moisture remains high.

Monday will feature the best conditions with the least chance
of showers of the next few days.

Wet weather is expected to move back into the area after
Monday.

Outlook...

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

&&

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

&&

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

&&

$$

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