NWS Forecast Discussion
210
FXUS61 KCTP 200551
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
151 AM EDT Sun Sep 20 2026
.WHAT HAS CHANGED...
* Added slight chance of showers far western sections of central
PA for into early evening.
* Overall amounts of rainfall for Sunday trending lower.
&&
.KEY MESSAGES...
1) Rain moves in tonight, heavy at times into Sunday.
2) Rainy pattern continues into much of next week, although
uncertainty remains in the details. On the cool side as well.
&&
.DISCUSSION...
KEY MESSAGE 1: Rain moves in tonight, heavy at times into
Sunday.
Some dry air at low levels, most of the radar returns this
morning so far have been at mid levels, but added slight
chance POPS far western PA to match others, as some rain
reaching the ground across the far west as of early aft.
High pressure over Quebec will give way to a fast moving
low from the central states moving eastward across PA on
Sunday. Trends are for the low to be a bit further south
and faster now. Expect steady rain to move into western
areas later this evening. Bulk of the activity is over
by early evening. A few showers could linger into Monday.
The airmass is rather cool and dry to start. However, still
have to watch the far south for thunder, given fcst temps.
Thunder could be a bit further north, but mainly elevated
in that case.
It has been wet, but with the trend with lower QPF and
a bit faster movement, not really expecting hydro concerns
at this pt.
-------------------------------------------------------------
KEY MESSAGE 2: Rainy pattern continues into much of next week,
although uncertainty remains in the details. On the cool side
as well.
A large high over Quebec will push southward on Monday, giving
the area the best chance for dry conditions. Monday looking
like the best day to be outside.
As one heads into Tuesday and Wednesday, a wedge of colder
and more stable air will be over the area, given this CAD
pattern. At this time, the highest POPS are over the west
and south, given an inverted trough.
Perhaps some improvement later Thursday, as a coastal low
ramps up off the southeast coast.
While low temperatures will be not that far from normal,
high temperatures will be colder than normal.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Rain will continue overspreading central Pennsylvania through
this morning as a low pressure system begins trekking across the
area. Periods of +RA with IFR visibilities are possible as a
plume of rich moisture (PWATs around 2") accompanies this
system, with the Northern Tier (KBFD) being less likely to see
+RA being on the periphery of greatest moisture, though low
stratus will likely bring IFR-LIFR restrictions to KBFD
nonetheless.
A period of borderline LLWS is also expected through this
morning, mainly south and east of KBFD, as a LLJ develops (925
mb winds to around 35 kts from the S/SSE).
TSRA cannot be ruled out across our southern tier of counties
(KJST/KAOO/KMDT/KLNS) through Sunday afternoon as MUCAPE
approaches 1000 J/kg. However, tall/skinny CAPE profile and deep
warm cloud layer (10-15 kft between MULCL and freezing level)
will favor rainfall efficiency over lightning production,
ultimately precluding TSRA mentions in the TAFs.
As the system progresses toward the coast later this evening,
surface winds will shift northerly and advect dry, continental
air across much of the Commonwealth. This will scour out low
cloud ceilings and result in a north-to-south VFR trend Sunday
night. The main uncertainty will be timing of improvements,
especially across SE PA (KMDT/KLNS) where easterly component to
the wind may slow improvements due to marine influence, though
guidance nevertheless favors VFR across all forecast terminals
by Monday morning.
Outlook...
Tue-Thu...Restrictions possible from -SHRA/BR and low ceilings,
mainly S.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
WHAT HAS CHANGED...Martin
KEY MESSAGES...Martin
DISCUSSION...Martin
AVIATION...Teare
NWS CTP Office Area Forecast Discussion
