792
FXUS61 KCTP 170915
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
515 AM EDT Mon Aug 17 2026

.WHAT HAS CHANGED...
*Minor adjustments in POPS and QPF today in the warm and muggy
 air ahead of a cold front


&&

.KEY MESSAGES...
1) Scattered to numerous, brief showers ahead of a cold front
into the early/mid afternoon hours

2) High pressure yields a relatively short dry window for late
today afternoon through Wednesday morning, before more storms
arrive Wednesday afternoon into Thursday.

&&

.DISCUSSION...
KEY MESSAGE 1: Scattered to numerous, brief showers ahead of a
cold front into the early/mid afternoon hours

Warm and humid conditions cover the CWA with anomalously high
PWAT values of around 2 inches. SFC cold front pushing just SE
of the Interstate 90 corridor ATTM.

Latest mesoanalysis shows MU CAPE of over 1000 J/KG just ahead
of the aforementioned cfront from the lowlands of Western PA,
int far SW New York. This instability axis was supporting some
low-topped TSRA near KJHW with a channel of numerous showers
extending south along and to the west of the RT 219 corridor.

The frontal boundary will cross the CWA during the late morning
and afternoon hours, likely clearing the PA/MD border by dusk.

MU Cape values ramp up across the SE half of PA (to over 1500
J/KG) for the mid to late afternoon hours, supporting the
development of scattered to numerous showers with scattered
TSRA. Very weak diffluent flow aloft and the lack of significant
llvl convergence ahead of the front should temper the intensity
of the TSRA updrafts, but it wouldn`t surprise me to see a SPC
upgrade to MRGL DY1 risk for SVR TSRA across Southern and
eastern PA with their late Dye morning update.

SFC TDs in the upper 60s to low 70s today (and PWAT AOA 2
inches) will be the fuel for some brief heavy downpours with the
showers and isolated to scattered TSRA. QPF could be on the low
side in some spots today, where a 10 minute heavier shower or
TSRA could bring pinpoint 0.25 of an inch amounts.

Dewpoints will drop 5-8 degrees from today to tomorrow
afternoon accompanied by abundant sunshine on Tuesday.


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

KEY MESSAGE 2: High pressure yields a short dry window for late
today through Wednesday morning, before more storms arrive
Wednesday afternoon into Thursday.

A cold front moves through Monday. Dewpoints don`t drop much at
all until later in the day Monday. So, there will still be
plenty of time on Monday for instability to develop and pop
showers and perhaps a thunderstorm or two during the daytime. By
sunset, these will be gone as dry air and loss of heating kill
them off. Dewpoints drop into the 50s for many Tuesday morning.
Large scale subsidence should yield a mostly sunny day, then.
Return flow Tuesday night and Wed will bring the humidity up and
a cold front will approach on Wednesday. Storms are expected
mainly in the Wed-Wed night timeframe, but speed of the CFROPA
will determine if all/part of Thursday will be dry. If showers
linger, they would be over the south.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Main issue this morning into at least early this afternoon will
be areas of low CIGS, upslope dense fog on the west-facig
slopes, and some showers and even a brief low-topped TSRA across
the SE half of the state - along and ahead of a SE moving cold
front.

Conditions improve to VFR late today, which should last into
at least Wednesday morning. Main issue Tuesday and Wednesday
morning will be the potential for patchy valley fog.

Outlook...

Mon-Tue...VFR most of the time. Chance of showers/tstm early
Monday.

Wed-Thu...Afternoon showers or a TSRA with brief restrictions
possible. Otherwise, VFR conditions.

Fri...Chance of showers across the south, otherwise dry.

&&

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

&&

$$

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