365
FXUS61 KCTP 021120
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
720 AM EDT Tue Sep 2 2025

.SYNOPSIS...
* Isolated showers today mainly in the mountains.
* The next widespread chance for showers comes Thursday with a
  cold front.
* More showers and storms are possible on Saturday with strong
  cold front.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Clouds and an isolated sprinkle or two are sliding west through
the western half of the CWA this morning. A small shower ran
right along the Centre-Huntingdon Co border in the past couple
of hours and did make measurable rain for at least two highly
reliable meso-net locations. We are under the center of an upper
low. Shallow instability is forecast by most models over much of
Central, especially areas to the west of Chambersburg-State
College-Mansfield line. The cloud cover today will probably
become rooted in the boundary layer, but the instability/lift
seems to be all aloft currently. Current cloud bases are
around 6-8kft. As the heating kicks in, though, there should be
more diurnal convection. So, we`ve added a 20 PoP to the western
half or so of the CWA. Max temps will be very close to Monday`s
numbers, but perhaps 1F cooler where it is more cloudy. A slight
uptick in dewpoints will also help minRH stay about 10 percent
higher vs Monday. Some 30-40% minRHs are still possible between
State College and Bradford on the higher ground of the Allegheny
Plateau.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
Loss of daytime heating should help diminish any tall cu and end
the chance for a --SHRA early this evening. 5H heights rise on
Wed. Little or no instability is seen. This should keep Wed
dry. The light sfc wind should finally turn southerly on Wed.
However, the dewpoints do not rise much at all. So, the RH could
be 10% lower on Wed vs Tues. However, very few pixels of <30% RH
are seen, and the wind remains light. So, no worries for Red
Flag (Fire Weather) conditions. Maxes Wed will be in the 73-82F
range.

The southerly flow begins to increase on Wed night as the sfc
pres gradient tightens in advance of the cold front approaching
from the west. The moisture plume at our latitude seems to stay
near to the front and dewpoints don`t rise above 60F over
Central PA (even over western PA) until after 12Z Thurs. So, the
PoPs for Wed night have been trimmed to <20pct except for Warren
Co where timing is becoming more-certain that they will have
SHRA/TSRA nearing around sunrise Thurs.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
The 3 AM Update holds very little in the way of changes to the
forecast. The timing of a Thursday-Thursday evening passage of
the cold front is becoming more solid. PoPs are still going to
be highest west of the Susq Valley. SHRA/TSRA could still
affect the SE (60-70 PoPs) where a decline of forcing is
expected along with a decline in heating/diurnal instability.
So, expect the coverage of SHRA/TSRA to diminish slightly as
they pass through the SE/Lower Susq.

Prev...
A deep upper level low will result in some showers and perhaps
a storm on Thursday, as the cold front moves into central PA
by late Thursday.

The upper level support will be lifting northeast of the area,
so the chance of strong storms and heavy rain limited. As was
the case last Thursday evening, the highest chance of such
activity will be over Lake Erie, where the warm waters can add
moisture.

The next cold front moves into the area late Friday night -
Saturday, followed by below normal temperatures. Dynamics could
support strong storms, but not under any outlooks at this point.

Similar to yesterday (Sunday) at this time, GFS`s timing of the
Cfropa is still 6+ hours faster than the EC (and during the
late night/early morning hours Saturday) placing much of the CWA
under a pronounced dry slot and a precip min for most or all of
the daylight hours of Saturday. 01/23Z NBM guidance indicates
only 25-30 pops for the 12Z Sat- 00Z Sunday period (splitting
the diff of the operational GFS and EC).

Models not in the best agreement on the details as one gets
out to day 10, but little signal for any extended warm spells.

Flow for late Friday into Saturday a bit too much west to
southwest for much late effect, but did adjust POPS a bit
higher for a few small areas across the NW.

&&

.AVIATION /11Z TUESDAY THROUGH SATURDAY/...
VFR conditions are being observed at all Central PA TAF sites
as of 11Z, though brief periods of MVFR ceilings will be
possible at LNS through the first half of the morning as some
low clouds have formed in the area. Expect an increase in cloud
cover through the day with cloud bases likely around 6000 feet.
Isolated showers will also be possible, but coverage will be too
low to include any mentions of rain in the TAFs for now. The
best chance for a shower or two (~20%) will be near JST, AOO,
and UNV.

The chance for showers will come to an end after sunset and
cloud cover will gradually decrease. The 00Z HREF suggests that
valley fog may be more widespread tonight, though the chance for
any TAF sites to see sub-VFR visibility is still low (generally
less than 40%).

Outlook...

Wed...Mainly VFR. Isolated SHRA possible in the late afternoon
mainly south and west of JST.

Thu...Widespread SHRA/TSRA ahead of a cold front.

Fri...Showers lingering, mainly across the east.

Sat...Chance of SHRA with TSRA possible.

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Lambert/Dangelo/Martin
AVIATION...Bauco