081
FXUS61 KCTP 200005
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
805 PM EDT Thu Sep 19 2024

.SYNOPSIS...
*Pleasantly warm this evening with clearing skies and late-
 night valley fog into early Friday morning
*Increasing odds for rain/showers to start the weekend; Fall
 begins on Sunday
*Daytime temperatures peak +5-15 degrees above average into
 Saturday before trending seasonably cooler next week

&&

.NEAR TERM /UNTIL 7 AM FRIDAY MORNING/...
High pressure ridge over PA will result in fair weather
overnight. Mostly clear skies and a calm wind should promote
late night valley fog. The fog may become locally dense early
Friday morning and result in slowdowns and increased travel
times during the peak AM commute. See no reason to deviate
significantly from NBM min temps, which range from near 50F in
the coolest hollows of the Alleghenies, to around 60F in the
Lower Susq Valley.

&&

.SHORT TERM /7 AM FRIDAY MORNING THROUGH SUNDAY/...
Fog to start Friday; otherwise ridging at the surface and aloft
will result in a mostly sunny and warm Friday with max temps in
the 75-85F range or +5-15F above daily climo. Dry air above a
weak inversion in the model soundings supports undercutting NBM
dewpoints by a couple of degrees during the afternoon.

Can`t rule out patchy valley fog over parts of Eastern PA late Friday
night. However, increasing clouds and a developing southeast
breeze in advance of an approaching warm front should result in
no fog for most of the area and a fairly warm night by late
September standards.

Consensus/blended model data continues to signal increasing
odds for rain showers (and perhaps a PM t-storm) on Saturday in
response to a mid level shortwave diving southeast across the
state. The emerging precip signal was strong enough to cause a
notable change in the forecast for Saturday which had looked to
be a dry one just a few days ago. A ribbon of relatively strong
mid level flow over Southwest PA in the model guidance could
support a few strong to severe afternoon tsra over that part of
the state. There is some uncertainty if the surface warm front
and greater instability pushes east of the Alleghenies, so the
greatest severe threat currently appears to be over the Laurel
Highlands.

The global guidance indicates the shortwave and weak surface low
pass east of the region Sat night, then a cold air damming
scenario begins to develop between a stalled warm front along
the OH/PA border and high pressure over the Canadian Maritimes.
Forecast soundings indicate an upsloping southeast flow will
result in persistent stratus and perhaps a bit of drizzle over
the Central Mtns, with partly sunny skies possible over Eastern
PA. The cloud cover and flow off of the Atlantic should result
in markedly cooler afternoon temps Sunday than on Saturday, with
highs likely stuck in the 60s over the Central Mtns.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A trend toward cooler and cloudier weather appears likely into
the middle of next week associated with a cold air damming
scenario ahead of a slow moving warm front in the Ohio Valley
and high pressure over the Canadian Maritimes.

As for rainfall, a weak shortwave and associated plume of
enhanced pwats overrunning the warm front could produce
scattered showers Sunday night into early next week. Upsloping
flow could also yield patchy drizzle over the Central Mtns early
next week. The best chance for rainfall will come during the
middle of the week as an upstream trough approaches the region.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
A few scattered high clouds are lingering across the airspace
this evening, but most sites will see mainly clear skies tonight
into tomorrow morning. Current model soundings suggest that fog
will form once again overnight across the northern half of
Central Pennsylvania, with BFD, IPT, and UNV being most likely
to see IFR or lower visibilities. The HREF and GLAMP suggest
that fog could be possible (~30% chance) at sites further to the
south as well, but confidence is low. The fog will dissipate by
14Z and give way to VFR conditions for Friday. Most of Friday
will feature calm winds and clear skies before clouds begin
building into Friday night ahead of a frontal system expected to
approach on Saturday.

Outlook...

Sat-Sun...Valley fog in the morning; scattered -SHRA/TSRA.

Mon-Wed...Scattered showers.

&&

.CLIMATE...
The first day of Autumn 2024 (Fall Equinox) begins at 8:44 am
EDT on September 22nd.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Steinbugl
LONG TERM...Fitzgerald/Bauco
AVIATION...Bauco/Bowen
CLIMATE...Steinbugl/NPB