645
FXUS61 KCTP 180757
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
357 AM EDT Thu Jul 18 2024

.SYNOPSIS...
- The cold front will continue to trek across central PA
   tonight along with a band of mainly stratiform rain showers.

 - Patchy fog is possible tonight mainly across the NW
   mountains and Allegheny Front.

 - High pressure will build in from the Great Lakes on Thursday
   and bring mainly fair weather with seasonable temperatures
   through the end of the week.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
A cold front, which lies across the N Mtns at 07Z, will press
southeast across the forecast area early this morning. There is
strong large scale forcing ahead of the associated upper trough.
However, SPC mesoanalysis indicates virtually no instability, so
expect nothing more than an isolated shower across the southern
half of the forecast area during the pre-dawn hours. Valley fog
appears likely to remain confined to the Alleghenies, with a
decent pressure gradient keeping breeze up further south and
east. Temperatures are on track to bottom out from the mid 50s
in the coolest valleys of the NW Mtns, to around 70F across the
Lower Susq Valley.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH FRIDAY NIGHT/...
The cold front is progged to exit the southeast corner of the
forecast area by noon, with a much drier northwest flow
ensuring fair weather the rest of the day. Upstream satellite
imagery and model soundings indicate cirrus will continue to
stream into PA ahead of the upper trough approaching from the
Grt Lks. Therefore, partly sunny wording should suffice for most
of the region. Model soundings indicate mixing this afternoon
to 800mb, where model temps support highs from the mid 70s
across the N Mtns, to the mid and upper 80s in the Lower Susq
Valley.

A bit of high cloudiness could linger into this evening over the
eastern counties, then mainly clear skies are anticipated with
the passage of the upper trough. The arrival of surface ridging
and an associated low-pwat airmass should result in the coolest
night we have seen a quite a while. The weakest gradient and
most efficient radiational cooling is anticipated over the NW
Mtns, where we have slightly undercut NBM min temp guidance.
Air/water temp differences of >25 degrees should result in
patchy late night fog in the deep river/stream valleys of the
Alleghenies.

Fair and seasonable conditions with light winds are expected
Friday, as high pressure ridge remains over the state. An
approaching warm front is likely to spread increasing clouds
into at least Southern PA Friday night, but the odds of any rain
look slim.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
On Saturday, there could still be enough moisture working into
the state from the south that a shower or two could develop over
the SE and/or ridge-and-valley region if the ridge tops can help
nudge the moisture high enough. It`s only worth a 20pct chc at
this point based both on coverage and probability. This is the
only mar in an otherwise stellar weekend forecast.

During the early part of the new week, the humidity levels will
creep back up as the deep upper low over ern Canada slides a
little more to the east and the Bermuda High pushes moisture
farther to the north and into the state. The stationary
boundary to our south may struggle to move northward, so we`ll
keep the increase in precip chances slow for the time being.

Overall, we will see muggy nights again by mid week and a
gradual increase in cloud cover and PoPs. By Wed, PoPs get close
to 70pct. Confidence is higher than normal in the extended
pattern. Of course, confidence is lower on the day- to- day
details. But, normal diurnal trends in convection have been
leaned on for most of the long range.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
Convection and relatively widespread rain showers dwindling
across the Lower Susq airspace and will done by 06z/18.

There is decent model signal for post- frontal upslope low MVFR
cigs particularly at KBFD and KJST. With the widespread
rainfall today, expect a good deal of light valley fog
overnight, and potential IFR fog impacts at KBFD/KIPT late
tonight into early Thursday morning.

Outlook...
Thu...MVFR cigs psbl northwest 1/2; low VFR elsewhere.

Fri-Mon...AM valley fog. Otherwise, no sig wx/VFR.

&&

.CLIMATE...
The max temperature hit 100 degrees at Harrisburg yesterday
7/16. The last time KMDT hit 100 was back on July 19, 2020.

&&

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

&&

$$

SYNOPSIS...Bowen
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Bowen
LONG TERM...Dangelo/Gartner
AVIATION...Steinbugl/Gartner
CLIMATE...Steinbugl