725
FXUS61 KCTP 181933
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
333 PM EDT Thu Jul 18 2024

.SYNOPSIS...
High pressure will bring mainly fair weather with seasonable
temperatures through the end of the week. Humidity increases
a bit this weekend with some areas seeing a scattered shower
or thunderstorm on Saturday, but most areas will remain dry. The
next best chance for rainfall will come late Monday and Tuesday
of next week as a slow moving frontal system lifts across the
region.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Comfortably lower dewpoints are pushing into the Lower Susq
River Valley this afternoon, with upper 50s soon replacing mid
to upper 60s dewpoints that are still over southern and eastern
parts of York and Lancaster Counties.

A bit of high cloudiness could linger into this evening over
the eastern counties, but mainly clear skies eventually win out
later tonight with the passage of the upper trough. Surface
ridging and an associated low PW air mass 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.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
Another day of tolerable warmth and generally comfortable
humidity levels is in store on Friday, thanks to high pressure
over the region. An approaching warm front is likely to spread
increasing clouds/humidity into at least Southern PA Friday
night, but the odds of any rain look slim, at least until
Saturday when isolated to scattered coverage of shra/tsra
develops over parts of the Laurels, SC Mountains and Central
Mountains. Temps start to creep up on Saturday, along with
dewpoints, but will be even more pronounced on Sunday as high
temps across the south approach 90 once again Sunday afternoon.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
With the large-scale, upper-level pattern next week, it appears
that amplified ridge axes will stay in place across the
Intermountain West, as well as from the Southwestern Atlantic
into the Southeastern CONUS. In between these two ridge axes, a
mean upper-level trough axis will extend from Eastern Canada
into the Midwest and the Ohio Valley.

In general, the above described pattern will keep excessive
heat suppressed to the south and southwest of the Commonwealth.
However, southwesterly flow aloft will bring increasingly humid
conditions locally. Also, the proximity of the aforementioned
upper trough, as well as several surface fronts, will bring the
likelihood of diurnally driven (mainly during the afternoon and
evening hours) showers and thunderstorms, especially in the
Tuesday-Thursday time frame. The silver lining here is that
additional beneficial rains could be in the offing for drought
stricken sections of PA.

For the most part, we can expect daytime highs in the 80s and
overnight lows in the 60s, which is rather seasonable for mid to
late July. Some of our northern mountainous areas may see
afternoon highs stay in the upper 70s, while normally hotter
sections of the Lower Susquehanna Valley could sneak into the
lower 90s.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
18z update... There is high confidence (80-90%) of
VFR/unrestricted conditions across Central PA through the day
on Friday.

There are two small flies in the ointment. First, patchy MVFR
ceiling bases are out there early this afternoon in the
Alleghenies. Thus, we did add a short window for this
possibility at KJST through 19-20z. Second, at least patchy fog
is likely late tonight into early Friday across Northwest PA. As
a result of this, we added a small window at KBFD for fuel
alternate-IFR visibilities.

NW surface winds 5-10 kt this afternoon, should become
light/nearly calm overnight and Friday.

Outlook...

Sat through Mon... Primarily VFR/unrestricted conditions. Patchy
late night/early morning fog and low ceilings are possible.
Tue... More widespread afternoon and evening showers and
thunderstorms could lead to at least brief restrictions.

&&

.CLIMATE...
The max temperature hit 100 degrees at Harrisburg Tuesday,
7/16/24. The last time KMDT hit 100 was back on July 19, 2020.

&&

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

&&

$$

SYNOPSIS...DeVoir/Bowen
NEAR TERM...DeVoir/Fitzgerald
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...Jurewicz
AVIATION...Jurewicz
CLIMATE...Steinbugl