175
FXUS61 KCTP 181729
AFDCTP

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

.SYNOPSIS...
- A cold front will exit Southeast PA early today.

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

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Sfc cold front has settled southeast of the Lower Susq at mid
morning, with a secondary trough/moisture boundary draped across
the SC Mountains through the ridge and valley region, separating
lower 60s dewpoints from upper 60s/lower 70s dewpoints over the
Lower Susq. Plenty of clouds streaming across central and
southeast portions of the area, and a sprinkle can`t be ruled
out over the SC and SE along and ahead of the aforementioned
boundary, but by and large it will be a drier and more
comfortable day for most in the wake of the exiting FROPA.

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.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
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 /SUNDAY NIGHT THROUGH WEDNESDAY/...
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 /18Z 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...Fitzgerald
LONG TERM...Jurewicz
AVIATION...Jurewicz
CLIMATE...Steinbugl