696
FXUS61 KCTP 050226
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1026 PM EDT Thu Jul 4 2024

.SYNOPSIS...
Warm and humid conditions will prevail through Saturday with
daily chances for showers and thunderstorms. A few storms could
produce strong winds and heavy rainfall on Friday. Low pressure
tracking north of Pennsylvania will drag a cold front east of
the state on Saturday, ushering in drier and more comfortable
conditions for Sunday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A few clusters of showers and isolated thunderstorms across
south central PA and far northwest PA late this evening. Outflow
boundary just south of the office late this afternoon is helping
keep activity just to the south of State College for a nice
view of local firework show.

The activity has been weakening, and expect this trend to
continue.

Very high dewpoints will limit temperature drop overnight.
Current low temps look to be on track.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Mid evening update.

Did cut POPS down for the morning hours, hard to see much going
on at this time of day, with warm mid levels.

Also did edge high temperature up a small amount, given the
airmass in place, and that I cut down the chc of showers and
storms in the morning hours.

Earlier discussion below.

Leftover outflow boundaries, increasing/swrly deep layer shear
and healthy CAPE in the afternoon will set the stage for more
Showers/TSRA later in the day.

Previous...

The stalled front over Central PA is progged to return north as
a warm front Friday PM ahead of low pressure lifting across the
Great Lakes. Falling heights and surging pwats ahead of an
upstream shortwave and associated surface low lifting across the
Great Lakes should bring a round of showers/tsra in the latest
Friday PM to Saturday AM timeframe. Model shear/instability
profiles indicate strong to severe tsra can`t be ruled out Fri
PM. SPC expanded the previous DY2 MRGL risk area for SVR to
cover all but the far eastern parts of our CWA.

Current guidance suggests the mid level shortwave and bulk of
the large scale forcing will pass north of PA, leading to
unimpressive mean qpf in the ensemble plumes of 0.25 to 0.50
inches Fri PM to Saturday. However, locally heavier amounts will
accompany stronger convection. The Weather Prediction Center
has placed all of Pennsylvania in a Marginal Risk of Excessive
Rainfall for 8am Friday through 8am Saturday to account for
the multiple rounds of showers and potential for rainfall
amounts approaching 2 inches in a few spots. Flash flood
guidance across most of the region remains quite high (3" or
more in 3 hours), so most of this rainfall should be beneficial.

It is also worth noting that heat index values will approach
or briefly touch 100F on Friday afternoon in southeast PA.
Dewpoints in the low to mid 70s combined with high temperatures
approaching 90 will result in a very hot and humid afternoon.
With scattered convection in the forecast, there is not yet
enough confidence to warrant a heat advisory but one may need to
be considered if temps/dewpoints trend higher. Overnight lows
into Saturday will also be quite mild, ranging from the upper
60s in northwest PA to the middle 70s in the Lower Susquehanna
Valley.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Models show some variation from day to day, but main hint
is that the eastern part of country is in a weakness at 500 mb.

While we may still be warmer than normal, there will be a
tendency to see at least some showers and storms from time to
time. As noted below, after Friday, a decrease in dewpoints will
result in a lower chance of showers and storms for the weekend.

Main chance for showers and storms will be in the Tuesday to
Wednesday time frame.

Earlier discussion below.

The aforementioned cold front is expected to mostly clear the
region by Saturday morning, but some lingering showers across
eastern Pennsylvania cannot be ruled out. Thunderstorms are
slightly less likely at this time given increased cloud cover
and lower instability of the early morning hours, but cannot
rule out a thunderstorm across far southeastern Pennsylvania
with some elevated instability. After the cold frontal passage,
cooler and less humid air will rush in by Sunday morning.

All medium range guidance supports fair weather and above
average temperatures Sunday into early next week with upper
level ridging indicated over the northeast. At the surface, high
pressure is progged to build over Pennsylvania Sunday, then
pass off of the east coast early next week. The return southerly
flow should result in an uptick in heat/humidity early next
week.

Diurnally driven showers and thunderstorms appear possible on
Monday based on recent GEFS plumes but guidance continues to
suggest a better chance of precipitation on Tuesday with the
arrival of a cold front during the afternoon hours. There is
still a fair amount of uncertainty with regards to the cold
front clearing eastern Pennsylvania later on Wednesday, so have
retained PoPs through this timeframe. Towards the end of the
period, deterministic guidance begins to outline high pressure
influence into the region; however, given so much uncertainty
earlier in the forecast period have opted not to deviate from
NBM PoPs at this time.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Showers and a few thunderstorms over the southeast will continue
to push off to the east into the late evening and will largely
be out of the area by 03Z. Another area of weakening showers is
moving in from the west ahead of an MCV located over western PA.
Most guidance indicates that a few showers will remain possible
across the northwest through the night.

Fog and low ceilings will likely develop across almost all of
Central PA overnight. The highest probabilities for IFR
visibilities are at BFD and IPT, and the highest probabilities
for IFR ceilings are at BFD, IPT, and JST. All other sites will
likely see MVFR conditions tonight with brief periods of IFR
possible.

Conditions will improve to VFR fairly quickly after sunrise
across most of the area, though it could take until late morning
for BFD and IPT to see the low ceilings improve. Scattered
showers and thunderstorms will be possible again Friday
afternoon, though coverage looks to be more limited than today.

Outlook...

Fri...Sct TSRA w/ possible impacts; Mainly PM w/ highest
coverage across the west.

Sat...Sct to Nmrs TSRA areawide, highest chances SE in PM.

Sun...AM fog possible; otherwise, no sig wx.

Mon...SHRA possible SE late PM; otherwise, no sig wx.

&&

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

&&

$$

SYNOPSIS...Lambert/Banghoff/Martin
NEAR TERM...Martin
SHORT TERM...Lambert/Banghoff/Martin
LONG TERM...Fitzgerald/Martin/NPB
AVIATION...Bauco