835
FXUS61 KCTP 031853
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
253 PM EDT Wed Jul 3 2024

.SYNOPSIS...
High pressure will push off of the Mid Atlantic coast today. A
dying cold front will push in from the Great Lakes tonight,
then stall out over the area late this week. Low pressure
tracking north of Pennsylvania will drag a cold front through
the state Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Midlevel ACCAS tells of the increasing deep layer moisture
across central PA this morning as H5 ridge axis retreats
eastward. 850mb temps on the rise, too and there will be a
noticeable uptick in humidity by this afternoon as a southerly
flow increases ahead of a weak cold front over the Great Lakes.
Diurnal heating and surging low level moisture should result a
fair amount of afternoon cumulus, especially over the western
mountains.

Temperatures will be a few degrees above normal over the W Mtns
and near average elsewhere, translating to highs well into the
80s areawide. Moisture advection and low level convergence along
an approaching low level jet could potentially support a
shower or thunderstorms in northwest PA this evening. A cold
front will move into the region overnight and weaken as it
approaches. It will help focus the potential for showers and
thunderstorms mainly north and west of the I-99/I-80 corridor
through daybreak Thursday. Rainfall amounts should generally
remain less than a quarter inch, but isolated amounts over 0.75
inches are possible. Clouds and increasing humidity will result
in low temperatures in the mid 60s to lower 70s by Thursday
morning.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
A mostly cloudy day is in store for the Fourth of July with a
noticeable uptick in humidity. Dewpoint temperatures will soar
into the 70s across much of the region. Morning showers and
storms associated with the decaying cold front will gradually
move southeast through the day and should remain scattered in
coverage. The front will be located over southern PA by Thursday
afternoon, which is where most of the shower activity should be
concentrated for any 4th of July and/or fireworks festivities.
Highs on Thursday afternoon will generally be in the 80s with a
few spots potentially reaching 90 degrees in the southeast
before convection arrives.

The threat for severe weather and flash flooding remains
relatively low and is maximized (Marginal risk) along and south
of I-76. The realization of any downburst winds or flash
flooding will likely be contingent on some breaks in the clouds
to generate instability. Bulk shear near the front will be
sufficient for organization, but CAPE may be lacking owing to
persistent cloud cover. Regardless, the chance of showers and
storms should be monitored for anyone who plans to take part in
outdoor festivities to celebrate Independence Day.

The front is progged to stall out in the vicinity of Southern
PA Thursday night, then return north as a warm front Friday
ahead of low pressure lifting across the Grt Lks. Falling
heights and surging pwats ahead of an upstream shortwave and
associated surface low lifting across the Grt Lks should bring a
round of showers/tsra in the Friday PM to Saturday timeframe.
Current guidance suggests the 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.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
Deterministic guidance continues to outline fair and seasonable
conditions on Sunday and into early Monday with surface ridging
and drier air working in behind the frontal passage. There is a
bit of uncertainty into the later hours on Monday as ECMWF
guidance outlines drier conditions prevailing across all of
central PA, with GFS outlining some showers and thunderstorms
Monday late afternoon/evening across mainly southern
Pennsylvania where moisture and lift will be slightly more
favorable. Given some uncertainty, have mainly kept PoPs
confined along the Turnpike and the higher elevations of
Schuylkill County for this forecast cycle, slightly cutting back
from NBM PoPs in this timeframe.

Both ENS and GEFS plumes begin to outline greater chances for
precipitation into Tuesday, as a low pressure north of the area
continues to push eastwards and drag a cold front across the
region. Some instability will bring some potential for storms
especially in the afternoon/evening hours, but cannot rule them
out throughout the morning hours during this forecast cycle.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
VFR conditions will prevail with moderate (50-60%) confidence
this evening with southerly flow gusting 15 to 20 knots. A cold
front will approach tonight and lay out W-E over the state on
Thursday. The deep moisture Wednesday PM and Thursday will
allow for scattered to numerous showers and thunderstorms.
Outlined KBFD/KJST with SHRA/VCTS due to the development of the
complex currently south of KCLE moving eastward. The first batch
of showers is expected to fizzle as it moves southeast through
tonight, with additional showers and storms developing in the
humid environment on Thursday, especially south of KBFD.

The 18Z package outlines potential for IFR conditions based on
low cigs in the 10-16Z where increased low-level moisture
coupled with calm-to-light winds late overnight. Lower
confidence (30-40%) on IFR conditions prevailing, due to some
residual cloud cover and/or rain narrowly missing the airfield.
There is lower confidence on exact coverage and placement of
SHRA/TSRA on Thursday, thus have kept it out of the 18Z TAF
package.

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...DeVoir/Fitzgerald
NEAR TERM...DeVoir/Fitzgerald/Banghoff
SHORT TERM...Fitzgerald/Banghoff
LONG TERM...Fitzgerald/Beaty
AVIATION...Beaty/Bruce/Stanley