360
FXUS61 KCTP 281038
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
638 AM EDT Fri Jun 28 2024

.SYNOPSIS...
Seasonable temperatures and comfortable humidity will close out
this workweek. Strengthening south to southwesterly winds
through a deep layer of the atmosphere will transport increasing
heat and humidity for Saturday and help to fuel strong to
locally severe Thunderstorms. Look for a dry start to July with
a return of heat and thunderstorms by the 4th.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today starts out on the chilly side (north) to comfortable in
the south with temperatures ranging from the mid to upper 40s
across the Northern Mtns to between 55 and 60 in the southern
valleys.

Some minimal valley fog was noted throughout the deeper river
valleys of northern PA.

Variable amounts of cirrus and cirrostratus will stream southeast
across the region this morning, followed by some periods of
opaque alto cu clouds during the midday and afternoon hours as
mid level warm advection increases after a ridge of high
pressure slides off to the east.

Highs temperatures today will range from 75-85F.

&&

.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
GEFS and NBM indicates an increasing/anomalously strong
south/SSW llvl return flow developing for later tonight through
Saturday with the anomaly of the LLVL v-component reaching
around plus 3 sigma across northern PA and a solid 2+ sigma
elsewhere across Central and Southern PA Saturday afternoon and
evening.

Latest model data suggests 30-40kt LLJ from the south-
southwest will drive some showers and elevated t-storms over
west central PA later tonight into early Saturday morning.

This strong vertical speed and directional shear coupled with
increasing meso-B lift associated with the Right Entrance region
of a 100+ KT jet to our north will support the likelihood of
another fairly widespread strong to severe convective events
with a distinct threat for isolated tornadoes with discrete
cells, BKN-S signatures that are accompanied by a near
perpendicular deep layer shear component to their long axis.

SPC not only expanded the SLGT risk across all but our far SE
CWA, but also introduced a 5% TOR threat across roughly the NW
40 percent of PA.

The belt of strong 850mb flow will transport rich low level
moisture (dewpoints in the upper 60s to lower 70s) northeastward
along/ahead of a cold front this weekend. PWAT values are
forecast to reach 2-2.5 inches on Saturday or +2-3SD. The
anomalous, deep-layer moisture will support risk of heavy to
potentially excessive rainfall with point amounts of 3 inches
possible in places experiencing multiple TSRA.

WPC has maintained a broad MRGL risk, but the setup will likely
yield an upgrade to SLGT risk particularly where FFGs are
reduced. Although mid lvl lapse rates may remain weak, high
dewpoints and diurnal heating should fuel at least moderate
buoyancy by mid/late afternoon.

The influence of early day clouds/waning overnight convection
could be a key/limiting factor. The mid level cap is similar in
strength to our past SVR event this past Wednesday with 700 mb
temps in the 8-9.5C range and weak broad scale forcing until the
afternoon/evening arrival of the better omega field beneath the
favorable RR Quad of the aforementioned ULVL jet.

Convection should decrease in coverage and intensity into
Saturday night, which will be warm and muggy with lows 65-75.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
On the large-scale, a fairly zonal upper-level flow pattern
will stay in tact over the northern tier of states next week,
with energetic short-waves traversing this flow every 3-4 days
or so. Consequently, expansive summertime upper ridging will
largely stay south of PA, keeping excessive heat mainly out of
the forecast for the time being.

Looking at the daily sensible weather, as one of the above
mentioned short-waves presses through eastern Canada and New
England early next week, it will push a surface cold front well
to the southeast of the Commonwealth, bringing another stretch
of dry conditions and comfortable temperatures/humidity levels
for Monday and Tuesday. Confidence in this scenario is
relatively high.

By the middle of next week, as a surface high pushes offshore
and heights aloft begin to build, summertime heat and humidity
should at least temporarily make a run at PA. At the same time,
though, the next upstream surface cold front and upper-level
trough will be approaching from the northwest. The most likely
scenario here is for increasingly muggy conditions and higher
chances for showers and thunderstorms. Just how hot temperatures
are able to get, or robust convection becomes, is fairly
uncertain. Better knowledge of these factors will require
considerably more time and additional model runs to see how
atmospheric features resolve themselves during this time frame.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
VFR conds will prevail through Friday with primarily high
cirrus and fair weather cu expected. The exception will be
patchy valley fog in the northern Alleghenies early this
morning. Winds will start the day light and variable, then veer
to become S to SE later in the day on Friday with gusts
generally less than 20 kts.

As a warm front approaches late Fri night into Saturday,
southeast flow will bring increasing moisture and the potential
for low stratus across southern and eastern PA. Confidence is
relatively high in restrictions after 06z Sat for airfields from
UNV eastward, with a 25-50 percent chance of IFR conditions at
MDT and LNS. Overnight rain and some thunder is possible
especially in the north, mainly after 06z. Some marginal LLWS
is also possible mainly in the north.

The low stratus is expected to lift and become broken to
scattered before more numerous showers and thunderstorms
develop later on Saturday. The chance for showers and storms
will linger across the southeast into Sunday as a cold front
swings through the area.

Outlook...

Mon-Tue...Dry weather with VFR conditions.

&&

.CLIMATE...
Through 6/26, June ranks as tied for the second warmest on
record at Harrisburg.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...Lambert
SHORT TERM...Lambert/Steinbugl
LONG TERM...Jurewicz/Steinbugl
AVIATION...Martin/Colbert
CLIMATE...Steinbugl