172
FXUS61 KCTP 150637
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
237 AM EDT Sat Jun 15 2024

.SYNOPSIS...
Canadian high pressure will push southeast into Pennsylvania
this weekend, then an anomalous subtropical ridge will build
over the East Coast next week.

&&

.NEAR TERM /THROUGH TODAY/...
The upper trough and associated cold front have exited the
southeast part of the forecast area as of 06Z. Large scale
subsidence behind this feature will ensure fair weather the rest
of the night. Breaking clouds, light wind and wet ground from
yesterday`s rainfall has resulted in fairly widespread valley
fog early this morning. Latest SREF prob charts indicate the
fog is likely to persist where it has formed through around
12Z.

The driest air and weakest pressure gradient lies over the NW
Mtns, where radiational cooling should result in daybreak min
temps around 50F. Elsewhere, expect min temps in the 50s to
around 60F across the Lower Susq Valley.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
Canadian high pressure building southeastward into PA will
bring fair weather this weekend, with a good deal of sunshine,
seasonably warm days and low humidity. Dry air above a weak
inversion in the model soundings suggest dewpoints will fall
below NBM guidance both Saturday and Sunday afternoon, so have
leaned toward the drier MAV guidance.

Ideal conditions for radiational cooling appear likely tonight
under the surface high, resulting in min temps a few degrees
below NBM guidance. Have therefore leaned toward the cooler MAV
numbers, with lows ranging from the low 40s in the coolest
northern valleys, to the mid 50s in the more urbanized locations
of the Lower Susq Valley.

The surface high should pass east of PA Sunday, resulting in a
slightly warmer return southerly flow. Model 850mb temps near
14C support highs a few degrees higher than today, with max
temps ranging from the mid 70s over the mountains north of KIPT,
to the low 80s most other locations. Warm advection will be
underway Sunday night, with low temps in the upper 50s to low
60s.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Little change with the late evening update outside of limiting
chances of diurnal showers/storms on Tuesday. Have kept chances
into the middle/end of the week due to some uncertainty.

Prev..

Confidence is increasing for a heat wave next week with the
potential for 4-6 consecutive days of MaxT 90F+ across much/all
of central PA. The prolonged nature of this heat wave may have
cumulative adverse effects on vulnerable populations exposed to
heat, with heat related illnesses possible if proper precautions
are not taken. Outdoor workers and individuals with preexisting
health conditions will be among those most at risk.

Moisture may be slow to advect into the region initially, with
dewpoints Monday afternoon expected to be in the range of
60-65F. Thus Mon heat index values are forecast in the mid to
upper 90s, with some valley locations across central/southern PA
pushing close to the 100F mark.

Tuesday through Thursday (and potentially Friday-Saturday) are
progged to be the warmest days of the week, with most guidance
showing a 595-600 dm 500 hPa ridge centered over the area.
Southerly flow will usher in higher dew points Tuesday that will
allow for heat index values to reach 100-105 degrees over a
large portion of the area. With the large high pressure system
overhead, winds will be light and clouds will be few. Keep in
mind that the sun angle will be at its max next week as we
approach the summer solstice. The intense sun and lack of a
breeze will exacerbate the impacts of heat. Beyond Thursday,
uncertainty begins to develop regarding the shape of the ridge
and the possibility of convection firing along the periphery of
the high pressure system, but the potential for highs in excess
of 90F continues through Saturday.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
06z update... Now that a cold front has pushed to the south and
east of the Commonwealth, skies have cleared out for the most
part. However, satellite imagery and surface observations have
depicted patchy valley fog in the pre-dawn hours, especially
where heavier rainfall occurred Friday afternoon and early
evening. For this reason, we have moderate confidence (40-60%)
in at least MVFR visibility restrictions through about 12z. At
this time, KUNV and KIPT seem to be the most likely sites to see
at least brief IFR restrictions.

Any fog patches should burn off quickly by 12-13z, given a deep
layer of dry air aloft and the expectation of large-scale
sinking motion. There is high confidence of VFR conditions
(90+%) for the remainder of the valid TAF period (through 06z
Sunday).

Surface winds should be light (mostly under 5 kt) through
13-15z, then pick up out of the NW to 8-10 kt, before
diminishing again by/after 00z.

Outlook...

Sat-Wed...Predominantly VFR, with building heat next week.

&&

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

&&

$$

SYNOPSIS...Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Colbert/NPB
AVIATION...Jurewicz/Evanego/RXR