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860
FXUS61 KCTP 130841
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
441 AM EDT Thu Jun 13 2024

.SYNOPSIS...
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High pressure will pass off of the Mid Atlantic coast today, as
a cold front pushes into the Great Lakes. The cold front will
push through Pennsylvania Friday, followed by Canadian High
Pressure building in for this weekend. An anomalous subtropical
ridge is likely to build over the East Coast next week.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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High pressure over the region is supplying the mostly clear
skies, dry air and light winds to allow temperatures to fall
below NBM guidance this morning. Expect daybreak lows to range
from the mid 40s in the coolest valleys of the Alleghenies, to
around 60F in the more urbanized locations of the Lower Susq
Valley. Air/water temps differences approaching 25 degrees will
result in patchy early morning fog in the deep river/stream
valleys of the Alleghenies.

The surface high will drift off the Mid Atlantic coast today,
resulting in a warmer return southwest flow. Upstream satellite
imagery and latest model RH profiles support mostly sunny skies
today and mixing down model 850mb temps of around 16C
translates to expected highs ranging from the low 80s along the
spine of the Appalachians, to the upper 80s in the Susq Valley.
Can`t completely rule out a late day shower/tsra across the
southeast corner of the forecast area, where models indicate
surging pwats and capes near 1000 J/kg. However, dry mid level
air in the model soundings suggest any convection will be
isolated.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
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Falling heights and surging low level moisture ahead of an
upper level trough working into the Grt Lks could spread a
shower into the N Mtns toward dawn Friday. Otherwise, fair
weather is anticipated, with markedly milder conditions than
recent nights in the warm advection regime ahead of the trough.
Mostly clear skies, light wind and rising dewpoints may lead to
some patchy late night valley fog in the central part of the
state per latest SREF prob charts.

All model guidance pushes the upper trough and associated cold
front through Central PA Friday, accompanied by a good chance of
showers and possible tsra. The 00Z HREF holds precip off until
afternoon over the southeast half of the forecast area, allowing
temps to rise above seasonal normals, while an early arrival of
showers is likely to cap temps in the low 70s across the N
Mtns. Modest instability and decent mid level flow supports a
chance of isolated severe weather Friday afternoon over the
southeast part of the forecast area, where HREF UH values >75
supports organized convection.

Strong large scale forcing ahead of the upper trough and
seasonably high pwats support POPs in the 60-80pct range Friday
over most of Central PA. Latest ensemble plumes indicate just a
few tenths of an inch rainfall for most locations, with isolated
amounts of 2+ inches possible from heavier tsra based on the
HREF LPMM.

Any evening showers/tsra over the southeast counties should end
shortly after sunset Friday, as the cold front exits the state.
Canadian High Pressure building in behind the front should
bring clearing skies and cooler air Friday night. Abundant
sunshine and seasonal temps are expected Saturday, as the high
pressure system and associated low-pwat air mass builds into the
region.

The center of high is progged to pass over Central PA Saturday
night, resulting in favorable conditions for radiational
cooling and low temperatures in the upper 40s and low 50s. This
will be the last time we see temperatures in the 40s in PA for
the foreseeable future.
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&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Dry conditions are expected to prevail through Tuesday
afternoon outside of some isolated diurnally driven showers
across the northern tier Monday afternoon and across much of
north and western PA Tuesday afternoon.

An extended period of above average temperatures is
increasingly likely as a large ridge builds across the eastern
US. This will allow for MaxTs and MinTs +10-15F above
climatology for the middle of June. There remains some model
difference with respect to the strength of the ridge, but
generally better agreement of abnormally warm temperatures
extending northward into PA.

Less humid conditions on Monday will bring heat index values
into the upper 90s, with some locations across southern PA
pushing close to the 100F mark. Humidity during the afternoon
hours will increase the risk for excessive heat on Tuesday with
some potential for heat index values in the 100-105F across the
Lower Susquehanna Valley. Humid conditions will continue into
Wednesday with heat index values slightly lower than Tuesday,
but still anomalously warm even for this time of the year. The
Climate Prediction Center has placed much of eastern PA in a
Moderate Risk for Excessive Heat for the middle and end of next
week, outlining the longevity of heat across the region.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
VFR will continue today through tonight as a result of a ridge
of sfc high pressure extending from the Delmarva Coast into
Central PA. There is a low probability (20 percent) for MVFR
VSBYS in light fog from radiational cooling of the ground in
the vicinity of KBFD this morning.

The ridge of high pressure will shift a bit to the east today
and tonight, causing a light and minimally gusty south to
southwesterly flow to develop.

Periods of generally thin cirrus will top flat cu (based between
4000-5000 ft agl) that will for during the late morning through
late afternoon hours.

A a period of scattered to numerous showers and TSRA will occur
on Friday with a cold front (mainly during the late morning and
early afternoon (NW PA) through the late afternoon/early evening
in the SE.

Timing of the system and the lack of real high dewpoints may
limit the coverage and intensity of the showers and storms.
Activity quickly clears out to the east Friday evening.

A dry weekend is shaping up with VFR conditions.

Perhaps a shower or storm late Monday, as a warmer airmass
is advected eastward toward PA.

Outlook...

Fri...Restrictions possible in CB/TSRA.

Sat-Sun...Predominantly VFR.

Mon...Mainly VFR, chance of convection mainly northwest.

&&

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

&&

$$

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