398
FXUS61 KCTP 131506
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1106 AM EDT Thu Jun 13 2024

.SYNOPSIS...
High pressure will pass off of the Mid Atlantic coast today, as
a cold front pushes into the Great Lakes. This front will cross
Pennsylvania on 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, bringing
increased heat and humidity.

&&

.NEAR TERM /UNTIL 11 PM THIS EVENING/...
Surface high pressure will drift off the Mid Atlantic coast
today, resulting in a warmer southwesterly flow.

Cu is quickly developing over the Lower Susq Valley in a
slightly muggier airmass (sfc dewpoints in the mid 60s). Can`t
rule out a late day shower/tsra down there, as models indicate
surging pwats and capes topping out near 1000 J/kg. Dry mid
level air in the model soundings, however, suggests that any
convection will be spotty.

Mixing down model 850mb temps of around 16C this aftn translates
to highs ranging from around 80 degrees along the spine of the
Appalachians to the upper 80s in the Susq and Cumberland
valleys.

&&

.SHORT TERM /11 PM THIS EVENING THROUGH 6 PM FRIDAY/...
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 late tonight. 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. Precip is expected to hold off until
afternoon across the southeastern half of the forecast area,
allowing temps to rise above seasonal normals, while an early
arrival of showers is likely to cap max temps in the low to mid
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. SPC has
highlighted the southeastern third of PA with a SLGT risk for
severe storms, with the primary threat being from potentially
damaging wind gusts.

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
1-2+" amounts in any storms.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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.

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 /15Z 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.

The ridge of high pressure will shift a bit to the east this
afternoon 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 form during the late morning
through late afternoon hours.

Areas of BKN100-120 Alto Cu spreads across the region overnight
as warm advection increases in the mid levels of the atmosphere.

Strongest LLVL pressure gradient will edge into NW PA late
tonight and will likely result in LLWS at KBFD around and
after 04Z Fri.

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/Evanego
NEAR TERM...Fitzgerald/Evanego
SHORT TERM...Fitzgerald/Evanego
LONG TERM...Fitzgerald/Banghoff/NPB
AVIATION...Lambert