883
FXUS61 KCTP 160910
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
510 AM EDT Tue Jul 16 2024

.SYNOPSIS...
The heat will peak today across the region as unseasonably warm
air is directed into the state on SW winds. Another round of
thunderstorms with gusty, to locally damaging wind gusts and
hail will move through the Commonwealth this afternoon and
evening.

A cold front will push through on Wednesday with another round
of strong to severe thunderstorms. High pressure will build in
from the Great Lakes and control things for the rest of the
week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Regional sat/radar loop early this morning looks quite similar
to Monday morning with respect to the approach of another MCV
from the Ohio Valley.

Timing of the warm advection arm with the bulk of the convection
headed toward our NW zones is about 2 hours faster than what we
saw Monday morning, though the intensity is fairly similar and
may warrant a Special Weather Statement during the mid to late
morning hours.

Mainly clear skies with patchy fog will start the day
throughout the valleys of northern PA

Temps to start the day will range from the mid 60s over the N
Mtns, to the low and mid 70s across the southern half of the
state, where PWAT values are the highest.

Elsewhere Abundant sunshine will occur this morning into early
this afternoon with the aforementioned, initial band of
convection weakening during the late morning.

Diurnal heating, combined with surging pwats ahead of the
approaching shortwave/MCV, should yield developing tsra during
the afternoon with the highest POPs across the central and
northern part of the state per latest guidance. The strongest
mid level flow and deep layer shear is progged over the northern
part of the state and the best combination of late day
instability/shear is targeted over the northeast part of the
forecast area, where HREF UHEL values are highest, signifying
the best potential storm organization. Line segments producing
severe/damaging gusts will be the main risk into early evening.

More specifically with respect to timing of the convection
today, the latest HREF and its members shows the main round of
storms firing up along a line from Near KELZ south to KFIG, KUNV
and KAOO between 17-18Z before solidifying into a likely line
of storms and plowing across the Susq Valley. A second, weaker
MCS near or just to the south of the Mason Dixon line will
support additional TSRA that could linger through the early
evening hours southeast of the I-81 corridor.

SPC`s SLGT area for today covers all of the CWA except for
Central and NW Warren county.

High temperatures today may be a deg or 2 higher than Monday
based on progged ensemble mean 850mb temps. An approaching
mid/upper level shortwave will be preceded by a dwindling area
of mainly mid and high clouds across the Western Mtns this
morning while the bulk of the Central Mtns and Susq Valley will
stay mostly sunny into the early afternoon.

Scattered afteroon showers and thunderstorms could lead to a
reduction in the heat, at least over the northern part of the
state this afternoon.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
Convection intensity and coverage should wane with loss of
heating tonight, but the region will remain in a ribbon of
anomalous pwats/instability and prone to at least a slight
chance of lingering showers/tsra overnight.

An upper level trough approaching from the Grt Lks will push a
cold front through the region Wednesday, accompanied by a round
of showers/tsra Wed afternoon into Wed evening. Cloud cover and
an early arrival of the fropa should keep the threat of severe
weather low over the northwest part of the forecast area.
However, pre-frontal heating of the a very moist/unstable
airmass, combined with a belt of relatively strong mid level
flow, support a possible threat of severe weather Wed PM across
the eastern counties. Cloud cover and convection should hold
temps down a bit Wednesday, even across the Lower Susq Valley.
However, surging dewpoints ahead of the front could still yield
heat indices near 100F across the southeast counties.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Deterministic guidance converges towards a return towards fair
and seasonable weather with lower humidity Friday as high
pressure builds from the Great Lakes. The bulk of guidance keeps
dry conditions through Saturday morning so have capped PoPs
below SChc (< 15%) through this timeframe.

A stalled front is expected to nudge northward into the weekend,
allowing for a return to diurnally driven convection. Have
capped PoPs mainly to a SChc north of the turnpike Saturday
afternoon/evening with the northward extent of SChc creeping
into portions of the Middle Susquehanna Valley Sunday evening
where the front could continue to drift slightly north.

Model guidance does outline mainly dry conditions for the
majority of the day on Monday; however, diurnally driven
convection cannot be ruled out in the afternoon/evening hours
with the best chances mainly south of I-80. Have capped PoPs at
low-end Chc (20-30%) given some uncertainty wrt boundary
placement and how this will impact any potential convection.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
16/06Z: GOES IR satellite shows valley fog in the vicinity of
KBFD and KIPT - but so far minimal to no restrictions observed
at the terminal. These two sites have the highest probability
for IFR through 10-12Z with VFR prevailing for the most part
elsewhere (patchy 5-6SM visby BR/HZ possible around sunrise).

Showers and t-storms are expected across the airspace from mid
morning through the evening - a few strong/severe storms are
possible with local wind gusts 45-55kt from ~270 degrees. Sub-
VFR cigs are most likely (>70%) at KBFD 06-12Z Wed with better
than 50/50 odds at KJST.

Outlook...

Wed...AM low clouds west. Another round of t-storms with CFROPA
especially central and southeast airfields.

Thu...AM Showers exit southeast; MVFR cigs psbl west bcmg VFR.

Fri-Sat...AM valley fog. Otherwise, no sig wx/VFR.

&&

.CLIMATE...
Daily record max temp of 99F was tied at Harrisburg on 7/15.
Previous record was set in 1995.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for PAZ019-025>028-
034-035-045-046-049>053-058.
Excessive Heat Warning until 8 PM EDT this evening for PAZ036-
056-057-059-063>066.
Heat Advisory from 8 PM this evening to 8 PM EDT Wednesday for
PAZ036-056-057-059-063>066.

&&

$$

SYNOPSIS...Lambert/Dangelo
NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Fitzgerald/NPB
AVIATION...Steinbugl
CLIMATE...Steinbugl