461
FXUS61 KCTP 161843
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
243 PM 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 10 PM THIS EVENING/...
Convection currently struggling to break the cap. High shear in
the nrn tier still warrants keeping an eye on things there for
another 1-2hrs, though. The shear may be too much and the heat
not enough in the N for storms to hold together long enough to
make good up/downdrafts. EHI is high right along the border, but
only for another 1-2hrs, also. Temps has dipped (tempo) to 74F
at BFD after they got a brief shower and those thicker clouds.

The cu are even more shallow to the S. Expect the congestion in
the clouds assocd with some convergence near the sfc from JST-
AOO-MDT to pop a few cells shortly. CAPE is climbing as heat is
almost to it`s peak. Heat index values are over 100 in many
places SE of UNV, and right at 105 in the urban areas. These
cells may grow tall enough to get some stronger up/downdrafts
(DCAPE >1000J there). The forcing stretched to the S of the line
of convection over BGM`s area is starting to light up, so they
could also see some tall storms in the next few hrs.

&&

.SHORT TERM /10 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
All this convection should wane as the sun sets or even before,
lasting longest in the S along the Turnpike/MD border. Lack of
clouds tonight could again make some valley fog, but lack of
rainfall today will be a tick in the negative column. Showers
may impinge on the wrn highlands by sunrise.

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, the pre-frontal heating of the a very moist/unstable
airmass, combined with a belt of relatively strong mid level
flow, will support a threat of severe weather Wed PM across the
southeastern counties. Cloud cover and convection should hold
temps down a bit Wednesday, even across the Lower Susq Valley.
The Heat Advy currently up for that area for Wed will be
allowed to continue as surging dewpoints ahead of the front
could still yield heat indices near 100F across the southeast
counties. PWs of nearly 2" in the SE could help feed very heavy
downpours. But, the fast storm motions and very high FFG
(widespread 4.5"/3 hrs values) keep the threat for flash
flooding low. The MRGL risk in the Day2 ERO was collaborated
with WPC, mainly in order to keep continuity with previous
forecasts.

Wed PM looks like the cfropa occurs for all but perhaps a few
towns on the MD border. Thus, the SHRA should press mainly or
entirely to the S of the border well before sunrise. Dropping
dewpoints may keep the threat of fog low, but the temps drop
right along with them. Have not added it into the wx grids at
this point.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Deterministic guidance converges towards a return towards fair
and seasonable weather with lower humidity during the day
Thursday 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 /19Z TUESDAY THROUGH SUNDAY/...
Current convection chances for the initial forecast period are
highest (>60%) near KBFD. Lesser chances (30%-40%) toward KUNV
and KIPT. Added VCTS wording to these airfields to account for
any isolated thunder that does develop.

Generally dry conditions will keep any overnight fog to a
minimum. Place VCFG in KIPT as the airmass has not changed and
expect similar conditions to last night.

The tail end of the forecast period includes a drop to MVFR for
most locations as a cold front approaches the region.

Outlook...

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...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Fitzgerald/Tyburski
AVIATION...Tyburski
CLIMATE...Steinbugl