-- Discussion containing changed information from previous version are highlighted. --
605
FXUS61 KCTP 230323
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1123 PM EDT Sat Jun 22 2024

.SYNOPSIS...
*Ongoing heat wave peaks this weekend with some relief in sight
 for Monday
*Severe thunderstorm risk will ramp up over the weekend with
 scattered damaging winds most likely Sunday afternoon/evening
*A shorter duration summertime hot spell will precede a round of
 t-storms into the middle of the last week of June

&&

.NEAR TERM /UNTIL 8 AM SUNDAY MORNING/...
Meso models handling the isold/sct convection moving up into the
south-central mtns very well. Severe wx is unlikely with this
stuff. The forcing for these cells will slide up and over
Harrisburg Metro area over the next few hours. Precip should be
spotty and mainly light. Training cells over Bloomsburg/Berwick
are producing mainly light precip. QPE is well under FFG, even
accounting for the earlier storms/rain. Lots of higher/mid
clouds for the overnight should help keep fog from becoming
widespread. However, many places that have had rain this evening
still have dewpoints in the u60s/near 70F. Will continue to
mention patchy fog across much of the area, mainly east of UNV
and N of the Turnpike. Temps are on track.

&&

.SHORT TERM /8 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Looking ahead to Sunday, bulk shear increases and a front will
enter the picture to potentially focus stronger storms to break
the heat. SPC Slight risk still stands for Sunday. The breakdown
of the upper ridge continues on Sunday with upper trough base
moving from the Great Lakes into the Northeast accompanied by
stronger low/mid level flow overspreading a moderately unstable
environment. Trailing cold front and prefrontal boundary should
help to trigger scattered t-storms by the afternoon with
potential for organized cells/clusters to produce damaging
winds.

WPC has maintained a MRGL risk ERO for Sunday over the
Alleghenies given ribbon of higher pwats along the cold front,
but forward progression will be limiting factor concerning
flooding potential. Recent dryness has caused a large increase
in FFG over most of CPA with the lowest values in the northern
tier. The projected instability and available moisture should
support local 1-2 in/hr rates in stronger storms, but overall
flood risk is low. Storms should weaken moving to the southeast
later Sunday night.

The 500mb trough swings through on Monday while sfc dewpoints
fall into the 50s. There could be another round of scattered
showers/t-storms, but with drier boundary layer and and PW
air mass working into the area, signs point to a General thunder
day for most. High pressure arrives by Monday night and will
provide a mainly clear and comfortable night with valley fog and
low temps dropping back closer to climo for this time of year
in the 55-65F range.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Late evening update holds no changes from National Blend for the
Wed and beyond time frame.

Prev...
A warming trend emerges on Tuesday as surface high pressure
builds across the Mid-Atlantic. Despite the warm-up into
Tuesday, MaxTs in the lower 90s across portions of the Lower
Susquehanna Valley will be the ceiling in this forecast cycle,
where 10-20% of ENS members outline temperatures exceeding 90F
during peak warming hours with less than 10% of GEFS members
outlining temperatures exceeding 90F.

Surging PWATs ahead of a sfc cold front begin to enter central
Pennsylvania late Tuesday evening into Wednesday morning, where
chances of precipitation return to the area. Deterministic model
guidance has notably shown less coverage in precipitation
Tuesday evening, and have limited PoPs towards the northern tier
where the best moisture and forcing will be available. PoPs
will begin to expand areawide through Wednesday, especially
during the afternoon/evening hours where the best daytime
heating will be available ahead of the cold front.

Mild conditions and drier air will return for Thursday in the
wake of the cold front and continue through Friday, with MaxTs
closer to seasonal averages for the end of June. Looking into
Saturday, considerable deterministic model spread begins to
bring uncertainty into the forecast with some potential for
diurnally driven showers/storms possible across the area.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
As of 03z, all TAF sites were VFR. A few isolated TSRA remain
across the eastern half of PA and are expected to gradually
dissipate through 06z.

Marginal LLWS was added to the BFD TAF from 09-13Z Sunday
as low level winds increase ahead of an approaching frontal
boundary. Otherwise, confidence is too low to include LLWS.

Patchy fog is possible overnight, specifically in places that
received rain earlier this evening and see a window of clearing
overnight. The highest chances for fog are at central and
eastern airfields (namely MDT, IPT, UNV, LNS).

The next batch of SHRA/TSRA will begin to form during the early
afternoon hours on Sunday ahead of a cold frontal passage.
Guidance (GLAMP/HREF/RAP) have shown some potential for SHRA in
the 15-17Z Sunday timeframe at BFD/AOO/UNV. Later in the
afternoon (mainly after 18Z), there is higher confidence in
SHRA/TSRA impacts at airfields across central PA with continued
daytime heating ahead of the front.

Outlook...

Mon...Predominantly VFR, with brief restrictions possible in
scattered SHRA/TSRA as a cold front crosses the area.

Tue...VFR, no sig wx expected.

Wed...Restrictions possible in TSRA.

Thu...AM SHRA/TSRA with restrictions possible, drying out late.
-- End Changed Discussion --

&&

.CLIMATE...
A heat wave will continue through the weekend with near-record
temperatures forecast in some locations on Sunday.

Daily record highs for Sunday June 23:

6/23
State College 91 (1966)
Harrisburg 97 (1965)
Williamsport94 (1923)
Altoona 90 (1994)
Bradford 86 (2013)

The following records have been set during this stretch of heat:

MDT:
* A record high temperature of 99 degrees was set at
  Harrisburg, PA on Saturday, Jun 22, breaking the old record of
  97 degrees set in 1988.

IPT:
* A record high temperature of 98 degrees was set at
  Williamsport on Friday June 21st, breaking the old record of
  97 degrees set in 1923 and tied in 1933.

BFD:
* A record high temperature of 89 degrees was tied at Bradford
  on Friday June 21st, tying the record set in 2022.
* A record high temperature of 90 degrees was set at Bradford on
  Thursday June 20th breaking the old record of 88 degrees set
  in 2012.
* A record high temperature of 88 degrees was set at Bradford on
  Wednesday June 19, breaking the old record of 87 degrees set
  in 1987.

AOO:
* A record high temperature of 96 degrees was set on Saturday,
  Jun 22, breaking the old record of 91 degrees set in 1988.

Highest Max Temperatures for Central Pennsylvania Observing
sites for June (date of occurrence is in parentheses:

State College 96 in 1952 (26th) and 1933 (29th)
Harrisburg 100 in 1966 (27th), 1952 (26th), and 1934 (29th)
Williamsport 104 in 1925 (5th)
Altoona 97 in 1971 (28th) and 1953 (21st)
Bradford 93 in 2022 (22nd)

Longest run of consecutive days with max temp >=90 in June:

State College 6 (24-29th 1966)   /current streak=1/
Harrisburg 10* (19-28th 1943) /current streak=6/
Williamsport 9 (18-26th 1923)   /current streak=6/
Altoona         8 (13-20th 1994)   /current streak=6/
Bradford        1 (23rd 2024)      /current streak=1/

*Harrisburg had a run of 11 days with temperatures greater than
 90 degrees that started on 26th and ended on July 6th in 1901.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Sunday for PAZ028-036-049>053-
056>059-063>066.

&&

$$

SYNOPSIS...DeVoir/Steinbugl
NEAR TERM...DeVoir/Dangelo/Steinbugl
SHORT TERM...DeVoir/Steinbugl
LONG TERM...Dangelo/NPB
AVIATION...Colbert/NPB
CLIMATE...Evans/Steinbugl/Colbert