415
FXUS61 KCTP 240241
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1041 PM EDT Mon Jun 23 2025

.SYNOPSIS...
* Significant and dangerous heat wave continues through
  Wednesday with major to extreme heat risk
* Record-breaking to record-challenging day and nighttime
  temperatures into midweek
* Not as hot, but increasingly unsettled Wednesday through the
  last weekend in June with daily chances for heavy downpours
* A little cooler by late week

&&

.NEAR TERM /THROUGH TUESDAY/...
Early evening update.

Aside from some mid and high clouds, a tame evening for a
change this year. Strong mid level cap noted on observed
12Z soundings has held down convection for a change. Minor
changes made to the fcst.

Earlier discussion below.

Record-breaking heat this afternoon with 18Z/2PM temps in the
85-95F range. 3 new record maxes appear to have been set at
BFD, AOO, and IPT. Max HX so far is 107F at KLNS. Visible
satellite trends show the fair wx cu that popped up over the
higher terrain now fading this afternoon beneath 594+dm 500mb
heat dome. Very warm/humid tonight with patchy fog and low
temps 15 to 20 degrees above climo in the upper 60s to mid 70s.
Record hi minimum temps very much in jeopardy at IPT and MDT.
Little relief overnight from the sweltering heat which continues
through Tuesday.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...
Early evening update.

Still looks like Wednesday will have more widespread showers
and storms, while Tuesday would be more limited to the
northwest. Still on the hot and humid side into Wed.

Earlier discussion below.

Very hot and humid conditions continue into the middle of the
week. Record-challenging to potentially record breaking max
temps are fcst on Tuesday (see climate section). Max heat
indices along with major to extreme heat risk continues to
support heat advisory and extreme heat warning for central PA.

SPC did not change the initial D2 convective outlook with a MRGL
risk still covering the NW part of the area. Large scale lift
remains almost non-existent with weak deep layer shear, so any
isolated storms that develop would be driven by mesoscale
forcing (terrain or lake-breeze boundary?) within a favorable
thermodynamic environment characterized by moderate to strong
instability and steep low level lapse rates. Odds are that the
majority of the forecast area will see another rain-free day.

There is a higher probability (% chance) for thunderstorms on
Wednesday, and some storms may be strong to potentially severe.
The uptick in rain/severe tstm probs is primarily due to better
lift/trigger associated with a southward advancing sfc cold
front. The updated D3 SPC outlook now includes all of CPA in
the MRGL level 1 out of 5 risk. While temperatures aloft
remain rather warm (+9-10F @700mb), diurnal heating will
support moderate to locally strong buoyancy. Deep-layer
flow/shear is forecast to be relatively weak, but unidirectional
west northwesterly flow could support outflow dominant clusters
capable of at least isolated wind damage. WPC also shows a MRGL
risk for excessive rainfall across the northern half of the
CWA. The pattern turns rather unsettled through late week as the
cold front becomes quasi stationary over the area.

Temps likely peak on Tuesday and begin a modest summertime
cooling trend into late week with highs by Thursday in the
80-90F range. It will remain muggy and humid with sfc dewpoints
60-70F providing ample fuel for daily tstms with the potential
for drenching downpours. WPC has included all of CPA in a MRGL
risk ERO for Thursday/D4 with locally heavy rain on the northern
periphery of the upper level ridge.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Late evening update.

As 500 mb heights lower later in the week, temperatures will
trend closer to normal. The main concern will be how much
clearing will take place late in the week into the upcoming
weekend. Best chance for dry weaother may be from route 6
northward.

Earlier discussion below.

Increasing low-level moisture under weak westerly flow
continues into Thursday. NBM PoPs increases into the 40-70 pct
range Thu afternoon as a slow moving cold front approaches
southern New York State and stability begins to erode. Chances
for rain increase further on Friday into Saturday with enhanced
lift over central Pennsylvania ahead of a midlevel shortwave
trough. Repeated bouts of heavy rainfall during the middle and
end of the week may result in flooding concerns, particularly if
the steering flow lines up parallel with thermal boundaries.
PoPs are a bit lower on Sunday, but increase again into Monday.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Very high (~100%) confidence in VFR conditions with clear skies
overnight across all of central Pennsylvania. Fog potential
appears to be less likely across the northern tier tonight
compared to yesterday evening. Very high (~100%) confidence
remains in VFR conditions all of central Pennsylvania, outside
of some potential for an isolated afternoon shower or
thunderstorm possible across NW PA (BFD). At this time, have
kept any mentions out of the BFD 00Z TAF package due to low
(~10%) confidence on any impacts at the airfield. Despite VFR
conditions during the day on Tuesday, hot and humid conditions
will continue to bring high density altitude to central
Pennsylvania.

Outlook...

Wed...Mainly VFR with increasing chances of SHRA/TSRA,
especially north.

Thu-Sat...Increasing impacts from SHRA/TSRA. Less hot.

&&

.CLIMATE...
Ongoing extreme heat wave will bring record breaking to record
challenging max/min temps early this week.

The following climate sites broke or tied their daily record
high temperatures for June 23rd:

Harrisburg: 97F tied the record set in 1965
Williamsport: 97F broke the previous record of 94F set in 1923
Altoona: 93F broke the previous record of 90F set in 1994
Bradford 89F broke the previous record of 86F set in 2013

Daily record high temperatures for June 24 & 25th:

Harrisburg     98 in 1966 | 98 in 1997
Williamsport  100 in 1923 |100 in 1952
Altoona        91 in 1966 | 93 in 1952
Bradford       86 in 2013 | 89 in 1988
State College  94 in 1952 | 96 in 1952

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Wednesday for PAZ004>006-010>012-
017>019-024>028-033>035-037-041-042-045-046-049>053-058.
Extreme Heat Warning until 8 PM EDT Wednesday for PAZ036-056-
057-059-063>066.

&&

$$

SYNOPSIS...Steinbugl/Martin
NEAR TERM...Steinbugl/Martin
SHORT TERM...Steinbugl/Martin
LONG TERM...Martin/Colbert/NPB
AVIATION...NPB
CLIMATE...Steinbugl/Banghoff/NPB