423
FXUS61 KCTP 240817
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
417 AM EDT Tue Jun 24 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

&&

.NEAR TERM /THROUGH TONIGHT/...
Clear skies and light winds have allowed for efficient
radiational cooling this morning and valley fog has formed over
northern PA. This will quickly dissipate after sunrise, giving
way to another day of dangerously hot conditions. Similar to
yesterday, dry air above a weak inversion should mix down to the
surface during the afternoon, dropping dew points into the mid
60s for areas north of I-80, but with temperatures in the mid to
upper 90s, the impact on heat indices will be minimal. Much of
the region will see another day with heat index values exceeding
100 degrees and Heat Advisories and Extreme Heat Warnings
remain unchanged for today.

Some of the hires guidance continues to show a couple of
thunderstorms developing during the afternoon, but with the
strong ridge still overhead, widespread convection appears
unlikely. SPC has trimmed back the marginal risk for today and
it now only clips far northern Pennsylvania.

&&

.SHORT TERM /WEDNESDAY/...
A cold front will move southward into Central PA on Wednesday
and will bring increased cloud cover along with strong to severe
thunderstorm chances to the region. This should keep
temperatures cooler relative to previous days across the
northern and western mountains and the Heat Advisory for those
areas will be allowed to expire Tuesday evening as a result.
Another very hot and humid day is expected east of the Allegheny
Front, however, and Heat Advisories and Extreme Heat Warnings
will remain in effect.

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, 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.

&&

.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 weather 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 /08Z TUESDAY THROUGH SATURDAY/...
Dense fog has set in at KBFD this morning. Conditions will
improve toward daybreak with VFR conditions prevailing for the
day.

Elsewhere, VFR conditions will prevail at all airfields for a
majority of the TAF period. There is a low (<10%) probability of
brief reductions from isolated storms. Best chance is at KBFD
this afternoon.

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 record challenging max/min temps
early this week.

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

Altoona: Low of 72F broke the record of 71F set last year.

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

The following temperature records are in jeopardy of being tied
or broken:
                    June 24th             June 25th
                 Low Temp   High Temp     Low Temp
Harrisburg     75 in 2010 |    -         75 in 1976
Williamsport   72 in 1899 |    -             -
Altoona        68 in 1994 | 91 in 1966       -
Bradford           -      | 86 in 2013   66 in 1997
State College  70 in 1948 | 94 in 1952       -

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for PAZ004>006-
010>012-017-018-024-033-037-041-042.
Heat Advisory until 8 PM EDT Wednesday for PAZ019-025>028-034-
035-045-046-049>053-058.
Extreme Heat Warning until 8 PM EDT Wednesday for PAZ036-056-
057-059-063>066.

&&

$$

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