-- Discussion containing changed information from previous version are highlighted. --
359
FXUS61 KCTP 190151
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
951 PM EDT Tue Jun 18 2024

.SYNOPSIS...
*Isolated strong/severe T-storms this evening
*Long duration and potentially dangerous heat wave this week
*Near-record high temperatures 90+ degrees into the weekend

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Aerial coverage of convection has begun to wane as of 23Z.
However, the threat of a strong to severe tsra remains over the
NW Mtns, where SPC mesoanalysis shows MLCAPES still near 2500
J/kg. Expect any remains showers/tsra to fade with loss of
heating around sunset.

It will be another warm and muggy night under the upper level
ridge. Patchy late night valley fog seems a good bet, especially
where rain fall earlier today. Latest NAMNest and SREF prob
charts target the central mountains for the best chance of fog.
See no reason to deviate from NBM min temps, which are in 65-70F
range or generally +5-15F above average.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Heat wave will continue through late week, as subtropical ridge
remains parked over the Mid Atlantic region. Wednesday`s model
850mb temps are very similar to today, so expect highs once
again ranging from the mid 80s over the highest elevations of
the Alleghenies, to the 90-95F range in most valley locations.
Lower pwats and somewhat lower afternoon dewpoints, especially
over the Lower Susq Valley, suggest max heat indices will
be in the 90s across the forecast area.

Mid level temps warm a bit Wednesday, likely limiting
diurnally-driven PM convection to the NW Mtns. Weak shear
indicates convection will be of the pulse variety with little
risk of organized severe weather. However, high pwats and
instability indicate locally heavy downpours are possible, with
a chance of localized 2-3 inch amounts based on the 12Z HREF.

Surface front sinks south across the US/CN border on Thursday
and will encounter a very warm/moist environment. Favorable
timing with peak heating suggests scattered storms are likely
with a MRGL risk SWO over the northern tier of central PA.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
The heat and humidity will continue into Saturday, although we
could begin to see some slight relief working into northeastern
PA in the form of a backdoor cold front. It will be another hot
day for much of the area though, and could easily see
continuing to push the advy out into the weekend for much of the
CWA. The proximity of the cold front will bring a slight
increase in PoPs, esp across north-central and northeastern PA.

Sunday into Monday should see the (slightly) cooler temperatures
expand southward as a cold front crosses the area. This front
will be accompanied slightly increased PoPs areawide Sunday
into Monday.

Any subtle cool down early next week looks like it will be
short-lived, with heat building once again by midweek.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
VFR will continue for the entire region for the bulk of the
overnight hours with just varying amounts of high clouds
streaming east across PA. Included a tempo group for some MVFR
low end VFR (4-6SM FG/HZ) during the hours leading up to dawn.

For the mid to late week period, hazy, hot and humid conds will
be the rule across central PA, which will be under a huge dome
of mid/upper level high pressure leading to a stagnant airmass
with very light wind up through several KFT AGL.

A few spotty pulse tstorms can`t be ruled out during the mid to
late afternoon hours Wednesday (especially across the NW Mtns
where slightly cooler mid level temps, boundaries left over from
this evening`s TSRA, terrain influences and the presence of a NW
breeze off Lake Erie will be present). However, the areal coverage
will be less than we experienced this tuesday afternoon/evening.

Brief reductions in CIGS/VSBYS and gusty winds are possible in
any storms.

Outlook...

Thu-Sun...Predominantly VFR, with continued heat and iso TSRA.
Density altitude concerns possible.
-- End Changed Discussion --

&&

.CLIMATE...
-- Changed Discussion --
A period of warmer than average temperatures is expected across
much of central Pennsylvania through the end of the week, with
record high temperatures at multiple cities being challenged
every day through Saturday.

Two records were either set or tied for sites today:
* A record high temperature of 92 degrees was set at Altoona
  today that ties the old record of 92 degrees set back in 1994.
* A record high temperature of 90 degrees was set at Bradford
  today that breaks the old record of 87 degrees set back in
  1993.

The record high temperatures for some sites across
central PA that could be challenged are outlined below:

 Jun 18 Jun 19 Jun 20 Jun 21

Harrisburg      97/1957     98/1994     98/1931     98/1923
Williamsport    97/2018     96/1929     101/1923    97/1933
State College   94/1923     94/1931     94/1953     94/1988

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)
Harrisburg 10* (19-28th 1943)
Williamsport 9 (18-26th 1923)
Altoona 8 (13-20th 1994)
Bradford 0 (has not occurred since POR started at site in 1957)

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

&&

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

&&

$$

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