014
FXUS61 KCTP 202142
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
542 PM EDT Thu Jun 20 2024

.SYNOPSIS...
The center of a subtropical upper level high over Pennsylvania
will sink southward over the next few days. A weak cold front
will approach and stall out over the region Friday and Saturday.
A more significant cold front is likely to push through Sunday
night or early Monday bringing brief relief from the humid
weather.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A weak mid and upper level shortwave over Eastern Lake Ontario
with a southwestward trailing trough/narrow vort lobe into NCENT
and NW PA will continue to focus any convection over the
northern 1/4 of our CWA into this evening.

Hodographs, very short MBE vectors and high PWAT values near
2.00 inches across that part of the state suggest the potential
for strong to briefly severe pulse storms with frequent
lightning, wet microbursts and locally very heavy rainfall of
over 2 inches in just 30 minutes. Dual Pol Max instantaneous
rainfall rates of 4.5-5.5 inches/hr are observed beneath these
tall, slow-moving TSRA.

The storms will slowly back build to the WSW and into the
region where an elevated mixed layer is present, with potential
development to near the intersection of this EML with the Lake
breeze Boundary near the NW tip of Warren County.

Further south, POPS tail off quickly to less than 10 Percent
south of Interstate 80.

As the storms diminish tonight, fog is expected to form across
the north and could get locally dense for a few to several hours
late tonight/early Friday. Mins hold in the 65-70F range.

&&

.SHORT TERM /6 AM FRIDAY THROUGH 6 AM FRIDAY/...
As the mid/upper level high continues to retrograde south and
west, the flow across Northern PA/NYS will become increasingly
diffluent above the main axis of high PWAT air.

This likely ring-of-fire will develop with convective clusters
to become spread across a larger area with more notable East or
ESE progression than we`ve seen in recent days as deep layer,
(0-3KM) shear will increase to around 20 kts across the Northern
Mtns Fri afternoon and evening.

SPC has a MRGL risk over most of the CWA, but the risk may be a
little higher than advertised at this point, and we could see
us get bumped up to a SLGT risk (at least across the Northern
half of PA) with later updates.

Temps will start out 3-5F higher on Fri AM vs Thurs and help the
SErn 2/3rds of the CWA get into the m90s or better. The higher
Td on Fri will give us just enough of a boost to have more
places get at or above 100 heat index.

The storms should diminish from W-E Fri night. Since more
places should receive rainfall Fri and early Fri night and some
clearing is expected behind the storms, we should get a more-
widespread fog to form.

&&

.LONG TERM /FRIDAY THROUGH THURSDAY/...
Heat builds to a crescendo Saturday through Sunday with daytime
heat indices likely to eclipse 100F both days over the far
south and southeast, and nighttime lows peaking Sat
night/Sunday morning in the mid to upper 70s in these areas.
Ring of fire convection still looks likely Saturday and Sunday
as the upper ridge flattens, especially along the northern tier
of the state. The chance for organized severe may increase over
northern PA on Saturday with increasing bulk shear. At some
point, heat advisory for Day 4 (Sunday) will need to be extended
for the southeast half of central PA.

Most locations should see a round of showers/tsra Sunday PM into
Monday AM associated with the flattening of the upper ridge and
passage of a shortwave trough and cold front. Behind this
feature, expect a return to fair and more seasonable conditions
early next week. A surge of warmer weather currently looks
likely midweek ahead of an upstream cold front, which could also
be accompanied by our next round of showers/tsra. A more
refreshing air mass is being teased for Thu/Fri of next week
in the medium range, something we would welcome at that time.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
VFR conditions are expected across the bulk of the area for
the rest of the day and tonight. A line of slow-moving
thunderstorms across the Northern Tier of PA will continue to
back build to the west and will need to keep an extended period
of VCTS around KBFD through 02Z Friday before this activity
diminishes.

Brief visibility reductions will be possible in any
thunderstorms, along with the potential for strong winds.

Model soundings support fog development overnight across the
north and the HREF shows greater than 50% probabilities of
visibilities dropping below 1/2 mile after 06Z at BFD.

Outlook...

Fri-Sun...Predominantly VFR, with continued heat and isold
aftn/eve SHRA/TSRA. Density altitude concerns possible.

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

&&

.CLIMATE...
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.

One record was set on Thursday:
*
* A record high temperature of 90 degrees was set at Bradford on
  Thursday Jun 20th. breaking the old record of 88 degrees set in
  2012.

One record was set on Wednesday:

* A record high temperature of 88 degrees was set at Bradford on
  Wednesday Jun 19, breaking the old record of 87 degrees set in
  1987.

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.

&&

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

&&

$$

SYNOPSIS...Lambert/Dangelo
NEAR TERM...Lambert/Dangelo
SHORT TERM...Dangelo
LONG TERM...DeVoir/Fitzgerald
AVIATION...Lambert/Bauco
CLIMATE...Evans