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000
FXUS61 KCTP 010020
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
820 PM EDT Wed May 31 2023

.SYNOPSIS...
The dry, low humidity pattern will continue through Friday with
temperatures rising to near-record levels in some areas by the
end of the week. Rain risk will trend higher into Saturday
afternoon with scattered showers and a few t-storms possible.
There is considerable uncertainty over how the pattern evolves
into the first full week of June with conflicting signals in the
computer model guidance.

&&

.NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
Clear skies combined with a calm wind and unseasonably dry air
will lead to another cool night in CPA with lows in the 45-55F
range. Have used a blend of NBM/NBM10pct due to the very favorable
conditions for radiational cooling.

Some patchy fog may develop under the surface ridge axis over
southeast PA late tonight. Also, given the large difference
between air and water temps, there could be some patchy late
night fog in the deep river/stream valleys of the Alleghenies.

&&

.SHORT TERM /7 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Anomalous sfc-500mb ridging should ensure fair and increasingly
warm weather Thursday. 850mb temps rising to around 15C support
highs a few degrees above those of today, ranging from the low
80s over the Laurel Highlands, to the mid and upper 80s
elsewhere. BFD could approach their record daily record of 86F.

Similar to today, mixing of very dry air aloft should result in
dewpoints falling below NBM guidance during the afternoon with minRH
20-30%. Mostly clear skies, light wind and dry air favor efficient
radiational cooling once again Thursday night, allowing temps
to fall close to 30 degrees, with lows in the 50s. The latest
SREF and NAMNest suggest low level moisture creeping into the
Lower Susq Valley could support patchy late night fog southeast
of KMDT. Also expect patchy fog to form in the deep river/stream
valleys north of I-80.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Surface high pressure ahead of an approaching cold front will
result in dry and very warm weather on Friday. Ensemble mean
850mb temps surge to around 18C by Friday, supporting highs from
the mid 80s NW Mtns, to the low 90s in the Susq Valley. Have
blended in 10th percentile dewpoints both days due to the
potential for more mixing than the models show.

All model guidance indicates a cold front will push through the
region Saturday associated with a deepening upper trough over
New England. The best large scale forcing looks to pass well
northeast of PA. However, diurnal heating and low level
convergence along the front should lead to several showers or a
thunderstorm in spots. Unfortunately, any rain that does fall
should be relatively light.

Model spread and forecast uncertainty ramp up Sunday into the
middle of next week. The bulk of guidance, which represents the
most likely scenario, supports a return to fair and seasonable
weather Sunday and Monday as the upper trough pushes off the New
Eng coast and high pressure builds south into PA. However, some
guidance, mainly the GFS, pinches off a cut off upper low over
the Mid Atlantic, which would result in showery weather for a
good part of the week.

The bulk of medium range guidance shows a deepening upper
trough over the northeast CONUS by Tuesday, with an associated
cold front passage. This will bring the next chance of showers.
However, lack of deep moisture should result in limited rainfall
at best. Overall there is good confidence that temperatures will
be cooler next week than this week, but low confidence in
precipitation.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR conditions will continue through the TAF period. Expect
mainly clear skies along with light winds out of the east-
southeast as high pressure remains in place over the area.

Outlook...

Thu...VFR. Patchy fog/low clouds possible southeast airspace.

Fri...VFR. Stray P.M. shra/t-storm possible northeast airspace.

Sat...PM shower/t-storm most likely.

Sun-Mon...Low chance for rain showers.

&&

.CLIMATE...
Today is the last day of meteorological/climatological Spring
(MAM). June 1st marks the beginning of
meteorological/climatologicalSummer. The Summer Solstice marks
the start of astronomical Summer which occurs on June 21st at
10:57 a.m.

May 2023 will rank as the driest May on record at Harrisburg and
Williamsport. It will also rank as the 6th/7th driest month
on record. MTD rainfall deficits (as low as <5% of normal
across parts of the lower Susquehanna Valley) and potential
drought concerns will need to be monitored heading into June and
Summer 2023.

Top 5 Driest May

Harrisburg
1. 0.19" 2023 (1 day left)
1. 0.29" 1902
2. 0.46" 1903
3. 0.51" 1964
4. 0.54" 1939
5. 0.84" 1957

Williamsport
1. 0.44" 2023 (1 day left)
1. 0.80" 1964
2. 0.97" 1941
3. 1.02" 1977
4. 1.27" 1955
5. 1.28" 1911

Daily Record High Temperature for June 1st and 2nd:

Site June 1June 2
Harrisburg 97/1895 96/1895
Williamsport 96/192595/1923
Altoona 90/201189/1969
Bradford     86/202283/2007
State College 93/189594/1934

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Steinbugl
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Steinbugl
LONG TERM...Fitzgerald/Travis
AVIATION...Steinbugl
CLIMATE...