392
FXUS61 KCTP 170240
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1040 PM EDT Sun Jun 16 2024

.SYNOPSIS...
*Partly to mostly sunny and warmer for Father`s Day
*Long duration and potentially dangerous heat wave this week
*High temperatures 90+ degrees Monday into next weekend

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
1030 pm update... Recent satellite imagery has shown the
development of a SE-NW oriented band of shallow cumulus clouds
across central PA this evening. This cloud band appears to have
formed at the leading edge of warmer, more humid air above the
boundary layer (within the 925-850 mb layer). Present
indications are that this band of clouds will push to the ENE
and slowly disperse overnight, as this pseudo-warm front aloft
moves steadily to the northeast.

No other changes at this time.

8 pm update... The current forecast is in excellent shape, so
just a few near-term tweaks were made based on the latest
observational data.

A clear and pleasant summer night is in store, with a diurnal
cumulus field across the Alleghenies quickly fading at this
time. It appears that most, if not all of the mid and upper-
level convective cloud debris circulating around the building
upper ridge axis will stay well north and west of the region
overnight, lending high confidence in skies remaining clear.

Despite decent radiating conditions overnight, fairly strong
warm advection just above the boundary layer will still lead to
a milder night than what we`ve seen recently, with lows by
daybreak ranging from the upper 50s in the northern mountains,
to the mid 60s in the Lower Susquehanna Valley.

Earlier discussion... A nice Father`s Day evening with partly
cloudy to mainly clear skies into tonight. There may be a couple
patches of fog around daybreak Monday, but overall a seasonably
mild night for mid June with min temps in the upper 50s to
lower 60s or +5-10F above climo.

A heat wave begins Monday starting an extended period of max
temps 90+ degrees. An anomalous 500mb subtropical ridge builds
over the region and will bring hot and humid weather to Central
PA. Warm mid level temps should largely suppress convection, but
can`t rule out (10-20% chance) an isolated shower or t-storm
Monday afternoon along the spine of the Alleghenies -- where
the elevated heat source could aid in breaking the cap.

Trending warmer and more humid Monday night with low temps in
the 65-70F range or about +7-15F above climo.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
Increasing heat and humidity should allow heat index values to
reach the century mark in most places Tuesday afternoon. We
issued a heat advisory in coordination with neighboring WFOs
between 12-8pm. Scattered, pulse-type convection remains
possible under the heat dome Tuesday afternoon -- primarily
along the spine of the Alleghenies. The threat for PM convection
looks even more limited on Wednesday as temps continue to warm
aloft. The heat wave rolls on through midweek with highs 90-95
forecast with max HX approaching 100F. Additional heat headlines
may be needed.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
All medium range guidance continues to show a prolonged heat
wave will occur throughout the extended forecast period. A
595-600 dm 500 mb ridge will be situated over Central
Pennsylvania and temperatures will easily reach the 90s across
most of the region each day. Temperatures will ramp up each day
giving us our hottest day by midweek. Heat indices will be in
the upper 90s and low 100s, with the Thursday-Friday timeframe.
Some models indicate the potential for a few showers or
thunderstorms each afternoon across the northern tier, but
coverage should be very limited and elevation driven.

Ensembles show the ridge beginning to flatten out a little by
Saturday which would allow for a slightly higher chance of
showers or storms, particularly across the northern half of the
area.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
High pressure will support widespread VFR conditions with mainly
clear skies and light winds overnight. Not expecting any fog
formation as it should be too dry. VFR conditions continue
throughout the day on Monday and skies will remain mainly clear
other than any cumulus that develop in the afternoon. A few
models show some showers developing across the western half of
the area, but this is a low confidence solution at this point.

Outlook...

Tue-Fri...Predominantly VFR, with building heat. Density
altitude concerns possible.

&&

.CLIMATE...
A period of much warmer than average temperatures is expected
across much of central Pennsylvania next week, with record high
temperatures being challenged. The record high temperatures for
some sites across central PA 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

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Jurewicz/Fitzgerald/Steinbugl
SHORT TERM...Fitzgerald/Steinbugl
LONG TERM...Tyburski
AVIATION...Bauco
CLIMATE...NPB