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342
FXUS61 KCTP 170716
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
316 AM EDT Mon Jun 17 2024

.SYNOPSIS...
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*Long duration and potentially dangerous heat wave this week
*High temperatures 90+ degrees into next weekend
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Early morning satellite imagery shows a broken band of shallow
cumulus clouds across central PA associated with the leading
edge of warmer, more humid air above the boundary layer (within
the 925-850 mb layer). Latest model guidance indications this
band of clouds will push slowly eastward this morning, exiting
the eastern edge of the forecast area by around midday. A
light southerly breeze and rising dewpoints will result in a
milder morning than we experienced recently, with daybreak temps
in the 60s.

A long duration heat wave will begin later today, as an
anomalous 500mb subtropical ridge builds over the region. Warm
mid level temps should largely suppress convection, but can`t
rule out (10-20% chance) an isolated shower or t-storm this
afternoon along the spine of the Alleghenies, where the
elevated heat source could aid in breaking the cap. Slightly
higher POPs near 30% have been placed along the NY border late
today. This is associated with a mid level vort max linked to
ongoing convection over Southern Michigan. All current guidance
tracks this feature across upstate NY late today.

Any convection should fade with loss of heating after sunset.
Mostly clear skies, light wind and surging low level moisture
appears likely to result in patchy late night valley fog across
the Central Mtns based on latest NAMNest and SREF prob
charts. See no reason to deviate from NBM min temps, which range
from 65-70F.
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&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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The heat and humidity are progged to ratchet up slightly Tuesday
and Wednesday, as the center of the subtropical high lifts north
over PA. Current guidance suggests heat indices will reach
95-100F in valley locations across Central PA Tuesday afternoon.
Upon coordination with neighboring offices, have issued a Heat
Advisory Tuesday afternoon.

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.
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&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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Medium range guidance continues to show that 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 days for the second half of the week. 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.
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&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
No big changes to the 06Z TAF package. Still some mid level
clouds, as radar VAD winds at 3000 ft are 30 knots.

Earlier discussion below.

High pressure will support widespread VFR conditions with mainly
clear skies and light winds overnight. Not expecting any fog
formation, given the fairly low dewpoints and a bit of a breeze.

VFR conditions continue throughout the day on Monday as just a
few cumulus develop in the afternoon. Some 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...Fitzgerald
SHORT TERM...Fitzgerald/Steinbugl
LONG TERM...Bauco/Tyburski
AVIATION...Martin/Bauco
CLIMATE...NPB