-- Discussion containing changed information from previous version are highlighted. --
153
FXUS61 KCTP 040016
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
816 PM EDT Mon Jun 3 2024

.SYNOPSIS...
*Mainly dry the next 36 hours, with a stray afternoon shower or
 thunderstorm Tuesday.
*More widespread rain on Wednesday afternoon and Thursday.
*Cooler this weekend with scattered PM showers/storms.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
An isolated shower remains possible through early evening over
Eastern Lancaster County and the Laurel Highlands, where
satellite shows decent vertical cu development at 2330Z.
Otherwise, expect scattered cumulus to give way to mainly clear
skies after sunset. A nearly calm wind appears likely to promote
late night patchy valley fog, primarily in the favored
deep/river stream valleys of the Alleghenies. See no reason to
deviate from NBM min temps, which range from the mid 50s in the
coolest valleys of the NW Mtns, to the mid 60s across parts of
the Lower Susq Valley.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Upper level ridging over PA should result in generally fair and
warm weather Tuesday. However, diurnal heating may be enough to
break through a weak capping inversion, resulting in isolated PM
convection. Latest HREF suggests the best chance of a pulse-type
shower/tsra will be along the ridgetops of Southern PA, where
progged pwats are highest. Mixing down progged 850mb temps of
around 15C translates to expected high temps in the low to mid
80s for most of Central PA Tuesday.

An increasingly moist southeast flow ahead of an upstream warm
front over the Ohio Valley may result in a isolated shower
Tuesday night over Southern PA and will likely yield developing
stratus per latest soundings.

The next notable chance for rain arrives Wednesday afternoon,
as a low pressure system drifting across the Great Lakes helps
bring surging Gulf Coast moisture into the region. Southeast
flow ahead of the approaching low pressure systems sets up a
classic "cool" air damming scenario on Wednesday with persistent
clouds and little to no instability ahead of the approaching
warm advection lift. Temperatures will stay below 80 degrees
everywhere except perhaps far northwest PA and could even
struggle to get much above 70 at higher elevations.

Latest suite of medium range guidance brings the warm front
into southwest PA during the day on Wednesday with showers
moving in Wednesday afternoon and evening. As mentioned before,
instability will be lacking so not overly concerned about the
severe weather threat on Wednesday evening. WPC has painted a
big Marginal Risk across Central PA with the potential for some
heavier downpours and localized rainfall amounts exceed 1 inch.
Not overly concerned about flooding at this point given dry
pattern lately and meager instability, but threat bears watching
as hi-res guidance gets a better handle on the precipitation
distribution and magnitude.

By Thursday morning, most of PA will be in the warm sector, but
without much forcing would not be surprised to see lingering
light showers/drizzle Thursday morning. Cold front will sweep
through sometime on Thursday and could generate a could stronger
showers/storms as it sweeps through. Once the front moves
through, the airmass will noticeably change with lower dewpoints
and cooler temperatures aloft.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The main weather feature for Central PA through next weekend
will be a persistent cold core, upper low centered somewhere
from the eastern Great Lakes region across southern Ontario and
Quebec. As a result, at least hit and miss showers and
thunderstorms are expected on a daily basis, with diurnally more
numerous coverage anticipated in the afternoon and early evening
hours, particularly for the northern tier of the Commonwealth.

Current indications are that by early next week, the upper low
should begin to fill and drift northeast, with showers and
storms becoming less prevalent over time.

Temperatures are likely to average somewhat below climatology
for early to mid-June, with daily highs in the upper 60s and
70s, and overnight lows in the 50s to lower 60s.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
VFR conditions are expected to continue through 06Z Tuesday
with very high (> 90%) confidence. The main concern overnight
will be radiation valley fog across central PA with localized
impacts at the various airfields. Both GLAMP and HREF guidance
continue to suggest BFD/AOO/UNV/IPT have the highest probs of
fuel-alternate restrictions with sub-MVFR conds after 06Z
Tuesday. Have continued to keep IFR and a period of LIFR conds
in the 06Z-12Z Tuesday range with moderate-to-high (60-70%)
confidence, with mainly timing adjustments from previous
forecasts.

Outside of these airfields, MVFR conds seem like the most
likely prevailing condition at JST in the 08Z-12Z timeframe with
VCFG in the valleys surrounding the terminal. A brief (1-2hr)
period of high-end IFR to low-end MVFR conds remains possible
around 09Z, but confidence in LIFR conds have lowered from
previous cycles (30-40%) with recent GLAMP guidance suggesting a
MVFR-to-IFR outcome during this timeframe. Recent GLAMP
guidance has also suggested a period of MVFR vsbys across the
LSQ airfields (MDT/LNS) in the 10Z-11Z timeframe. Low (< 30%)
confidence has kept mentions of MVFR conds out at this time as a
light breeze lingering around overnight could bring lower
probabilities of sub-VFR conditions.

After sunrise, conditions are expected to gradually improve
with VFR conditions prevailing area-wide after 15z Tuesday. Some
model guidance has started to suggest scattered -SHRA across
the southern tier around 18Z Tuesday, but lower (< 30%)
confidence in coverage and timing keeps any mentions out of the
00Z TAF package.

Outlook...

Wed-Thu...More numerous showers and thunderstorms, with at
least brief restrictions.

Fri-Sat...Hit and miss afternoon showers and thunderstorms with
brief restrictions, otherwise mostly VFR.
-- End Changed Discussion --

&&

.CLIMATE...
Prelim May and Spring 2024 Temperature & Precipitation Rankings

Harrisburg: T12th warmest; 76th driest May
 T3rd warmest; 33rd wettest Spring

Williamsport: 9th warmest; 22nd wettest May
4th warmest; 11th wettest Spring

Altoona: 9th warmest; 13th wettest May
2nd warmest; 3rd wettest Spring

Bradford: 4th warmest; 36th driest May
Warmest; 21st wettest Spring

&&

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

&&

$$

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