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Area Forecast Discussion
||Wed, Dec 31, 7:00pm EST
FXUS61 KCTP 202357
Area Forecast Discussion
National Weather Service State College PA
757 PM EDT Fri Jul 20 2018
The recent stretch of pleasant and conformable weather across
central PA will come to an end this weekend, as the pattern
turns decidedly unsettled, muggy and rather wet through next
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Enjoy and take advantage of the dry weather late this afternoon
and evening; changes are afoot.
North-south line of convection has developed as expected near/along
the I-79 corridor in WPA. Hires model consensus still suggests
this line may drift eastward and clip the border counties
adjacent to WFO PBZ. However, this is low probability with the
majority -if not all- of central PA remaining dry through early
Based on the latest hires model blends/ensemble means, there is
high confidence in showers spreading northward from the
Delmarva/Chesapeake Bay region into south central/southeast PA
early Saturday morning. An increasingly moist, southeasterly
low level flow will also help to bring low clouds into much of
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Hybrid coastal low will track north along the mid Atlantic
coast from eastern NC across the Delmarva on Saturday and
approach southern New England by Sunday morning. This low will
eventually be absorbed by the anomalous deep-layer cyclone that
is expected to move slowly southeastward into the Ohio Valley.
Confidence has increased significantly in a period of heavy rain
spreading northward across the eastern 1/3 of the CWA later
Saturday afternoon into Saturday night. The 12Z HREF mean shows
a cyclonically curved, 50+kt LLJ drawing deep moisture inland
ahead of the hybrid low, with PWs reaching 1.5 to 2.5 inches
over southeast PA. There is definitely a short-duration flash
flood risk given the impressive PWs, strong lift and low level
moisture transport, but limiting factors include dry antecedent
conditions, high FFG and low CAPE. 1-2 inch amounts are likely
with localized higher amounts possible. Despite high confidence
in a period of heavy rain, decided to hold off on FF watch given
aforementioned factors and preference toward a more short-fused
issuance. Added heavy rain/ff threat in the HWO.
Clouds will hold daytime temps in the low to mid 70s, and it
will feel more humid and muggy.
.LONG TERM /SUNDAY THROUGH FRIDAY/...
By 12z Sunday, compact coastal low will be sliding north of the
area. But very gradually filling inverted low will edge toward
western PA while continuing to channeling tropical-like
moisture into the region - keeping unsettled weather ongoing
through much of next week - peaking in the afternoons. Best
daily chances for tstorms shifts to western/central sections
Tue/Wed before returning eastward Thu as a cold frontal boundary
finally pushes across the state.
Temperatures will be below normal Sun with thicker cloud cover
and moist SE/E flow, then highs return closer to normal for
next week while lows look to remain on the muggy side.
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions across the region this evening. Banded showers
moving south to north over western Pennsylvania. Expect VFR
conditions to continue into Saturday morning, followed by
lowering conditions during Saturday as low clouds and showers
develop across the airspace.
Low VFR to MVFR ceilings are probable Saturday into Saturday
night, with some pockets of IFR Saturday night into early
Showers are expected to spread northward from the Delmarva/Chesapeake
Bay region into the south central/southeast airspace early Saturday
morning. Expect a period of moderate to heavy rain later Saturday
afternoon into Saturday night across the eastern airspace.
Unsettled weather with showers and isolated thunderstorms to
continue into mid week.
Sat...VFR start early, then conditions lowering to MVFR in all
areas except VCTY KBFD.
Sun-Wed...Frequent showers/isolated T'storms with associated