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929
FXUS61 KCTP 220823
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
423 AM EDT Sun Sep 22 2024

.SYNOPSIS...
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Weak high pressure builds over central Pennsylvania today.
While clouds will be plentiful, it should be rain free finish
to the weekend in most areas. A slow moving weather system
brings the next chance of rain to Central Pennsylvania from
Monday through midweek.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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The second half of the overnight has been much quieter than the
first, with areas of fog becoming more widespread and lingering
showers dropping south of the Mason Dixon line. Pockets of dense
fog showed up just after midnight, and we collaborated a dense
fog advisory from the Alleghenies into parts of the N Central
and Central Mountains. Continuing to monitor for any eastward
expansion as we reach dawn.

As mentioned by previous shifts, model forecast soundings
indicate southeast upslope flow for a good part of today and
tonight supporting widespread clouds and perhaps even some
spotty drizzle. Extensive cloud cover and easterly component
will result in much cooler temps than Saturday, with highs
staying in the 60s over the Central Mtns. Tonight still looks
mainly dry with shortwave ridge axis over central PA, but
watching moisture increase to our west as disturbance tracks
into the Ohio Valley.
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&&

.SHORT TERM /MONDAY/...
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Zonal flow flattens the upper ridge axis over central PA and
delivers increasing deep layer moisture with PW surging above
1.5" over central and southern portions of Central PA. With slow
moving forcing mechanisms and no shortwave of available
moisture, Monday will be the first of at least three days of
much needed rainfall, after the first three weeks of September
have been anomalously dry. It appears that all will fall into
the beneficial rain category, with no particularly high risk of
excessive rainfall or much in the way of severe potential
through midweek.
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&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Model guidance outlines another surface low-pressure system
tracking northeastward across western portions of the Upper Ohio
Valley and into southern Ontario Tuesday into Wednesday, with
slightly more moisture and lift available as the warm front
aligns itself north-to-south across west-central PA. Given
slightly better lift with this low-pressure system coupled with
enhanced moisture, have retained likely PoPs in the Tuesday to
Wednesday timeframe. Given PWATs in the 1.50-1.75" range on
Wednesday, locally heavy rainfall will be possible and this has
been outlined with marginal (level 1/4) risks in the D4 (W) and
D5 (E) Excessive Rainfall Outlooks from the Weather Prediction
Center. Impacts at this time look less likely at this time given
ongoing dry conditions across especially SW PA where D2 drought
conditions persist; however, any heavier rainfall in the
preceding days could allow for slightly more impacts.

As we shift into the later part of the week, slightly more
model uncertainty with regards to low-pressure moving N/E of the
area and how this will impact rainfall chances for Central PA.
At this time, have capped PoPs at a chance for Thursday as the
low-pressure system will be slightly closer to our eastern half,
and capped at a slight chance for Friday, keeping close to NBM
model guidance in this timeframe.
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&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
06Z TAFS sent.

More in the way of weather than I expected when I came in early.
Last of the storms now south of the TAF sites. Key to fcst seems
to be having southeast flow of slightly higher dewpoints with
a drier airmass building in from east. This happen a few weeks
ago. Storms get caught in similar locations, most likely aided
by terrain features.

Anyway, main issue will be fog and low CIGS overnight. Expect
conditions to improve during the day, but I did now bring
conditions up too fast, given time of year. First day of fall
today, so days are getting shorter with less intense sun to
burn off fog and low clouds as fast as back in the summer.

Setup for showers and storms similar to yesterday, but left
mention out of the TAFS for now. Less chance today, as dewpoints
fall off more. Also coverage of activity during the day time
on Saturday was rather limited.

Outlook...

Mon-Thu...Scattered showers, restrictions possible.

&&

.CLIMATE...
The high temperature in Bradford on Friday set a new record
high of 82 degrees. This broke the record of 81 degrees set in
1978 and 2016.

The first day of autumn 2024 (Fall Equinox) begins at 8:44 am
EDT on Sunday September 22nd.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
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Dense Fog Advisory until 10 AM EDT this morning for PAZ004>006-
010>012-017-018-024-025-033-034.
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&&

$$

SYNOPSIS...DeVoir/Dangelo
NEAR TERM...DeVoir/Dangelo/Gartner
SHORT TERM...DeVoir/Dangelo/Gartner
LONG TERM...Gartner/NPB
AVIATION...Martin
CLIMATE...Steinbugl/Martin/NPB