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473
FXUS61 KCTP 100310
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1110 PM EDT Thu May 9 2024

.SYNOPSIS...
- A stationary front will continue to be present across
  southwestern PA to northern VA for the next 24 hours as a few
  waves of low pressure move east along it.
- The front will push southeast to the Delmarva Coast late
  Friday.
- Several upper level troughs will move across PA through
  Saturday, bringing periods of light to moderate rain.

&&

.NEAR TERM /THROUGH FRIDAY/...
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Rain is expected to continue across central PA through the
near-term with chances of thunderstorms on a sharp decline with
very low probabilities of occurring across SW PA. Rain will be
scattered in nature, but widespread enough to promote high-end
PoPs throughout the overnight period.

Enhanced lift over a quasistationary front will allow for some
periods of heavier rainfall rates overnight along the
Alleghenies and northeastern PA. Six hour flash flood guidance
remains fairly high, with the lowest guidance of 1.25-1.50"
across portions of SW PA. Some periods of locally heavy
rainfall could lead to moderate rises on small creeks/streams
and ponding of poor drainage areas, as outlined in the D1
Excessive Rainfall Outlook from the Weather Prediction Center
but generally expect any impacts to be minimal.

Rapidly changing road conditions will be possible throughout
the terrain of central PA overnight with some concerns for
patchy areas of dense fog across the Laurels this evening. HREF
model guidance depicts moderate probabilities (40-60%) of less
than 1/4SM along the Laurels after 2AM Friday and throughout the
morning hours. Have opted for no SPS or DFA at this time due to
the patchy nature and being confined to the highest ridgetops
although future shifts may lean towards issuing products.
Lifting of visibilities after sunrise is less certain with
increased low- level moisture, but HREF/HRRR consensus leans
towards the 10AM timeframe and have outlined that in the
forecast this cycle. There are some signals for lowered
visibilities across the Lower Susquehanna Valley and along the
Endless Mountains, but less confidence at this time.

The upper low and an inverted sfc trough will become collocated
over the area Friday morning, bringing a continuation of widespread
thick clouds and frequent showers. If showers do not manifest,
expect light drizzle. The best chances for rainfall shift
towards eastern Pennsylvania later in the day Friday as the
upper-level low moves towards the east.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
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Rain continues at the beginning of the short-term and into
Saturday morning, where some uncertainty on timing of the
upper-level low movement continues SChc of PoPs. Have cut back
from NBM PoPs with a brief period of height rises across W PA to
keep the best chances of precipitation (if any) towards the
Poconos and Endless Mountain regions of central PA.

Height falls ahead of another sfc low is progged by
deterministic model guidance to move towards the area, allowing
for another period of unsettled weather into the weekend. There
remains some uncertainty on strength of the sfc low pressure
and associated cold front, with ECMWF guidance indicating a
slightly weaker solution which will bring more scattered
coverage in precipitation while the GFS brings about a slightly
stronger solution with higher chances of precipitation.

Some instability later in the afternoon/evening hours on both
Saturday and Sunday will allow for some thunderstorm potential,
especially in areas where the best forcing is present.
-- End Changed Discussion --

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Tendency to have a large scale upper level ridge over the west
this weekend, will result in much below normal 500 mb heights
over the east into next week.

While some milder and drier conditions will be possible Monday
into Tuesday, much of the time it will be cooler than normal
and wet from time to time for much of the upcoming week. Sunday
will be one day that will feature gusty winds and cold temperatures.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
A surface low approaching Central PA is supporting developing of
widespread light to moderate rain across the airspace. This will
continue through the evening hours and overnight with
coincident lower cigs and visbys.

Reductions in visibility will develop early tonight with CIGS
lowered into the IFR to LIFR range later tonight and continue
through at least the midday hours on Friday.

Latest guidance has the surface low tracking to the south of
Pennsylvania, meaning the heaviest rains and greatest instability
for widespread t-storms will also track to the south, but cant
rule out a rumble or two/vcts mainly across srn airfields.

Outlook...

Fri...Low cigs/drizzle possible, especially in the morning.

Sat...PM showers/low cigs possible, mainly W Mtns.

Sun...AM low cigs possible W Mtns. Sct afternoon showers/brief
vis reductions possible.

Mon...AM dry and mainly VFR. Showers return PM.

Tue...Showers and tstms.

&&

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

&&

$$

SYNOPSIS...NPB
NEAR TERM...NPB
SHORT TERM...NPB
LONG TERM...Martin/Gartner
AVIATION...Lambert/Gartner