Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 282033
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
433 PM EDT Sun May 28 2017

.SYNOPSIS...
A warm front over southwestern Pennsylvania late this afternoon
will drift slowly northeast across the state tonight and early
Monday. A cold front will push east from the Ohio Valley and
cross the state during the day Monday. Numerous showers and
isolated to scattered thunderstorms will bring locally heavy
rain across mainly the southwest third of the state. Low
pressure will become stalled over northern Ontario during
mid-week and will lead to a slightly cooler than normal and
unsettled weather at times during the upcoming week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Widespread overcast deck of stratus and stratocu will remain
locked in across practically all of the region through this
evening as low-level southeasterly flow ahead of a warm front
transports moisture well inland from the Wrn Atlantic.

Increasingly strong llvl theta-E convergence within the
favorable upslope serly llvl flow regime across the Laurel
Highlands and south-central mtns will concentrate the most
numerous and heaviest showers and thunderstorms there through
dusk.

ML cape will also continue to slowly increase along the southern
and western perimeter of our CWA late this afternoon and early
this evening, within an area of nearly 1.5 inch PWAT air. FFG
values are quite low, and the slow moving (and anticipated
training/terrain anchored) convection will bring a distinct
Flash Flood threat across our SW CWA through early this evening
(with a lesser threat across portions of Scent PA that will be
deeper into the cool llvl airmass0.

Coordinated earlier with KLWX and KPBZ to post a Flash Flood
Watch, and that runs until 02Z Monday for Somerset and Bedford
counties. Again FFG values are lowest there with the 1-hr
amounts needed being in the 1-1.5 inch range, and 3-hour
guidance between 1.5 and 2.0 inches.

Increasing and moderately strong/veering low to mid-level
profile indicates that showers and isolated to scattered TSRA
will spread northeast across the entire CWA this evening and
overnight. locally moderate to heavy (0.75-1.00 amounts) appear
likely, though the steady SW-NE progression of the rain tonight
across the Central and NE zones should preclude any appreciable
flood threat, other than some ponding and moderate rises on
small streams/creeks.

The warm front and upper shortwave embedded in the WSW flow
aloft will translate to nearly 100 POPs for most of the CWA
tonight (though portions of the far SE will see slightly lower
POPs after sunset).

High temps in the mid 60s to L70s will slide to only the u50s to
l60s for overnight lows.

Will mention the isold severe threat in the west and SC mtns in
the HWO.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
Cold Front will be slicing through Central PA during the mid to
late morning hours, crossing the Susq Valley during the early-
mid afternoon hours.

It should turn out to be a really nice day with just a westerly
breeze in the west, but the slowing front may keep it muggier
in the east and isold storms would then be possible in the east
early in the aftn. Temps may be a bit higher than currently
advertised due to some earlier clearing and the downslope
effect (especially near the I-99/Route 220 Corridor.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
The long term period will be dominated by a large upper level
low the will slowly moving through the upper Great Lakes and
southern Canada. As that quasi stationary low slowly moves to
the northeast, it will bring surges of cool moist air across the
region.
 The first surge of cooler air moves across Monday night. This
will bring showers in from the W/NW. However, any precipitation
will cease as the night continues due to lack of diurnal
heating.
 A reinvigorated boundary should bring a chance of precipitation
through the northern half of PA. Several successive shortwave
will move through mid to late week which will bring the
possibility of scattered showers with preference for the
majority of the QPF (albeit quite light at that)to be across the
typical west-nwrly flow upslope prone areas of the Laurel
highlands and NW mtns. The chance for any thunder will be very
minimal Tuesday through Thursday.

Generally dry NW flow occurs late in the week into next weekend as
a 1020 sfc high over the upper midwest Friday evening builds SE twd
the region. Pops Thur night through Fri night will be 30 percent or
less.
 Late in the week the models begin to diverge on the location
and timing of the upper level low so there is less confidence on
precipitation late in the week. However depending where the
boundary sets up there could be periods of showers Friday
through Saturday, though currently should be mainly along the
Southern border.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
Early morning fog and very low stratus has lifted to IFR and
areas of LIFR cigs across KJST/KAOO and vcnty, while CIGs are
mainly a solid MVFR deck across the central mtns of PA (KUNV and
KFIG). the best flying conditions this afternoon over northern
and eastern PA will slowly deteriorate into the MVFR range late
this afternoon and early this evening as a growing area of
showers and thunderstorms (along and ahead of a warm front)
drift gradually to the NE across the state.

The showers (and isolated-sctd mid afternoon to evening training
heavier showers and thunderstorms) will lead to localized,
greatly reduced cigs and vsbys for brief periods asp across the
SW half of the state.

More widespread showers, and possible thunder, overnight, with
widespread restrictions are expected.

A cold front will move through on Monday, ushering out
precipitation from west to east during the day.

.OUTLOOK...

Mon...Showers ending W to E. Restrictions possible.

Tue...Scattered showers possible mainly NW. Otherwise no sig wx
expected.

Wed...Slight chance of showers with reduced ceilings.

Thu...No sig wx expected.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 10 PM EDT this evening for PAZ033-034.

&&

$$
SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Dangelo
LONG TERM...Lambert/Ceru
AVIATION...Jung/Lambert



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