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000
FXUS61 KCTP 220350
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1150 PM EDT Tue May 21 2019

.SYNOPSIS...
A ridge of high pressure will build east across the Commonwealth
tonight and slide off the Mid Atlantic Coast by Wednesday
evening. Fair weather will prevail through Wednesday afternoon,
but much higher humidity will surge into the state from the
Ohio Valley Wednesday night and Thursday, bringing an increasing
chance for showers and Thunderstorms. Pennsylvania will be on
the northern periphery of a building subtropical ridge late this
week and over the upcoming weekend. This will mean occasional
bouts of mainly afternoon and evening showers and thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Fair weather and light wind expected overnight, as surface ridge
builds over the region. Satellite loop shows some mid and high
level cloudiness poised to overspread Pa from the west
overnight. Therefore, believe earlier concern for patchy frost
over the NW Mtns is diminishing. Min temps at sunrise Wed should
generally vary from the upper 30s in the perennial cold spots
of the north, to around 50F in the larger metro areas of the
southeast.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
After a fair tranquil and cool start with high pressure
overhead, southeasterly llvl flow will increase during the day
as the high pressure ridge drifts off the NJ Coast. Several
layers of clouds will also form/advect east into region as the
nose of much higher PWAT air (30-35mm or +2-3 sigma) spreads
into Western PA late in the day.

A small chc for showers exists across the Alleghenies of
west-central PA from mid afternoon into early evening, as low
level jet pushes into the western part of the state.
NBM/Superblend numbers support fairly uniform max temperatures
across the forecast area, ranging from the upper 60s to low
70s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
NAEFS indicates Pennsylvania will be on the northern periphery
of a building subtropical ridge later this week into the weekend.

The most significant weather during the extended looks like it
will be on Thursday when the ingredients for a severe storm
outbreak look most likely.

Models show an advancing warm front late Wednesday night into
Thursday morning. The deterministic models all show some remnant
convection sliding through PA associated with the warm front and at
least one weak shortwave aloft that will be racing over the top
of the eastern ridge.

Progged stability indices indicate the warm front will move
through the CWA Thursday morning, with moderate instability
developing over the region during the late morning into the
afternoon hours. A robust shortwave is made to approach during
the second half of the day pushing a potent mid level speed max
down and through the area during the afternoon hours. Deep layer
flow will be out of the WNW with the models developing
impressive helicity on the order of 2-3(m^2/sec^2). The most
likely scenario will be for storms to develop over the lower
lakes and spread ESE across the region during the afternoon in
short lines and bowing segments along with the possibility of
isolated supercells.

In the wake of the Thursday system a slightly cooler and drier
day is in store for Friday. By Saturday the humidity will begin
to return along with a chance of mainly diurnal showers/storms.
as a weak shortwave once again races over the top of the eastern
ridge. We look to get a break on Sunday as the 12Z models
show a mainly dry day, but by the Monday-Tuesday timeframe more
showers become possible as we stay in fast flow aloft near the
top of the subtropical ridge.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
A ridge of high pressure will build east across the Commonwealth
today and slide off the Mid Atlantic Coast Wednesday evening.
VFR expected over all routes today and tonight. Winds will
light and variable overnight. VFR conds prevail overnight and
Wednesday, with winds shifting to the southeast and increasing
later Wednesday morning afternoon.


.Outlook...

Tue-Wed...Mainly VFR.

Thu...VFR into the afternoon, then strong thunderstorms possible
mid afternoon into Thu night.

Fri...Ceiling restrictions poss NW early, then mainly VFR.

Sat...scattered restrictions possible from potential showers
and thunderstorms.

&&

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

&&

$$
SYNOPSIS...DeVoir
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Lambert
LONG TERM...La Corte
AVIATION...DeVoir/Gartner