Area Forecast Discussion
Issued by NWS State College, PA

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595
FXUS61 KCTP 140027
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
827 PM EDT Mon May 13 2024

.SYNOPSIS...
A warm front will lift north of the Commonwealth by tonight,
with mainly fair weather expected into Wednesday. A cold front
may touch of a few afternoon showers on Tuesday. A wave of low
pressure tracking south of the Commonwealth will continue
showery conditions on Wednesday with drier conditions expected
Thursday and Friday.

&&

.NEAR TERM /THROUGH TUESDAY/...
Warm front is making the jump northward early this afternoon,
with stratus and light showers lifting north of the PA/NY border
and Endless Mountain region and a good deal of sunshine north of
I-80. Areas south of I-80 have been mostly sunny since morning
fog burned off, and will continue that way through this evening.
An examination of latest guidance indicates quite a bit of mixed
layer Yin in the wake of this morning`s warm frontal showers
over N Central PA. MLCAPEs do recover sufficiently for perhaps
an isolated shower or storm, especially along and north of Rt 6,
but coverage appears less than earlier anticipated and have
shaved POPs for the remainder of the daylight hours after the
current showers over Sullivan County exit shortly.

For the overnight, shortwave ridging along and sfc high
pressure moving off of the east coast and a resulting southerly
breeze will result in much milder conds than last night. Lows
will range through the 50s. A weakening shortwave lifting out
of the Ohio Valley could support a late night shower over
primarily the southwest part of the forecast area.

745 pm update... Earlier isolated showers over the far northern
tier of the Commonwealth have weakened and moved up into NY
State.

Otherwise, a broken mid-level cloud deck from the Ohio
Valley (owing to warm and moist advection aloft) is tracking
into southwestern PA. This cloud mass will gradually thicken
across central PA overnight. There is an outside chance that
some light showers (resulting from weak short-wave ripples
lifting northeast out of the TN and OH Valleys) could sneak into
the Laurels towards daybreak. This scenario seems well handled
by the low chances (20-30%) for showers in the gridded forecast after
about 5 am in this area.

As mentioned in the earlier discussion, tonight will be milder
than recent nights, with lows by daybreak only falling into the
50s area-wide.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
After a much needed but too short reprieve, we`ll see increasing
chances for showers and possible afternoon tsra Tuesday associated
with an approaching southern stream shortwave lifting northeast
from the Southern Miss Valley. Model RH profiles support mainly
overcast skies, which should act to limit heating and the
chance of tsra. However, surging low level moisture, combined
with modest diurnal heating, should support fairly widespread
showers and isolated tsra by late afternoon based on the 00Z
HREF.

Guidance continues to track surface low linked to the
approaching shortwave south of PA Tuesday night into Wednesday,
resulting in another period of rain. Ensemble plumes suggest
around a half inch of rain is likely in most spots by Wednesday
evening. Have tweaked temps downward slightly from NBM guidance
Wednesday due to the expected rain and easterly flow. Raw
NAM/GFS surface temps peak in the 60s over most of the region
Wed. Expect rain to end Wed evening, as the low exits the Mid
Atlantic coast.

Thursday still has the possibility of being dry for most
locations. Some guidance is depicting somewhat of a ring of fire
feature across western and northern areas with isold diurnal
shra or tsra possible, but for most areas the shortwave ridging
should keep it dry. Left the 20-30 PoPs in for Thurs given by
the National Blend respecting the low predictability of timing
and strength of mesoscale features, like the aforementioned
small ridge aloft, at this range.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Lingering unsettled weather is likely late this week into early
next week.

Northern stream trough and veering return flow will reintroduce
shower chances Thursday night and Friday. Lightning chances
certainly in the cards given our placement in a warm sector
airmass with a surface low in southeast Canada.

The weekend`s sensible weather remains far from certain as a
southern stream upper low meanders to our southwest and
potentially phases into the aforementioned northern stream
trough. Positive phasing would likely result in an unsettled and
potentially wet weekend yet again, while clearer skies would
prevail if this low becomes cutoff from the northern stream and
brings shortwave ridging. Heights aloft however look to remain
fairly steady at this point, keeping temperatures on the
seasonably warm side with highs in the 70s and lows in the 50s.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
VFR conditions persist overnight and into the day on Tuesday as
high pressure slowly gives way to increasing moisture and
cloudiness ahead of our next weather system. There is an outside
chance (<10%) at some fog development in the eastern part of the
Commonwealth toward daybreak Tuesday, but have opted not to
mention it at IPT and MDT given the low probability of
occurrence. It is also worth noting there will be some ~30kt
winds at ~2kft this evening for a few hours, which will remain
below LLWS criteria.

By daybreak Monday, expect thicker clouds to begin advecting
into the region with gradual lowering throughout the day. MVFR
ceilings will move in from southwest to northeast during the
afternoon as occasional showers and a few thunderstorms drift
across the region. Not enough confidence in coverage/timing to
include any mention of thunder, but would not be surprised to
see some impacts tomorrow afternoon and evening.


Outlook...

Tue Night...Showers continue with IFR restrictions likely.

Wed...Restrictions in showers/t-storms and low ceilings.

Thu...Slow improvement, with a few lingering showers possible.

Fri...Deteriorating conditions with showers increasing.

Sat...Showers continuing with reductions.

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Jurewicz/DeVoir/Fitzgerald
SHORT TERM...DeVoir/Fitzgerald
LONG TERM...Guseman/Dangelo
AVIATION...Banghoff