Area Forecast Discussion
Issued by NWS State College, PA

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406
FXUS61 KCTP 300355
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1155 PM EDT WED JUN 29 2016

.SYNOPSIS...
High pressure will drift east and bring generally dry weather
with comfortable humidity into Friday. A cold front will move
east across the state Friday afternoon and evening followed by
more high pressure for Saturday through Independence day.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Skies are clear to scattered over most of the region and the wind
has dropped off to the 5-10 mph range.

Areas of valley fog are likely late tonight through the hours
just after sunrise Thursday as strong radiational cooling causes
the air/water temperature difference to expand beyond 20F in the
typically colder central and northern PA river valleys, a good
rule of thumb for fog.

Min temps will range from the unseasonably very chilly lower 40s
across the NW mountains...to the mid 50s and lower 60s in most
other locations.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Thursday remains somewhat of an interesting forecast, with the
potential for a very minor short wave trough lifting NE from the
Ohio Valley and Central Appalachians and dampening out a bit while
moving across southern and eastern PA and during the daytime
hours. The airmass will be pretty dry, and there will be just a
few triggers for isolated/weak convection across the south
(especially on the ridge tops) where dewpoints will be closer to
60F.

Maxes will warm significantly in most places compared to the cool
temps of Wed...especially across the nrn and western mtns. highs
will be in the upper 70s to lower 80s. However...the Laurel
Highlands may hold in the mid 70s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
A vorticity lobe rotating around the south-side of a closed mid
level low over James Bay will send a cold front from the Great
Lakes through the Mid Atlantic and Northeast states on Friday.
Model QPF continues to point toward spotty light to moderate
rain amounts with local maxes from upstate NY southward along the
Mid Atlantic piedmont. The best combination of low level moisture
(60+F surface dewpoints) and marginal instability will be located
over the eastern 1/2 to 1/3 of the area including the middle and
Lower Susquehanna Valley. The severe T-storm outlook from SPC
indicates severe storm potential is very low at this time. The
front shifts off the coast Friday night with high pressure and
abnormally dry airmass moving into central PA for the weekend.

What appeared to be a fairly predictable/confident forecast in
dry weather lasting through the 4th of July has begun to degrade
with recent deterministic model runs showing increasing
differences in shortwave details from the Central U.S. into
southeastern Canada. More specifically, the 29/12z GFS and CMC
show a northward trend or shift in the stationary boundary
located along/north of the I-70 corridor with pcpn arriving in
western PA around the time fireworks are getting underway. The
29/00z ECMWF keeps the boundary and bulk of associated pcpn
further south of the Mason Dixon line along the I-64 corridor.

Given the increasing model differences, will utilize a blend of
the latest guidance with the previous forecast which increases
POPs a bit over the southern counties around Mon-Tue but still
keeps continuity for a mainly dry and seasonable Holiday weekend.

&&

.AVIATION /04Z THURSDAY THROUGH MONDAY/...
Clearing skies overnight will lead to another round of MVFR to
IFR cigs and vsbys. As the region is drier today then tomorrow it
will take a little longer to develop. However, the clearer skies
and the high dewpoints will make it easier to develop fog/mist and
low stratocu. Expect the winds to decouple and go calm between 05Z
to 09Z with reducing conditions forming shortly after.
 The latest SREF and short range models show decent Boundary layer
moisture forming between 06Z to 15Z across most of central
Pennsylvania. MDT and LNS may take a little longer, between 08Z to
10Z.
 Reducing conditions will slowly dissipate tomorrow morning, with
all TAF sites improving between 14Z to 17Z. The next chc for
showers and storms will be late Thursday afternoon and Thursday
Night across the south and east. There is a chance for showers across
the entire area on Friday...as a cold front approaches from the
west.

OUTLOOK...

Fri...Isold tsra impacts possible.

Sat and Sun...No sig wx expected.

Mon...a slight increase in humidity for Monday with a low
chance of showers and thunderstorms across the south.

&&

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

&&

$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Lambert
LONG TERM...Steinbugl
AVIATION...Lambert/Ceru



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