Area Forecast Discussion
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FXUS61 KCTP 291919
Area Forecast Discussion
National Weather Service State College PA
319 PM EDT WED JUN 29 2016
High pressure over the western great lakes region this afternoon
will drift east and bring generally dry weather with comfortable
humidity into early friday.
A few, isolated showers and thunderstorms are possible across the
Susquehanna Valley and South-Central part of the state late
Thursday afternoon and evening. A cold front will move east
across the state Friday afternoon and evening, bringing scattered
showers and thunderstorms. Another area of high pressure will move
in for Saturday with mainly clear, dry conditions and low
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Strong cold advection focused near the 925mb level helped to
strengthen the subsidence inversion and trap/maintain a shield of
bkn-ovc stratocu across much of the region outside of the
mid/lower Susq Valley. Skies in those areas were mainly sct...but
as the colder air aloft spreads across that region through the
rest of the afternoon/early evening hours, expect periods of bkn
high based strato cu invof kthv and kmdt too.
Max temps in most places will occur between 21-23z as the strato
deck dissolves, and the coldest air in the upper blyr drifts
south toward the mason/dixon line.
A transition to mainly clear skies and light wind will occur from
00z through 06z Thursday as the center of high pressure moves
across the Ohio River Valley and into western PA.
Areas of Valley Fog are likely during the early to mid morning
hours as a result of strong radiational cooling and the air/water
temp diff expands to exceed 20F in the typically colder central
and nrn PA mtn/river valleys.
Min temps will range from the unseasonably very chilly lower 40s
across the NW mtns...to the mid 50s and lower 60s in most other
.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
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 /19Z WEDNESDAY THROUGH MONDAY/...
The mvfr to low end vfr cloud deck will persist through the
late afternoon...before quickly dissipating early this evening as
high pressure builds in from the west.
NW winds of 7-11 kts will contain some minor gusts into the mid
be gusty in the upper teens to around 20 kts this afternoon...especially
across the Susq Valley where more sun and a greater depth of
vertical mixing will occur.
The next chc for showers and storms will be late Thursday
afternoon and Thursday Night across the south and east. Maybe
across the entire area on Friday...as a cold front approaches from
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.