Area Forecast Discussion
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FXUS61 KCTP 301141
Area Forecast Discussion
National Weather Service State College PA
741 AM EDT THU JUN 30 2016
High pressure is overhead today. A cold front will move east
across the state on Friday followed by another high pressure area
which will cover the region for most of the holiday weekend. A
chance of showers is in the forecast for Monday (Independence
Day) as low pressure approaches from the Ohio Valley.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
No real changes to the forecast other than to remove fog from many
areas. Dewpoint dropped 10+ degrees at KBFD overnight. Haven`t see
a 40 dewpoint reading in a while.
High pressure and subsidence will keep it dry today. Humidity will
drop into the 30-40 percent range. A very weak short wave trough
will move overhead this morning/early afternoon leading to some
high-level clouds. Enough moisture may be present to allow sct
cumulus to form this afternoon, especially in the south-central
mountains. POPs will stay unmentionable as nothing should grow
tall enough to rain. A light west wind will turn to the south.
Deep mixing will help temps rise 4-8F higher than Wednesday`s
.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
A cold front will be moving through the Upper Great Lakes tonight.
Light southerly winds over PA should keep min temps 5-10F milder
than Thurs morning. Deep layer moisture will increase but PWATs
don`t get too far above one inch by Friday afternoon. The best
PWATs will be in the eastern third to half of the area. The upper
trough axis and cold front will swing through late-day or early
night on Friday with the cold front ushering in another very dry
airmass from the Canadian plains.
The NAM and GFS both pop up some isolated showers over the south-
central and southeastern counties later tonight and move them NE.
But, the airmass is still pretty dry tonight and any showers might
have a tough time reaching the ground. But, the right entrance
region of a jet max will provide a positive environment for some
lift and showers in the SE. Will call for scattered-30 POPs late
tonight in the SE. As the moisture increases on Friday and an
advance/lee trough develops the coverage of showers and some
thunderstorms will increase slightly for the daytime in the east.
The cold front will be arriving just after peak heating in the NW.
It will also be working on pretty dry air until it gets east of
State College. Will keep POPs lower in the west but increase them
through the day. NAM generates more showers than other models as
the really dry moves in during the evening. Have allowed for this
possibility and lingered 20-30 pops through midnight. It should be
dry after that. Winds never get strong, but deep layer shear
increases - especially in the east. CAPES getting 1000-1500 range
in the northeast/Poconos could make a couple of stronger storms
there in the afternoon/evening. SPC DY2 outlook has introduced a
MRGL risk into the eastern counties.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Refined POPs a bit on the 4th and 5th based on a slightly better
consensus amongst the models that low pressure could slide into
the Ohio Valley and end up bringing some showers/storms to
(mainly the southern half of) the forecast area. The GFS is
slower, pinching off a closed 5H contour for a brief time to our
west. This causes it to be slower with the potential precip
arrival and would keep the 4th and fireworks time dry. This is
still 4-5 days out, so....
The front shifts off the coast 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 /12Z THURSDAY THROUGH MONDAY/...
High pressure and associated dry air mass over Pennsylvania should
ensure widespread vfr conds and light wind today.
Fri...Sct tsra impacts possible...mainly east.
Sat and Sun...No sig wx expected.
Mon...Slight chance of pm showers/reduced cigs.