Area Forecast Discussion
Issued by NWS State College, PA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 251142
Area Forecast Discussion
National Weather Service State College PA
742 AM EDT MON JUL 25 2016
A cold front will push southeast across Pennsylvania late today
and tonight...accompanied by a likelihood of showers and scattered
TSRA. High pressure will return for mid week with continued warm
temperatures. Temperatures may trend back to near or slightly
below normal over the weekend.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A hot and humid airmass will be in place across the region
today...ahead of a cold front currently extending from southern
lower Michigan...SSWD to the Chicago area.
Significant breaks in the high based strato cu and alto cu cloud
decks will allow instability/ml cape to ramp up significantly this
afternoon bringing the threat for a few clusters of potent
thunderstorms to move quickly east across the region.
The southern two thirds of the CWA is under a SLGT Risk for svr
tsra today with the primary triggering mechanisms being the
aforementioned cold front...and well-defined entrance region of an
80 kt upper jet that will be sliding over southern New York state
and NWRN PA.
By 18z, 2 or 3 areas of quite high...0-1 km EHI of 2-3m2/s2
develops across the Alleghenies of nrn and wrn penn, then shifts
SE to the Lower And Mid Susq Valley and increases even a little
more to pockets of 2.5 to 3.5 m2/s2.
A couple of short-lived HP supercells...transient mini bow echoes
and a few compact MCV are possible across much of the region today
with localizedstrong/damaging wind gusts, and some instances of
Lagging upper trough and sfc cold front (briefly elongating to a
more west/east direction this evening into the first half of the
overnight hours) will combine with the very high...2+ inch PWAT
values to bring the threat of some training TSRA with highly
localized very heavy rainfall of 2 inches plus within just an
Headwater Flash Flood Guidance values are extremely high and
4 inches plus for the 1-3 hour period, so at this point there
isn`t a big concern for flash flooding. However, PWATs are just
about as they head around this part of the country.
Timing for the larger scale - bkn line of significant shra/tsra
will be across the nw mtns between 15-18Z...then bisecting the
state from NE to SW around 19z...before impacting the Lower Susq
Valley mainly after 20Z.
Patchy fog will occur through about 13z in some of the valleys in
central and southern PA where the more widespread light to
moderate rainfall occurred Sunday evening.
Temps to start the day will range from he u60s across the mtns of
northern and western PA, to between 70 and 75 degrees across the
ridge and valley region of Central PA.
Ens mean 8h temps support max temps today from the u80s across
the Allegheny Plateau, to the m90s across the Susq Valley. The
combination of heat and humidity warrants continuation and slight
northward expansion of the heat advisory across roughly the SE
half of the fcst area.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
The relatively weak sfc cold front will slide SE across the SE
half of the state late today and tonight, accompanied by
scattered showers and perhaps a few tsra early tonight.
Clearing skies lower PWAT air, and a rather light WNW breeze of 5
kts or less could lead to some patchy dense stream/river valley
fog...esp north late tonight and early Tuesday morning.
low temps early Tuesday will vary from the l60s across the
north...to the lower 70s across the SE zones.
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Big story in the extended fcst is the likelihood for modest
cooling by Tue/Wed behind the weak cold front. However, temps
still likely to remain somewhat abv normal within a generally
Midweek weather looks dry again, with just low pops for isolated
tstms. Fri looks to be the next higher chance for tstm impacts
areawide as another cool front progged to move through.
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
-- Changed Discussion --Fog pretty much gone. Just a little hazy now. NW mountains already
feeling the effects of weak short wave trough moving through the
lower Great Lakes. Timing from most sources would take most of
the storms to our south by 02z. There could be some
stronger/gusty storms over the southern terminals this aftn/eve,
as heating and a longer-wave upper trough slides in right behind
the first trough. Dewpoints do not dip all that much tonight, so
fog is almost likely with some clearing and residual llvl moisture
from the rain earlier. However, if there is enough time to dry it
up before nightfall/clearing, we may not fog up. Will carry 3-5sm
for most places overnight.
Air does get slightly drier for the middle of the week. It should
not be cold enough at night to make much if any fog in the valleys
of the north. The airfields will likely stay VFR into Thursday.
THU-FRI...Mainly VFR. SCT PM SHRA/TSRA.
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Record high for Harrisburg today is 99 degrees set in 1940.
Record high for Williamsport is 100 set in 1934.
Heat Advisory from 3 PM this afternoon to 8 PM EDT this
evening for PAZ027-028-035-036-049>053-056>059-063>066.