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Area Forecast Discussion
||Wed, Dec 31, 7:00pm EST
FXUS61 KCTP 181924
Area Forecast Discussion
National Weather Service State College PA
324 PM EDT Thu Jul 18 2019
----Dangerous heat and humidity possible this weekend---
We will be dealing with hazy, hot and very humid conditions
until early next week when some relief is in sight. Dangerous
heat will build Friday and Saturday, with heat indices peaking
on Saturday afternoon, easily exceeding 100 over southern and
especially southeastern areas.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Showers/storms over the SE have already started to slink to the
SE. There are some heavy downpours but not much lightning with
very warm temps aloft. PWATs very high, so there could be a spot
or two with local, minor, short-lived flooding. These should
continue to slide SE, and may be gone well before sunset. A
stray shower is possible off the LE lake breeze, but will leave
PoPs low there. Otherwise, a muggy night is in store. A little
fog is possible with a mainly clear sky, high dewpoints and
little if any wind.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Hoisted widespread heat advys and excessive heat warnings - many
of which will last into Sat. Tried to time/place them
appropriately with just a bit of a broad brush. While numbers
may not get to 100 everywhere over the Alleghenies/Laurels, it
will be close, and will likely get there in the valleys. The
chance for the convective cloud debris running overhead from the
NW and some isold/sct convection could keep temps down and bust
up the heat index values. Will hold onto some low chc PoPs for
the nrn tier with short wave energy running in from the NW, but
it will be running into the warm air aloft.
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Excessive heat continues this weekend. Maximum heat index
values peak in the 105 to 110 range Saturday before lowering
slightly again for Sunday. Excessive Heat Watch remains in
effect from noon Friday through 8 pm Sunday for areas from
Harrisburg to Williamsport and east. Area in watch may need to
be expanded later if confidence increases. Will also continue to
highlight heat risk via HWO, social media and DSS briefings in
addition to the watch.
Very warm mid-level temperatures look to limit/cap t-storms
Fri- Sun. That said, models hint at the potential for MCS
activity propagating along wavy frontal zone on the northern
periphery of summertime upper ridge/heat dome.
Flow is fast and strong across the US and Canada border overall
for mid July, but we are south of the main westerlies. The
airmass is warmer than what we have seen lately. 1991 and 1995
featured such warm air. In this case, the warmest air is
advected toward BUF late Friday. Warmest air for central PA is
Friday into Saturday. 850 mb temperatures fcst to be near plus
24 degrees at 850 mb late Friday across Lake Erie. Will be
interesting to see how fast water temperatures come up on Lake
Erie by next week.
A cool down is expected by next Monday, as the mean upper level
trough is nearby.
.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
The showers to the S/E of MDT will slide SE, and should not be
a factor after 22Z at LNS. The next worry would be for fog, but
only mentioning some MVFR fog for now for the overnight. Low
clouds may try to form with a slight upslope over the wrn mtns
(JST/BFD), but held off on any IFR mentions.
SHRA/TSRA should be nearing BFD late in the morning, so I did
add in a mention of TS late in the TAF period. Otherwise, looks
VFR with light wind for Fri.
Friday night and Saturday will still have a threat of isold
SHRA/TSRA, mainly in the aftn.
Sat-Sun...Mainly VFR with isolated to widely scattered PM
thunderstorms possible. Heat/humidity will make the density
altitude much higher - takeoffs/landings will take more
Mon...Still a chance of showers and storms as CFROPA occurs Mon
or Mon PM.
Tues...No sig wx.
Heat Advisory from noon Friday to 8 PM EDT Saturday for
Excessive Heat Warning from noon Friday to 8 PM EDT Saturday
Heat Advisory from 8 PM Saturday to 8 PM EDT Sunday for PAZ028-
Excessive Heat Warning from noon to 8 PM EDT Saturday for
Heat Advisory from noon Friday to noon EDT Saturday for PAZ019-