987
FXUS61 KCTP 141948
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
348 PM EDT Sun Jul 14 2024

.SYNOPSIS...

A prolonged, significant heat wave will continue into the middle
of the week. Poorly organized storms are expected in the SE and
NW through this evening. Better organized, and potentially
strong to severe thunderstorms are expected each afternoon and
evening, Monday through Wednesday as successive shots of energy
roll in from the west.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Subsidence killing lots of the cu over the central and Swrn Cos
this aftn. Thus, we may be able to back off on the PoPs for
there. But, still some heating left. They should continue to
slide to the east late this aftn. The SHRA/TSRA moving in from
the NW are a little quicker than adjustments from this morning
had them. The weak shortwave driving them will likely keep them
going into the NWrn third of the area. However, loss of heating
may kill them off. Have kept small PoPs for much of the night,
though, and ramped them back up after 2 AM due to the
appch/passage of another wave aloft.

It should stay sticky through the night. Clouds over the NW may
thwart fog formation in the valleys. So, we`ve left mentions of
fog out at this point. Mins in the 65-72F range are anticipated
with little wind to speak of.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Any SHRA going on in the morning will likely fizzle, but heating
will pump the clouds up again. More organization is expected
with storms on Monday and Monday night. While a weak trough
hangs around over far SErn PA, it could still help a couple
storms form there. But, the best PoPs and expectations for
stronger storms will be over the nrn half of the area. SPC still
has us in a MRGL risk for svr (wind threat) for Monday.

The more-certain wx trouble is the heat. Have converted the
watch to a warning for Mon and Tues. Wed also looks hot, but
more like advy numbers for the SE only. To keep confusion to a
minimum and play up the danger in the nearer two days, we`ve
chosen to make the simple change to a warning for M & T at this
point and left Wed out of it.


&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Heat pattern ramps up and peaks Tuesday afternoon as a large
Bermuda high pumps increasingly hot and very humid air into CPA.
850mb temps rising to around 22C supports highs peaking between
90-100F with max heat indices 100-110F. High confidence in
excessive heat risk lead to the issuance of a heat advisory for
the south central Alleghenies and middle Susquehanna Valley Mon
& Tue and xheat watch for the lower Susq where max heat index
could reach 105-110F.

The interaction of modest shortwave trough with very warm and
humid airmass should trigger PM t-storms on Monday. Shear will
likely be weak, mitigating the organized storm potential and
keeping the severe threat isolated/limited. Another round of
at least semi-organized/possible severe convection is possible
Tuesday PM ahead of cold front pressing southeast through the
Great Lakes toward Lake Erie.

The aforementioned cold front, expected to push through
Wednesday night, will provide some relief from the heat as well
as the best chance for widespread showers and Thunderstorms on
Wednesday afternoon. Thursday should see a return to seasonable
temperatures with scattered convection possible as the front
stalls out. Friday will have fair weather return to the
commonwealth with high pressure building and humidity expected
to be lower for the end of the week.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
A few pop-up SHRA/TSRA have run through the SErn counties, but
have largely moved to the east of LNS and MDT. We can let
mentions of TS die off there. But, added it to BFD as there are
weak storms heading in from the west. A stray shower/storm or
two could pop up elsewhere across the airspace before dark, but
subsidence from earlier short wave passage will keep them to a
bare minimum. Not enough confidence in coverage or probability
to add anything of a mention of TS to any of the other terminal
forecasts at this point. Fog may again form overnight in the
valleys as the humidity remains. But, we`re not expecting IFR at
any terminal at this point as SCT-BKN cloud cover helps keep it
milder. High heat and humidity will make for slightly longer
than normal landings/takeoffs through at least Wed.

Monday will have a bit better organization to the storms in the
aftn/evening. The highest probability of having a storm will be
in BFD, UNV and IPT, as there will be a weak trough swing down
from the north.

A real/potent cold front does look like it will finally pass
through in mid-week (Tues night or Wed), and change it to a
much drier airmass.

Outlook...

Mon-Tue...Scattered, mainly aftn, SHRA/TSRA possible.

Wed...More widespread SHRA/TSRA, with brief restrictions likely.

Thu...Lingering -SHRA diminishing.

Fri...no sig wx.

&&

.CLIMATE...
The duration of warm nights is noteworthy. Here are the longest
stretches with temperatures at or above 70F on record at
Harrisburg.

# OF DAYS   DATES      YEAR
17        7/19-8/04    2020
13        8/16-8/28    2021
13        7/13-7/25    2010
12        7/18-7/29    2022
12        7/17-7/28    1999
12        7/20-7/31    1940
11        8/04-8/14    1977
10        8/10-8/19    2016
10        7/14-7/23    2013
10        8/01-8/10    1968
10        7/21-7/30    1898
9         12 times, most recently 7/3-7/11/2020
8         7/04-7/12    2024
     .................................................

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon Monday to 8 PM EDT Tuesday for PAZ019-
025>028-034-035-045-046-049>053-058.
Heat Advisory until noon EDT Monday for PAZ036-056-057-059-
063>066.
Excessive Heat Warning from noon Monday to 8 PM EDT Tuesday
for PAZ036-056-057-059-063>066.

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Bowen
AVIATION...Dangelo
CLIMATE...Evans