153
FXUS61 KCTP 150326
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1126 PM EDT Sun Jul 14 2024

.SYNOPSIS...
High pressure will remain near Bermuda for the first part of
this week, resulting in a prolonged heat wave over the region. A
cold front will push southeast across Pennsylvania late
Wednesday, then high pressure will build in from the Great Lakes
late in the week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
The main feature of interest in the near term forecast is a mid
level shortwave entering Western PA, which is progged to track
across Central PA late tonight. Modest height falls and surging
pwats ahead of the shortwave supports at least a slight chance
of an overnight shower over much of the area. Can`t rule out a
tsra across the Susq Valley, where RAP indicates higher
instability overnight.

The entire region will remain very warm and humid overnight with
increasing clouds and an overall uptick in humidity ahead of
the upstream shortwave aiding in keeping temps up. See no reason
to deviate from NBM min temps, which range from the mid 60s in
the coolest northern valleys to the mid 70s in the more
urbanized spots of the Lower Susq Valley.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Diurnal heating, combined with the approach of shortwave over
the Grt Lks, should result in scattered convection Monday
afternoon/early evening. Modest instability/shear profiles could
support some multicell storm organization and the threat of
isolated severe weather, mainly over Northern PA where progged
mid level flow is strongest. Convection should dissipate after
sunset, as the shortwave passes east of the area.

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 Monday and
Tuesday at this point and left Wed out of it.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Heat wave 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 100-105F southeast of the Alleghenies. High
confidence in excessive heat risk lead to the issuance of a heat
advisory for the south central mountains and Middle Susquehanna
Valley Mon & Tue and an excessive heat warning for the Lower
Susq Valley, where max heat index around 105F appear likely.

A 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. However, a better
chance of more widespread showers/tsra is in the cards for Wed
PM with the passage of the front.

All medium range guidance supports a return to fair and
seasonable weather with much lower humidity late in the week, as
high pressure builds southeast from the Grt Lks. Will maintain
just a slight chance of convection along the southern tier
Thursday to account for some uncertainty regarding how far the
dying cold front makes it south of the Mason Dixon Line.

The stalled front is likely to return northward next weekend,
resulting in the return of diurnal convection, mainly over the
southern counties.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Line of showers/storms moving east across Ohio continues to
weaken, but still expecting BFD and possibly JST to see a few
showers from this later on this evening.

Overnight, BFD stands the best chance (50-60%) of seeing MVFR
ceilings while all other sites see much lower probabilities and
thus have maintained VFR conditions at all other sites. Given a
good deal of cloud cover, have opted to maintain VFR
visibilities at this time with fog more confined to deeper
valleys. Sub-VFR probabilities for visibility cap out at 30-40%.

Monday will bring a better chance of showers and storms in the
afternoon and 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. Still too early to nail down a
specific time for TSRA/CB mention.

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

Outlook...

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...Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Dangelo
LONG TERM...Fitzgerald/Bowen
AVIATION...Guseman/Dangelo
CLIMATE...Evans