836
FXUS61 KCTP 170926
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
526 AM EDT Wed Jul 17 2024

.SYNOPSIS...
 - A cold front will push through the state today accompanied by
   another round of strong to severe thunderstorms that will be
   focused across Central and Eastern Pennsylvania.

 - High pressure will build in from the Great Lakes on Thursday
   and bring mainly fair weather with seasonable temperatures
   through the end of the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Surface cold front was situated from the peninsula of
Southwestern Ontario to Northwest Ohio early this morning. This
airmass boundary will bring beneficial rain to the bulk of the
state today (in the form of a few rounds of showers and
Thunderstorms) and will be followed by a lengthy string of dry
days with comfortably lower humidity.

Low-level theta-E advection (specifically in the 925-850 mb
layer) will congeal and become focused across Central PA (near
and just to the South of the I-80 corridor late this morning
through about 18-19Z before shifting to the Lower Susq Valley
and adjacent SE PA between 19-21Z. These time intervals will
mark the greatest chance for severe weather today in the form of
primarily strong to locally damaging straight line winds and
isolated instances of 1 inch diameter hail, given the very
straight line hodographs, moderate values of CAPE, but fairly
weak LLVL speed shear.

The broad right entrance region of a 110 kt upper jet stretched
from NW Ohio to Southern Quebec late this afternoon supports a
better chance for initial discrete TSRA and small multi-cell
clusters, prior to a bkn-solid QLCS feature or two forming
across Central PA and progressing through the Western Poconos
and Lower Susq Valley in the 17-21Z time frame. The element
missing with Tuesday`s convective potential was larger scale
lift beneath favorable segment of the mid/upper lever jet. Most
of Central PA fell within an area of moderate mesoscale
subsidence beneath the thermally indirect, right exit region of
a moderately strong jet.

The Heat Advisory for our SE zones remains in effect through
00z Thu with temps starting the day in the mid to upper 70s.
the lack of clouds through the overnight hours has led to some
patchy valley fog, but lack of rainfall today will be a tick in
the negative column.

Developing morning showers will be focused mainly over the NW
and Wcent Mountains through 13z before expanding in coverage and
growing in intensity just SE of the Allegheny Front between
14-16Z.

PWs of nearly 2" in the SE could help feed very heavy
downpours. But, the fast storm motions and very high FFG
(widespread 4.5"/3 hrs values) keep the threat for flash
flooding low. The MRGL risk in the Day2 ERO was collaborated
with WPC, mainly in order to keep continuity with previous
forecasts.

High temps this afternoon will vary from the mid and upper 70s
over the North and Western Mtns to the 80-85 range near a KAOO
to KUNV and KIPT line and in the upper 80s to low 90s in the SE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
The cold front slides through all but perhaps a few towns on
the MD border by 03-04Z Thursday. Thus, the SHRA should press
mainly or entirely to the S of the border well before sunrise.

Falling dewpoints should lead to a lower threat of fog, but the
temps drop right along with them. Will keep the mention of fog
from the wx grids at this point.

Thursday will mark the start of the beginning of a stretch of
fair and seasonable weather with lower humidity during the day
Thursday and through the end of this week as high pressure
builds from the Great Lakes.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Much drier air will continue to work into the region Friday,
as high pressure builds into the area.

While there could be an isolated shower Saturday afternoon, the
weekend looks dry at this point.

By early to mid week next week, humidity levels will creep back
up. This will result in muggy nights again by mid week and more
in the way of a chance of showers and storms by then.

&&

.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
MVFR cigs are forecast to develop across the northwest airspace
by 12Z along with some rain showers downwind of Lake Erie. Cigs
could dip into the IFR range, but MVFR is more probable (>60%
chance) at KBFD. Showers and thunderstorms are expected to
develop this afternoon into the evening along and ahead of a
cold front pushing southeast from the Great Lakes. Storms should
decrease in coverage and exit/dissipate over the south/eastern
airspace between 03-06Z. There is decent model signal for post-
frontal upslope low MVFR cigs particularly at KJST and
potential IFR fog impacts at KBFD/KIPT late tonight into early
Thursday morning.

Outlook...

Thu...MVFR cigs psbl northwest 1/2; low VFR elsewhere.

Fri-Sun...AM valley fog. Otherwise, no sig wx/VFR.

&&

.CLIMATE...
The max temperature hit 100 degrees at Harrisburg yesterday
7/16. The last time KMDT hit 100 was back on July 19, 2020.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for PAZ036-056-057-
059-063>066.

&&

$$

SYNOPSIS...Lambert/Bowen
NEAR TERM...Lambert/Bowen
SHORT TERM...Dangelo/Bowen
LONG TERM...Martin
AVIATION...Steinbugl
CLIMATE...Steinbugl