Latest Area Forecast Discussion for Central PA

Here is the latest Area Forecast Discussion for Central PA

This text statement is the latest forecast reasoning from the NWS in State College, PA

See the links at the bottom of the page for previous issuances/versions of the statement as well as our other text statements.

239
FXUS61 KCTP 171731
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
131 PM 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 7 PM THIS EVENING/...
Surface cold front has crossed Lake Erie this morning and is
moving onshore over far NW PA. Shra (no thunder attm) scattered
about western PA with an organized cluster of moderate to hvy
rain associated with a weak MCV tracking from the WV panhandle
into far SW PA. Overall, a beneficial rain will be brought 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. However,
there is a MRGL-SLGT severe threat over mainly southeast
portions of the area.

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. DCAPE is a third lower than what we saw
yesterday afternoon/evening, but is still maximized over my
southeast counties, which will experience several hours of full
surface heating.

Regarding mode, 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 /7 PM THIS EVENING THROUGH FRIDAY 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 /SATURDAY THROUGH TUESDAY/...
On Saturday, there could still be enough moisture working into
the state from the south that a shower or two could develop over
the SE and/or ridge-and-valley region if the ridge tops can help
nudge the moisture high enough. It`s only worth a 20pct chc at
this point based both on coverage and probability. This is the
only mar in an otherwise stellar weekend forecast.

During the early part of the new week, the humidity levels will
creep back up as the deep upper low over ern Canada slides a
little more to the east and the Bermuda High pushes moisture
farther to the north and into the state. The stationary
boundary to our south may struggle to move northward, so we`ll
keep the increase in precip chances slow for the time being.

Overall, we will see muggy nights again by mid week and a
gradual increase in cloud cover and PoPs. By Wed, PoPs get close
to 70pct. Confidence is higher than normal in the extended
pattern. Of course, confidence is lower on the day- to- day
details. But, normal diurnal trends in convection have been
leaned on for most of the long range.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
MVFR cigs cover northwest and north central PA, and are overspreading
central airfields at mid morning, along with scattered rain
showers. Cigs could dip into the IFR range, but MVFR is more
probable (>60% chance) at KBFD. Showers and thunderstorms will
become more numerous this afternoon and last into the evening
along and ahead of a cold front slowly 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/DeVoir/Bowen
NEAR TERM...Lambert/DeVoir/Bowen
SHORT TERM...Dangelo/Bowen
LONG TERM...Dangelo
AVIATION...Steinbugl
CLIMATE...Steinbugl

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