Harrisburg, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

250
FXUS61 KCTP 141748
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
148 PM EDT Sun Jun 14 2026

.WHAT HAS CHANGED...
* Higher confidence in timing of most thunderstorms (2 PM
  through 11 PM). Increased POPS for SHRA/TSRA layer this
  morning and this afternoon across the Wcent and Northern Mtns.

&&

.KEY MESSAGES...
1) Strong to severe storms expected for Central PA this
afternoon and evening.

2) Rare SPC Day 5 outlook for SVR TSRA potential across much of
PA on Thu 6/18

&&

.DISCUSSION...
KEY MESSAGE 1: Strong to severe storms expected for Central PA
this afternoon and evening. SPC`s late morning upgrade added a
higher wind threat across NW PA (similar to the elevated, 30%
wind threat near and to the SE of the I-81 corridor in PA.

Plenty of multi-layered WAA clouds will cover the NW half of PA
late this morning and early this afternoon with a high
probability for a 30-90 minute period of showers associated with
an area of showers (and possibly a rumble of thunder) mainly to
the north of a line from KJST to KUNV and KIPT.

This initial area of convection is linked to a relatively weak
mid/upper level vort max lifting NE across the region ahead of
the main show (i.e. an anticipated line of strong to severe TRSA
that will sweep SE across the CWA this afternoon and evening).

This lead area of convection shouldn`t intensify much, if any,
as its moving over an area with plenty of cloud cover and SBCIN
of 200-500 j/kg.

In contrast, partly sunny skies should last into the mid
afternoon hours near and to the east of I-81. SFC Based CAPE is
with no CIN is already up into the 1000-1500 J/KG range across
the Lower Susq - south of KMDT and KLNS thanks to the better sfc
heating and injection of higher llvl moisture (Sfc Tds in the
mid 60s) north off the Chesapeake Bay.

The temperatures should still get near convective temp in the
early afternoon in the west. Storm motion will bring these into
Central PA while additional but isolated storms pop up over the
CWA.

A cold front will be sweeping across the CWA later today and
early tonight. That front will be the main focus for
thunderstorms late this aftn and this evening. A pre- frontal
trough may develop a few storms in the more-humid region of the
Lower Susq in the afternoon, but models have backed off somewhat
on this possibility with the 00Z runs. Time- lagged ensembles
still hold onto some hope for this, but the trend is drier and
for fewer storms in the air over the central mountains and Susq
Valley. A cap aloft will probably stifle deep convection in
those areas before 5 PM EDT until heights start to fall and
lapse rates steepen.

The dewpoints in the SE are already a little higher than the
rest of the CWA, and will rise even more through the day, but
high moisture (Td in the m-u 60s) will also pool ahead of the
front. Deep-layer (0-6km) shear ramps up to nearly 45KT and
CAPE could touch 2000J/kg in the S and more than 100 in the N.
Hodographs get slightly curved before the front, and the NAM
generates helicity over 300 in the late aftn and early evening -
just ahead of the front - in many places. So, supercells are
possible for a brief window. Mostly, the storms will be multi-
cell clusters. Wind damage will be the most probably threat.
Hail less so, and tornadoes even lower. However, the LCLs will
be low which could make it easier for tornado formation should
discrete cells develop. The front picks up speed in the evening,
and should push all the storms past BFD close to 8 PM, and
through LNS around 11 PM.

   ------------------------------------------------------

KEY MESSAGE 2: Rare SPC Day 5 outlook for SVR TSRA potential
across much of PA on Thu 6/18

The nose of a very strong, 40+ KT swrly 850 mb jet 50+ KT at 700
mb (both being 3+ sigma on the standardized anomaly scale), the
the right entrance region of a 100 KT 250 mb jet and PWATS
around 1.5 inches (with the potential of a EML surging in from
the west ahead of a strong sfc cold front) will bring the ideal
synoptic setup for a severe weather outbreak here in the CWA. As
always, even with the moisture, instability and shear present,
such strong forcing could produces plenty of clouds and early
day convection to stabilize the atmos and decrease the potential
for significant afternoon severe weather. We`ll be monitoring
this potential closely as we head into the new week.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Upper level shortwave energy is slipping through western PA
early this afternoon ahead of potent cold frontal boundary.
Expect just a glancing blow from this feature with only VCSH
generally across northern PA through the next few hours.

VFR to MVFR conditions will remain until the onset of showers
and convection moves steadily across the state through the late
afternoon and evening hours. Some timing diffrences in the
short term high resolutions models, but the trend is for
convection to enter northwest PA in the late afternoon and exit
southeast PA during the late evening. As with any convection
scenario, expect wind shear, heavy rainfall/wet runways and
lightning as storms cross any airfield.

Once the storms exit and the frontal boundary passes after
midnight, conditions will improve to MVFR then VFR overnight
with winds shifting to the northwest near 10KTS.

With cold air aloft on Monday, a BKN cloud layer will form but
it will remain VFR. An isolated -SHRA is possible after this
forecast period - especially over northern PA.

Outlook...

Tue...Mostly VFR with isolated -SHRA/-TSRA possible.

Wed...Higher chances for -SHRA/-TSRA, restrictions more likely.

Thu...Restrictions possible in -SHRA/-TSRA.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

WHAT HAS CHANGED...Lambert/Dangelo
KEY MESSAGES...Lambert/Dangelo
DISCUSSION...Lambert/Dangelo
AVIATION...Beaty/Tyburski