Harrisburg, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

975
FXUS61 KCTP 030131
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
931 PM EDT Wed Apr 2 2025

.SYNOPSIS...
A warm front will lift into Pennsylvania tonight as low
pressure tracks west of Pennsylvania through the Great Lakes. A
trailing cold front will push through Central Pennsylvania late
Thursday, then stall out out of just south of the region late
this week. A wave on the stalled front is likely to lift up the
Ohio Valley and across Pennsylvania this weekend.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Seeing a lull in rainfall across the area tonight with a weak
upper ridge over PA and a surface trough now north of the PA/NY
border. South-southeast winds have really picked up over the
last few hours as a deep surface low moves into the Ohio Valley.
Expect winds to stay gusty overnight and through the day
tomorrow as a tight surface pressure gradient and 60-70kt low-
level jet traverses the region tonight. Later tonight, an upper
trough will enhance lift over the NW as a surface warm front
continues to approach southwest PA. The warm front will still
be wrapped around the western and southern borders of the CWA in
the morning with cold air wedged east of the mountains. A
potent line of storms will trek across Indiana and Ohio tonight
before moving into western PA before sunrise. That line of
storms will weaken with eastward extent, but some hail and
damaging wind gusts are possible west of I-99 and in the
northwest mountains before the storms weaken.

Stability remains high over the east while a surge of deep
moisture will roll in overhead overnight. Persistent southeast
flow should result in lots of low clouds and fog blanketing the
ridges tonight. Some patchy DZ is also expected. Temps rise
after midnight, hitting the 50s almost everywhere and near 60F
in the Laurels at sunrise.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
The low pressure center with this storm will be around the srn
tip of James Bay in mid-day, with a trailing cold front pushing
into the NW in late AM (before noon). The showers/storms in the
morning could still pack a punch, but the prob for SVR wind/hail
is low. The low crud over the east will start to clear out, but
likely be stubborn to leave. The stability will again thwart the
chc for deep convection for much of the area during the daylight
hours. However, the disorganized look to the convection in the
aftn on the HREF guidance may be because of the wide spread in
the members on where and when to pop convection and when the
front moves in/thru. Will keep mentions of SHRA and TSRA in the
forecast for all day in the south, but the nrn tier should
stabilize as the front presses south in the aftn. A large cap is
evident over the srn tier in the aftn up around 7-8kft, so
it`ll have to be strong forcing to overcome it. The front could
do it.

Highest PoPs will come later Thursday night after the cold
front has pushed into MD and perhaps into nrn VA. The
overrunning will also have good/steep lapse rates and
instability aloft over our srn tier. SPC SLGT risk SVR on Day2
is still painted over our srn half, probably more so for the
daylight hours Thurs than the late night (early Fri AM). But,
the cap and initial stability at the sfc are two negatives.
Could be a similar situation to what we experienced earlier this
week as storms failed to intensify anywhere except the far
southern tier of PA.

Temps will get into the 70s for many places on Thursday, as 8H
temps get into the mid teens C in the morning, even if they
slide a little in the aftn. Clouds will hinder temperatures
somewhat, but a gusty southwest wind should be effective at
helping temperatures rebound well on Thursday afternoon.  A big
range will be found for mins Thurs night, near 40F N and upper
50s SE.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Latest EPS/GEFS indicate cooler and drier weather is likely
Friday/Friday night across most of CPA as sfc high pressure
migrates eastward from the Great Lakes through northern New
England. The most likely area for rain on Friday is over the
southern tier of CPA particularly the southwest mtns/Laurel
Highlands on the eastern edge of the deep moisture plume
extending eastward from the Ohio Valley and in close proximity
to the wavy/pivoting q-stnry frontal zone near or just south of
the MD line.

Waves of low pressure riding east/northeast along the stalled to
lifting frontal boundary will result in periods of soaking
rainfall (with some embedded convective elements) this weekend.
Latest WPC/NBM QPF fcst projects the heaviest rain (0.50-1.50")
over the western and northern Alleghenies with <=0.50" across
the south central ridges into the lower Susquehanna Valley
(where it is needed the most).

There is a broad consensus among the medium range operational
and ensemble guidance that the primary cold front slides to the
east of the area early next week followed by anomalous upper
level troughing building into the northern Mid Atlantic and
Northeast states next Monday-Wednesday. This pattern will be
accompanied by high confidence in below normal temperatures.
The colder cyclonic/NW flow should also favor scattered
rain/snow showers downwind of Lake Erie over the Allegheny
Plateau.

There are some long range model signals that suggest upper level
troughing will reload into the back half of next week which
would favor a continuation of temps below the historical
average for the second week of April. There may also be an
opportunity for frost/freeze conditions as the spring growing
season gets underway in the Lower Susquehanna Valley.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
A few rain showers continue to linger across the area as of the
beginning of the 00Z TAF package. These showers should move out
of the region within the next few hours. The resulting south-
southeasterly flow will lead to increasing low- level moisture
over much of Central PA. This will cause MVFR ceilings to
develop almost everywhere tonight, with the potential exception
of JST. RAP model soundings suggest that the low clouds would
make it there, but the GLAMP and HREF show a less than 40%
chance of MVFR ceilings developing. Given the uncertainty at
that site we kept site borderline VFR overnight.

The other concern tonight will be LLWS as a 45 to 55 knot low-
level jet moves in and surface wind gusts decrease. BFD will be
the first airfield to see wind shear develop and the threat will
spread southeastward through the late evening. The potential
for LLWS will reach MDT and LNS in the 06-08Z timeframe.

A decaying line of convection will reach the central PA area
during the pre-dawn hours Thursday morning. Instability will be
limited the further east these storms move, however sites in the
west such as JST/AOO/BFD could see damaging wind gusts and
rumbles of thunder. As these storms reach eastern PA by late
morning they`ll likely be light or nothing more than drizzle.
Reductions in visibility will still be possible over MDT and
LNS. Latest HREF shows a break in precipitation before another
round of convection initiates across the southern half of PA
with the passage of the cold front. Guidance still is showing a
wide spread of solutions as to the exact timing convection will
initiate come Thursday afternoon.

Outlook...

Thu...MVFR poss in widespread rain showers. TSRA poss, mainly S.
CFROPA aftn/eve.

Fri...MVFR cigs and visby expected, mainly S.

Sat...Widespread showers; impacts likely.

Sun...Widespread showers; impacts likely.

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Dangelo/Banghoff
SHORT TERM...Dangelo/Banghoff
LONG TERM...Steinbugl
AVIATION...Bowen