Harrisburg, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

525
FXUS61 KCTP 220731
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
231 AM EST Sun Dec 22 2024

.SYNOPSIS...
* Coldest airmass of the season so far brings single digit low
  temperatures by Monday morning
* Christmas Eve system with mixed precip impacts travel while
  temperatures continue to moderate through the end of the week.

&&

.NEAR TERM /THROUGH TODAY/...
Dwindling lake effect snow showers/flurries are expected
early this morning over the Alleghenies, as high pressure
approaches from the Great Lakes. Stratocu, which covers the
northern and western portion of the forecast area at 07Z, should
begin to break up, as inversion heights fall. Latest model RH
profiles support mostly sunny skies over all but parts of Warren
County by this afternoon.

Breaking clouds, a diminishing breeze and fresh snow cover over
much of Central PA should allow temps to fall steadily this
morning. Daybreak readings are expected to range from the low
single digits over the Mtns north of KIPT, to the mid and upper
teens across the Lower Susq Valley.

Model soundings become mixed this afternoon to 900mb, where
temps around -14C support highs ranging from the mid teens over
the Mtns north of KIPT, to the upper 20s in the lower elevations
along the Mason Dixon Line. Even though highs will be several
degrees below those of Saturday, the combination of sunshine and
lighter winds may actually make it slightly more pleasant to be
outside.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
High pressure is progged to build over PA tonight, providing
nearly ideal conditions for radiational cooling with clear
skies, a calm wind and a fresh snowcover over parts of the area.
Have therefore undercut NBM min temps by a few degrees. Tonight
should undoubtedly be the coldest yet this winter, with daybreak
readings likely ranging from the single digits below zero in the
coldest hollows north of KIPT, to around 10 above over the
southern tier counties.

Return southerly flow behind the departing high will help
temperatures rebound some on Monday as high clouds stream in
ahead of the next system. Current medium range guidance
indicates most of the day will be dry, but precipitation could
arrive in northwest PA by Monday evening.

A fairly fast moving, northern stream shortwave will cross PA
late Monday into Tuesday and bring some light snow to the area.
Best chance for -SN and a light accum of a coating to 2 inches
will be across the Northern Mtns of the state. Some travel
disruptions are possible for I-80, but significant accumulations
appear unlikely at this point. GFS and its ensembles are
farther north with the track of the mid and upper level trough,
but QPF along the trailing cold front leads to a similar
outcome to the EC with respect to Snow Probs/Amounts.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
On the large-scale, the amplified, cold eastern
Canadian/northeastern CONUS upper trough dominating at the
present time should be a thing of the past by Christmas Day, as
this feature lifts out into the northern Atlantic. It will
replaced by building heights and a generally more zonal flow
pattern aloft. This translates into more seasonable temperatures
for late December across PA, even trending above climo towards
next weekend.

As for the sensible weather, there is increasing confidence that
surface high pressure from southeastern Canada down into the
northeastern U.S. will keep the weather dry for the Commonwealth
from Christmas Day into at least Thursday.

Uncertainty grows later in the week, as low-level easterly flow
and the approach of weak short-wave energy from the Midwest
could bring bouts of light precipitation, especially for
southern and western sections of the state. At this early
juncture, light rain appears to be the most probable
precipitation type, but pockets of light wintry mix are not by
any means off the table.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
Bands of snow off Lake Erie continue to stream across the
airspace this evening. These snow bands will mainly impact the
western sites of BFD and JST. There`s a less than 30% chance AOO
and UNV could see some brief reductions in visibility from
bursts of snow. Otherwise VFR conditions will prevail for all
sites east of the Allegheny front.

As we approach daybreak subsidence and dry air should be moving
into region. JST and BFD are still the two most likely sites to
see lower flight categories from low clouds, but they will be
borderline MVFR/VFR. All other sites should experience clouds
scattering out throughout the day and clear skies coming into
play by Sunday afternoon.

Light winds and clear skies are expected for Sunday night into
the first part of Monday.

Main issue for the area after Monday would be for lower
CIGS and even some mixed precipitation from time to time,
mainly after early Monday evening, as a milder and higher
dewpoint airmass works into the area.

Outlook...

Mon...No sig wx.

Tue...Snow enters W PA AM, overspreads area by afternoon.

Wed...No sig wx.

Wed Night...Patchy freezing rain possible.

Thu...Light rain possible south.

&&

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

&&

$$

SYNOPSIS...Banghoff
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Banghoff
LONG TERM...Jurewicz
AVIATION...Bowen