Lancaster, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

525
FXUS61 KCTP 211147
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
647 AM EST Thu Nov 21 2024

.SYNOPSIS...
An upper level low over the Lower Great Lakes will track
southeast across Pennsylvania tonight into Friday. The upper low
will lift out of the region this weekend, then a a cold front
will likely push southeast across the state Monday night into
early Tuesday.

&&

.NEAR TERM /UNTIL 4 PM THIS AFTERNOON/...
A dry slot has moved into Central PA early this morning in the
wake of an occluded front passage last evening. However, falling
heights and upper level diffluence ahead of an upper low over
Lower Michigan will spread snow/rain showers into the western
half of the forecast area later this morning. Model sounding are
cold enough for snow showers across the Alleghenies, but amounts
should be light and progged surface/road temps should be just
above freezing, so don`t expect many travel issues through mid
afternoon. See no reason to deviate from NBM temps, which peak
this afternoon in the low to mid 30s across the Laurel Highlands
and the mid 40s in the Susq Valley.

&&

.SHORT TERM /4 PM THIS AFTERNOON THROUGH FRIDAY NIGHT/...
Overall confidence is continuing to increase for the first
impactful winter weather storm of the season tonight into
Friday, as the closed 500mb low tracks across Southern PA,
causing the associated surface low south of New England to
retrograde westward through upstate NY. A deep, moist westerly
flow on the northern and western periphery of the upper low
should result in persistent orographically-enhanced precipitation
over Central PA tonight into Friday.

Model thermal profiles are cold enough to support primarily snow
over the forecast area tonight into Friday, with some rain
possible tonight over the Lower Susq Valley. However, marginal
boundary layer temps will result in highly elevation-dependent
accumulations across the Alleghenies and downsloping flow
should yield lower precip rates east of the Alleghenies.

The highest confidence of heavy snow is focused over
high-elevation Sullivan County, as well as the Laurel Highlands,
where the 00Z HREF supports a likely period of 1-inch/hr rates
between 10-16Z Friday. The greatest impact to travel should be
late tonight through Friday morning. Most likely snow totals by
late Friday should range from up to a foot over the highest
elevations of Somerset and Sullivan counties, to an inch or so
from Altoona/State College into the Susq Valley.

Diminishing precipitation is expected in general late Friday
into Friday night, as the upper low lifts out. However,
lingering lake effect will affect the W Mtns. Forecast thermal
profiles moderate with the departure of the upper low to the
point that lake effect snow showers may mix with rain over the
Alleghenies Friday night.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Lingering lake effect/orographic rain showers over the Northern
and Western Mountains Saturday, as one or more fast-moving and
weak shortwave moves SE from the Glakes Region. This light
precip will dwindle by late Sunday afternoon, as subsidence
inversion heights fall and high pressure approaches from the
Tennessee Valley. Milder conditions look likely next Monday
ahead of an approaching, rather potent cold front, which could
produce late afternoon/early nighttime rain showers with the
core of energy aloft progged to move across the Upper Great
Lakes region.

Brisk west winds and colder air pushing into the region for
Tuesday with scattered rain showers in the valleys and mixed
rain/snow showers over the higher terrain of the Laurels and NW
Mtns.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
12z update... Areas of fog have formed just prior to daybreak
near KIPT, so we did include brief IFR restrictions only til
around 13z.

Otherwise, lower clouds and some flurries will have the upper
hand today at KBFD and KJST, with mostly MVFR restrictions (high
confidence in this scenario - 80 to 90%). Unrestricted/VFR
should prevail during the daylight hours at KUNV, KAOO, KIPT,
KMDT, and KLNS.

Tonight, conditions should deteriorate from south to north with
time, as steadier snow wraps down and around an incoming storm
system. KIPT, KBFD, KUNV, and KJST should all see IFR reductions
in snow prior to daybreak (60-70% confidence). Restrictions at
KAOO, KMDT, and KLNS should occur after 12z.

Surface winds 10 kt or less for much of today, should increase
and become gusty late tonight and Friday (gusts of 20-25 kt
common, locally up to 30 kt).

Outlook...

Fri...Restrictions in snow at KBFD and KJST, with a period of
snow likely elsewhere (mostly before 18-19z). Windy.

Sat...Periodic restrictions in rain and snow showers, mainly
across the mountains (KBFD and KJST). MVFR much of the time for
KUNV/KIPT/KAOO. Mainly VFR at KLNS and KMDT. Continued breezy.

Sun-Mon...Lingering restrictions possible at KBFD and KJST,
otherwise mainly VFR.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 1 PM this afternoon to 7 AM EST
Saturday for PAZ004-005-010>012-017-018.
Winter Storm Watch from 4 PM EST this afternoon through Friday
afternoon for PAZ006-037-041-058.
Winter Storm Warning from 1 PM this afternoon to 7 AM EST
Saturday for PAZ024-033.
Winter Storm Warning from 4 PM this afternoon to 4 PM EST
Friday for PAZ042.

&&

$$

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