Lancaster, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

972
FXUS61 KCTP 041508
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1108 AM EDT Fri Apr 4 2025

.SYNOPSIS...
*Break in the rain today with some sun in the northern tier
*Periods of rain return tonight and last through the weekend
*Unseasonably cold temperatures to start early next week with
 rain and snow showers downwind of Lake Erie

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
Drier llvl flow from the north circulating around high pressure
migrating ENEWD from Lake Huron into Quebec will result in
mainly dry weather for the rest of today (spotty dz late
this morning over the Laurels). Visible satellite trends show
brightening skies over the northern counties with a good deal of
sunshine likely along the PA/NY border this afternoon. After a
very mild night by early April standards, max temps should reach
the 55-65F range -- +5-10F above daily climo but ~10-15 degrees
lower vs. yesterday (Thursday 4/3). Hires model data indicates
rain returning to the southwestern quadrant of the forecast area
by 8pm/0000UTC as warm advection ramps back up across the region.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH SUNDAY NIGHT/...
A wave of low pressure on the stalled front in the Ohio Valley
is progged to lift northeast to near Lk Erie by 12Z Saturday.
Rain along the attendant warm front could spread into the
western part of the forecast area as early as this evening.
However, the best chance of rain will come late tonight, when
surging PWATS and isentropic lift at the nose of a potent low
level jet work into Northwest PA. Elevated instability and
strong forcing at the nose of the low level jet could result in
embedded tsra across the NW Mtns late tonight, even though the
surface warm front should remain west of the area. +3-4SD PWATs,
combined with modest elevated instability, could support some
heavy downpours early Sat AM over the NW Mtns. The 00Z HREF
indicates the potential of >1 inch in spots of Warren County by
12Z Sat.

Cloud cover and low level warm advection should result in a
very mild Friday night, with lows ranging from the low 40s N
Mtns, to the low 50s in the south.

The surface low is progged to pass north of the region
Saturday. Additional showers should accompany the slow-moving,
trailing cold/occluded front Sat into Sat night. EPS plumes
support rainfall Sat-Sat night ranging from 1-2 inches, with the
greatest amounts over the NW Mtns and the least over the Lower
Susq Valley. Modest instability, combined with +3-4SD PWATS,
could support tsra with locally heavy downpours.

Current guidance indicates the slow-moving cold front will push
south of the Mason Dixon Line Sat night, but make very little
additional progress Sunday due to southwest flow aloft. Fgen
forcing beneath the right entrance of a jet streak over the Grt
Lks will likely result in lingering light post-frontal
precipitation into Sunday. Model soundings indicate it could
become cold enough for a light rain/snow mix over the N Mtns by
Sunday PM, where a light accum is possible Sun night. Cloud
cover, precipitation and low level cold advection should make
for a markedly chillier Sunday, especially across the N Mtns
where NBM maxtemps are in the low 40s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
There is a broad consensus among the medium range operational
and ensemble guidance that the primary cold front (and
associated band of rain) slides to the southeast of the area by
early Monday. Model data favors a period of dry weather during
the day on Monday with noticeably cooler max temps (~55F) over
the southern tier of CPA (-10 to -15 degrees cooler vs. Sunday).

The focus will shift to a cold upper trough digging through the
Great Lakes into the Northeast Monday night into Tuesday. This
feature should bring unseasonably cold temps (-15 to -25F below
the historical average) and unsettled wx with rain/snow showers
likely along with some potential for strong blustery wind gusts.
The colder cyclonic/NW flow should linger snow showers downwind
of Lake Erie over the Allegheny Plateau into Tuesday night and
possibly Wednesday morning. Temps should hit a nadir Tuesday
into Tuesday night.

There are some long range model signals that suggest upper
level troughing will reload (with potential for a closed low to
move deep into the southeast US) into the second half of next
week. This pattern 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 /15Z FRIDAY THROUGH TUESDAY/...
At 11z Fri, VFR conds were observed at all TAF sites except for
JST and AOO, where MVFR stratus was present. Upslope NW flow
will likely maintain MVFR cigs there for much of the day, with
low confidence in temporary improvement this afternoon before
conditions deteriorate again later this evening and tonight.
After a lull in precip today, the boundary that crossed as a
cold front yesterday will return as a warm front, overspreading
lowering cigs and another round of showers and storms later
tonight into Saturday. Marginal LLWS is also expected late
tonight into early Sat morning across mainly the northern and
western TAF sites.

Outlook...

Sat...Widespread showers and thunderstorms; impacts likely.

Sun...Lingering rain/snow showers; restrictions poss especially
N/W.

Mon-Tue...Restrictions likely NW Mtns. Snow showers possible.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Fitzgerald/Steinbugl
SHORT TERM...Fitzgerald
LONG TERM...Lambert/Steinbugl
AVIATION...Colbert/RXR