Lancaster, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

052
FXUS61 KCTP 310121
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
921 PM EDT Sun Mar 30 2025

.SYNOPSIS...
Low pressure over Michigan will track north of PA early Monday,
with the trailing cold front pushing through the region Monday
afternoon and evening. Another low is likely to take a similar
track west of Pennsylvania through the Great Lakes Wednesday
night into Thursday. The front with that mid-week storm will
likely stall just to the south of Pennsylvania at the end of
next week.

&&

.NEAR TERM /UNTIL 7 AM MONDAY MORNING/...
A weak mid level vort max lifting into South-Central PA will
support scattered showers this evening over the southeast half
of the forecast area. However, focus for later tonight is on an
upstream squall line entering Central Ohio at 01Z. The
associated potent shortwave over W Michigan is progged to lift
northeast overnight, taking the best large scale forcing west of
PA. CAMs still indicate a weakened version of the squall line
will enter the NW Mtns around midnight. However, given
strengthening mid level flow, can`t rule out locally strong to
severe wgusts as this convection enters Warren County.

Waning large scale forcing and a more stable air mass across
Central PA should cause convection to dwindle as it pushes into
the Alleghenies after midnight. Cloud cover, an active southerly
breeze and anomalous surface dewpoints will result in a very
warm night for late March, with lows in the mid 50s to low 60s
over most of the area.

&&

.SHORT TERM /7 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday will be active, at least across the SErn third to half
of the area. A strengthening surface low will track north of PA,
dragging a trailing cold front through Central PA during the
afternoon and early evening. Latest guidance indicates the pre-
frontal low level jet and plume of deepest moisture will be over
Southeast PA. Thus, the highest POPs and best chance of severe
weather is targeted over that part of the state. RH profiles
support midday breaks in the cloud cover over the eastern half
of the forecast area, which is expected to fuel developing
afternoon convection across primarily Southeast PA based on the
latest CAMs.

Strong mid level wind/shear profiles, combined with EPS CAPES in
the 500-1000J/kg range over the Lower Susq Valley, support the
potential of severe weather Monday PM. The latest SPC Slight
Risk area extends west into the Central Mtns, but HREF updraft
helicity values target areas southeast of I-81 for the best
potential of organized severe convection. Relatively modest
instability, combined with strong forcing favoring linear
rather than discrete convection, suggests damaging wind gusts
are the main threat, with large hail/isolated tornadoes much less
likely. The threat of severe weather should end around 00Z, as
the cold front pushes southeast of the forecast area.

Ensemble mean qpf suggests rainfall Monday will range from 0.05
to 0.25 inches over most of Central PA. However, instability and
much higher PWATs southeast of KMDT should support more
substantial rainfall in that area, with heavy downpours
potentially leading to localized amounts in excess of 1.5
inches based on some HREF members. This would be beneficial
rainfall in a region that has been very dry. FFG values indicate
significant flooding is very unlikely.

Monday will be the last day of the unseasonable warmth, with
NBM guidance indicating highs ranging from around 60F over the
NW Mtns, to the mid 70s across the Susq Valley.

A much drier northwest flow will overspread the region Monday
night behind the exiting cold front, leading to breaking clouds
over most of the region. Lake effect stratocu are expected to
linger over the Alleghenies through Monday night. However,
progged inversion heights look too low to support anything more
than a few late night flurries over Warren/Mckean counties. See
no reason to deviate from NBM Monday night min temps, which
range from the upper 20s over the NW Mtns, to around 40F across
the Lower Susq Valley.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Cooler and dry conditions are forecast to start April on
Tuesday and continue into early Wednesday as high pressure
moves across PA. Guidance then tracks another surface low west
of PA through the Great Lakes next Thursday. Rain along the
attendant warm front could spread into Central PA by Wed PM,
with a chance of showers accompanying the trailing cold front
Thursday.

A cold air damming scenario ahead of the approaching warm front
with surface high east of New England supports undercutting NBM
max temps slightly Wed. However, much milder conditions are
likely Thursday, with the region potentially breaking into the
warm sector south of the surface low.

A trailing cold front is currently progged to stall out just
south of PA Thursday night. A potential wave on this boundary
looks increasingly likely to result in a period of rain Thursday
night into early Friday, especially across Southern PA. Latest
EPS/GEFS suggest a brief period of cool and drier weather is
likely Friday PM into early Saturday associated with a surface
high passing north of PA. However, another wave of low pressure
approaching from the Ohio Valley could spread rain back into the
region by Saturday PM.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
An interesting feature on radar as of 715 PM, looks like
gravity waves coming out of the area of showers southwest
of the Harrisburg area.

Not a lot of change to the 00Z TAF package. Mainly a steady
CIG for most overnight, with borderline LLWS. A few showers,
along with a chance of thunderstorm across the far west, mainly
at sites like BFD and JST late tonight.

Expect winds to pick up from the southwest on Monday, ahead
of a cold front, with a slight risk of strong to severe
storms. Timing of the front would be such at the southeast
sites like MDT and LNS have the higher chance of a gusty
storm.

Turning much cold late Monday night, along with a gusty
wind into Tuesday.

Outlook...

Tue...No significant wx or restrictions expected.

Wed...Rain moves in west-to-east late. Restrictions likely PM.

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

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

&&

.FIRE WEATHER...
Cooler and drier conditions are forecast to start April on Tuesday
as high pressure moves across PA. Dry air should support relative
humidities Tuesday afteroon falling into the 30 percent range,
and possibly lower, across most of central PA. Moderately strong
and gusty northwest winds are also possible Tuesday, but at
this time it appears the strongest winds will be in the morning.
Will continue to monitor the forecast and coordinate with BOF
and ANF for any potential need for fire weather statements and
or FWW/RFWs.

&&


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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Dangelo
LONG TERM...Fitzgerald/Gartner
AVIATION...Martin
FIRE WEATHER...Gartner