Lancaster, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

789
FXUS61 KCTP 091007
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
607 AM EDT Sat May 9 2026

.WHAT HAS CHANGED...
* Upped PoPs for today with mentions of TS.

&&

.KEY MESSAGES...
1) Periods of light rain/showers through Mother`s Day weekend

2) Frost/freeze risk Monday night into Tuesday morning over the
western and central Alleghenies

3) Cool/unsettled pattern through much of next week; sizable
warmup on the horizon? into third week of May

&&

.DISCUSSION...
KEY MESSAGE 1: Periods of light rain/showers through Mother`s
Day weekend

Flow aloft is buckling just to our west due to an approaching
short wave trough. A very weak sfc low will slide thru the Mid-
Atlantic today. Some instability could develop SE of I-81 this
aftn. However, the amount of cloud cover could limit the CAPE.

Shear is in the 35-45KT range, so it`s not too shabby. The CAPE
is the uncertain part of the forecast today...not only in the
aftn in the SE, but then a few hours later (likely after
sunset) over the far NW, too. SPC has placed both the far SE and
far NW into MRGL risks of svr wind and hail, acknowledging the
potential limiting stability. While worth mentioning, it affects
only a small portion of the area and there should only be
isolated cells in our CWA that could approach svr thresholds.
The incoming frontal system will be poor in the way of moisture.
The low will pass well to our north and the cold front will pass
slowly tonight and Sunday. The upper heights will be rising
tonight even as the front is moving through. SHRA and any TSRA
that enter the NW in the evening/early night will probably break
apart and dry up by 2 or 3 AM as they would be arriving in JST-
UNV-IPT. There should then be a break in precip until after
noon on Sunday when precip is generated north of the front as
the base of the long-wave trough/low swings across the Great
Lakes. Models differ on the poleward extent of precip that
should be generated Sunday night and Monday. For now, we`ll keep
with middle of the road PoPs for the whole SE half of the area
Sun night, and shrink them southward Monday morning.

It won`t be a total washout with total rainfall hard-pressed to
exceed 0.50 inch over the neat 48 hrs. Rain ends/shifts to the
east by Monday evening.

------------------------------------------------------

KEY MESSAGE 2: Frost/freeze risk Monday night into Tuesday
morning over the western and central Alleghenies

Confidence is increasing for another frost/freeze situation
Monday night into early Tuesday morning over the western and
central Alleghenies (to the northwest of I-81).

But first...Clouds may slow cooling Sunday night over the NW.
But, there is certainly a low (20-40%) chc for frost/freeze in
the nrn tier Monday morning. The possibility is highest
then/there if no additional clouds move across LE into PA and
the high stuff clearing to the SE does as expected. Will
continue to mention frost for the nrn tier Monday AM.

The almost-certain time for a frost and freeze to happen next is
Monday night/Tuesday morning. Forecast min temps for Tuesday
morning have been dropping slowly and consistently over the
past few days. Clearing should be near-total. A light wind in
the SE and generally warmer temps should limit the frost
potential SE of Blue Mountain to a minimum. There is a medium to
high (60-80%) confidence in a freeze for the nrn Alleghenies,
even at this range (Day 3.5), given the constant downward trend
in all guidance minTs and favorable sky and wind. Frost is
expected (90-100%) NW of AOO-UNV-IPT. Even AOO and UNV and the
higher valleys S/SW of IPT should frost up Tuesday morning. As
we get closer to the event, we`ll likely be issuing frost
advisories and freeze warnings should the set up/pattern look
as it does right now.

------------------------------------------------------

KEY MESSAGE 3: Cool/unsettled pattern through much of next
week; sizable warmup on the horizon? into the 3rd week of May

Mean troughing keeps cool/unsettled pattern in place through
much of next week with below normal temperatures and several
opportunities for rain next Wednesday-Friday.

There are signs of a pattern shift starting next weekend (~May
15-16) that returns more typical/warmer late Spring conditions
to central PA heading into Memorial Day or the "unofficial"
start of Summer.

&&

.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
TAFS overnight held up well, with conditions really only down
to MVFR and IFR levels across the northwestern sites like BFD.

More information below.

As been the case this Spring, showers will track across the
northern tier of PA today, tapering off from west to east
later this aft. Still expect some showers over the southeast
areas, but lighter amts. Main sites to have MVFR and IFR
conditions will be mainly at BFD, and at times JST and IPT.

A break expected between systems later this afternoon,
before the next shortwave moves into the northwest early
this evening. With very cold air aloft, there could be
a gusty shower or even a thunderstorm after sunset, mainly
at BFD.

Another shortwave will bring another chance for showers and
lower conditions again later on Sunday.

Outlook...

Sun...VFR favored early, with restrictions becoming more likely
in the afternoon as another cold front moves SE. SHRA with
isolated TSRA possible as cold front passes through.

Mon-Tue...VFR conditions expected to prevail.

Wed...Restrictions possible with rain.

&&

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

&&

$$

WHAT HAS CHANGED...Dangelo
KEY MESSAGES...Dangelo/Steinbugl
DISCUSSION...Dangelo/Steinbugl
AVIATION...Martin