Lancaster, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

836
FXUS61 KCTP 200530
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
130 AM EDT Thu Aug 20 2026

.WHAT HAS CHANGED...
Lowered daytime temps and stratified rain for Thursday
Added +RA and gusty winds to SPC/WPC MRGL risk overlap
Increased fog coverage Thursday night into Friday morning

&&

.KEY MESSAGES...
1) Locally heavy rain and a few strong thunderstorms possible
across south central Pennsylvania Thursday

&&

.DISCUSSION...
KEY MESSAGE 1: Locally heavy rain and a few strong thunderstorms
possible across south central Pennsylvania Thursday

A broken and thin line of convective rain showers (not much
ltg) continue to track south southeastward this afternoon along
a weak llvl convergence boundary drifting southward from US-6
toward I-80. Most places in CPA stay dry through tonight with
increasing cloud cover. This puts fog formation in a pickle, but
any period of prolonged clearing could result in late night
valley fog particularly over north central PA.

CAMs are in decent agreement in bringing a slug of moderate to
locally heavy rain across CPA from southwest to northeast Thursday
morning into Thursday afternoon -- most likely impacting locations
near and south of I-80. Heavy convective signals for both +RA
and potential strong to severe t-storms ramp up just south/east
of the CWA closer to the I-95 corridor tomorrow afternoon into
the early evening.

Rain exits CPA by Thursday evening with clouds gradually
clearing out by late Thursday night. This should allow for
widespread valley fog to develop into early Friday morning. The
cold front can`t penetrate much farther south of the MD line, so
can`t rule out a spotty shower/t-storm in far southern PA Friday
afternoon. However, most of CPA will see a dry end to the week.

An upper trough carving out over the Great Lakes will bring
increasingly unsettled weather conditions over the weekend.
There is still considerable uncertainty with timing, intensity,
and coverage of storms, but it shouldn`t be a washout by any
stretch. This system will also deliver some relatively cooler
air both at the surface and aloft. This setup could prove
favorable for clusters of gusty t-storms with small hail. The
troughing pattern holds on into next week which favors temps
near to slightly below the historical average for late August.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Some fog is beginning to develop across northern PA and IFR
ceilings have developed at IPT. Expect continued expansion of
the fog through the rest of the night, with BFD and UNV having
the next highest chance of seeing IFR cigs/vsby at some point
tonight. Confidence in fog formation is lower at the other TAF
sites.

A swath of steady rainfall will overspread central PA this
morning, with KUNV/KIPT looking to be within the core of this
swath (meaning higher confidence in MVFR-IFR visibility
restrictions), with KBFD/KJST/KAOO more-so on the periphery
(more intermittent MVFR-IFR restrictions, especially where rain
is more showery). Rain at KMDT/KLNS looks to be more
showery/convective in nature, with a few strong to severe
thunderstorms possible in the afternoon. Rumbles of thunder may
occur in the steadier, more stratiform swath of rain where
MUCAPE may rise to 100-250 J/kg (primarily KUNV/KJST/KAOO).

Winds will tend to be variable near the system`s track over
southern PA, with winds generally N/NE north of the system &
S/SE to its south. Cloud ceilings lower to MVFR-IFR later
during the afternoon and evening in the vicinity of the low
pressure center, with low stratus and/or fog possible overnight
as low-level moisture persists while mid/high clouds clear out
and winds lighten.

Outlook...

Fri...AM fog, otherwise trending VFR.

Sat-Sun...Scattered to numerous showers/t-storms likely. Breezy.

Mon...VFR returns for early next week.

&&

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

&&

$$

WHAT HAS CHANGED...Steinbugl
KEY MESSAGES...Steinbugl
DISCUSSION...Steinbugl
AVIATION...Bauco/Teare