Lancaster, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

473
FXUS61 KCTP 260127
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
927 PM EDT Sat Jul 25 2026

.WHAT HAS CHANGED...
Minor changes changes to the cloud cover forecast for the rest
of the day.

&&

.KEY MESSAGES...
1) A few showers over the region overnight.

2) Turning more humid and unsettled early next week with the
highest probability for showers and thunderstorms Monday
afternoon and evening and again on Tuesday and Tuesday night.

&&

.DISCUSSION...
KEY MESSAGE 1: A few showers over the region overnight.

Broad, low-level streamline convergence with its N/S axis near
the RT 219 corridor in Western PA has resulted in some showers
since earlier this afternoon. Not real warm to the west this
evening, but western areas have dewpoints into the lower 60s.
compared across most of the Susquehanna Vly. Also while winds
are rather weak, directional shear is there on the 00Z soundings
this evening.

Surface convergence becomes more focused over the eastern half
of the forecast area for tomorrow. Slightly higher dew points
will allow for instability to be a little higher than it is
today, possibly approaching 1000 J/kg in a few locations. Though
upper level forcing looks to be weak, we would expect to see at
least a few showers and thunderstorms develop during the
afternoon. This location of the fcst activity is different than
what was noted the other day. Location could shift more as we
near Sunday aft.

KEY MESSAGE 2: Turning more humid and unsettled early next week
with the highest probability for showers and thunderstorms
Monday afternoon and evening and again on Tuesday and Tuesday
night.

Main chance for widespread showers and storms will be Tuesday
into Wednesday. Fcst dewpoints not all that high for late July,
and there has been a slight downward trend with fcst dewpoins
over the last few days.

Main things supporting showers and storms is a deepening low,
and a large scale pattern that supports directional shear to
be present into next week. Models today do show a pattern change
out toward day 10, a change from recent model runs the last few
days. Thus will have to seen if this trend holds.

Earlier discussion below.

Minor modifications for this period that will be highlighted by
a warm front moving across western PA Monday afternoon/evening,
followed by a rather potent/digging mid/upper level shortwave,
that will support a sub-995 mb sfc low over the Lower Glakes and
Western NY Tuesday afternoon and evening. Latest model runs have
trended several hours or so slower compared to runs 24 hours
ago.

The timing of the favorable lift associated with the thermally
indirect, left front quad of the 80+ KT jet max moving across
the Ohio Valley, WVA and southern PA Tuesday afternoon and
evening will help to enhance a low level lee trough and
convection along it. Scattered strong to severe TSRA are likely
Tue afternoon and evening over at least the eastern half of the
CWA with a second line of TSRA likely along the cold front
across NW PA Tuesday afternoon.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
For the 00Z TAF period, flight restrictions will be possible due
to overnight fog (mainly across the Allegheny Front/Plateau for
KBFD/KJST/KAOO, with localized fog with lower coverage possible
around KMDT/KLNS downwind of the Chesapeake) and due to
scattered showers/thunderstorms tomorrow afternoon (primarily
along and downstream of a north-south oriented sfc trough
situated near KUNV/KMDT/KLNS/KIPT tomorrow afternoon).

Spotty showers have developed along the sfc trough which will
slowly continue eastward through tomorrow, with localized flight
restrictions possible (20-30% chance) but not prevailing.
Increasing moisture via light southerly flow will promote
overnight fog development across the Allegheny Front/Plateau
(mainly KBFD/KJST/KAOO), with lower confidence in fog
development at KUNV/KIPT. A secondary moisture axis around
KMDT/KLNS, where southerly flow may bring enhanced moisture
from the Chesapeake Bay, may result in localized overnight fog
in this area as well, with lower confidence in visibility
restrictions at the terminals.

Overnight fog will mix out during the morning hours on Sunday,
with prevailing VFR expected regionwide outside of any
afternoon/evening showers/storms. Garden-variety, isolated
instability showers are possible across the area, though
shower/storm activity will mainly be focused around the north-
south sfc trough over central PA, around KUNV/KMDT/KLNS/KIPT.
Visibility restrictions from heavy rain would be the primary
impact, though gusty winds primarily around 15-20 kts with
variable wind direction may occur as well.

Outlook...

Mon...Restrictions likely in afternoon -SHRA/-TSRA. Patchy
overnight fog possible.

Tue...Restrictions likely with scattered -SHRA/-TSRA.

Wed-Thu...Restrictions possible as -SHRA/-TSRA becomes less
numerous. Patchy overnight fog possible.

&&

.CLIMATE...
Cooler than average temperatures across the region led to
multiple record low temperatures being broken for July 23rd and
July 24th across central Pennsylvania.

On July 23rd:

 * Altoona set a record low temperature of 47 degrees, breaking
   the previous record of 50 degrees set back in 1981.

 * Bradford tied a record low temperature of 38 degrees which
   was previously set in 1981.

 * Johnstown tied a record low temperature of 49 degrees which
   was previously set in 1983.

On July 24th:

 * Altoona set a record low temperature of 47 degrees, breaking
   the previous record of 50 degrees set back in 1957.

 * Bradford set a record low temperature of 41 degrees, breaking
   the previous record of 44 degrees set back in 1993.

&&

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

&&

$$

WHAT HAS CHANGED...Lambert/Martin/Bauco
KEY MESSAGES...Lambert/Martin/Bauco
DISCUSSION...Lambert/Martin/Bauco
AVIATION...Teare
CLIMATE...Beaty