Lancaster, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

050
FXUS61 KCTP 040522
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
122 AM EDT Wed Jun 4 2025

.SYNOPSIS...
* Wildfire smoke lulls overnight before increasing slightly on
  Wednesday with air quality concerns across the Lower
  Susquehanna Valley.
* Warm and increasingly humid on Wednesday promotes a moderate
  HeatRisk across the western highlands of central Pennsylvania.
* Unsettled weather begins on Thursday and into the first full
  weekend of June.

&&

.NEAR TERM /THROUGH TODAY/...
Recent satellite outlines lingering smoke aloft with no surface
impacts at this time. Recent HRRR smoke guidance outlines
decreasing smoke throughout the overnight period, thus have
removed any mentions of haze generally after sunset when
concentrations shift north of the forecast area. Westerly flow
aloft allows for an influx of smoke after sunrise on Wednesday,
with deep mixing allowing, in decent agreement with the near-
surface smoke product from recent HRRR runs. Surface visibility
restrictions from wildfire smoke are not expected throughout the
near-term; however, increased concentrations of ozone have
allowed for the Pennsylvania Department of Environmental
Protection to declare a Code Orange Air Quality Alert for the
Lower Susquehanna Valley on Wednesday. A Code Orange AQA
outlines air quality that is unhealthy for sensitive groups,
such as children, the elderly, and those with respiratory
problems will be increasingly vulnerable to the effects of air
pollution, and should limit outdoor activities on Wednesday.

Rinse-and-repeat forecast tonight across central Pennsylvania
compared to yesterday evening`s forecast. Clear skies under the
influence of high pressure will allow for ample radiational
cooling, especially across northwestern Pennsylvania. Given this
set-up, have once again undercut NBM MinTs overnight to range
between the mid-50s across northwestern Pennsylvania. Further
south, southerly flow continues overnight which will allow for
low-level warm air to be advected into the region, pushing MinTs
closer to the upper 50s across the southern tier. Temperatures
rebound quickly after sunrise on Wednesday with ample surface
heating under mostly clear skies. Warmer than average
temperatures virtually certain on Wednesday, with high
temperatures +10F above climatological averages in play,
forecast in the mid-to-upper 80s with maximum heat index values
pushing into the lower 90s across south-central Pennsylvania.
Moderate HeatRisk is forecast across the western highlands of
central Pennsylvania on Wednesday, mainly attributed to lack of
heat acclimation given recently cool and wet weather.

In this forecast cycle, have also retained ~15-20% PoPs across
the spine of the Appalachians, mainly NE of the State College
area given a notable rise in dewpoints and given the ample
heating along the mountains. Combination of heat, moisture, and
lift will likely lead to some towering cumulus development with
model guidance indicating some lower probabilities of a
measurable precipitation across NE PA.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...
Dry conditions are expected to remain through Wednesday night
as recent guidance indicates slightly slower progression of an
approaching cold front across the Great Lakes. Surging PWATs
begin knocking on the door across central Pennsylvania ~12Z/7am
EDT Thursday, promoting initial slight chances for showers;
however, low-level dry air in place could lead to even later
arrival time of precipitation. Once precipitation enters central
Pennsylvania, fairly high confidence in showers overspreading
the area with afternoon thunderstorms possible given ample
instability and moisture in place. Unsettled pattern remains in
place through the short-term with increasing rainfall chances
into Friday. Severe threat remains fairly limited in the short-
term given the lack of shear in place over the region. Rainfall
from this system will bring a Marginal Risk for Excessive
Rainfall across far western Pennsylvania on Thursday (although
wouldn`t be out the question to see the ERO on Thursday getting
pulled west of the region, given best moisture remains west of
the region) and area wide on Friday.

Temperatures on Thursday will remain fairly close to readings on
Wednesday with high temperatures in the 80F-90F range. The
humidity will also trend slightly higher with maximum heat
index values reaching the low 90s across higher elevations of
eastern Pennsylvania. Moderate HeatRisk will be in place across
portions of east-central Pennsylvania, once again due to the
lack of heat acclimation and recent cool/wet weather.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Late evening update.

While EC and GFS are trending toward warmer weather in the
long run, EC has more shortwaves tracking across the country
overall, so while warmer than normal temperatures are likely,
there may be several rounds of showers and storms into late
next week.

Thus the best chance to be dry will be Sunday and later next
week. For Sunday, the guidance has been consistent. As noted
below, Saturday could be wetter than what it looked like the
other day, especially if a wave tracks across northwest PA.

Earlier discussion below.

Recent ensemble guidance shows a wetter trend on Saturday as an
area of low pressure developing west of the region along a
stalled frontal boundary that will move eastward towards central
Pennsylvania. This area of low pressure is expected to be
stationed across western Pennsylvania by Saturday morning,
promoting likely PoPs late Friday through Saturday. Exact
placement of the low remains uncertain; however, and could
heavily influence QPF amounts, with ensemble ranges generally
between 0.50 to 1.00". Chances for thunderstorms are maximized
during the afternoon/evening hours on Saturday; however, severe
threat looks minimal given lack of bulk shear in this timeframe.

The front finally pushes east of Pennsylvania on Sunday and
upper-level ridging attempts to build in behind it, bringing a
period of drier weather with seasonable temperatures to end the
weekend. Rain chances return to the forecast on Monday as a
trough approaches from the west.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions remain virtually certain at all central
Pennsylvania airfields through 12Z Thursday. Elevated smoke
from the Canadian wildfires will remain across the forecast area
although recent HRRR model guidance does indicate a relative
minimum overnight. Near- surface smoke does highlight some smoke
concentrations in the lower-levels tomorrow; however,
visibility restrictions below 6SM remain very unlikely (~10-20%
at BFD/JST, lesser probabilities elsewhere) throughout the TAF
period. Some recent guidance has continued outlining increasing
moisture, coupled with surface heating and lift that SCT/BKN
clouds may begin to form closer to higher elevation locations
(all but MDT/LNS) after 18Z Wednesday. Have retained some
chances for precipitation, mainly focused in the vicinity of
IPT; however, confidence remains too low to include in the 00Z
TAF cycle. The better chances for precipitation comes Thursday
PM at BFD before an unsettled pattern brings widespread
restriction potential Friday and into the weekend.

Outlook...

Thu...Potential brief restrictions in SHRA/TSRA BFD.

Fri...Numerous SHRA/TSRA, esp NW. Brief reductions to MVFR and
IFR in the TSRA.

Sat...Showers/PM TSRA continue, gradually tapering off across
NW PA late.

Sun...VFR/no sig wx expected.

&&

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

&&

$$

SYNOPSIS...NPB
NEAR TERM...NPB
SHORT TERM...NPB
LONG TERM...Martin/Bauco/NPB
AVIATION...NPB/Bowen