York, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

058
FXUS61 KCTP 122221
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
Issued by National Weather Service Binghamton NY
621 PM EDT Mon May 12 2025

.SYNOPSIS...
* An extended period of wet weather is expected, with at least
  some rainfall anticipated on a daily basis, from Tuesday right
  into next weekend
* Temperatures will average near to somewhat above seasonal
  normals for mid-May

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
630 pm update... Surface dew points are steadily on the rise now
across the southern tier (namely near and south of the PA
Turnpike), with 55-60f values now common near the Mason-Dixon
line. As moisture advection continues to increase and build
northward this evening, we think showers will indeed develop
over the Laurels and the south-central mountains by 7-8 pm.
From there, a slow, but steady north-northeast progression in
shower activity is anticipated overnight.

Previous discussion... Residual dry air continues to hang on
late this afternoon in the lower levels of the atmosphere. Thus,
steadier rain has been held at bay well south of the Mason-
Dixon line, with a fair amount of sunshine still prevailing
across the northern tier.

However, that will start to change tonight, as high pressure
gradually moves farther offshore, allowing a deepening and moist
south-southeast flow to develop across the Commonwealth.

Showers should first reach southern portions of the Laurel
Highlands this evening (7-10 pm), with a steady march to the
northeast thereafter. All but the far northern tier are expected
to see at least some light rainfall prior to daybreak.

Lows by daybreak will range from the upper 50s-mid 60s.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
315 pm update... The main concern for Tuesday and Wednesday is
locally heavy rainfall. Synoptic signals for enhanced QPF are
there (deep S-SE flow that is oriented, in some cases, in a
perpendicular fashion to the ridge lines, as well as anomalously
high PWAT values (1.5-1.7") making for good rainfall
efficiency), particularly for the Laurel Highlands and the
south-central mountains. At this early vantage point, we opted
to try to get a better handle on subtle, but important details
like rain band persistence in any one area, available
instability/convective potential, and rainfall rates derived
from those ingredients, before jumping into a Flood Watch. We`ll
continue to look at this possibility as the event approaches and
then begins.

By Thursday, the deepest moisture supply is progged to start to
lift away from PA. However, with upper-level energy still
upstream and a sufficiency of remaining moisture, additional
showers and thunderstorms seem like a good bet.

Thick cloud cover and persistent rainfall will keep daytime
highs in the 60s-near 70 Tuesday and Wednesday, with potential
breaks of sunshine by Thursday allowing readings to warm well
into the 70s for many areas.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
1130 am Monday update... On the large-scale, a blocky upper-
level pattern will become a bit less blocky later this week to
allow more progression of systems across the CONUS. Thus, the
cutoff low expected to plague the Commonwealth during the
middle of the week is expected to have opened up and largely
lifted north of PA by later Thursday. However, on its heels, a
northern stream trough and associated surface frontal complex
will cross the northern Great Lakes and into the Northeast,
retaining our unsettled weather pattern into the weekend.

As for the daily sensible weather, diurnally favored showers and
thunderstorms appear likely both Friday and Saturday. Given the
seasonally vigorous nature of the aforementioned trough, as
well as exact thermodynamic and shear profiles on each of these
days, some strong to locally severe convection appears to be a
plausible scenario.

There remains uncertainty as to how quickly things dry out by
Sunday. At this early juncture, given the still somewhat
energetic upper-level pattern, we`ve retained 30-50% shower
probabilities.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
Fcst in good shape. The airmass remains quite dry over most
of the area. Higher dewpoints pushing up into far south central
PA. However, the rain is a little further south. Thus only
minor changes for the 00Z TAF package planned. Timing looks good
at this point for lower conditions.

Earlier information below.

For the 18Z TAF package, made the following changes.

Winds on the gusty side, running higher than guidance, given
the pressure gradient and southeast flow.

Also slowed down the rain and lower conditions some, given
the very dry air in place at low levels.

Anyway the fine early Spring weather will give way to increasing
high and mid clouds from southwest to northeast this afternoon
and evening.

Rain will overspread the JST, AOO areas first, reaching the
far northern sites of BFD and IPT later. The upper level ridge
and dry air will slow the leading edge of the rain as it nears
route 6 late tonight.

Warm advection and higher dewpoint air will keep poor CIGS
and visibilities across the region once conditions lower late
tonight and early Tuesday. No real improvement likely before
later Thursday.

Outlook...

Tue-Wed...Restrictions are likely, with lower clouds and
numerous showers.

Thu...Early restrictions in lower clouds, fog, and showers are
possible. Some improvement is possible by afternoon prior to
additional showers and storms developing.

Fri...Showers and afternoon thunderstorms, along with
restrictions.

Sat...Showers and afternoon thunderstorms likely, along
with restrictions.

&&

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

&&

$$

SYNOPSIS...Jurewicz
NEAR TERM...Jurewicz
SHORT TERM...Jurewicz
LONG TERM...Jurewicz
AVIATION...Martin