624
FXUS61 KCTP 151913
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
313 PM EDT Sun Jun 15 2025

.SYNOPSIS...
* Showers will be concentrated over the Laurel Highlands and
  adjacent Southwestern PA today with a few thunderstorms
  possible there. Elsewhere, look for cloudy skies and cool
  conditions with isolated to scattered brief showers tracking
  east across the Central Mountains and Susquehanna Valley.

* Cloudy skies with a few showers from time to time and areas of
  late night and early morning drizzle.

* A strong warmup for Wednesday and Thursday with daytime highs
  several degrees above normal, with additional showers and
  thunderstorms expected.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
10 am/14z update... Late morning satellite imagery shows
expansive lower clouds across much of the state, with some
breaks in the clouds restricted to areas of southwest PA.
Meanwhile, an area of light showers is tracking eastward aligned
with I-80, from near State College east into the Poconos, then
a few more bubbly, heavier showers are trying to form west of
the mountains in southwest portions of the Commonwealth.

As we head through the afternoon, our forecast philosophy has
not changed a great deal from earlier this morning, with a
summer-time cool air damming pattern solidly in place for
central PA, leading to plenty of lower clouds and relatively
cool readings for mid-June. Showers will be most common through
the afternoon over the southern Alleghenies/Laurel Highlands,
closer to the primary OH Valley mid to upper-level disturbance,
and also where a few potential breaks in the clouds could lead
to marginal instability, especially towards southwest Somerset
county. Shower activity looks more spotty and lighter in
intensity farther north and east, in a more stable and
stratiform regime.

As for high temperatures this afternoon, they will largely be in
the 60s again and probably only a few degrees above late morning
values. The best chance to see some lower 70s will be over the
Laurels, where the clouds may thin at times.

Previous discussion... Latest surface analysis shows a
relatively weak, 1013 mb low pressure center over the Middle
Ohio River Valley with a quasi- stnry boundary extending into
the SW Corner of PA then SE across the DC area to the mouth of
the Chesapeake Bay.

Thick cloud cover will persist today through tonight across
practically the entire CWA with a light easterly breeze as the
aforementioned sfc low and it`s initially compact, single-
closed contour low aloft weakens and drift east to the south of
the Mason Dixon line.

SREF Probability for SFC-Based CAPE over 500 J/KG reaches a max
of only around 50 percent during the mid afternoon hours over
Laurel Ridge in SW Somerset Cty (and increases west from there).

Furthermore, Instab aloft is almost entirely lacking with the
15/06Z NAM showing 925-850 LI`s barely below zero C late this
morning through late this afternoon.

The mean westerly flow, averaging just 10-20 kts aloft, will
steer the convection into Somerset County, where WPC continues
its SLGT Risk ERO. Over the West Central and Scent Mtns, WPC`s
ERO is in the MRGL range, but individual members of the HREF and
the ensemble blend itself shows 24 hour PMM values of generally
under 1 inch (far less than what we saw forecast for yesterday
across parts of the Central and Western Mtns with no flooding
occurring).

So, with fcst basin-average rainfall from 06Z today to 06Z
Monday only being in the 0.5 to 0.8 of an inch range over
Somerset Cty (well below 1 and 6 hour Flash Flood Guidance
values), decided to hold off on any Flood Watch for now.

Elsewhere, rainfall amounts through this evening will average
less than one quarter of an inch in most places. A few small
clusters of generally brief (albeit moderately heavy) SHRA will
form near and to the North of an E/W sfc trough, extending
along the Interstate 80 corridor, and move slowly ESE.

Temps today will struggle to rise 10 deg F from their current
values - in the upper 50s to 60s over the NE two thirds of the
CWA to the low to mid 70s in Warren County, where a drying
downslope easterly flow will prevail.

for tonight, we`ll see very similar conditions to what we`re
seeing now. Lots of clouds but little wind and precip tonight.
Lows early Monday will vary from the mid 50s over Sullivan
county to the upper 50s and low 60s over the remainder of the
CWA.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
By Monday, high pressure off of the east coast may try to build
westward into our area. This may keep the eastern half of our
forecast area relatively dry, though easterly flow will keep
plenty of low clouds around. Rain chances will stick around
farther to the west.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Midday Sunday update... On the large-scale, the upper-level
trough/closed low that will continue to plague central PA into
the short-term period, is forecast by our suite of ensemble
guidance to minor out and drift eastward by later in the week.
This should allow the flow pattern to become more progressive in
the northern stream.

The aforementioned, fairly vigorous short-wave is progged to
approach the region by later Thursday. As this wave passes,
depending on the exact timing, it could trigger strong to severe
thunderstorms across the Commonwealth Thursday afternoon or
evening. We`ll watch this evolution closely over the coming
days.

Once the short-wave passes, upper-level heights are expected to
build over the central and eastern CONUS from next weekend into
the following week. After lots of cool, wet weather for much of
May and the first half of June, this could lead to our first
sustained period of summertime heat and humidity, starting later
this weekend.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
Poor flying conditions will prevail today and the next several
days, as there is nothing really out there to push out the wet
pattern. Widespread MVFR conditions are ongoing with some areas
of IFR mixed in near the PA/MD border.

Most numerous showers today will be in southwest PA extending
toward JST/AOO. More isolated showers will stretch across the
central mountains UNV-IPT and lower susq valley MDT-LNS.

Ceilings drop to IFR most places overnight with a very slow
improvement back to MVFR on Monday.

Outlook...

Mon-Wed...Daily chances for showers and thunderstorms, peaking
during the afternoon/evening hours each day.

Thu...A better chc of more numerous showers and storms with a
cold frontal passage.

Fri...Improving conditions.

&&

.CLIMATE...
A record rainfall of 1.21 inches was set in Williamsport
on Saturday.

This broke the old record of 1.20 inches set in 1969.

&&

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

&&

$$

SYNOPSIS...Jurewicz
NEAR TERM...Jurewicz
SHORT TERM...Jurewicz
LONG TERM...Jurewicz
AVIATION...Martin/RXR
CLIMATE...Martin