426
FXUS61 KPBZ 171517
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1117 AM EDT Tue Jun 17 2025

.SYNOPSIS...
Showers and thunderstorms continue today, and the ongoing flood
threat has expanded to include areas farther north above the
I-80 corridor as a stalled front currently to our south lifts
north across the region. The ongoing active pattern should
break Friday, followed by drier conditions and area temperatures
climbing into the 90s by the end of the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:

- Moderate Risk of flash flooding for much of the region today
- Flood Watch in effect until 10pm
- Isolated instances of a damaging wind threat south of I-70
---------------------------------------------------------------

Morning radar shows showers already developing and pushing through
the area aided by weak synoptic lift. Coverage is expected to
increase over the next couple hours both in tandem with
achievement of convective temperature of 80F as well as support
from localized boundaries and a quasi-stationary front overhead.
With further development, we face another day of a risk for
flash flooding, some potentially significant, with a primed
ground and ripe atmosphere.

Our morning sounding depicts a classic heavy rainfall environment.
Skinny MUCAPE with the bulk of the instability packed below -10C,
PWAT of 1.82" (daily max) and increasing in deep moist southwest
flow, warm cloud depths up to 14kft, and area dew points in the low
70s will be very supportive of dominant warm rain processes
with very efficient rainfall producers. In fact, even lightning
is lower probability today given the depth and width of the CAPE
profile. Will likely see very heavy rainfall with reflectivity
values not topping much higher than 30-40 dbz. While storm
motion vectors are a bit higher than previous days, PWAT values
are at record levels, so all we`ll need is a short period of
backbuilding over the same area, especially those that have
gotten hit hard in the past 48-72 hours, and flash flooding will
be likely. It`s also possible that heavier strips of rainfall
concentrate along the aforementioned boundary that will push
north as a warm front through the day today, but confidence in
placement is still on the lower side given the lack of stronger
surface convergence.

HREF probability for >1"/hour rates are high, highest up to 80% east
of Pittsburgh. Further, bumping up the neighborhood probability to
25 km over a window of 12 hours from 10am-10pm (accounting for
placement discontinuities among the CAMs) shows 10-20% probability
for up to 3"/hour rates. HREF max 24 hour QPF values through
Wednesday morning show strips of as high as 4", so while these types
of values are not expected across most of the area, this can give an
idea of the highest end, worst case scenario.

Given all of these factors in play, a Moderate Risk (3/4) is in
place for excessive rainfall for the WV panhandle and southwest PA
south of a line from Butler to Dubois, though it should be noted
that any location that gets hit repeatedly today will be at risk of
flash flooding... WPC Moderate Risks correlate to numerous flash
flooding events with significant flash flooding possible. Typically,
our area has only been placed in Moderate Risks or higher with
landfalling tropical systems. Never drive through flooded roadways
and remain vigilant for rapidly changing conditions in heavy
rainfall.

One other low end threat to be noted is a damaging wind/weak tornado
possibility. With weak low level shear, the threat should be
limited, but forecast soundings do have 100+ J/kg of 3CAPE with
low LCLs this afternoon. If a favorable interaction with remnant
boundaries or other showers/storms occurs, a quick spin up is a
low but not zero threat.

Coverage of rain will decrease with loss of daytime heating, but 850
mb convergence on the nose of an impinging low level jet is likely
to drive additional showers overnight, especially south of
Pittsburgh. A lower flooding threat will exist, but remnant MUCAPE
>250 J/kg and still high PWAT values will support additional heavy
rainfall producers.

&&

.SHORT TERM /WEDNESDAY/...
KEY MESSAGES:

- Showers and thunderstorms continue into Wednesday, with
  increased potential for strong to severe storms

---------------------------------------------------------------

Unsettled southwest flow continues overnight as additional
embedded shortwaves and jet induced ascent support rounds of
showers and isolated thunderstorms, though the focus for
greatest coverage shifts to areas generally south of Pittsburgh.
The flood risk could continue with these into early Wednesday
morning, especially if they impact any locations that have
already experienced flooding issues due to recent rain.

A trough will then advance eastward across the Great Plains and
towards the Great Lakes, resulting in strengthening deep- layer
west- southwesterly flow downstream over the Ohio Valley. Weak
500mb height rises over the local area could provide enough
subsidence aloft to inhibit shower and thunderstorm activity
Wednesday afternoon and evening, with model soundings suggesting
a rather stout capping inversion forming near 700mb. This would
be for the best, as the same soundings also suggest that the
strengthening deep-layer flow, lingering low-level moisture, and
dry air aloft (due to the aforementioned subsidence) would
otherwise support damaging winds (1000+ J/kg DCAPE) and large
hail (2500+ J/kg SBCAPE) in storms.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
KEY MESSAGES:

- Showers and thunderstorms continue Wednesday and Thursday,
  including increasing severe potential
- Hot and dry weather returns this weekend into next week
-------------------------------------------------------------------

The upper trough continues to advance eastward across the Great
Lakes Wednesday night into Thursday. As it approaches, height
falls and strengthening large-scale forcing overspread the
region, leading to showers and thunderstorms forming over Ohio
and moving east across the local area. These storms will still
carry a severe weather threat, primarily for damaging winds and
large hail. The Storm Prediction Center currently has much of
the local area in a Marginal Risk (Level 1 out of 5) during that
period. The heavy rain and flooding threat will likewise
continue with these storms, although faster motions will help
limit residence time in any one location and therefore the
threat will become more isolated to areas that already flooded
due to heavy rains in recent days.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
A wide mix of conditions are ongoing across the area to start
the TAF period as decaying showers and weak overrunning along a
stalled boundary are producing instances of MVFR/IFR at some
terminals while VFR prevails elsewhere. This mix of conditions
continues through the morning until heating and mixing allows
for general improvement to VFR, save for FKL/DUJ where MVFR may
persist into the afternoon. Scattered showers and thunderstorms
develop across the area late morning through the afternoon and
evening as an upper trough approaches from the west. Maintained
TEMPOs to reflect the most likely window for heavier rain,
thunder, and associated restrictions. Outside of convection, low
VFR or potentially high MVFR cigs prevail. Widespread IFR
settles in overnight as shower activity tapers but low-level
moisture lingers. Winds remain light through the period and
generally out of the south or southwest.

Outlook...
Periodic restrictions remain possible through Wednesday as
another upper level wave crosses the region. More widespread
showers/thunderstorms (and associated restrictions) are
expected late Wednesday into Thursday with the approach and
passage of a cold front. Late night/early morning stratus and
fog is also likely. General VFR is expected to return Friday
through the weekend as ridging begins to build in.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch until 10 PM EDT this evening for PAZ007>009-
     013>016-020>022-029-031-073>078.
OH...Flood Watch until 10 PM EDT this evening for OHZ039>041-
     048>050-057>059-068-069.
WV...Flood Watch until 10 PM EDT this evening for WVZ001>004-012-
     021-509>514.

&&

$$

SYNOPSIS...88
NEAR TERM...MLB
SHORT TERM...88
LONG TERM...Cermak/Frazier/88
AVIATION...Cermak