042
FXUS61 KPBZ 161917
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
317 PM EDT Mon Jun 16 2025

.SYNOPSIS...
A Flood Watch remain in effect for the southern half of the
forecast region today due to potential for more heavy rain and
thunderstorms. The flooding threat continues Tuesday but expands
areawide while Wednesday and Thursday may each have lower
probabilities. The active pattern should break this weekend,
followed by area temperatures climbing into the 90s.

&&

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

- Locally heavy rain in showers and thunderstorms may result in
  flash flooding again this afternoon/evening. A Flood Watch
  remains in effect through 10pm.
- Rain chances continue overnight and may continue low-end
  flooding concerns primarily across eastern OH, the northern
  WV panhandle, and southwest PA.

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

A quasi-stationary boundary across the region and lingering deep
moisture will continue the broken record forecast we have
observed the past couple days. Precipitable water (PWAT) values
2-3 standard deviations above normal, deep warm cloud depth
ranging from 11,000 to 13,000ft, and instability will provide an
environment ripe for heavy rainfall. Additionally, storm motion
will continue to remain relatively slow, increasing the
residency time of heavy showers and storms over the areas where
they develop. There is a Flood Watch in effect until 10pm this
evening roughly south of an Indiana-Butler-New Philadelphia
line, where recent heavy rainfall has left some locations
especially vulnerable and the greatest coverage of shower and
thunderstorm activity is expected this afternoon and evening.
The probability of rainfall rates reaching 1-2 inches per hour
are elevated (around 20-40%) and most concentrated over portions
of northern West Virginia that have already seen significant
rainfall in recent days. Similar to Sunday, the highest
rainfall potential is expected between 12pm to 10pm. The threat
from damaging winds are very low given weak deep- layer flow
and the absence of dry air aloft.

Normally, the loss of diurnal heating and the environment being
worked over by outflow boundaries would result in decreased
shower coverage and low rainfall rates during overnight hours.
However, generally after 03z (11pm), a weak 700mb "jet"
approaches the area from the southwest with convection likely
ongoing along its leading edge. Hi-res model soundings suggest
upwards of 500-750 J/kg elevated CAPE focused below -10C, which
coupled with PWATs increasing to near 1.8 inches, would
continue supporting efficient warm rain processes. As a result,
there is some concern that showers with moderate to heavy rain
rates could persist overnight, particularly along a swath from
Zanesville, OH to Pittsburgh or Butler in SW PA. We will closely
monitor upstream observations and hi-res model trends over the
course of the evening and may need to extend and/or expand the
existing flood watch as appropriate.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
KEY MESSAGES:

- Flash flood threat spreads areawide, with probabilities
  highest in locations previously impacted by flooding.
- Isolated instances of a damaging wind threat south of I-68.
----------------------------------------------------------------

A lower Ohio River Valley trough will start to slide east as
embedded 700mb shortwaves within increased southwesterly flow
are expected to promote more widespread shower and thunderstorm
coverage during the day Tuesday. The environment will remain
similar to the Sunday/Monday setups (near record high PWATs,
saturated grounds) save for two points which may counter each
other: stronger forcing will better aid storm development and
coverage (increasing flood threat) and storm motion will be
closer to 20kts (lowering the flood threat). Latest ensembles
suggest the focus for the heaviest rainfall could be across the
northeastern portion of the local forecast area, roughly between
Pittsburgh and Dubois, with more scattered or isolated instances
of heavy rainfall elsewhere across the area. However, given
that the region has be inundated with recent rain and many
counties have already seen impactful flooding, the messaging
remains the same areawide: Heavy rain showers and thunderstorms
pose a flash flood risk with potentially impactful flooding,
especially in locations that have previously seen flooding.

Unsettled southwest flow continues Tuesday night 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.

&&

.LONG TERM /WEDNESDAY 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.
-------------------------------------------------------------------

Convection from Tuesday night departs the area to the east
Wednesday morning. Meanwhile, a more potent upper trough
advances 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.

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 /18Z MONDAY THROUGH FRIDAY/...
MVFR to IFR cigs will show marginal improvements through the day
north of a stagnant boundary thanks to some diurnal
heating/mixing. HREF probabilities favor enough heating/lift to
produce showers and isolated thunderstorms focused around
KMGW/LBE during the afternoon/evening. Confidence is low on
storm coverage extending to other TAF sites given weak flow, but
kept mention for nearby terminals (KPIT/KHLG/KAGC) in case
storm outflow boundaries initiate farther north/west than model
depictions.

The largely stagnant airmass should favor cig lowering overnight
towards MVFR/IFR, though weak SE flow could limit drops at KLBE.
The noticeable difference tonight will be weak shortwave
movement that could generate isolated to scattered showers
mainly after 06z; rainfall rates aren`t likely to be high and
impact visibility much but it could help drive lower cigs.

Outlook... Periodic restrictions are expected through Thursday as
disturbances track along the stalled frontal boundary across the
Upper Ohio Valley region. Late night/early morning stratus and fog
is likely, along with showers and thunderstorms peaking in the
afternoon and early evening. More organized showers/storms are
expected with a Thursday cold front.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch until 10 PM EDT this evening for PAZ021-029-031-
     073>076.
OH...Flood Watch until 10 PM EDT this evening for OHZ049-050-058-
     059-068-069.
WV...Flood Watch until 10 PM EDT this evening for WVZ001>004-012-
     021-509>514.

&&

$$

SYNOPSIS...Cermak
NEAR TERM...Cermak
SHORT TERM...Cermak
LONG TERM...Cermak
AVIATION...Frazier