566
FXUS61 KPBZ 290108
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
908 PM EDT Tue May 28 2024

.SYNOPSIS...
Crossing disturbances will maintain shower and thunderstorm
chances through Wednesday. Cooler than average temperatures are
expected through Friday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
KEY MESSAGES:

- Scattered showers and thunderstorms diminish this evening
- Additional showers overnight with another approaching
  shortwave
-------------------------------------------------------------------

Additional showers and thunderstorms have developed along a
couple of outflow boundaries, generally in the vicinity of a
line from PHD to PIT to LBE. The 00Z PIT sounding shows around
450 j/kg of surface based CAPE, with ML CAPE 100-200 j/kg. This
has been sufficient to maintain showers and storms along these
outflows, though the latest CAMS indicate the instability will
continue to wane through the evening. A few of the more
organized storms have produced small hail this evening, though
this potential will also diminish with the waning instability.

The latest mesoanalysis shows some lingering mid level troughing
across western PA, though this will also shift eastward this
evening. Partial clearing has occurred over portions of the
area. This could result in patchy fog overnight, especially
where rain occurred earlier. Cloud cover will increase again
later tonight as the next shortwave approaches from the Great
Lakes region, and this should help limit the coverage of the
fog. Shower chances will also increase from W-E with the
approach of the shortwave.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:

- Rain and thunderstorms chances continue into Wednesday with a
  new disturbance.

- Temperatures will continue to remain below average through
  Wednesday night.
-------------------------------------------------------------------

An ejecting shortwave trough over the Midwest will initiate
showers and thunderstorms Wednesday across the region.
Instability and effective shear will be considered weak, MUCAPE
400J/kg to 800J/kg and less than 25kts. However, training storms
could create a swath of heavy rain (between 0.45 to 0.65
inches) across the region during the late morning to late
afternoon.

Precipitation chances will quickly diminish between 9pm and
11pm Wednesday night with the loss of surface heating and the
shortwave exiting east.

Below average temperatures will continue Wednesday afternoon
into Wednesday night under cool, northwest flow.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
KEY MESSAGES:

- Dry weather and cooler temperatures are expected Thursday into
  Friday under high pressure.
- Rain chances may increase Sunday into Monday with a shift in
  the synoptic pattern. However, confidence is still considered
  low on timing and strength of the overall disturbance.
-------------------------------------------------------------------

Surface high pressure builds into the area on Thursday. Dry,
cool conditions will continue into early Friday.

A ridge will advance into the Ohio River Valley late Friday into
Saturday and return warm conditions.

Thereafter, spread in the models increases regarding how quickly the
upper ridge moves off/breaks down and how quickly deeper moisture
returns. NBM suggests low PoPs for Sunday and Monday (30 to 40
percent) with temperature expectations of near to slightly
above seasonal levels. Stout ridging in place as this next
disturbance arrives may lead to a difficult forecast given the
subsidence and drier air in place to start the new week.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
Activity should continue to wane this evening. Widespread cig
restrictions settle in early Wednesday morning with lingering
low-level moisture and cold advection dominating. Hi-res
ensemble guidance is suggesting high probabilities (70%+) for
widespread MVFR/IFR and even medium probabilities (40-60%) of at
least some instances of LIFR occurring at all area terminals.
Another round of scattered to numerous showers also develops
Wednesday morning as the upper trough axis finally rotates
through the region. Another round of showers/storms is possible
Wednesday afternoon, but lightning overage is expected to be
minimal due to limited instability. Light and variable winds
tonight become north-northwest around 5-10 knots on Wednesday.

.Outlook...
High pressure builds into the area Wednesday night through the
end of the week, bringing VFR conditions back to the area
through that time.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...WM/Hefferan
NEAR TERM...WM
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...Cermak/22