-- Discussion containing changed information from previous version are highlighted. --
646
FXUS61 KPBZ 241541
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1141 AM EDT Fri May 24 2024

.SYNOPSIS...
-- Changed Discussion --
Isolated showers may develop after 7pm south of I-70 today. The
risk for more widespread showers and storms return Saturday
afternoon. Sunday may be dry as high pressure moves across the
Mid- Atlantic region.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
KEY MESSAGES:

-Shower activity in the vicinity of the West Virginia ridges
 will diminish over the next 3 hours.
-Probability of showers and an isolated storm slightly increases
 after 7pm; activity will be sporatic/disorganzied.
 _____________________________________________________________

Remnant showers will continue to track through the West
Virginia ridges over the next 1 to 2 hours. With a decent deep
warm cloud deck, rainfall rates ranging from 0.15 to 0.50
inches/hr, and weak flow aloft, 6 hour rainfall amounts have
ranged from 0.45 to 0.65 inches. There have been a few
lightning strikes, likely due to orographic lift as showers
advance across 2kft-4kft terrain. Elsewhere, a noted low-level
cloud deck has continued to form under a lingering moisture
boundary south of Pittsburgh. Despite, available instability
aloft (PIT ACARS sounding depict MUCAPE nearing 2000J/kg) there
is no promising lifting mechanism for convection to form through
the late evening. Therefore, probability of precipitation
through sunset will be low.

By 7pm, the ridge over eastern Ohio will likely star to break
down and an increase in southerly flow loft will likely occur as
a large scale disturbance over the Midwest tracks northeast.
Sporatic showers may evolve between 7pm to 9pm south of
Pittsburgh. Thunderstorm chances are considered low given
warming in the mid-levels, subsiding the chances of strong
vertical lift. Isolated showers will likely be slow moving and
produce small bullseyes of 0.25 to 0.50 inches of rain through
midnight.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
-- Changed Discussion --
KEY MESSAGES:

-A crossing shortwave will return the risk for showers and
 storms Saturday.
 _____________________________________________________________

A weak ridge will continue to break down across the Ohio River
Valley early Saturday as an ejecting low out of the northern
Dakotas tracks into the Great Lakes. With a flux of low-lvl
moisture Saturday morning, our environment has the potential to
support storm development Saturday afternoon as a weak shortwave
trough swings through. Some models are suggesting a lack of a
trigger despite a decent environment. So confidence is still low
on how much development will occur and how strong it will
become.

Another weak ridge will cross the region on Sunday. This should
keep most of the area dry. Popup storms cannot be completely
ruled out Sunday, but most of this may be confined to the higher
elevations.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
KEY MESSAGES:

- Variability remains high on long term forecast and may be
  predicated on prior day`s convective outcomes.
- Overall, periodic showers and thunderstorms with slightly
  above normal temperature is favored through the holiday
  weekend and into next week.
  ____________________________________________________________

A strong, well-organized low pressure system is becoming the
favored pattern towards the end of holiday weekend in the Ohio
River Valley. Timing and the position of the center of the low,
along with environmental moisture profiles, are currently not
in phase between the long range models and some of the newer
runs of the CAMs. There is a very large difference between
800J/kg (GFS) to 3000J/kg (NAM). At the moment, the Storm
Prediction Center (SPC) has focused the convection outlook
southwest of our county warning area.

Long range suggests a shift to a cooler, dry pattern by the
middle of next week as upper troughing develops over the Great
Lakes. Expect temperature to fall below the seasonal average,
with Tuesday potentially being the transition day from shower
activity to dry weather.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
Low VFR / high MVFR cu will persist through the afternoon
(primarily south of KPIT), with light winds under the influence
of high pressure through the TAF period.

.Outlook...
Shower and thunderstorm chances return Saturday afternoon and
evening, but may be dependent on evolution of storms that occur
across the western Great Lakes. Any thunderstorm poses a risk
for gusty, erratic winds and lowered visibilities.

Thunderstorm probabilities are highest late Sunday into Monday
as a more robust low pressure system moves through the Great
Lake region. A pattern shift thereafter will introduce periodic
precipitation chances and potential for more prolonged cig
restrictions.

&&

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

&&

$$

SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Hefferan/22
LONG TERM...Hefferan
AVIATION...88