-- Discussion containing changed information from previous version are highlighted. --
074
FXUS61 KPBZ 180552
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
152 AM EDT Sat May 18 2024

.SYNOPSIS...
The risk for showers will continue through at least Saturday
morning. Near to above normal temperatures through the weekend.
Dry weather returns by Sunday afternoon, and continues into
early next week with a warmup.

&&

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

- Showers will continue into the evening as a trough passes.
- Localized heavy rainfall totals and water issues are possible,
  and rotating cells will need to be monitored.
  _____________________________________________________________

PoPs have been updated for the evening and overnight hours to
account for the area of showers that will exit to the east early
this evening and more showers that are possible overnight with a
passing shortwave trough. Left out the mention of thunder as the
atmosphere will stabilize this evening and we have not seen much
lightning with any of the previous activity. Overnight lows were
adjusted as well.

Previous discussion...

Showers, and a thunderstorm or two, will remain possible this
evening as a shortwave trough axis crosses. Any further severe
potential looks limited to these low-topped, short-term
rotations that could drop a very brief tornado. The storms are
too short to produce large hail, and there is not much potential
for straight-line wind from these storms either. We also need to
continue to monitor the heavy rain/isolated flash flooding
potential, although the more scattered nature of the storms will
help to mitigate this to some degrees.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
KEY MESSAGES:

- Shower chances continue along with above normal temperatures.
  _______________________________________________

The upper trough will continue to slowly sag to the east Saturday
afternoon and evening. Forcing overall becomes more diffuse, and
thus more scattered activity is foreseen.  Activity will be a bit
more concentrated along the ridges though, as some left entrance
region jet dynamics skim the region. Severe chances remain
negligible, and the heavy rainfall threat overall will be lower.

The majority of the CWA should dry out Saturday night as the trough
departs and ridging expands over the Ohio Valley.  Still, a few
showers may linger in the ridges to the southeast of Pittsburgh into
Sunday morning, thanks to lingering moisture and easterly flow.

Sunday afternoon and night will feature a relative lack of clouds as
the upper ridge settles in and surface high pressure takes control.
Temperatures will nudge a bit higher in the sun, with readings in
the mid 70s to around 80 fairly widespread, around 5 degrees above
average.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
KEY MESSAGES:

- Ridging should result in dry and warmer weather into early
  next week.
- Rain chances return for Wednesday and Thursday, with some
  potential for strong thunderstorms..
  ____________________________________________________________

A dry forecast continues for Monday and into Tuesday as ensembles
largely agree on 500mb ridging and surface high pressure. The rising
heights will lead to increasing warmth; temperatures may climb well
into the 80s by Tuesday, levels last seen early in May.

The ensembles start to diverge a bit on the handling of the next
shortwave trough, which crosses the northern/central Plains and into
the Great Lakes during the Wednesday to Friday period. Cluster
analysis shows some strength and timing differences with this wave,
with GEFS generally more in favor of a slower, weaker wave than many
of the ENS members. These differences point to different scenarios
regarding rainfall amounts and severe weather chances. Still, given
the warmth and potential instability ahead of the system, along with
increased shear, we will certainly need to watch for the chance of
impactful thunderstorms.  Indeed, both CIPS and CSU machine-learning
guidance point to severe potential on Wednesday and Thursday.  In
any case, PoPs in the 50-70 percent range as suggested by the NBM
are justified. Temperatures will remain above normal, but will
likely be muted by Thursday given clouds/rain and a possible cold
frontal passage.

By Friday, scattered showers may remain in a continued troughing
pattern and moisture in low-level northwest flow.  Temperatures may
be closer to seasonable levels by this point.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
Save DUJ and FKL which have intermittently observed IFR or VLIFR
this morning and will continue to through daybreak, most ports
are generally sitting VFR to MVFR with temporary drops to IFR
possible in cig and visibility by morning in a saturated airmass
and calm winds.

Scattering and lifting is forecast into the daytime with an
increase in mixing. All ports should return to VFR before fog
and visibility restrictions return overnight again tonight.

.Outlook...
VFR and dry weather become high probabilities Sunday into
Monday under the influence of high pressure.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...22/CL
NEAR TERM...22/CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...Milcarek