-- Discussion containing changed information from previous version are highlighted. --
887
FXUS61 KPBZ 300525
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
125 AM EDT Thu May 30 2024

.SYNOPSIS...
Scattered showers and thunderstorms will dissipate this evening.
Dry weather returns Thursday through Saturday as high pressure
builds with cooler than average temperatures. An unsettled but
warmer pattern looks to take hold by late weekend into next
week.

&&

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

- Potential for peridawn fog favoring river valley locations
  south and east of Pittsburgh.
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Exiting of the upper shortwave trough axis east has promoted a
downward trend in shower activity. This shifts the focus
overnight from showers to potential for fog amid a slowly
clearing cloud deck as temperature falls between 5 to 10 degrees
below the daily low average.

Current probabilities favor river valley locations south and
east of Pittsburgh where boundary layer moisture remains more
entrenched; weak surface dry advection has started to drop area
dewpoints in the northwest forecast zones and thus limiting fog
potential. The quickness of residual stratocumulus clearing
overnight will also play a role in overall coverage of fog for
those south/east of Pittsburgh zones.

&&

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

- Dry weather expected to close out the week.
- Temperatures remain below average.
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The upper trough will finally begin to make its exit on Thursday.
High pressure will build as one final shortwave traverses the area
in northerly flow aloft, but associated subsidence and increasing
mid-level dry air will keep the area rain-free and mixing will erode
residual cloud cover below a sinking inversion save for the ridges
where low level moisture may be a bit slower to clear. Cool air will
overspread the area with ensemble mean 850 mb temperature ranging
from 3-6C supporting highs in the mid 60s, about 10 degrees below
average, and a northerly gradient breeze through the day as the high
builds in. Lows will bring a bit of a chill to the air with 40s
expected and even a 40% probability of less than 40 mainly for the
higher elevations and north of I-80.

There is slight timing difference with the departure of the trough
lending the chance for slightly cooler highs than forecast on
Friday, but overall dry weather continues to close out the week with
high confidence. Temperature will begin to moderate some with rising
heights and with a dry atmosphere and sunny skies, adjusted NBM dew
points down a bit and highs up a touch to account for mixing bias.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
KEY MESSAGES:

- Shower and thunderstorm chances increase late Saturday into early
  next week.
- Temperatures rebound back toward normal by Saturday.
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Upper level clouds increase on Saturday as ensembles eject an upper
wave out of the Plains. Uncertainty comes into play with variations
in strength and timing of the wave with some showing a flatter, more
progressive solution and others a more amplified, slower solution.
Temperatures will rebound Saturday as southerly flow on the backside
of the departing high promotes warm, moist advection.

Thereafter, the overall pattern trends toward weak westerlies aloft
through early next week. Embedded shortwaves may offer periodic
shower/thunderstorm chances but will be much more dependent on
convective evolution to the west to determine
timing/coverage/probability of occurrence for the forecast area.
There is higher confidence that broad height rises should enable
further warming areawide, making low to mid 80 values more likely by
Tuesday.

&&

.AVIATION /05Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
Areas of IFR fog and stratus have developed near and east of a
line from FKL-AGC-MGW, with lingering low level moisture behind
an exiting shortwave trough. Light NW wind and dry advection
should help to prevent fog formation for much of the area,
through areas along and east of the line mentioned above should
be last to see this dry advection and improving conditions.

After any early morning fog and stratus dissipates, VFR is then
expected Thursday and Thursday night as surface high pressure
builds across the Upper Ohio Valley/Lower Great Lakes region. NW
wind around 10kts on Thursday should become calm Thursday night
under the high.

.Outlook...
VFR is expected through Saturday under high pressure.
Restriction potential returns late Saturday and Sunday with
crossing low pressure.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...MLB
NEAR TERM...Frazier
SHORT TERM...MLB
LONG TERM...Frazier/MLB
AVIATION...WM