430
FXUS61 KPBZ 301920
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
320 PM EDT Thu May 30 2024

.SYNOPSIS...
Dry weather and moderating temperature are expected through
Saturday under the influence of high pressure. Late Saturday
through early next week will feature scattered showers and
thunderstorms. Temperatures climb back above normal early next
week with lower to mid 80s forecast.

&&

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

- Dry and seasonably cool weather continues.
- Mid/upper 30 lows forecast tonight across the higher terrain
  and I-80 corridor.
-------------------------------------------------------------------

Welcome to the first cool AND dry day across the area since May
12th! In a break from our previous pattern of rain, heat,
(and occasional tornadoes), amplified central CONUS ridging
wedged between eastern and western CONUS troughing, along with
building surface high pressure across the Great Lakes, have
left us pleasant, dry, and cool for the next several days.

Sunny skies this afternoon will be marred only with afternoon
fair-weather cumulus across much of the area. Ample sunshine
battling cool northwesterly flow will drive regional
temperatures near the 70F mark, with mid-60s forecast north of
I-80 and in the higher terrain.

For tonight, clear skies and light/calm wind will allow for
efficient radiational surface cooling. Temperatures in the upper
30s are expected across the I-80 corridor and in the ridges.
Spots in eastern Tucker County, WV could see temperatures dip
into the mid-30s with usual frost pockets potentially below
freezing by early Friday morning. For this reason, a Frost
Advisory was issued for eastern Tucker. Cooling conditions and
lingering BL moisture may also allow for patchy fog across
portions of NW PA, especially in the river valleys.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
KEY MESSAGES:

- Dry weather persists with moderating temperature.

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

Little sensible change in pattern is expected on Friday as the
ridge axis slowly creeps east across the Great Lakes and into
the Ohio Valley. After a cool start to the morning, high
pressure will sunny skies will allow temperatures to moderate
back to near normal Friday afternoon. Much of the area is
forecast to hit mid-70s Friday afternoon.

The ridge axis will cross the CWA Friday night as surface high
pressure begins to shift east. This will boost southerly return
flow into Saturday ahead of our next system. The result will be
gradually increasing cloud cover through the day Saturday, with
afternoon temperatures pushing into the lower 80s outside of the
I-80 corridor and ridges.

A few showers may be creeping into our far western zones near
ZZV by late afternoon Saturday, but for now, timing for rain
with the next system appears to be later overnight into Sunday.

&&

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

- Shower and thunderstorm chances return Saturday night.
- Periodic rain chances are then expected for much of next week.
- Temperatures rebound back toward normal by Saturday.
-------------------------------------------------------------------

There is good ensemble agreement in the aforementioned ridge
shifting east on Saturday as shortwave troughing crosses into
the Ohio Valley. This shortwave will cross our area overnight
into Sunday, with a weak low and cold front at the surface.
Showers and thunderstorms are expected by Saturday night,
lingering through Sunday. Nocturnal arrival and excessive cloud
cover Sunday should keep lightning probabilities lower (along
with severe threats). Clouds and rain will also keep afternoon
temperatures a bit cooler on Sunday.

Quick passage of the trough should lend to broad ridge
development just south of the region Monday into Tuesday. This
synoptic pattern would favor above normal temperature with low
probability afternoon thunderstorms that will be predicated on
shortwave movement and convective evolution over the western
Great Lakes. Much variability in outcomes is seen within model
ensembles, which muddies any chance of entertaining severe
probabilities.

There is growing consensus on the development of a notable
upper low pressure system mid to late week that would pose a far
greater probability for convective development and, to some
extent, severe chances. However, there remains high uncertainty
in the timing and eventual evolution of that system.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Residual moisture in a heating boundary layer has yielded sct-
bkn cu in the 3-4kft layer for much of western PA this morning/
early afternoon. As mixing continues today, and dry air is
entrained into the boundary layer from above, there should be an
eventual erosion of clouds, with skc anticipated by early this
evening as high pressure becomes more assertive. Wind gusts
15-20 kt are common this afternoon amid the deep mixing, but
these will subside this evening amid decoupling and the building
high pressure. Despite a cool overnight, the drying boundary
layer is likely (90% confidence) to suppress fog formation at
most terminals, except perhaps FKL and vicinity of PIT (where
there is a 10-20% probability of vsby below 6SM late tonight).

Otherwise, there is a high-confidence VFR forecast next 24
hours.

.Outlook...
VFR is expected through Sat under high pressure. Potential for
flight restrictions returns late Sat and Sun with crossing low
pressure.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...Frost Advisory from 2 AM to 8 AM EDT Friday for WVZ514.

&&

$$

SYNOPSIS...Frazier
NEAR TERM...Rackley
SHORT TERM...Rackley
LONG TERM...Rackley/Frazier
AVIATION...Kramar/McMullen