363
FXUS61 KPBZ 171751
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
151 PM EDT Fri May 17 2024

.SYNOPSIS...
Unsettled weather returns today through Saturday with periodic
showers and a few thunderstorms. Near to above normal
temperatures will continue.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:

- Showers and a few thunderstorms will continue today with the
  passage of a weak trough.
- Localized heavy rainfall totals and water issues are possible.
- Near-normal high temperatures and above-normal low
  temperatures can be expected.
  _____________________________________________________________

Showers with a couple of embedded thunderstorms continue to
cross the region this morning with a relatively weak mid-level
trough and a nearly nonexistent surface reflection. Nearly
saturated low-level profiles and precipitable water values of
1.3 to 1.4 inches have led to locally efficient rainfall, with a
few radar-estimated totals above an inch in eastern Ohio.

Although SBCAPE may modestly increase into the 600-750 J/kg
range this afternoon, the overall lack of shear will keep any
severe concerns to a minimum. However, conditions favorable for
locally heavy rainfall will continue. Coverage will become a bit
spotter and more convective this afternoon, but isolated high
water issues are still possible if any one location gets hit
with multiple rounds of rain.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
KEY MESSAGES:

- Shower chances continue along with above normal temperatures.
  _______________________________________________

Upper troughing still transitioning across the region will
maintain shower chances on Saturday. Favored left entrance
region jet dynamics lie closer south and east of PGH, so have
maintained higher PoPs across the southern CWA. Again, NBM
24-hour half- inch probabilities remain below 50 percent with
the same north- to- south gradient. Severe threat remains very
low as well.

Diurnal temperature spreads will be fairly low given the expected
clouds and rain, with near-normal maximums but above-normal
minimums.

&&

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

- Ridging should result in dry and warmer weather Sunday and
  into next week.
- Rain chances return for Wednesday and Thursday.
  ____________________________________________________________

The earlier trend towards a more southerly track for the main
shortwave trough on Sunday continues in the recent guidance. This
does lead to generally low PoPs on that day, focused on areas south
of Pittsburgh where moist easterly flow lingers during the morning.

Ensembles then seem to be in decent agreement in keeping this
trough/upper low near or just off the southeast CONUS coast, while
slowly rising 500mb heights take control over the Upper Ohio Valley.
This points to mainly dry weather from Sunday night through Tuesday,
with increasingly above-normal temperatures through early next week.

The next shortwave trough then drives across the Upper
Mississippi Valley towards the Great Lakes during the midweek
period. Model cluster guidance shows strength and timing
differences with this, which point to various scenarios for
precipitation amounts and severe weather chances. In any case,
PoPs topping in in the likely range and muted, but still warm
high temperatures looks to be the forecast of least regret at
this time.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
A scattering in the precipitation shield and cloud deck is now
noted working into eastern Ohio this afternoon as slightly drier
air intrudes from the west. Some CIG recovery is expected into
the early afternoon based on upstream obs and hi res guidance save
FKL and DUJ which are favored to remain MVFR.

Precipitation coverage will take on more of an isolated to
scattered nature this afternoon, though with that we`ll see
increasing thunder probabilities. Confidence in coverage and
exact timing of a thunderstorm at any site remains low at this
time, but any that do see a heavier shower/thunderstorm could
experience a brief drop in both CIG and VIS to as low as IFR.
Outside of the scattered showers, conditions should remain low
end VFR/high end MVFR with increasing probabilities for MVFR
after 23z. By the overnight hours, all sites should see MVFR to
IFR conditions with a 70-90% confidence. With lingering low
level moisture from earlier rainfall, low confidence chances for
fog increase after 06z; the wrinkle is a passing wave that will
likely reinvigorate showers after midnight, with best chances
south and east of Pittsburgh, which may result in more stratus
formation than fog formation.

MVFR conditions will be slow to erode Saturday morning with
probability for MVFR CIGs remaining 60+% through 16z but will
slowly begin to see improvement from the west.

.Outlook...
Upper trough passage to the south Saturday will maintain
SHRA/TS chances focused south of KPIT. VFR and dry weather
become high probabilities Sunday into Monday under the influence
of high pressure.

&&

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

&&

$$

SYNOPSIS...88
NEAR TERM...CL/88
SHORT TERM...CL/88
LONG TERM...CL/88
AVIATION...MLB