839
FXUS61 KPBZ 122342
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
742 PM EDT Sun May 12 2024

.SYNOPSIS...
Southerly flow will bring dry and much warmer conditions on
Monday as temperatures warm about 10 degrees above normal.
Showers and thunderstorms return Tuesday and Wednesday as low
pressure crosses the Ohio Valley.

&&

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

- Clearing trend and cool temperatures overnight tonight.
-------------------------------------------------------------------

No major changes to the overnight period needed. Previous
forecast is in good shape.

Previous discussion...
Vertically stacked low pressure currently centered over New
England continues pushing away to the east through tonight,
allowing a weak upper shortwave ridge to build in its wake.
Clearing skies and quiet weather can be expected overnight as a
result, with temperatures trending around, or perhaps a few
degrees below, normal for this time of year.

&&

.SHORT TERM /MONDAY NIGHT/...
KEY MESSAGES:

- Mostly dry weather likely with lower humidity
- A few isolated showers and storms possible north of I-80
- Sunshine will bring temperatures close to 80F
-------------------------------------------------------------------

Weak shortwave ridging prevails overhead, with height rises and
warm advection combining to push afternoon temperatures upwards
of 10 degrees above climatological normals (near 80 degrees for
most). An 850mb jet and region of enhanced WAA traverses the
lower Great Lakes from west to east, which could produce some
low-end shower and thunderstorm chances along and north of
I-80. However, the bulk of any precip is expected to remain
north of the area.

Farther upstream over the Great Plains, an upper low moves
eastward across Kansas and into Missouri during the period. This
will be the system that brings another round of showers and
storms to our local area midweek.

&&

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

- Midweek showers and thunderstorms likely, with limited severe
  and flooding threats.
- Dry conditions likely on Thursday
- Ensemble spread is high Friday and Saturday, but another
  trough appears to bring shower chances
-------------------------------------------------------------------

Upper trough expected to move across southern IL Tuesday and
then along IN/KY border Tuesday night. This feature then
progresses across southern Ohio and northern West Virginia
Wednesday and Wednesday night.

Warm and moist advection will push precipitable water values up
around 1.3" by Tuesday afternoon and support showers and
thunderstorms through Tuesday night. Lingering showers Wednesday
morning taper off in the afternoon and evening with the upper
low departing and high pressure building in from the west.

NBM 48 hour Probabilities of exceeding 1" of rainfall have
lowered somewhat and now range from about 20% in the northwest
portion of the forecast area to about 40% over the ridges.
Probabilities for 2" are less than 10% everywhere and in many
cases less than 5%. Instability will be marginal and 500 mb flow
quickly drops below 20 knots Tuesday, so it appears that the
probability of significant impacts for convection are low.

Upper ridging brings sunshine and temperatures in the 75-80F
range on Thursday. Another trough with potential for showers
and thunderstorms appears to be on tap for Friday and Saturday,
though considerable standard deviation is noted in ensemble
guidance during that period over the Great Lakes and upper
Midwest.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Surface high pressure will shift east overnight and promote
light southerly winds and clear skies overnight. Tomorrow, winds
up to 10kts are possible out of the southeast as as the at the
pressure gradient increases. A weak mid-level wave will pass
tomorrow, though the best precipitation forcing will remain
north of the area. Nonetheless, local ports may see in increase
in mid- level clouds.

.Outlook...
Restrictions are likely, along with showers and possible
thunderstorms, Tuesday through early Thursday as slow moving low
pressure crosses the region.

Another crossing low pressure system with precipitation and
restriction chances is becoming more likely for next weekend as
well.

&&

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

&&

$$

SYNOPSIS...Cermak/Craven
NEAR TERM...Cermak/WM/22
SHORT TERM...Cermak/Craven
LONG TERM...Cermak/Craven
AVIATION...Milcarek