229
FXUS61 KPBZ 051320
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
920 AM EDT Sun May 5 2024

.SYNOPSIS...
Intermittent rain and a few storms are possible today.
Temperatures will moderate as southerly flow returns. A break in
the widespread rain is possible Monday.

&&

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

- Showers continue today.
- Strong afternoon thunderstorms possible with the passage of a
  cold front.
-------------------------------------------------------------------

Updated the grids to input the latest values for temperature
and dew point and trended them into the afternoon. Touched up
pops to account for the low topped convection this morning as
well. Overall, showers and a few storms will continue through
noon. Would like to see at least some clearing before gauging
the severe threat today. The progression of cloud cover will be
a key decider in development later today.

Previous discussion...A weak shortwave trough will move across
the Upper Ohio Valley today. This wave will weaken and push the
east coast ridge out over the Atlantic. A surface cold front,
trailing the upper wave, will cross the region today, reaching
the eastern edge of the forecast area by early evening. The main
moisture plume, that has been parked over the region for the
last couple of days, will drift eastward with another weak
shortwave behind the exiting ridge. This decrease in deep
moisture, and loss of upper level support, should allow for a
brief respite in the widespread showers. As the aforementioned
cold front moves eastward across Ohio early this afternoon,
showers and a few storms will redevelop and accompany the
boundary as it clears the rest of the forecast area. SPC
continues to advertise a marginal risk for severe storms today.
The main driver in this assessment is the rapid destabilization
of the atmosphere ahead of the front. However, latest model data
continues to show a weak sheared environment, which will work
against updraft enhancement, and plenty of cloud cover that will
hinder day time heating. Additionally, weak warm air advection
aloft may also work to cap the atmosphere. There could be some
breaks in the cloud cover this afternoon with the warm
advection, but will there be enough time to further destabilize
the atmosphere?

With the surface flow veering to the south then southwest, and
the warm air advection aloft, temperatures will again rise
above seasonal averages.

&&

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

- Break in the rain possible Monday for a large portion of the
  region.
- Temperatures remain above normal Monday.

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

A shortwave trough will dig into portions of the Upper Midwest
Monday morning. This will promote modest height rises over the
region. Weak cold air advection behind today`s cold front will
spread somewhat drier air over the area. This should allow for a
break in the rain and some decrease in cloud cover Monday
afternoon. A weak shortwave moving eastward around the main
trough, could bring the risk for isolated to scattered showers
over locations mainly south of I-70.

Temperatures will cool a bit on Monday, but still remain above
normal.

Lots of uncertainty on Tuesday that will depend on the path of a
weakening shortwave trough and the crossing of a surface warm
front. If the trough digs further south, rainfall coverage
would be more focused on the southern half of the forecast area
as the surface boundary would not make as much headway to the
north. If the wave shifts further north and the warm front does
as well, then the showers would do the same. Further
complicating Tuesday is the speed of the wave. A faster exit
could cause modest 500mb height rises during the afternoon.
Latest blended guidance is leaning toward a more northerly and
slower track of the wave, so will ride with that solution.

Temperatures will warm once again on Tuesday.

&&

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

- Rain chances continue through the week but more uncertainty
  lends to lower confidence.
- Temperatures favored to remain above normal.
-------------------------------------------------------------------

An active weather pattern will remain in place for our region,
with decent daily precipitation chances through Friday. Deep-
layer shear will increase as well behind the departing ridge, so
severe weather chances will need to be monitored as well.

&&

.AVIATION /13Z SUNDAY THROUGH THURSDAY/...
Waves of showers will continue on and off through the morning
as weak shortwaves traverse the upper flow. Movement will be
rather slow and low ceilings will persist through at least
midday as IFR or below conditions. By this afternoon, some cigs
will lift to MVFR and even VFR in some spots.

Height rises and diurnal heating will lift area cigs by 16Z and
will result in a brief lull from convective activity. The
passage of a shortwave and associated weak surface cold front
will then create scattered thunderstorm coverage primarily after
19Z - lingering into the early overnight.

.Outlook...
A moist boundary layer behind the frontal passage and evening
thunderstorms Sunday night likely will lead to widespread
MVFR/IFR restrictions. Some improvements are expected Monday
with influence of high pressure to the north, but shortwave
movement across the TN River Valley may maintain some
restriction/precipitation chances for southern terminals.

The rest of the week will remain active with varying periods of
precipitation and restrictions amid low pressure passage.

&&

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

&&

$$

SYNOPSIS...22
NEAR TERM...22/Shallenberger
SHORT TERM...22
LONG TERM...22/CL
AVIATION...Rackley/Shallenberger