-- Discussion containing changed information from previous version are highlighted. --
869
FXUS61 KPBZ 040924
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
524 AM EDT Sat May 4 2024

.SYNOPSIS...
Intermittent rain and a few storms are possible through the
weekend. With clouds and rain, temperatures will be cooler
today, but will rebound Sunday as a southerly flow returns. A
brief break in the rain is possible Monday.

&&

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

- Showers taper off overnight.
- Showers slowly move back over the region later this morning.
- Cooler temperatures today.
-------------------------------------------------------------------

East coast ridge will move very little today and amplify this
morning in response to trough digging into the northern Plains.
We will continue to rest on the western side of the ridge where
a shortwave will drift northward throughout the day.

Deep moisture will flow northward on the backside of the ridge
axis keeping in plenty of clouds and the risk for showers all
day. An increasing southeasterly flow at the surface will pump
Atlantic moisture into the region aiding in the shower
development. For the most part, rainfall should be on the light
side. HREF probs for 24 hour rainfall ending at midnight tonight
for >0.25 generally range from 30 to 50% with some pockets of
60 to 70% over portions of northern WV and the higher
elevations.

Clouds, showers and a cool easterly flow will keep temperatures
slightly below normal today.

&&

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

- Unsettled pattern remains with rain chances continuing
  through Sunday. Thunder possible on Sunday.
- Temperatures push back above normal Sunday and Monday.

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

East coast ridge will flatten and drift eastward on Sunday. The
shortwaves riding northward on the western flank of the ridge
will also shift to the east. Shower coverage looks to dissipate
Sunday morning. A weak cold front will slowly cross Ohio
Sunday. Models are hinting that scattered storms could develop
ahead of the front Sunday afternoon. However, ample cloud
cover,limited instability, and lack of upper level support
should work to shunt storm development and intensity.

Temperatures will warm on Sunday as the low-level flow veers to
the southwest ahead of the front.

Ensembles have been consistent in showing a shortwave trough over
the Middle Ohio Valley approaching, but weakening, on Monday as it
interacts with a weak ridge over our region. A south-to-north
gradient in PoP values still seems appropriate for the
Monday/Monday night period.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
KEY MESSAGES:

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

Uncertainty still reigns after Monday. Most guidance depicts a
ridge centered over the Great Lakes at 12Z Tuesday, along with a
deep closed upper low in or near the Dakotas. The upper low
appears likely to fill during the midweek period, and as it does
so, shortwaves rotating around it appear to flatten out the
ridge as it moves across the Upper Ohio Valley, finally eroding
it almost completely in the northeast CONUS. Some strength and
timing issues remain with the details of this process, which in
turn could impact precipitation amounts and timing.

Nevertheless, a warm front is likely to cross on Tuesday as the
ridge progresses eastward. This will lead to the persistence of a
warm and moist airmass, with precipitable water values at or above
the 90th percentile in the climatology. Along with the previously
mentioned shortwave activity, this will keep an active weather
pattern 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.  According to CSU machine-learning guidance
and NBM CWASP probabilities, Wednesday and Thursday may be the
days to watch.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
Ceilings will lower into MVFR this morning, with highest
probabilities north and west of Pittsburgh. East of PIT,
downsloping southeasterly winds may help keep low-level moisture
profiles slightly less saturated and thus, mitigate the
formation of widespread MVFR/IFR ceilings.

Showers are expected on and off through the morning, with more
widespread rainfall expected again after 18Z. Locally lower
ceilings and visibilities can be expected in the heavier
showers. Continued to leave thunder out of the TAFs during that
period given uncertainty surrounding how much instability will
develop. If lightning does occur, the best chances according to
hi-res ensembles would be southwest of PIT, so a mention of
thunder at ZZV and HLG may be needed in future updates.


.Outlook...
Restriction potential continues through Sunday morning, with
additional storm chances Sunday afternoon. Periodic restrictions
may continue through early next week as multiple disturbances
pass through the region.
-- End Changed Discussion --

&&

.CLIMATE...
Some record warm minimum temperatures may be approached on Saturday.
Below is a table showing the latest forecasted low temperature for
each climate site, their respective record value, and the year it
was set.

                  Forecast    Record     Year
Pittsburgh          60          65       1938
Wheeling            62          63       1931, 1939, 1941
Morgantown          61          63       2021
New Philadelphia    60          60       2012
Zanesville          63          65       1902

&&

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

&&

$$

SYNOPSIS...22
NEAR TERM...22
SHORT TERM...22/CL
LONG TERM...CL
AVIATION...Cermak/Rackley
CLIMATE...