PBZ issues Area Forecast Discussion (AFD) at Jul 29, 8:20 AM EDT991
FXUS61 KPBZ 291220
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
820 AM EDT Mon Jul 29 2024
.SYNOPSIS...
Scattered showers and thunderstorms will increase in coverage
west of Pittsburgh this afternoon. Heavy rain and thunderstorms
chances continue mid-week a new low forms early Tuesday morning.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Scattered showers and storms return today.
-------------------------------------------------------------------
A band of weak showers continues to track through central Ohio
this morning, riding along a well-defined moisture boundary (dew
points in the 50s near PIT/70s in ZZV). The moisture boundary is
having a difficult time tracking north as a surface low over
the New England area keeps mid to upper-lvl winds prevailing
from the north and dry air in place in northwest PA. However,
cloud coverage has increased early this morning from noted
outflow.
A mesoscale convective system (MCS), that brought abundant
rainfall and gusty winds to the Midwest over the last 12 hours,
is currently tracking through central Illinois. Outflow
associated with this disturbance will likely regenerate the
potential for showers and thunderstorms to develop over eastern
Ohio after 12pm today.
The potential for strong to severe storms is considered low
given weak effective shear (less than 20kts) and little dry air
aloft to produce cold downdrafts.
The probability of excessive rainfall could increase in eastern
Ohio with slow moving storms under a warm cloud layer (15kft)
and PWATs well above the climatological average (the Ohio River
Valley is expected to be in the 90th percentile for PWATs at
1.8 to 1.9 inches).
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
KEY MESSAGES:
- Better chances for showers and thunderstorms on Tuesday.
- Unsettled weather will continue on Wednesday.
- Conditions warm and muggy each day.
-------------------------------------------------------------------
Isolated to scattered showers will remain a threat tonight as
the initial trough slowly crosses the region, but models are
showing a rapid decrease in coverage with the loss of daytime
heating. A few thunderstorms will remain possible, especially
in the evening, as instability wanes. A second trough axis will
track across the Upper Ohio Valley region on Tuesday, with
additional showers and thunderstorms expected. Slightly better
moisture should be available on Tuesday, with PWATs 1.7 - 1.9.
MU CAPE is progged near 1000 j/kg on Tuesday, with 0-6km shear
around 20kt. Plenty of uncertainty remains on Tuesday in the
coverage/timing of any convection. The main reasons are the
threat for showers/storms in the morning and the additional
cloud cover those will bring. Also seeing differences in timing
of the shortwaves embedded within the trough.
High temperatures will generally remain in the 80s, and humidity
will remain high.
Not much change in the pattern on Wednesday with high levels of
uncertainty for strength, coverage, and timing of any
convection. Another trough will cross the area during the
afternoon. However, it may weaken as it does. Additionally, the
most unstable air could remain south of the region. Timing of
the trough will be important, if it swings through earlier in
the day, we could actually see some weak riding behind it which
would work to limit convection. Lots to be determined for the
middle of the week.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
KEY MESSAGES:
- A few rounds of disturbances pass into the Ohio River Valley
Thu-Sat; shower and thunderstorms continue into the weekend.
-------------------------------------------------------------------
Precipitation chances remain elevated into the weekend with
numerous shortwaves ejected into the region from the northwest.
Temperatures will likely remain near to above average through
Saturday.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
VFR will persist while mid level cloud cover increases south and
west of KPIT this morning as low pressure slowly approaches
from the Midwest. ZZV cigs have bounced between MVFR to VFR this
morning due to a flux of low-lvl moisture. With diurnal heating
over the next 3 to 4 hours, it is anticipated that clouds will
return to VFR.
A few showers and possibly a thunderstorm will be possible
this afternoon (after 18Z) west of KPIT as a remnant mesoscale
convective system (MCS) interacts with the moisture boundary
over central OH, adjusted TAFs to include PROB30 for rain
showers. Amendments may be needed to include thunder and vis
restrictions.
The probability for widespread cig restrictions increases after
06Z Tuesday as low-lvl moisture overspreads the region under
southwest flow.
Rain and thunderstorm chances will likely increase after 12Z
Tuesday with diurnal heating and new low forms over the Ohio
River Valley.
.Outlook...
Periodic restrictions are expected with scattered showers and
thunderstorms through the week through with a series of low
pressure troughs.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Air Quality Alert until 8 PM EDT this evening for PAZ014-
020>022-029-073-075.
OH...None.
WV...None.
&&
$$
SYNOPSIS...22/Hefferan
NEAR TERM...22/Hefferan
SHORT TERM...22
LONG TERM...Hefferan
AVIATION...Hefferan
Source:
PBZ issues Area Forecast Discussion (AFD) at Jul 29, 8:20 AM EDT---------------
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