PBZ issues Area Forecast Discussion (AFD) at Jul 22, 11:32 AM EDT444
FXUS61 KPBZ 221532
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
1132 AM EDT Mon Jul 22 2024
.SYNOPSIS...
Shower and thunderstorm chances persist today with an
approaching disturbance from the south. Temperatures remain
seasonable throughout the week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Showers and storms continue through the day with a 1 out of 4
chance for flash flooding caused by excessive rainfall,
primarily south and east of Pittsburgh.
______________________________________________________________
Probability of thunderstorms increases significantly (above 50%)
within the Hi-Res model guidance after 1pm southeast of
Pittsburgh, PA as surface instability ranges between 700J/kg to
1200J/kg and warm front advances. There is a noted maxima in
low- level convergence over Tucker, Preston, Fayette, and
Westmoreland county that remains stationary between 2pm to 8pm
due to southeast flow over the Laurel Highlands and northwest
winds prevailing over Pittsburgh at 850mb.
Along with thunderstorms, higher rainfall rates will be
generally focus along the ridges as PWAT values range above
average (1.6-1.8 inches noted in Hi-Res model soundings).
Probability of rainfall totals (0.5 inches or higher for the
ridges) ranges between 60% to 80% through the late evening.
Isolated areas may receive over an inch of rain with training of
robust storms.
With effective shear weak (below 30kts) and DCAPE values likely
below 600J/kg, strong to severe wind gust potential will be
low. Small hail may form for updrafts that produce strong
reflectivity above 20kft.
Probability of thunderstorm decreases after 10pm with the loss
of surface heating and as the shortwave exits northeast.
With clouds and precipitation chances throughout the day,
afternoon high temperatures will likely trend near or below
average.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
KEY MESSAGES:
- Fog is expected to impact the region early Tuesday morning.
- Precipitation chances will remain low Tuesday morning and
early afternoon with ridging.
- A new weak shortwave may return isolated showers and storms
Tuesday evening.
_________________________________________________________________
As precipitation chances decrease early Tuesday morning, the
probability of low visibility due to fog increases to 60% for
portions of the region between 2am and 7am. A special weather
statement (SPS) and/or Dense Fog Advisory may be needed if a
prolong period of dense fog (1/2NM -1/4NM develops. At the
moment, Hi-Res model guidance is spatially favoring fog
developing east of Pittsburgh (mostly associated with the
potential of heavy rainfall Monday afternoon/evening). However,
probabilities could increase further west if convection
ventures near the border of eastern Ohio.
Fog may linger as late as 9am or 10am due to cloud coverage
delaying diurnal mixing.
Precipitation chances will likely remain low through Tuesday
evening under ridging.
Probability of isolated showers and thunderstorms increases
between 4pm to 8pm with a new weak shortwave advancing from the
southwest.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
KEY MESSAGES:
- Shower and thunderstorm chances continue through Thursday.
- Near-normal to slightly above average temperatures are
expected through Friday.
- Above average temperatures and dry conditions are expected
over the weekend.
________________________________________________________________
The Great Lakes trough and ridge axis off the Atlantic Coast will
continue to push moisture from the southwest into the Upper
Ohio Valley Wednesday and Thursday, keeping rain and
thunderstorm chances in the forecast. A cold front is expected
to cross the region early Thursday morning. Probability of
strong to severe storms during this period is low (less than
10%).
A shift in the synoptic pattern, a building ridge over the
Midwest and western Great Lakes, will return dry weather and
above average temperatures into the weekend. Probability of
>=90F afternoon high temperatures range between 25% to 50%
across the region on Sunday.
&&
.AVIATION /15Z MONDAY THROUGH FRIDAY/...
Surface low pressure currently just south of the Mason-Dixon
line will track NNE over the course of the day, spawning
scattered showers with isolated embedded thunderstorms.
Instability is marginal at best and only a scant amount of CG
strikes are currently being observed. Have not included TSRA
mention in TAFs attm, but may have to amend early in the
afternoon based on trends. Visibility restrictions are
possible in any showers/storms. Convection will exit the region
this evening, with mainly mid level clouds continuing. Areas
near DUJ could see MVFR cigs/vsbys developing toward midnight,
especially if rain occurs during the day.
.Outlook...
Restrictions in stratus/fog are possible Tuesday morning,
especially where rain occurs today. Scattered showers and
thunderstorms and restrictions, especially during the afternoon
and evening hours, are expected through Wednesday, as shortwaves
embedded in southwest flow cross the region. Showers and
thunderstorms are likely on Thursday with the passage of a cold
front. VFR returns Friday under high pressure.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Hefferan/Milcarek
NEAR TERM...Hefferan/Milcarek
SHORT TERM...Hefferan
LONG TERM...Hefferan
AVIATION...88
Source:
PBZ issues Area Forecast Discussion (AFD) at Jul 22, 11:32 AM EDT---------------
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