PBZ issues Area Forecast Discussion (AFD) at Aug 31, 1:19 AM EDT155
FXUS61 KPBZ 310519
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
119 AM EDT Sat Aug 31 2024
.SYNOPSIS...
An approaching and crossing cold front will bring the risk for
widespread showers and thunderstorms today and into early
Sunday. Severe weather is possible, mainly today. A big change
in the pattern will bring dry and more comfortable conditions
next week.
&&
.NEAR TERM /THROUGH TODAY/...
KEY MESSAGES:
-The threat for showers and storms will increase today with the
passage of an upper level wave.
-There remains a slight risk for severe weather.
----------------------------------------------------------------
Still seeing scattered activity to the west of the CWA. This
activity is weakening as it moves eastward. A shower or brief
storms cannot be completely ruled out overnight, but the
activity should be isolated. Pops have been updated as well as
overnight lows.
Modest height falls anticipated today as a slow moving shortwave
trough will cross the region this afternoon, well ahead of a
surface cold front. This upper level wave will increase the risk
for widespread showers and storms beginning late this morning
and continuing through the afternoon hours. Latest CAM analysis
is indicating some destabilization of the atmosphere today,
however, they are pointing to the more buoyant air pooling to
the south of Pittsburgh late this morning. Models are also
advertising an increase in wind shear today, with the strongest
(25 to 30kts) south of Pittsburgh. The trend to shift the risk
for more potent convection to the south can also be seen in the
model QPF as the higher amounts, related to stronger convection,
are mainly south and east of Pittsburgh. Cloud cover and warmer
air aloft could limit convective coverage and strength.
High temperatures today will be tricky, due to the
aforementioned cloud cover and rain.
&&
.SHORT TERM /TONIGHT THROUGH MONDAY/...
KEY MESSAGES:
-Scattered to isolated activity will continue tonight into
Sunday morning as a cold front crosses the region.
-Noticeably cooler and drier Monday.
-------------------------------------------------------------------
Scattered showers and thunderstorms may linger tonight into
Sunday morning until the cold front finally exits to the east by
early Sunday afternoon. Drier air will filter in behind the
surface boundary as well as cooler temperatures.
A cool northwest flow is expected on Monday. This should mean
dry and much more comfortable conditions. This flow would likely
mean increased cloud cover as colder air aloft overspreads the
region. Monday's highs will dip down below seasonal averages.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
KEY MESSAGES:
- High likelihood for another prolonged dry and seasonable
weather pattern.
-------------------------------------------------------------------
Long range ensemble analysis favors a prolonged period of dry
and seasonable weather as the Upper Ohio River Valley remains
under waning NW flow and ridging persists over the Rockies.
Variation in potential outcomes increases toward the end of the
week depending on potential shortwave trough progression from
the west coast over the ridge. If it is able to flatten the
ridge Tuesday/Wednesday, the likelihood is for it to advance
towards the east coast and offer low probability rain chances
and trend area temperature downward after it passes. If it
remains stuck over the Pacific NW, the ridge may shunt east and
maintain dry weather while causing temperature to rise well
above the daily averages. Current forecast remains in between
due to ensemble means, but look for these values to trend one
way or another as those larger pattern changes are better
resolved.
&&
.AVIATION /05Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions are expected overnight ahead of an approaching
shortwave trough. A few showers and isolated thunderstorms are
possible through early morning, though current indications are
these should miss the TAF sites.
Increasing mid level cigs are expected by morning with
increasing moisture ahead of the trough. Showers are expected to
begin from late morning through mid afternoon from NW-SE as the
trough approaches. The latest HREF guidance indicates MU CAPE
reaching 1000-1500 j/kg this afternoon, when thunderstorms are
expected to develop. Included a tempo mention for most airports
for the most likely time of thunderstorm occurrence.
A few showers will remain possible behind the initial shortwave
and pre frontal trough, with cigs/vsby restrictions returning by
Saturday night with low level moisture in place.
.Outlook...
Cig restrictions are possible Sunday with a reinforcing cold
front. VFR is then expected through mid week under building
high pressure.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...22
NEAR TERM...22
SHORT TERM...22
LONG TERM...Frazier
AVIATION...WM
Source:
PBZ issues Area Forecast Discussion (AFD) at Aug 31, 1:19 AM EDT---------------
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