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946
FXUS61 KPBZ 212152 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
552 PM EDT Sat Sep 21 2024

.SYNOPSIS...
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Very warm weather is expected through the weekend. Fog is
possible overnight and early Sunday morning.  A wetter pattern
is becoming increasingly likely next week.
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&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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KEY MESSAGES:

- Clearing skies late with areas of fog overnight.
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Update...
The latest water vapor imagery shows the shortwave trough
beginning to exit the region. Most of the convection is now out
of the forecast area, with a couple of isolated showers/storms
remaining along old outflows. These should diminish through
sunset as diurnal instability wanes.

Surface analysis shows a boundary across western PA into SE
Ohio. Very dry air has mixed down behind it, with dew points in
the uppper 30s to lower 40s in Ohio. Expect some recovery in the
dew points after sunset, with fog still expected especially for
areas that saw ran earlier today.

Previous discussion...
Some areas of dense fog tonight are possible with hi res
ensemble probabilities up to 70%, especially where rain falls
combined with clearing skies, a stagnant airmass, and
achievement of crossover temperatures.
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&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/...
KEY MESSAGES:

- Dry with above average temperatures on Sunday.
- Rain chances (yes, rain chances) increase starting Monday.
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A shortwave ridge axis will slide overhead in the wake of the
departing disturbance from Saturday with height rises and warm
advection supporting temperatures again into the 80s, warmest in
eastern Ohio, with 90 not out of the question there. High clouds
will increase in the evening from the west ahead of approaching low
pressure.

The main takeaway headed into the next workweek is that we are
finally seeing appreciable chances for beneficial rain. The upper
ridge axis will quickly be shunted east by an approaching trough,
and a shift to southwest flow aloft on its backside will open the
door for better moisture to work its way into the region. Clustered
ensembles exhibit pretty good agreement through Tuesday night with
just some strength and timing differences of the progression of the
responsible upper trough. Rain chances will increase Monday morning
as surface low pressure progged to be across Michigan pulls a trough
through the area. Ensemble probability for >0.5" of rain through
Tuesday night is still high (up to 80%) and a 50-70% chance of >1".

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
KEY MESSAGES:

- Rain chances increase Monday and Tuesday with a widespread,
  beneficial rainfall possible.
- Rain chances continue for the latter half of the week but
  confidence in amounts is low.
- Temperatures closer to average through the week.
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Uncertainty then increases significantly with ensembles
becoming much more spread on how the upper pattern evolves. The
majority consensus is that the Ohio Valley remains in a
troughing setup with significant differences on placement and
amplitude of the trough, but even one solution is attempting to
establish a ridging pattern. For continued beneficial rain, we
would want the solution(s) that sets up a trough deeper and off
to our west. Long story short, scenarios exist where additional
beneficial rain sticks around for the latter half of the week,
and scenarios exist for a drier period.

Despite this uncertainty, at least continued low precipitation
chances are appropriate through the end of the work week. 72 hour
precip totals have seen a slight eastward nudge in the past several
ensemble runs with probability for another >0.5" from Wednesday
through Saturday morning at 40-50% east of Pittsburgh and 20-40%
further west. A few high end, low probability scenarios exist
pending tropical influence. All told, the wetter pattern next week
holds some promise to at least somewhat mitigate the ongoing
drought. Temperatures moderating to seasonable levels (for daytime
highs at least) will help as well.

&&

.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
Scattered showers and storms have formed ahead of an advancing
cold front, supported by a shortwave trough aloft. These are
already east of a rough FKL/AGC/HLG line, and will continue to
move east, largely exiting the region by 22Z. Along with brief
downpours creating potential drops to IFR visibility, the
stronger storms will be capable of producing gusty wind and
hail. Expect locally lower cigs/vis in and around showers and
storms, while VFR is expected to prevail outside of convection.

Southwest wind around 10 knots away from thunderstorms this
afternoon with a shift to west/northwest expected behind the
boundary, with speeds of 5 to 10 knots.

Skies will largely clear after sunset behind the front. Fog
potential tonight will depend on where precipitation occurs/has
occurred today and where the best clearing occurs tonight. DUJ,
LBE, and MGW appear to have the highest threat of IFR to LIFR
visibility after 06Z. Fog will lift by 14Z, with VFR conditions
for the remainder of Sunday.

.Outlook...
VFR returns Sunday afternoon under building high pressure
before restriction potential increases again next week as a more
unsettled weather pattern sets up.

&&

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

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...WM/MLB
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...CL