Mount Lebanon, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

761
FXUS61 KPBZ 221210
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
710 AM EST Sun Dec 22 2024

.SYNOPSIS...
Dry weather but cold on Sunday. The next chance of
precipitation comes Monday night into Tuesday with gradually
warming temperatures through the upcoming week.

&&

.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:

- Dry under high pressure.
- Cold with highs in the 20s and overnight lows in the teens to
  single digits.
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The last of the remnant snow showers extending back to Saturday are
waning overnight tonight and will continue to do so as subsidence
and drying of the low-levels ultimately win out. The one last
threat to note is the potential for icy spots on area roads this
morning, especially those that are untreated, as air
temperatures tumble into the teens. Will have this threat
covered with an SPS this morning.

High pressure will otherwise be the dominant feature for today
with clouds lingering this morning in residual low-level
moisture. Gradual warm advection aloft will scatter out the
clouds through the day allowing for some sunshine to return this
afternoon. It will be a cold one out there as highs will be in
the 20s for most, save eastern Ohio where some locales may
breach the 30 degree mark. We won`t be contending with much wind
today as the gradient is weak underneath the high, so apparent
temperature will be very close to that of the air temperature.

Looks like a decent setup for efficient radiating tonight as the
high meanders overhead with light wind. Some cloud coverage may try
to work back in from the northwest overnight and put a damper on the
cooling, but confidence in that occurring early enough to effect
lows isn`t very high right now, so erred on the colder side of the
distribution for overnight lows which have a 60% chance of dipping
into the single digits across Forest, Jefferson, and Clarion
locales. Elsewhere, mid teens are probable.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
KEY MESSAGES:

- Light precipitation returns Monday night with some
  snow accumulation possible north and east of Pittsburgh.
- Warmer on Christmas Eve with afternoon highs challenging the
  chances of a white Christmas.
--------------------------------------------------------------------

Most of the daytime hours on Monday are likely to be dry with the
influence of departing high pressure. Ensembles are in
respectably good agreement on the progression of a trough
crossing the area Monday night into Tuesday morning with little
deviation on its strength or timing lending higher confidence. A
weak attendant surface low will track east across the Great
Lakes pulling a weak boundary through as it passes by.
Precipitation probabilities are high at 80%+ with this feature,
but moisture return ahead of it appears paltry given a lacking
meridional component to the flow ahead of its arrival.
Precipitable water values only have around a 50-60% chance of
exceeding 0.5". That said, with the timing being in the
overnight hours, probability of dominant precip type to be snow
is highest north and east of Pittsburgh coincident with the
colder air where overnight lows <32F are 80-100% (30-50% in the
urban areas). Probability of total liquid >0.10" is as high as
60-70% north of Pittsburgh closer to the best forcing. In terms
of snow, NBM probability for 1" is up to about 60% concentrated
in Forest, Clarion, and Jefferson Counties; the reasonable high
end of the goal posts sits at around 3" at this point with the
low end <1", so there`s still some uncertainty in amounts, but
generally are favoring the 1-3" range. Elsewhere, rain or a
rain/snow mix are more likely given the warmer temperatures.

If at least 1" of snow does fall overnight and provide at least that
much snow depth headed into the day on Christmas Eve, we`re looking
at a high probability for afternoon highs to exceed the freezing
mark, so snow depth may be challenged as could a White Christmas (1"
of snow on the ground at 7am on Christmas Day). A transition to rain
showers then becomes more likely on Tuesday with lingering moisture
and shortwave passages as the trough exits, but additional
measurable rain chances are only peaking around 50%.

&&

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

- Low precipitation chances on Christmas Day.
- Warming trend through the end of the week.
- Uncertainty in the pattern by next weekend.
--------------------------------------------------------------------

In the wake of the Christmas Eve disturbance, ensembles converge on
a brief ridging solution downstream of another quickly approaching
trough across the Midwest that is favored to weaken and flatten out
as it approaches locally on Christmas Day. Some uncertainty comes
into play with potential phasing of a northern stream wave
traversing north of the Great Lakes with the weakening southern
wave, but this is only represented by one ensemble cluster while the
others suggest higher heights. This would be a non-trivial solution
though should it come to fruition and provide greater moisture
return in a bit more amplified flow compared to other solutions that
suggest only low-end probability scattered rain showers. If precip
does occur, profiles aren`t favorable for snow with probability near
100% to exceed 32 degrees for highs.

For the latter half of the week, all clusters suggest building
ridging by Thursday, again save one solution that hangs back the
upper disturbance and associated precipitation chances into early
Thursday morning. Regardless, ridging will finally take hold with
570+ dam heights presenting as increasing probability. Deep layer
southerly component flow will support a warming and moistening trend
as highs rise above 50 degrees south of Pittsburgh with a 40-60%
chance on Thursday and incrementally stepping up further north
into the weekend. Confidence in a warming trend is increasing.
Another disturbance is possible come next weekend, but deviance
from the grand ensemble solution increases substantially in
regard to precipitation chances.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Most places will lift to VFR by 12Z or shortly afterward. The sites
at FKL and DUJ may hang onto MVFR a tad longer but should improve by
18Z. Most guidance maintains scattered coverage, with high
confidence in lifting and scattering after noon-time. Winds will
become light throughout the day as high pressure sits overhead.
From tonight through tomorrow evening, VFR conditions are
expected to persist. Tomorrow, winds will freshen up to 7-10
knots out of the south. Gusty conditions expected to develop by
tomorrow evening.


Outlook...
The next upper level system crosses into the region tomorrow
night into Tuesday, bringing another round of light snow and
areawide restrictions. The highest chance for IFR conditions
(40%-55%) is expected between early Tuesday morning through
Tuesday afternoon. DUJ and FKL hold on to a 35%-45% chance for
IFR through late night on Tuesday while majority of other
terminals will return to MVFR conditions.

&&

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

&&

$$

SYNOPSIS...MLB
NEAR TERM...MLB
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...Lupo