Area Forecast Discussion
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FXUS61 KPBZ 100738
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
238 AM EST Sat Dec 10 2016

.SYNOPSIS...
Lake effect snow will wind down north of I-80 this morning with a
few breaks in the clouds across the area. Cold air will remain in
place in advance of the next system that will affect the area
tonight through Monday with snow, rain, and the potential of a
wintry mix before much colder air arrives late in the week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Low level flow has turned decidedly southwest, bringing in some
drier air in the lower levels. however, flow up toward 850 mb
remains stubbornly northwesterly with model indications revealing
little trend toward any more westerly or southwesterly component
at this level over the next six hours or so. Luckily, this is
leaving us with a fair amount of directional shear in the lower
levels of the atmosphere, preventing a true dominant band of snow
downwind from Lake Erie. However, given that northwesterly flow
remains in the most unstable portion of the column which is also
co-located with the dendritic growth layer, it seems the current
radar depiction over Mercer and Venango Counties will likely
linger for several more hours. It seems reasonable thus given snow
rates over the past few hours to expect around two more inches of
snow in the more decent lake effect bands over northern Mercer and
Venango County through the night. The lake effect snow advisory
was thus extended until 5 AM.

Elsewhere, flurries will be possible as somewhat unstable lapse
rates remain even with a much drier column. Fries

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
High pressure will begin to move east Saturday with flow becoming
westerly as weak shortwave exits. Temperatures will continue well
below average.

Complex low pressure will approach Sunday and move across the
Great Lakes Monday. Warm advection snow will develop across the
region Sunday and continue into Sunday evening, before mixing
briefly with freezing rain and then changing to plain rain except
for areas north of I-80 where cold air will hang in until mid
morning Monday. With surface low so far west, warm air should be
able to move north fairly quickly, keeping snow accumulations in
check for the most part. Best estimate for now is 4-6 inches north
of SR 422 in PA, with only an inch or two across Pittsburgh. Areas
south of Pittsburgh will have little in the way of accumulation.
Some light icing possible mainly in the ridges for a time Sunday
night. Warm advection will push temperatures into the upper 30s to
mid 40s Monday before a cold front drops temperatures back toward
normal in the afternoon.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Main feature will be an arctic cold front Tuesday night crossing
east of the ridges early Wednesday. Temperatures will be 15 to 20
degrees below average through late week. While snow showers will
be scattered mainly across the north, no significant snow is
expected.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
Lake effect snow bands will continue to impact KFKL and KDUJ into
the dawn hours. Elsewhere, MVFR cigs will gradually improve to VFR
today as drier air arrives from the SW. The next system will roll
into the area tonight with snow overspreading all sites near the
end of the TAF valid period.

.OUTLOOK...
Widespread restrictions are likely Sunday and Monday, and again
Wednesday, with crossing areas of low pressure.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...Lake Effect Snow Advisory until 5 AM EST early this morning
     FOR PAZ007.
WV...None.

&&

$$



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