Area Forecast Discussion
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FXUS61 KPBZ 161037

Area Forecast Discussion
National Weather Service Pittsburgh PA
537 AM EST Sat Dec 16 2017

Light snow this morning, mainly north of Pittsburgh.
Temperatures will begin to moderate to near seasonal averages
this weekend.


Light snow moving back in from the west. This activity is
associated with a strengthening low-level jet moving overhead
and coincides with noted cooling on GOES-16 Clean IR channel.
This snow will slide southeast, over the area but will start to
fight warm and dry advection from the southwest.

High pressure will begin to nose in from the south midday
Saturday, pushing lingering downlake snow showers further
north and leading to some level of clearing. That said, will
continue to carry likely snow showers north of I-80 through the
afternoon where favorable fetch continues. All of this will lead
to a sharp gradient in sky and thus temperatures as well.
Locations south of I-76 should warm up much warmer than areas
further north, which will likely stay in the clouds.

Any remaining snow showers will cease and lift north by Saturday
evening. With high pressure continuing its northern push, dry
weather will carry through Saturday night. Saturday`s low
temperatures will remain near seasonal averages.


High pressure will gradually take over the area Sunday, but the
dry weather will be fleeting. Despite brief ridging aloft
locally, a wave ejecting out of the southern Plains will ride
over the ridge Sunday afternoon bringing light precipitation
back to the area. The weakening disturbance will stream southern
moisture northward along an axis of modest isentropic ascent.
Models still differ on the placement of the main precipitation
band Sunday, but more importantly on the boundary layer
temperatures and subsequent precipitation types. Will continue
to use a blend for the placement of high chance PoPs and will
keep p-types fairly broad. Regardless of precipitation type,
this system looks to have relative minor impact on the forecast

The weak wave will depart quickly to the east Sunday night,
leaving a period of mostly zonal flow aloft. Monday and
Tuesday`s precipitation forecast appear a bit nebulous at this
time. With abundant low-level moisture left below a strong mid-
level inversion, it looks as if clouds and light precipitation
or drizzle could plague the area in the beginning of the week.
With a lack of organized ascent, precipitation chances will
hinge on weak waves passing through the zonal flow. Will follow
the previous forecast and continue to keep PoPs in the
neighborhood of climatology. Temperatures will continue to warm
to above average values Monday and Tuesday, despite continuous
cloud cover expected.


A broad trough will drop into the central CONUS Tuesday night
sweeping a cold front through the area. This could re-invigorate
showers Tuesday night into Wednesday, but will help drive
temperatures back to near-normal values. Upper-level flow
returns to zonal behind the front, bringing a drier and warmer
trend until the latter part of the week. Models still have
another system/cold front for Friday, but strength and placement
of the low have changed with newest guidance. Will hold close to
the SuperBlend for precipitation details, and look for clarity
in the coming guidance packages.


MVFR this morning as light snow showers can be expected this
morning with improvement to VFR in the afternoon...except for FKL/DUJ
where IFR cig/vis restrictions are possible and persistent MVFR
for much of the day.

The next chance for general restrictions arrives by Sunday with
an advancing warm front. Model guidance shows good consensus
with abundant low level moisture in the warm sector. Based off
analogs...ports could see continued restrictions (including IFR
and lower at times) through Tuesday.




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