Area Forecast Discussion
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FXUS61 KPBZ 161844

Area Forecast Discussion
National Weather Service Pittsburgh PA
144 PM EST Sat Dec 16 2017

Light snow north of Pittsburgh will taper off this afternoon.
Temperatures will begin to moderate to near seasonal averages.


Area of convergence along a lifting boundary continues to
support some light snow to our north. Expect this to lift north
and dissipate through the rest of the afternoon as high
pressure builds to the south. Little additional accumulation is

Skies are clearing rapidly south of the area of snow, with
temperatures warming close to seasonal averages with the help of
warm advection.

Building ridge will lend to a quiet night tonight. Warmth aloft
should hold temperatures up slightly, given mostly clear skies
and light wind - though it doesn`t appear we will fully
decouple. Stayed close to persistence for lows.


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 area.

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.


Near and north of I-80, MVFR ceilings will linger through most
of the period as clouds remain locked in. Snow showers may still
produce brief MVFR/IFR visibilities until mostly shutting off
by 00Z. Ceilings may drop to IFR during the overnight/early
hours for a period before lifting by mid-morning once mixing
kicks in.

Further south, building high pressure will keep conditions VFR
through the period. Mid clouds will mostly clear out this
afternoon, with scattered clouds at most tonight. Overcast
conditions may return by midday Sunday ahead of a weak
disturbance, with most light precipitation holding off until
after 18Z.

Restrictions are possible from Sunday night through Tuesday, as
abundant low-level moisture may become trapped underneath an
inversion for an extended period. IFR conditions are possible at




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