Area Forecast Discussion
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FXUS61 KPBZ 140521 AAC
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
1221 AM EST Thu Dec 14 2017

.SYNOPSIS...
Rapidly moving low pressure will continue the snow overnight.
Snow will end across much of the region around dawn save some
lingering snow showers over the ridges. Cloudy and cold for the
rest of the day.

&&

.NEAR TERM /THROUGH TODAY/...
No changes to the overnight period. The event is ongoing and
will leave forecast as is.

Wind gusts on the higher ridges bear watching, as instability
could partially mix down 40-50 knot winds just off the surface
in tight isobar packing behind the low.

Low will quickly transition to the coast shortly after dawn. As
this occurs, the strong upper level support and deep moisture
will also rapidly shift to the eastern seaboard. This will bring
a quick end to the bulk of the snow with the exception of the
ridges and perhaps the I-80 corridor, as much colder air rushes
southward behind the exiting system. Winds behind the system
will turn to the northwest, allowing for lake influence and
upslope to commence. However, inversions rapidly drop this
morning, which will push most of the saturated level below the
dendritic growth zone. This will greatly hinder the development
of lake bands and also will cutoff the ridge snow by mid to late
morning. PoPs transition downward after dawn, and will end by
late morning in the north and east.

Plenty of clouds remain today in the strong cold air advection
and temperatures will be well below normal.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/...
Clouds will linger overnight.

Weak shortwave trough will approach the area late Friday,
returning the risk for snow showers. Temperatures remain well
below normal on Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Trough will quickly swing through Friday night and snow showers
will linger into Saturday.

Slow height rises aloft begin Saturday afternoon, bringing and
end to the snow shower activity and allowing for warmer air to
overspread the region.

Flow goes zonal over our area by Sunday as our trough lifts out
and energy digs into the southwest U.S. This will result in
continued temperature moderation towards more seasonal levels.
The next system arrives on Sunday and will be mainly a rain
producer from the southern branch of the jet stream. The pattern
could remain unsettle thereafter with weak waves in the west-
southwest flow aloft, with perhaps another cool down by the
middle of next week.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Expect widespread IFR overnight as fast moving low pressure
spreads snow over the area. Conditions will improve rapidly on
Thursday although MVFR stratocu are expected to persist through
the remainder of the forecast period, as cold northwest flow
upslopes off the lakes.

.Outlook...
Next chance for restrictions is late Friday into Saturday.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...Winter Weather Advisory until 10 AM EST this morning for
     MDZ001.
OH...Winter Weather Advisory until 7 AM EST this morning for
     OHZ039>041-049-050.
PA...Winter Weather Advisory until 7 AM EST this morning for
     PAZ007>009-013>016-020>023-029-031-073>075.
     Winter Weather Advisory until 10 AM EST this morning for
     PAZ076.
WV...Winter Weather Advisory until 7 AM EST this morning for
     WVZ001>003-509-510.
     Winter Weather Advisory until 10 AM EST this morning for
     WVZ511>514.

&&

$$


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