Area Forecast Discussion
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FXUS61 KPBZ 221943
Area Forecast Discussion
National Weather Service Pittsburgh PA
243 PM EST Sun Jan 22 2017
Low pressure will spread rain, and some snow over the region
tonight through early Tuesday.
.NEAR TERM /THROUGH TONIGHT/...
Adjustments for the late afternoon update included timing and
coverage changes to precip probs given the latest radar trends as
an area of showers continues to work northward toward the region.
Deepening low pressure will emerge from the Lower Mississippi Valley
tonight and spread widespread rain over the entire area. Escalating
precip probs were adjusted for faster onset.
.SHORT TERM /MONDAY THROUGH TUESDAY/...
Forecast confidence remains hampered as model depictions of the
cutoff low pressure set to dig toward the Upper Ohio Region, have
again deviated from previous days solutions with a southward track
of the center. Nevertheless, increasing ascent via deformed flow
and warm advection with increased moisture through the mid levels
all support categorical precip probabilities into Monday, with a
diminishment into Tuesday as the system exits.
With the northern branch of split flow holding colder air north and
west of the region, and with warm advection into the mid levels
of the cutoff, this still looks to primarily remain a rain event
for the Upper Ohio Region; however, the NAM, and to a much lesser
extent the GFS, continue to develop sub-zero air over the region
immediately above the boundary layer, probably due to dynamic
cooling as the low deepens. Have decided to move toward this
potential and have introduced a rain/snow mix-to snow mainly for
the elevations and extreme northern zones on Monday and into
Monday night, then more-so into Tuesday as colder air briefly
wraps into the departing system.
Should the low track and strengthening magnitude remain
consistent and the cooling materialize, then an advisory for
several inches of snow accumulation may be needed for the
ridges and zones north of I 80. An HWO mention was included for
this potential, although a warm boundary layer and dry advection
into the maturing mid levels may hamper the possibility.
QPF was progged using a RFC/WPC blend for the period. On the
order of a half, to one inch of rainfall is anticipated.
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The long term period will feature a change to more seasonal
weather a midweek cold front initiates a temperature reduction
toward, and then below the averages during the latter half of the
week. Tweaked, especially POPs, Superblend guidance was used in
construction of the period.
.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
VFR conditions are expected through the evening with mid clouds
ahead of approaching low pressure. The approaching low should
result in a deterioration to MVFR, and eventual IFR, overnight
and Monday with rain. Increasing E winds are expected tonight and
Monday with an increasing pressure gradient.
Restrictions are likely through Tuesday as low pressure moves off
the coast, and again late Wed through Fri with a crossing cold
front and subsequent upper troughing.