Area Forecast Discussion
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FXUS61 KPBZ 230423
Area Forecast Discussion
National Weather Service Pittsburgh PA
1123 PM EST Sun Jan 22 2017
Low pressure will spread rain, and some snow over the region
tonight through early Tuesday.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --Made some PoP adjustments for this update, with the first
deformation band weakening as it crosses. Expect rain to focus
more on the eastern slopes for the next few hours per hi-res
models, before overspreading the area towards morning as more
generalized deformation develops. Minor updates to temperatures as
-- End Changed Discussion --
.SHORT TERM /6 AM MONDAY MORNING 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 /04Z MONDAY 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. The easterly flow may
keep cigs up a bit around KMGW and KLBE until the upper level
system moves overhead on Monday.
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.