Area Forecast Discussion
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FXUS61 KPBZ 221135

Area Forecast Discussion
National Weather Service Pittsburgh PA
635 AM EST Sun Jan 22 2017

The run of mild weather will continue through midweek. Rain will
move back over the area later today and continue into Tuesday.


Minor adjustments to hourly trends for the pre dawn update.
Previous...Still seeing the models trying to get the final
solution for the upper level low which will be the main player in
our weather through early Tuesday. Even ensemble data is
struggling to come to a consensus on the path and speed of the
upper level low.

Have backed off on the timing of the showers today as ensembles
have slowed the eastward movement of the system and are
advertising a track that is a bit further south. Operational
models, including the hires variety, agree with this idea, as qpf
only reaches Southern West Virginia by this afternoon. This is
mostly due to the aforementioned more southern path of the upper
low and also the further suppression south of the main jet
swinging around the low. Additionally, the first upper level wave
that is pushing the showers northward, splits from the main flow
and heads eastward into the still prevalent, although weak,
eastern ridge. Have continued to lean away from the NAM op
solution, as it has been an outlier during the entire evolution of
the system.

Today`s PoPs will mainly cover the southern third of the region
and will begin the process of overspreading these locales during
the afternoon.

Temperatures again will be well above normal.


Model depictions of the cutoff low pressure set to dig toward the
Upper Ohio Region, have deviated from previous days solutions
with a more westward track of the center. Increasing ascent via
deformed flow and warm advection with increased moisture through
the mid levels all support escalating precip probabilities to
categorical numbers tonight and into Monday.

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 looks to remain a rain event. The NAM again
deviates from other model solutions and develops sub-zero air
over the region at the 850mb level despite moist advection and an
otherwise warm column. Will continue to move away from the NAM
solution. This choice is also further supported when viewing the
plumes from the SREF and GEFS model. If colder air does make it
into the area, it would likely be late Monday night, when most of
the precipitation will have exited the area.

QPF was progged using a RFC/WPC blend for the period. An inch to
inch and a half is anticipated for the early week with limitations
imposed by low pressure progression and mid level dry slotting.

Relative warmth will continue, although the diurnal temperature
spread will be restricted by clouds and precip.


By the beginning of the long term, upper level ridging will take
over, but will not last long as the next system quickly moves
across the northern plains/upper midwest and across the northern
Great Lakes on Wednesday. Scattered showers will cross the area
Wednesday and above normal temperatures will remain.

A pattern change is expected to ensue on Thursday, with a return
to January temperatures that will remain through the remainder of
the long term. Snow showers will return as well.


Patchy MVFR to IFR fog is expected to dissipate this morning as
mixing begins. Otherwise, expect VFR conditions today with mid
clouds ahead of approaching low pressure. The approaching low
should result in deterioration to MVFR with rain tonight.
Increasing E winds are expected especially tonight with an
increasing pressure gradient.

Restrictions are likely through Tuesday with slow moving low
pressure, and again with a Thursday cold front.




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