Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
116 am EST Wednesday Dec 2 2015
showers across the area will gradually diminish through midday
Wednesday. An upper disturbance will bring scattered snow showers
later Wednesday night into early Thursday.
Near term /through today/...
current surface observations showing the dry air behind the front has
made it as far east as the Ohio/West Virginia border...confirming
what can be inferred from satellite imagery. With upper-level flow
running parallel to the front that is currently bi-secting the
forecast area from north to south...the boundary has all but
stalled in our forecast area. On top of this...another
wave currently moving up the southern Appalachians is poised to
move north along the front and into our eastern zones...slowing
the eastward advancement of the dry air further. Have increased
probability of precipitation this morning for areas east of the Ohio River with this wave
passage. Areas west of the Ohio River should remain dry through
Not much of a break from precipitation with the dry slot today as
the upper-level low bowls its way into the southern Great Lakes
by this afternoon. Winds will increase while veering to
westerley...bringing in colder air aloft. This could develop a
few showers through this evening...primarily east where deeper
moisture will linger.
Short term /tonight through Friday/...
parent closed middle level low will sweep across the eastern Great
Lakes Wednesday night and early Thursday. A swath of light snow
will accompany the main vorticity center with the low.
Accumulation of an inch or so across the I-80 corridor now looks
likely Wednesday night...with similar amounts in the ridges in
brief northwest flow behind the low during the early morning hours
Thursday. Elsewhere a coating on grassy surfaces is possible.
Snow showers will diminish quickly Thursday as middle level low
exits and surface high turns flow quickly to the west.
Temperatures will remain relatively mild Wednesday ahead of
system and then cool to near seasonal norms Wednesday night into
Thursday with cold advection. Cool and dry high pressure for
Long term /Friday night through Tuesday/...
surface high pressure over the region should keep weather quiet
through the weekend. Low pressure is expected to develop along the
southeastern Atlantic coastline and move up the East Coast Monday
into Tuesday. Appears that the bulk of the rainfall will remain
east of the region...but will continue some chance probability of precipitation depending
on where the western edge of precipitation reaches. Temperatures
will remain above normal for this time of year. Grids were based
on blended guidance.
Aviation /06z Wednesday through Sunday/...
fairly complex aviation forecast this period as an occluded front
bi-sects the local forecast area from north to south. This will
continue to leave ports east of kfkl/kmgw line in at least MVFR restrictions
the longest today. Any improvements made through about 08z for
these eastern ports will be lost as another wave moves north along
the stalled front. Expecting IFR or worse to last through about
Elsewhere...kzzv has a good chance to remain VFR through the
duration of the taf period as dry air has moved in behind the
front. Ports between these...kpit/khlg/kagc/kbvi...will
unfortunately be in the transitional zone where dry air has led to VFR/MVFR
conditions as of 06z. With the next wave of rain moving through
the area...ceilings and visibilities are expect to bounce around
quite a bit but should go down to IFR for a time near 12z. This is
the portion of the forecast with the least amount of confidence.
All restrictions are expected to gradually increase through this
evening. Light southerly flow will veer to westerly today and
increase through this evening as colder air moves in. Additional
precipitation will arrive late tonight as the upper-level low
moves into the southern Great Lakes. This could bring additional
MVFR restrictions just beyond the current taf period.
Outlook...Wednesday night through Sunday/...
restrictions are likely through Thursday as an upper low crosses the
region. VFR conditions are expected then through the weekend.