Area Forecast Discussion
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FXUS61 KPBZ 271912

Area Forecast Discussion
National Weather Service Pittsburgh PA
212 PM EST Mon Feb 27 2017

A series of disturbances will keep periodic rain in the
forecast through mid week until the passage of a cold front
returns wintry weather for the last half of the week.


Light rain is just starting to overcome the dry air below 800 mb
that was present on this morning`s 12z KPBZ sounding. The first
reports of rain have started to trickle in over the past half of
an hour around Zanesville, roughly in line with both large scale
and hi-res model timing. As the wave generating the warm
advection light rain over the area slides ENEward over the
afternoon, this rainfall will likely develop farther ENE across
the area. Likely PoPs have been maintained for this activity,
however saturation is over a fairly limited time interval, and
lift is somewhat unimpressive, so QPF remains light.

The system looks to clear the eastern portions of the area this
evening. Layer RH values start to fall off late in the evening
from S to N, likely revealing some clearing before clouds look
to start to increase from the west ahead of the next system.
Temperature expectations overnight will likely be modulated by
the exact interval and longevity of clearing with the low
temperature forecast gradated from cooler east and warmer south
as a result. Fries


Models continue to depict a series of shortwaves to cross the
region Tuesday. These disturbances with the combination of
strengthening low level SW flow will support periodic showers
through Tuesday night. Thunderstorm chances increase gradually
throughout the day as elevated instability and shear increase.

By Wednesday, the western trough is progged to approach the
Great Lakes region as an associated surface low tracks from the
Midwest into Southern Ontario. Speed and directional shear will
continue to increase as the cold front progresses southeast but
models differ in the amount of instability progged to develop.
Preceding rainfall and cloud debris may inhibit greater
instability development. Hence, the severe weather coverage
remains uncertain at this time and will depend on how much CAPE
is present.

Though uncertain in the occurrence of damaging winds on
Wednesday, the possible threat will continue to be mentioned in
the hazardous weather outlook due to substantial shear and high
confidence in convection development.

Post-frontal cold northwest flow will lead to lake and terrain
induced snow showers on Thursday. Temperatures are expected to
be 20 to 25 degrees above average Tue and Wed, returning to near
or below seasonal levels Thursday.


Broad upper troughing is expected to continue through the late
week, with a reinforcing crossing shortwave/surface low with
some snow Thursday night and Friday. Some snow may accumulate
across the higher terrain areas. General zonal flow is then
progged by the weekend as the trough exits, with mainly dry
conditions and moderating temperatures. By Monday, temperatures
should rise to nearly 15 degrees above the average.


Restrictions of the MVFR variety will be likely shifting ENE
from ZZV toward PIT through the afternoon today as light rain
develops across the region ahead of a weak system. While
rainfall may not make it all the way to FKL, a period of MVFR
cigs may this evening for a time. Skies should start to scatter
out beyond the evening for a period at most sites with a window
of VFR conditions before the next system on Tuesday.

Restrictions are likely Tuesday as precip develops with another
shortwave in strengthening wsw flow. More restrictions and wind
problems can be expected with, and in the wake of a Wednesday
cold front.




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