Area Forecast Discussion
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FXUS61 KPBZ 280206 AAC

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
906 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.


905pm update...Have removed all PoPs and put in sprinkles across
the north, right along the warm front. South of the boundary,
surface dewpoints have been slowly rising which is allowing for
fog to form in some locations. Have included the mention of fog
overnight, especially in local valleys. Temperatures have been
adjusted with a blend of data.

Previous discussion...
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.


General VFR cig forecast through Tuesday morning. There may be
some MVFR cigs that pass through FKL and DUJ this evening, but
those too will dissipate. Will need to include the mention of
fog, particularly at those ports that rest near valleys and
rivers. Low level moisture is slowly increasing south of the
warm front and with temps doing very little today, it will be
easy for ambient temps to reach the dewpoint. Fog will dissipate
after dawn. Restrictions return Tuesday afternoon with rain and
low clouds.

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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