Area Forecast Discussion
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FXUS61 KPBZ 272319 AAB

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
619 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.


620pm update...PoPs again adjusted in line with latest radar
trends and hires model guidance. Any lingering showers will end
by 8pm. Clouds should begin to erode from the south later this
evening as warm air advection takes hold.

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.


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 forecast through Tuesday morning. There may be some
MVFR cigs that pass through FKL and DUJ this evening, but those
too will dissipate. 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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