Area Forecast Discussion
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FXUS61 KPBZ 010210
Area Forecast Discussion
National Weather Service Pittsburgh PA
910 PM EST Tue Feb 28 2017
A series of disturbances will keep periodic rain in the
forecast through tonight before a strong cold front results in
strong showers and thunderstorms Wednesday. Wintry weather
returns behind the front for the last half of the week.
.NEAR TERM /THROUGH WEDNESDAY/...
-- Changed Discussion --A modest short wave is tracking through downt the Mason-Dixon
line this evening with moderate and occasionally heavy showers
ahead of it. Some embedded thunder is evident as well generally
aroung Morgantown. This short wave is projected to track ENE
through the evening hours with deeper moisture likely to remain
along and south generally of Latrobe. North of this, very
little rain is expected through the evening and early portion of
the overnight hours. South of there, periods of moderate rain
will be likely with a bit of thunder over the next couple of
hours before precipitation ends for a while.
As the first wave exits to the east, most areas should
temporarily dry out even as warm advection continues. This will
keep temperatures from falling much at all and allow dewpoints
to stay very high overnight likewise.
The more substantial system approaches from the west by morning
with 0-6 km shear values already topping 80 kts over Ohio by
morning. A pre-frontal wave is likely track through during the
morning with categorical PoPs indicated for this as well as a
very rapid increase in thunderstorm coverage. Due to the wind
field, even with just modest instability, any amount of momentum
being channeled to the surface would be likely to result in
severe wind gusts. Likewise, the surface front itself will
approach for the afternoon. Should we be able to destabilize
between the two waves, another round of severe wind gust
potential may exist. We will be monitoring this going forward as
well as continuing to assess flood potential with successive
thunderstorm rounds. Fries
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.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
Confidence continues to increase for severe thunderstorms to
generate along the cold front on Wednesday. This is supported by
sufficient low level moisture, strong speed and directional
shear, and instability. However, the limiting factor to the
coverage of severe weather would be the amount of instability
due to cloud cover and precipitation from the previous
shortwave. Nonetheless, the other parameters should offset the
marginal instability to produce possible strong and damaging
winds from a scattered or a solid line of convection along the
front. Hodographs and model soundings depicted from latest
guidance south of PA suggest a brief tornado cannot be ruled
After the FROPA, upper troughing, cold advection, and limited
lake and terrain enhancement should result in scattered snow
showers through Thursday. After temperatures peak on Wednesday
around 25 degrees above average, a return to below seasonal
average temps are expected through the rest of the period.
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Clipper system which has been well-advertised by the models
blows in Thursday night with some light snow. A reinforcing shot
of cold air arrives behind the system Friday, as snow showers
linger and possibly reenhance Friday afternoon with sharp low-
level lapse rates. Accumulation rates may initially struggle
with warmish ground, but cannot rule out the eventual need for a
winter weather advisory in at least the ridges. Overall snow
totals were increased slightly for the 24 hour period.
Troughing pattern in the wake of the clipper Saturday
transitions to a more zonal/flat ridge pattern for Sunday and
Monday, and then a more amplified pattern once again by Tuesday
with another trough/front approaching. Mainly dry weather for
Saturday may be followed by a weak disturbance on Sunday, and
then better precipitation chances thereafter as southwest flow
and moisture ramp up again. Below normal temperatures at the
start will rise above normal once again by Sunday and continuing
into next week.
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
MVFR with areas of IFR for the forecast period. Rain this
evening will remain mainly over ports from PIT and south. Do not
expect restrictions with the evening showers. Increasingly
strong flow ahead of developing Great Lakes low pressure will
likely lead to a period of low level wind shear overnight.
Models are suggesting that a linear convective structure is
possible sometime after 08Z, but pinning down more exact timing
remains difficult. Have continued with previous thinking of a
fairly wide VCTS window at all TAF sites. Winds will also pick
up out of the southwest, with gusts between 25 and 35 knots
possible into Wednesday afternoon.
Widespread restrictions and wind problems can be expected with,
and in the wake of, the cold front through tomorrow evening.
Periodic restrictions are likely through Friday as cold low
pressure crosses the region.