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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 300829
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
429 AM EDT Fri Sep 30 2016

.SYNOPSIS...
Upper level low pressure will continue to linger near our region
into this weekend. Showers will be most numerous today, with more
scattered activity this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Strong upper low will linger over the lower Ohio Valley today, and
then begin to lift towards the lower Great Lakes tonight. Drier
air visible on water vapor loops is becoming entrained by the
system, which has pushed most of the rain west of the ridges. The
departure of the rain has allowed mountain wave activity to become
visible across the wind advisory area. Occluded boundary continues
to linger just to our south across central Ohio and West Virginia.
A few locations have received heavy rainfall totals of 2 to 2.5
inches over the past 12 hours, particularly in the flood advisory
area.

Will continue to focus higher PoPs closer to the occluded boundary
today, which should move little and place the most precipitation
across southeast OH, extreme southwest PA, and northern WV.
Rainfall totals and rates will be lower today, with generally a
half inch or less expected during the daylight hours. Kept some
thunder chances across our southwest counties, where some modest
instability remains possible. If any storms do manage to stand up,
there may once again be enough shear to allow one or two to become
strong.

Will keep the wind advisory going for now with the visible wave
activity and still favorable soundings, although observations to
this point have come in below criteria. Weakening of the low level
jet may allow the advisory to be canceled a bit early.

Tonight, the stacked low and occluded boundary will begin to lift
northward, with continued dry air entrainment behind it. This will
push the bulk of the shower activity ahead of it. PoPs will thus
decrease from the south with time, with most showers north of
Pittsburgh by 12Z. Temperatures were nudged towards the lower
side of the guidance envelope, with a model blend used with
the previous forecast.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
The mature low pressure system that has plagued our area much of
this week will linger through the weekend, bringing additional rain
chances. By Saturday, the occluded front will have gradually lifted
north spreading the best rain chances north of I-80. An expansive
feed of dry air wrapping around the south and east of the low will
push into our southern counties, resulting in a drying trend through
the day.

Model differences exist on the evolution and track of the low Sunday
into Monday, but the overall trend is to push the track further
south and slow it`s progress. This seems prudent, given the extreme
northern trajectory of the upper-level jet stream, and the
subsequent inability to capture the low and sweep it east. As a
result of this slower southern solution, have introduced chance PoPs
Sunday afternoon, mainly north of Pittsburgh, as low nears northern
Ohio. Temperatures through the weekend will be slightly above normal.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Model consensus exists on the eventual departure of the low
pressure system early next week and building a broad ridge through
the Great Lakes by middle of next week. This will result in
several days of dry weather next week. With little difference in
across model guidance, the Superblend was largely utilized in the
extended. Temperatures will be back above normal for the first
week of October. With the anomalously strong ridge in place,
forecast temperatures were bumped a degree or two above the
Superblend numbers.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Bands of showers are continuing to rotate over the area, although
coverage should wane a bit towards sunrise. Conditions will bounce
between VFR and MVFR through the night, with some brief drops to
IFR still possible. DUJ, in moist easterly flow, should remain
mainly IFR through sunrise. VFR will become a bit more prevalent
during the day Friday as moisture drops off a bit. Wind gusts of
15 to 25 knots are expected at most terminals during the afternoon
as the surface pressure gradient tightens a bit. Wind gusts of 35
to 40 knots are still possible in downsloping off of the ridges in
the LBE area, although these winds may not be seen at the airport
proper.

.OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/...
Scattered restrictions can be expected into Monday as the upper
level low lingers, then slowly lifts north of the region.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...Wind Advisory until noon EDT today FOR MDZ001.
OH...None.
PA...Wind Advisory until noon EDT today FOR PAZ073>076.
WV...Wind Advisory until noon EDT today FOR WVZ510>514.

&&

$$