Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus61 kpbz 232254 aaa 
afdpbz

Area forecast discussion...updated
National Weather Service Pittsburgh PA
654 PM EDT Wed Oct 23 2019

Synopsis...
dry weather and seasonable temperature is expected until a low
pressure system arrives late Saturday.

&&

Near term /through Thursday/...
7pm update...only real modification was to increase cloud cover
across the northern half of the region late tonight and Thursday
morning. Weak shortwave will cross the north, which will provide an
increase in higher clouds. Temperatures were refreshed with a blend
of hires model guidance.

Previous discussion...
wind speeds will relax this evening as diabatic heating and
diurnally driven mixing is lost. A light near- surface wind will keep
the temperature from completely plummeting overnight. Lows will be
near the climatological mean- within a few degrees on either side of
40.

&&

Short term /Thursday night through Friday night/...
Thursday and Friday will feature dry weather with seasonable
temperature.

A vigorous shortwave will dig southward across the Southern Plains
in response to a strong 120-140 knots jet maxima across the southern
rockies. Increase southwest flow and weak warm advection will lead to
a fairly mild day Thursday for most locations. A shortwave lifting
to our north will send a weak, mostly-dry cold front southward to our
County Warning Area by late Thursday into Friday. With upper-support now removed,
the cold front will ultimately under frontolysis as it crosses the
County Warning Area. Have limited pops to around 20 percents to the I-80 corridor,
where both moisture and low-level convergence will be maximized under
jet entrance region divergence... though still not entirely
confident in any shower production from this front.

With cloud cover and slightly cooler air aloft, Friday will run
about 5 degrees cooler than Thursday.

&&

Long term /Saturday through Wednesday/...
medium-range model guidance has finally come to reasonable agreement
with regards to this weekend.

The aforementioned vigorous shortwave will lift across the
Mississippi Valley Saturday morning. Initially, transient high
pressure will promote dry weather for the first half of the day
before warm air at the nose of a low-level jet begins to overrun the
comparatively cooler, stable surface air. Rain will likely begin at
some point mid-day Saturday for areas south of the I-70/76 corridor
and later in the evening for areas north.

As the system continues to lift towards Erie, steady rain should be
expected through the night Saturday given a strong diffluent pattern
and influx of anomalously high moisture. All signs point toward a
rather substantial rainfall for the area. Medium-range operational
runs and ensemble means all suggest somewhere between an inch and
inch and a half of rainfall with this system, with the bulk of it
occuring Saturday night.

Dry, cooler air will filter in through the day on Sunday as
shortwave ridging builds in behind the departed shortwave. Showers
will diminish through the day as a result.

Model solutions diverge once again after this weekend. The GFS is
much more progressive with longwave pattern than its Peers, the CMC
and European model (ecmwf). The former brings a deep trough and colder pattern to the
region by Tuesday, while the latter two are much slower and do not
bring the system and front through until late in the week. Have
trended towards the warmer solutions through the extended portion of
a forecast, limiting pops until the very end of the forecast.

&&

Aviation /00z Thursday through Monday/...
general VFR forecast. The only issue will be The Crossing of a low-
level jet after 06z. This will prompt the mention of low level wind shear at fkl,
duj, and bvi.

Outlook...
restrictions are possible late Sat/sun with crossing low pressure.

&&

Pbz watches/warnings/advisories...
Maryland...none.
Ohio...none.
PA...none.
WV...none.

National Weather Service Glossary of Abbreviations