Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Pittsburgh PA
241 PM EDT Thursday Apr 24 2014

Synopsis...
low pressure and its associated cold front will bring rain and a
chance for a thunderstorm Friday. Seasonal temperatures are
expected through the rest of the weekend.

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Near term /through tonight/...
high pressure will continue to shift eastward through the rest of
the day. High clouds have thinned over the region so have adjusted
sky cover wording through the evening before clouds thicken in
advance of the cold front. Despite the relatively thin cloud cover
expected for much of the night...strong warm advection and
increasing low level mixing should keep temperatures from falling
off too much tonight. Generally went with lamp guidance which kept
lows in the 40's across the forecast area.

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Short term /Friday through Sunday/...
moisture associated with the intensifying low pressure system
will reach the western zones early Friday morning. This is
slightly faster than last nights model runs...but with a high level
of agreement between them felt comfortable with speeding up the
system and adding categorical probability of precipitation. In addition to the probability of precipitation...have
added a slight chance of thunder to the forecast as the BUFKIT
profiles do suggest some weak cape ahead of the surface front.
Not sure whether this will materialize with the stabilization from
prefrontal rainfall but since all of the models suggest it...opted
to make at least a mention of thunder.

Moisture should push eastward as the upper trough pivots north and
east Friday night. Maintained a chance for showers into early
Friday night with cold advection behind the front and also with a
secondary cold front passage on Saturday. There is very little
lift associated with the secondary front but the colder air aloft
may contribute to the development of scattered showers.

Ridge of high pressure should build overhead by Sunday providing
for a dry day...but northwest flow may keep at least scattered clouds
across the region. Temperatures should remain seasonable through
the weekend.

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Long term /Sunday night through Wednesday/...
high pressure ridge will move east Sunday into Sunday night. The
upper level pattern is then expected to be quite stagnant. An
upper level low over Nebraska Monday morning will only drift as
far east as Illinois by Thursday morning. The associated surface
low will similarly make a lack of eastward progress. Although the
entire week should not be a washout with continuous rain for four
days...the pattern is expected to bring intermittent showers and
below normal temperatures.

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Aviation /18z Thursday through Tuesday/...
high pressure will maintain VFR and light surface wind through tonight. Shower and
restriction potential will increases on Friday with the approach of a cold front.

Outlook.../Friday night through Monday/...
restrictions are possible into Saturday to the north of I 70 as cool
northwest flow ensues in the wake of fridays frontal passage.

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

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