Area Forecast Discussion
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FXUS61 KPBZ 251701

Area Forecast Discussion
National Weather Service Pittsburgh PA
101 PM EDT Wed Apr 25 2018

Scattered showers are expected today with the approach and
passage of a cold front. High pressure should return dry weather
for Thursday before rain chances return with Friday low


Light rain showers skirting the eastern flank of our forecast
area in response to moisture streaming up the Laurel and
Chestnut Ridges. Further west, a band of light rain showers is
beginning to materialize over northwest PA, associated with a
upper trough crossing the Great Lakes. Most recent water vapor
imagery shows this feature well, but also shows a lack of
moisture available to it. This will ultimately be the limiting
factor in generating widespread rain this afternoon/evening.
Still, will continue to carry scattered showers for most, with
widespread mention north and east.

Expansive cloud cover evident on satellite will continue through
the afternoon/evening, keeping temperatures in check. Highs will
likely top out just below average.

The trough shifts east of the area tonight and west flow will
advect much drier air in. This will quickly end any remaining
showers and begin to scatter out low clouds that remain. The
exception will be in the higher elevations where lingering
moisture would keep low clouds and even drizzle in consideration
through the early pre-dawn. Lows tonight will be a few degrees
below averages.


The trough should exit the area this evening as high pressure
builds from the west and returns dry weather to the area through
Thursday night.

A srn stream low is progged to track across the Mid Atlantic
region Friday, as the next nrn stream trough advances out of
the Midwest. The GFS is slightly slower with the track of the
low than the ECMWF and NAM, and results in more phasing with the
nrn stream trough and more rain across our area. Sided close to
a guidance blend, which brings limited rain chances to the area
with the srn stream low, and rain chances area wide as the
trough and associated cold front approaches in the afternoon.
Maintained chance pops Friday night as another trough rotates
around an upper low in Canada. Warmer, but still below average
temperatures are expected.


Higher than average confidence through the extended period as
the rainy and cool end of the week gives way to a warm and
dry trend. High pressure will begin to build at the surface late
Saturday night into Sunday. This will bring an end to
precipitation chances and establish clearing sky. Temperatures
will temporarily be held in check Sunday with lingering
northwest flow aloft, but this will quickly change heading into
the middle of next week. A building ridge will pass to our east
by Tuesday evening enhancing warming with southwest flow. Highs
will soar into at least the mid and upper 70s by Wednesday. The
next appreciable chance of precipitation will come by late next


Low MVFR will drop to IFR on the backside of a crossing front
this afternoon. Visibility restrictions in scattered showers
will be brief but IFR cigs look slow to improve...especially
KPIT and north where IFR looks likely to persist overnight based
off latest soundings. General improvement is expected through
Thursday morning.

The next chance for general restrictions is expected with the
crossing of weak low pressure on Friday.




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