Area Forecast Discussion
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FXUS61 KPBZ 240158

Area Forecast Discussion
National Weather Service Pittsburgh PA
958 PM EDT Thu Mar 23 2017

A period of above-normal temperature and increasing chances for
rain is expected through early next week.


Looking at the latest model guidance and surface observations,
it appears precipitation generated by a lifting warm front will
be minimal, at best, south of I-80. This is supported by the hi-res
guidance and the latest nam/sref, and the fact that much of the
shower activity that is out over Indiana now is diminishing as
the warm front lifts northeastward. Still, a shortwave that
generated thunderstorms over Wisconsin and Lake Michigan is
expected to ride along the building upper level ridge tonight,
suggesting high chance PoPs are appropriate to our north. With
clear skies expected and light wind ahead of this wave,
temperatures should fall off early, which could lead to a p-type
issue initially depending on the exact arrival of the showers.
However, even with some wet- bulbing, the threat for freezing
rain appears low, with warm air surging aloft. Any glazing that
would occur would be brief and on elevated surfaces given the
warm daytime temperatures. Thus, have opted to take out the hwo

Any rain showers should end shortly after sunrise as we shift
into the warm sector. Southwest wind and strong warm advection
should support temperatures above average, despite mostly cloudy


A series of compact shortwave troughs will develop in the swrn
CONUS and eject newd beginning Saturday. As the first wave
acquires a negative tilt, shortwave ridging will amplify over
the Great Lakes region, leading to a likely-nwd displacement of
precipitation on Saturday and Saturday night.

Steady height falls will begin to spread across the region
Sunday morning as the ejecting wave nears. By afternoon, the
associated H5 jet maximum will cross the forecast area, likely
invigorating deeper convection with its passage amid modest

This wave will be exiting the region by Monday morning, with a
downward trend in precipitation expected by late Sunday night
as shortwave ridging develops in its wake.


In the wake of the Sunday wave, a brief respite can be expected
on Monday amid shortwave ridging before a second trough ejects
from the Plains. This second wave will be favorable for
widespread rain showers as it crosses on Tuesday as warm, moist
air is drawn poleward ahead of the system.

Behind the wave, seasonable air is expected to arrive mid-week
with highs in the 50s and lows in the 30s. Given ensemble
spread, there is considerable spread with the placement of the
pattern of upper-level troughs and ridges across the country
during this time, so the forecast details during this time
remains lower-confidence.


VFR ceilings and visibilities are expected in the main through
tonight, although clouds will thicken overnight as a warm front
lifts through. FKL/DUJ have a chance to get a brief MVFR
shower, otherwise VCSH will handle the situation in an initially
very dry atmosphere. An increasing low-level jet may bring low
level wind shear concerns overnight into Friday morning before
the low levels can mix. Ceilings may lower into prevailing MVFR
range north of PIT during the day Friday as moisture continues
to increase, although most rain showers should remain off to our
north. Winds will swing to the southwest on Friday and start to

The next chance for widespread restrictions is not expected
until the approach of low pressure early on Sunday.




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