Area Forecast Discussion
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FXUS61 KPBZ 231548 AAC

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
1148 AM EDT Thu Mar 23 2017

Sunshine and moderating temperatures today. Rain chances return
this weekend with a continued warming trend.


A cold start to the day will give rise to more-seasonal
temperature readings this afternoon. The shallow morning
inversion on the 12Z KPIT sounding has broken, with warm
advection expected to increase in the wake of departing surface
high pressure.

Despite breaking the morning inversion, full sun amid clear sky
or possible thin cirrus, and the expected warm air advection,
it will take considerable effort to reach the lower 50s in the
ongoing forecast. Given relatively-minimal ensemble spread,
confidence is high that it will be a challenge to eclipse the
mid-upper 40s today, so maxima were lowered slightly with this

A weak, low-amplitude disturbance will interact with the
strengthening low-level jet overnight to generate light
precipitation particularly late tonight and early Fri morning.
Although the focus will be in northern counties, latest hi-res
models support broader PoP coverage across the forecast area.

The strong warm air advection and increasing clouds tonight will
inhibit the typical diurnal temperature cycle. Initial cooling
and residual dry air may be enough to support wet-bulb values
below freezing in very isolated locales for a brief window late
tonight at the onset of any precipitation (e.g. a few sheltered
valleys in Garrett/Indiana Counties).

In general, temperatures are expected to remain above freezing,
but a brief period of light freezing rain may occur in those
sheltered valleys before warm air advection wins the thermal
battle. However, given the northern placement of the upper
disturbance, there is a lower confidence in precipitation with
southward extent, so it could be that little precipitation
occurs in the areas most thermally-favorable for any freezing


The disturbance responsible for overnight precipitation will
move east Friday morning, leaving the remainder of the day
mostly dry and warm. Another weak disturbance will affect
primarily the northern zones Friday night, given the
perseverance of an amplifying east-coast upper ridge.

With the possible exception of the far north, Saturday looks
dry as well. Plenty of subsidence with the eastern ridge firmly
in place and any upper level waves will be shoved well to the
north of the area. There will be additional cloud cover
Saturday, as the atmosphere slowly becomes more saturated. Even
warmer temperatures are expected on Saturday.


An upper low, ejecting from the Plains into the Great Lakes,
will push a front our way on Sunday with good rain chances. The
front may linger near the area Sunday night with some showers
before another low threatens to bring better rain chances
Tuesday. Dry weather and high pressure are expected by the
middle of next week. Above-normal temperatures throughout the
long term.


Building high pressure will ensure VFR and light wind through
today. A crossing shortwave in conjunction with a warm front
may generate some light rain for FKL and DUJ in the post 06z
period of Friday.

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





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