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Area forecast discussion...updated
National Weather Service Pittsburgh PA
445 PM EST Sat Feb 25 2017

cooler temperatures will again be replaced by well above normal
temperatures mid-week. More wintry conditions look to return
late in the week.


Near term /through Sunday/...
445pm update...made some minor changes to evening pops in
accordance with radar trends, latest hires guidance and latest
model soundings. Once the shortwave trough moves through this
evening, soundings are showing very dry air moving in aloft and
near the surface. This will make it tough for precipitation to
be produced, with the lack of lift to support a deepening of
the saturated layer. Additionally, with such a thin layer of
moisture, most soundings are showing the dendritic snow growth
zone barely touching the saturated layer. Thinking through the
evening and overnight will be to confine Post shortwave
precipitation to the north and ridges. The north will be reliant
on any lake streamers that develop in the cold air and the
ridges will likely take a little longer to see snow showers
develop as the coldest air aloft does not really reach those
locales until late this evening and after midnight. Temperatures
have been modified with a blend of hires guidance.

Previous discussion...
further upstream, a solid patch of clouds and scattered showers
can be found over central Ohio to Indiana. These will shift
eastward this evening as the upper- level low approaches.
Expecting shower chances to increase through the evening, per
latest hi- res model guidance.

Scattered rain showers will changeover to snow showers as
temperatures continue to descend through the evening. In
general, less than an inch is expected across northern counties
and into the mountains. Little to no accumulation is expected
elsewhere. Building high pressure will end precipitation chances
overnight with the ridges and locations along and north of I-80
the last holdouts.

Winds and associated gusts are increasing, in the enhanced cold
advection. Wind in the highest elevations could approach
advisory criteria towards dusk. This will bear further

Sunday will feature more docile weather as high pressure at the
surface builds in. This will slowly erode cloud cover, leaving
much sunnier conditions. Temperatures Sunday will moderate to
near normal values.


Short term /Sunday night through Tuesday/...
surface high pressure will begin to shift eastward early in the
short term period. This will mean dry and relatively clear
conditions will quickly be replaced by increasing cloud cover on
Sunday night. With a fairly linear jet streak parked directly
overhead the County Warning Area slowly beginning to migrate eastward into
Monday, a weak 500 mb vort looks to traverse the Ohio Valley on
Monday. Weak warm advection ahead of it may be just enough to
generate a shower or two through the day Tuesday. Some
soundings indicate that a brief window of snow may be possible
at the onset due to wide surface dewpoint depressions and low
wet bulb zero heights, however very light qpf expectations
combined with warm advection and no support for below freezing
temperatures should preclude any possibility of accumulation
should this occur.

With the northward migration of a warm front through the area
on Tuesday, temperatures during the short term look to return to
above normal yet again. Fries


Long term /Tuesday night through Saturday/...
a brief dry interlude follows th weak system from Tuesday
before much higher pwats follow for later Tuesday night into
Wednesday night. A couple of successive waves look to pass the
region in deep southwesterly flow. Some heavier rainfall may be
possible with these given precipitable water values running up toward 1.3
inches and a nicely couple jet structure to accentuate ascent.

A trailing cold front will pass the area on Thursday. This will
set temperatures into a free fall with model and ensemble
consensus 850 mb temperatures falling into the negative teens
celsius. This should bring lake and upslope snows back into the
picture. Additionally, some model indications exist of a weak
system dropping through the Ohio Valley on Friday in the colder
air. This could end up being a modest snow maker somewhere in
the region depending upon its track.

The extended forecast was generally favored colder than the
superblend guidance from Thursday night through Saturday due to
the amplitude of the pattern and magnitude of cold air set to
advect into the region. Fries


Aviation /22z Saturday through Thursday/...
cold front and associated showers pushing east of the area,
and strong westerly flow at the surface is taking hold. Winds
will commonly gust 20-30kts this evening. Expecting little in
the way of restrictions this afternoon as the increased mixing
in the near-surface has raised ceilings on incoming stratocu to
around 4kft.

Scattered rain showers will transition to snow showers this
evening, but coverage and intensity will be limited. MVFR cigs
are possible late tonight as the surface flow begins to weaken
and ceilings lower. This will especially be true for fkl/duj
where downlake moisture may be more prevalent.

occasional restrictions are again possible as the unsettled
weather pattern is maintained for the first half of the week.


Pbz watches/warnings/advisories...

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