Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 270530

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1130 PM CST Sun Feb 26 2017

.SHORT TERM...(tonight through Wednesday)
Issued at 315 PM CST Sun Feb 26 2017

Forecast concerns in the short term will be the details in the
temperatures with snow-covered and snow-free areas....the return
of deeper moisture...fog/drizzle/light rain...Monday into Tuesday
with a mix possible north near the South Dakota border Tuesday
and possibility of a band of rain to light snow trying to set up
near Kansas and Missouri Tuesday evening.

The 12Z sounding at KTOP showed quite a bit of moisture and steep
mid-level lapse rates and this was where an area of showers was
that remained mostly south of the area. Lingering moisture within
the low level convergence did spark a few afternoon cu in far
southeast Nebraska...otherwise generally clear skies prevailed
with temperatures in the 30s in northeast Nebraska and northwest
Iowa and 40s and 50s elsewhere with southwest to northwest flow.

Overnight the flow drops off with low dewpoint depressions and
melting snow lending to some patchy fog. Dropped temperatures into
the teens where the snowcover was better and 20s elsewhere.

The deepening trough over the Sierras results in surface low
pressure increasing on the lee side of the Rockies and Low level
flow increases from the south. This strengthening south flow
combines with weak lift and mid level warm air
advection/isentropic lift on the 285K surface Monday afternoon.
How much will temperatures warm with the increasing low level
moisture/clouds and lingering snowpack? Currently have highs in
the 40s northern Neb. and around 50 degrees or warmer south of
I80. There may be some sprinkles or drizzle later Monday afternoon
with a better chance farther east in Iowa.

A stronger shortwave with a pocket of instability moves into the
forecast area Monday night and Tuesday morning. There are still
some differences in the surface low track and attendant
temperatures. For now included fog and drizzle and in northeast
Nebraska forecast sounding show there could be a mix of very light
freezing drizzle/sleet or snow with the cooling once the
precipitation starts. As the surface low passes to the east,
northwest winds pick up and cold air advection increases with
rain changing to light snow in far southeast Nebraska and
southwest Iowa late Tuesday afternoon and Tuesday evening. The
better chance for precipitation appears to be south of the
area...however the 18Z NAM does hint at an embedded wave that
enhances a rain/snow band in southeast Nebraska. The GFS/EC/GEM
are not as robust, however show precip increasing south of the
forecast area Tuesday night.

Cooler air will remain in place for Wednesday, however
temperatures will be near normal in the 40s with northwest winds.

.LONG TERM...(Wednesday night through Sunday)
Issued at 315 PM CST Sun Feb 26 2017

The extended will be characterized by near normal temperatures
warming to 10 to 20 degrees above normal for the weekend along with
small chances of light rain.

A clipper type system is forecast to drop southeast from eastern
Montana toward Iowa Wednesday night into Thursday.  This takes the
track of light snow to our north and east and h85 temperatures
warming up overnight...then sliding back down with cold air
advection Thursday.  Brisk northwest winds Thursday will diminish to
light and variable overnight as surface high pressure builds in.
South flow returns as the surface high pressure system retreats to
the Ohio Valley Friday and a weak wave tracks across the Northern
Plains.  There may be some sprinkles with this weak system and
resultant thickening of mid clouds Friday.

South flow continues across the Plains Saturday as the surface low
travels from Manitoba into Ontario. Look for much above normal
high temperatures in the 50s and 60s. A wind shift does push
across South Dakota...Saturday night...however the precipitations
remains on the cold side/post- frontal across the Dakotas. The
front/colder air does push into the forecast area late Sunday,
however the GFS is stronger with the push compared to the EC and
has a little light rain compared to the dry EC. Sunday`s highs
should also be mild in the 50s and 60s.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1125 PM CST Sun Feb 26 2017

VFR conditions are forecast through Monday evening. There is a
chance for MVFR fog a couple of hours either side of 12Z at all
sites, but it is expected to be patchy and thus not mentioned in
TAF at this point. Otherwise, as a low pressure system approaches
Monday afternoon, southerly winds will increase into the 15 to
20kt range, while mid clouds increase in coverage. Cigs are
forecast to lower to near FL050 between 00Z and 06Z, but could
drop into the MVFR category before the end of the TAF period.




SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Dergan is the U.S. government's official web portal to all federal, state and local government web resources and services.