Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 121149

Area Forecast Discussion
National Weather Service Omaha/Valley NE
549 AM CST Tue Dec 12 2017

.SHORT TERM...(Today through Thursday)
Issued at 250 AM CST Tue Dec 12 2017

We will remain in a prevailing northwest flow pattern aloft today
into tonight ahead of the next vigorous short-wave trough which
will move through the mid-MO Valley tomorrow (Wed). In the low
levels, winds will back to westerly today, allowing for
downslope-induced warming to erode the cooler air mass which
filtered into the region behind yesterday`s (Mon) cold front.
While some warm-advection-related clouds could linger, afternoon
highs should range from around 50 in the west to 40-45 across our
southwest IA counties.

Tonight into Wednesday, the next strong cold front (associated
with the disturbance mentioned above) will advance through the
northern Plains and mid-MO Valley. Mild overnight temperatures
and late morning/early-afternoon highs on Wednesday will give way
to falling mercury by mid afternoon. Winds will be quite strong
again from the northwest and a wind advisory may become necessary.
While we will indicate a low-probability chance of precipitation
across our northeastern counties, better potential will remain to
our east. Additionally, we could see a brief window of elevated
fire weather conditions along the Kansas border Wednesday
afternoon where a favorable overlap of strong winds and
warmer/drier air will reside.

On Thursday, yet another short-wave trough and related cold front
will track from the northern High Plains into the region. It
currently appears that this system will contain a bit more
moisture, translating to a more meaningful chance of precipitation.
Model forecast soundings indicate light snow as the initial
precipitation type, changing over to light rain by afternoon as
the boundary layer warms. Our official forecast will indicate
accumulations approaching a half inch over portions of northeast
NE, tapering to trace amounts south toward I-80. The NAM and GFS
solutions depict a swath of 1.0-1.5" snow accumulation across our
area, so this is something we will continue to monitor.

.LONG TERM...(Thursday night through Monday)
Issued at 250 AM CST Tue Dec 12 2017

Latest medium-range model guidance is now in better agreement in
indicating that a multi-stream trough will track from the British
Columbia and Pacific Northwest coasts on Friday into the Great
Plains later Saturday into Sunday. Ahead of this system, we will
see continued mild conditions Friday into Saturday with highs in
the 40s to lower 50s. About the only model that shows QPF across
our area is the ECMWF, and we will include slight-chance PoPs
Saturday afternoon into Saturday night. Thereafter, we could see
some amplification of a broader-scale trough from central Canada
into the north-central U.S. early next week. Confidence in that
scenario remains low with our forecast indicating continued
above-normal temperatures.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 542 AM CST Tue Dec 12 2017

Surface high pressure over the region will give way to warmer
temperatures spreading east from the western High Plains. Some
MVFR/VFR ceilings fl025-040 are coming in a narrow north to south
band. The narrow band should continue to push east today with an
hour or two of MVFR/VFR ceilings possible. Northwest to west
southwest winds mostly 6-12kts. A cold front pushes through late
tonight after midnight. Surface winds will veer to the west and
northwest and increase to 15 to 25kts through 12Z.




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