Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 180931

Area Forecast Discussion
National Weather Service Omaha/Valley NE
331 AM CST Sun Feb 18 2018

.SHORT TERM...(Today through Tuesday)
Issued at 304 AM CST Sun Feb 18 2018

...Two Rounds of Icing Potential Expected Through Tuesday...

Very challenging forecast with many elements to consider over the
next three days, including strong winds 30 to 55 mph today along
with high to very high fire danger, then freezing drizzle/rain
developing tonight into Monday morning, and finally, a second
round of freezing rain/drizzle developing Monday night into
Tuesday morning.

Strong southerly winds today will help boost temperatures into the
50s to lower 60s. The pressure gradient is quiet strong ahead of
arctic front that moves into the area tonight. Once mixing
develops, very strong winds 3000-5000` will likely mix down
along/south of I80 which will create wind advisory conditions
through mid afternoon. Gusts could easily be above 50 mph 10am-
2pm, and would not be surprised if a few locations hit 60 mph in
southeast NE based on soundings and RAP/HRRR gust guidance. Thus
will issue a wind advisory for those locations today 15z-21z.

Focus then shifts to the first round of icing potential as an
overrunning situation develops, with shallow low level moisture
increasing tonight as the arctic front rolls southward into the
area. Warm air aloft combined with the shallow moisture will
allow drizzle or light freezing rain to develop in most areas
06-12 Monday, and then continue to spread a little further south
and east Monday morning. Icing amounts will generally be less than
1/10 of an inch, but nonetheless, will cause some travel problems
Monday morning. While it is a holiday for Washington`s Birthday,
the morning commute Monday could be dicey and thus will issue a
winter weather advisory from Midnight through Noon. Areas near the
SD border may be in a deep enough moisture profile to support all
snow, with less than an inch expected there. And there could be a
narrow transition area with some sleet in northeast NE too. Temps
fall through the day Monday with blustery northerly winds. Precip
should wind down Monday afternoon, although some light snow
chances may continue in northeast NE.

Then, focus shifts to the second round of icing potential, which
may have higher accumulations than the first. Again, areas south
of a line from about Columbus to Onawa, IA will be in too shallow
of a moisture profile to allow for ice, thus areas of freezing
drizzle or freezing rain are expected as the next area of low
pressure moves out of the Rockies along the stalled arctic front.
Areas south of the mentioned demarcation line could see icing from
0.05 to 0.15 through Tuesday morning. Again, north of that line
will probably have deep enough moisture to allow for all snow,
with an inch or two forecast in that area, higher amounts just to
the northwest into north central NE through southeast SD. Again,
in the transition zone, there will likely be some sleet. We will
likely need another winter weather advisory for the Monday night
through Tuesday morning time frame, for the combination of ice in
some areas and snow in others. Contemplated issuing a winter storm
watch for a few counties for ice in southeast NE and southwest IA,
but the heavier amounts of ice appear to be setting up just
southeast of our area.

.LONG TERM...(Tuesday night through Saturday)
Issued at 304 AM CST Sun Feb 18 2018

Cold weather at the beginning of the period with lows dropping
into the single digits above/below zero Tuesday night. Highs only
in the 20s for Wednesday, with slowly moderating temperatures
through the remainder of the period. Dry weather early, but spotty
precip chances of snow and rain return by Friday and Saturday.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1139 PM CST Sat Feb 17 2018

Low Level Wind Shear will be the primary Aviation through 18Z
Sunday, with strong surface winds also a concern during the day. A
strong low level jet will produce 55 to 65kt south to southwest
winds at FL020 from 06Z through 18Z at all eastern Nebraska TAF
sites. Those winds will translate to the surface between 12Z and
18Z when south winds average 25kt with gusts to 40kt. Winds should
decrease with the approach of a cold front Sunday evening, which
will turn winds to the north at KOFK between 00Z and 06Z, but
after this TAF period for KOMA and KLNK. MVFR cigs are likely
behind the front, with areas of drizzle or freezing drizzle
developing 06Z to 12Z Monday.


Issued at 304 AM CST Sun Feb 18 2018

Despite the recent snowfall and snowmelt, due to the combination
of warm temperatures today, low relative humidity, and very gusty
winds of 30 to 55 mph, very high grassland fire danger will exist
across portions of southeast NE and southwest IA. This is
generally along/south of a line from David City, NE to Red Oak,
IA. Minimum humidity percent values drop into the lower 30s during
peak heating. The combined weather values are not low enough for
Red Flag warning criteria at this time. However, any outdoor
burning should avoided or banned.


NE...Winter Weather Advisory from midnight tonight to noon CST Monday
     for NEZ012-015-017-018-030>034-042>045-050-051.

     Wind Advisory from 9 AM this morning to 3 PM CST this afternoon
     for NEZ045-050>053-065>068-078-088>093.

     Winter Weather Advisory from 3 AM to noon CST Monday for NEZ052-

     Winter Weather Advisory from 6 AM to noon CST Monday for NEZ067-

IA...Winter Weather Advisory from midnight tonight to noon CST Monday
     for IAZ043-055.

     Wind Advisory from 9 AM this morning to 3 PM CST this afternoon
     for IAZ055-056-069-079-080-090-091.

     Winter Weather Advisory from 3 AM to noon CST Monday for IAZ056.

     Winter Weather Advisory from 6 AM to noon CST Monday for IAZ069-



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