Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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970
FXUS63 KOAX 180542
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1142 PM CST Sat Feb 17 2018

.SHORT TERM...(Tonight through Tuesday)
Issued at 345 PM CST Sat Feb 17 2018

...Couple of Periods of Freezing Drizzle and Light Snow Sunday
night into Tuesday morning...

Forecast concerns over the next few days will be temperatures,
winds, precipitation type and coverage, and if headlines will be
needed.

Water vapor satellite imagery, radar, and upper air observations
from this morning revealed a fast-moving couple of shortwaves that
brought light snow to parts of northeast Nebraska and western
Iowa. Although most of the reports were a dusting to an inch and a
half, it created multiple car accidents on I80 and I35 in central
Iowa.

Behind this system we had sunshine, gusty northwest winds, and
temperatures mostly in the 40s and 50s. Visible satellite imagery
shows a few patchy cloud spreading into northeast Nebraska about
1500 to 3500ft and some cooler temperatures in the 30s.

Tonight, a 50 to 70kt low level jet develops over central Nebraska
and shifts eastward into western Iowa through the day. This will
feed into an area of low pressure from South Dakota into Minnesota
with accumulating snow for those regions. Challenging forecast
Sunday into Monday night as we have mild temperatures for Sunday
with windy conditions and may need a wind advisory, then colder
air and light precipitation combining to produce a mix or drizzle,
freezing drizzle and light snow depending on your location.

South winds increase to 20 to 25kts across northeast Nebraska by
morning and these stronger winds 20 to 30kts spread eastward
across the forecast area during the morning and into the afternoon
as the cold front moves into the area.

The models (EC/GFS/NAM/SREF) are similar in depicting
deteriorating conditions Sunday night, with the forecast soundings
moistening the low levels around 5,000ft or below. Temperatures
become critical overnight as the models agree that KOFK will drop
below freezing something between 03-06z with a low around 19. At
KOMA, the low of 31 is between 12-15Z, and KLNK, the low is in the
mid to upper 20s, but drops below freezing from 08-12Z with
falling temperatures during the day Monday.

A variety of precipitation is possible due to highs from around 50
near the South Dakota border to the mid 60s near the
Kansas/Missouri border Sunday and the overnight lows ranging from
15 to 45 Monday morning. The forecast soundings show warm air
aloft and not enough cold air for ice crystals, therefore we have
freezing drizzle mentioned until it is cold enough to mention
snow.We have drizzle, freezing drizzle, and light snow mentioned,
however there is instability present Sunday night and Monday
morning and the NAM does have some convective precipitation. We
do have some ice accumulations up to a .1 mainly along and north
of I80 (although we do have it as far south as Otoe and Mills Co.)
and light snow up to an inch in northeast Nebraska and west
central Iowa. With the cold air...north winds 10 to 20kts will
also develop Monday.

The upper level trough is still to the west and strong h85 flow
continues Monday night into Tuesday with the H85 boundary still
pushing through the forecast area with another shortwave in the
flow. This will produce another round of light precipitation.
Light icing with a tenth of an inch is possible from southeast
Nebraska into southwest Iowa. May also need to add a little sleet
in per the forecast soundings, but add these details later. Light
snow of 1 to 3 inches is possible in northeast Nebraska. Boosted
northwest winds for this time frame as well. Highs Tuesday should
only be in the teens and 20s.

.LONG TERM...(Tuesday night through Saturday)
Issued at 345 PM CST Sat Feb 17 2018

Cold temperatures with some sub freezing lows and single digits
Wednesday morning with diminishing winds. Wind chills should range
from zero to 15 below zero. Wednesday highs are forecast to be in
the 20s and 30s. Warmer highs in the 30s and 40s Thursday through
Saturday. With a boundary in the area Friday, we have a mix
mentioned.

&&

.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.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Dergan



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