Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 102230 CCA
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
359 PM CST Wed Jan 10 2018

.SHORT TERM...(Tonight through Saturday)
Issued at 302 PM CST Wed Jan 10 2018

Forecast concerns in the short term will continue to be the
evolution of the rain changing to snow and impacts related to
increasing winds and falling temperatures tonight and Thursday.

Some difficult forecast decisions related to the uncertainty in
snow amounts and the combination of falling temperatures (flash
freeze) and blowing snow. We issued a winter storm warning for four
counties in west central Iowa and have an advisory elsewhere in our
county warning area, however do not want to minimize the impacts
during the morning commute due to the flash freeze, snow and blowing
snow.

The most recent model trends continue to slide the snow band
farther southeast, however also have mesoscale bands of snow which
may develop outside of the band from Nebraska City/Peru toward
Hancock.

The storm system over Arizona/New Mexico is forecast to track into
the Texas Panhandle and western Oklahoma by 06Z. Very warm
temperatures in the 40s and 50s today ahead of the system.
Meanwhile...at 21Z the cold front is advancing from the north with
4 mb 3hr pressure falls over northeast Wyoming. Although the
surface front and northwest winds will commence between 00z and 06Z
north of I80, there is a lag of a couple of hours after the wind
shift for the cold air/below freezing temperatures to be realized.
We currently have the below freezing temperatures arrive after 9pm
at KOFK...after midnight at KLNK/KOMA/KCBF...and around 6am at KFNB.

The hi-resolution RAP/HRRR develop light drizzle/light
rain/showers ahead of and along the cold front with increasing
omega through the evening hours. The RAP/HRRR also pick up on a
narrow band of snow, possibly enhanced due to the coupled jet...as
the frontogenesis is still to the west. The frontogenesis
increases from 06-12Z across the forecast area and continues
eastward out of the area from 12-18Z. The lift in the dendritic
growth zone is for a limited time...thus it may snow heavily for a
period of time, however it will be short, compared to a longer
duration storm.  The moisture available per the Garcia method
remains in the 2 to 4 g/kg area with the higher amounts in western
Iowa. The lift period is limited for the snow...6 to 12hrs...which
will limited the snow. Our current forecast had 1 to 3 inches across
most of the area with 3 to 5 inches in a band from southeast
Nebraska into western Iowa with the higher amounts in western Iowan
and generally south of I80 in Nebraska. Highest sustained winds
should be in the 25 to 30kt range and highest gusts in the 30 to
40kt range.

The snow quickly moves out Thursday afternoon, however the winds
will continue through the afternoon...subsiding Thursday evening
and overnight.

Much colder air moves in through the day Thursday, thus falling
temperatures are forecast, so highs for the day will be before
daybreak in some locations and in the early morning elsewhere.
Lows Thursday night will drop down into the single digits above
and below zero for Friday morning.

A shortwave trough in the northwest flow will spread light snow
and flurries across the area Friday into Friday night.

Very cold temperatures last through Saturday and continue into the
extended.

.LONG TERM...(Saturday night through Wednesday)
Issued at 302 PM CST Wed Jan 10 2018

Another shot of light snow is possible Saturday night into sunday
with another shortwave trough in the northwest flow. Temperatures
remain below freezing through the extended.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1156 AM CST Wed Jan 10 2018

Ongoing IFR conditions at OFK and OMA...and MVFR at LNK will
persist in the near term but expect LNK to scatter out shortly
with OMA scattering out between 21-22Z. There is some potential
for OFK to remain IFR for much of the afternoon but at this time
have highlighted the most likely hours for scattered clouds late
afternoon into early evening. A strong cold front will bring a
sharp wind shift and increased speeds gusting 30-40 kts for
several hours. Precipitation...initially rain...will change to
snow with a brief period of sleet possible at the transition.
There is a high likelihood of IFR cigs following shortly after the
wind shift with a gradual improvement to MVFR cigs but likely
reduced visibility with falling snow combined with wind.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory from 3 AM to 6 PM CST Thursday for
     NEZ068-090>093.

     Winter Weather Advisory from midnight tonight to 6 PM CST
     Thursday for NEZ034-044-045-050>053-065>067-078-088-089.

     Winter Weather Advisory from 9 PM this evening to 6 PM CST
     Thursday for NEZ011-012-015>018-030>033-042-043.

IA...Winter Storm Warning from midnight tonight to 6 PM CST Thursday
     for IAZ055-056-069-079.

     Winter Weather Advisory from 3 AM to 6 PM CST Thursday for
     IAZ080-090-091.

     Winter Weather Advisory from midnight tonight to 6 PM CST
     Thursday for IAZ043.

&&

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Barjenbruch



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