Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 181818
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1218 PM CST Sun Feb 18 2018

.UPDATE...
Issued at 942 AM CST Sun Feb 18 2018

Update issued for strong winds today. Locations along the Missouri
River and points east are taking a bit longer to veer around to
the southwest but should over the next hour or two. Once those
locations come around to a more southwesterly direction at the
surface, we should start to mix down and see gusts up toward
40kts or so. In addition, KOFK gusted to 46kts at the 15Z ob so
did expand the wind advisory to include the surrounding area. The
strong gusts should be fairly short-lived across northeast
Nebraska and are not expected to last much past 18-19Z.

&&

.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 18Z TAFS through 18Z Monday afternoon)
Issued at 1204 PM CST Sun Feb 18 2018

VFR conditions are expected until aroun 06z when ceilings are
expected to become MVFR to possibly IFR behind a strong cold front.
Gusty south/southwest surface winds to near 50kts will subside by
late this afternoon before becoming north/northwest along a
strong cold front that drops through the TAF sites by 06z. For
KOFK, put in a mention of FZDZSN as some freezing drizzle may mix
with snow after 12z. As for KOMA and KLNK, any precipitation
should remain liquid before 12z, but as temperatures drop below
freezing about that time, have mentioned FZDZ from 12z and beyond.

&&

.FIRE WEATHER...
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.

&&

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

     Wind Advisory until 3 PM CST this afternoon for NEZ012-015-017-
     018-031>034-042>045-050>053-065>068-078-088>093.

     Winter Weather Advisory from 3 AM to noon CST Monday for NEZ052-
     053-065-066-078.

     Winter Weather Advisory from 6 AM to noon CST Monday for NEZ067-
     068.

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

     Wind Advisory until 3 PM CST this afternoon for IAZ043-055-056-
     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-
     079.

&&

$$

UPDATE...Kern
SHORT TERM...DeWald
LONG TERM...DeWald
AVIATION...Kern
FIRE WEATHER...DeWald



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