Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 191203
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
603 AM CST Fri Jan 19 2018

.SHORT TERM...(Today through Sunday)
Issued at 333 AM CST Fri Jan 19 2018

Relatively benign weather into Saturday before impending storm
system begins affecting our area Sunday.

Southerly winds have begun overspreading eastern Nebraska and
southwest Iowa, and with a veil of high clouds overhead,
temperatures have halted their drop for the most part this morning.
Will likely start the day with temps in the low to mid 30s with
winds turning more southwesterly with time, suggesting nice warming
potential today. However with insolation tempered by high clouds,
still will not reach maximum potential. But highs well into the 40s
and lower 50s certainly seem reasonable.

Southwest winds will turn northwesterly tonight as a weak cold front
drops through the area. Southward progression of front looks to be
hindered on Saturday by deepening low pressure in the High Plains
providing increasing southerly flow across Kansas into our southern
CWA. So we could see a wide range of temperatures from north to
south if low clouds remain south of southeast Nebraska and southwest
Iowa Saturday afternoon. But for now, will maintain thinking low
level moisture/clouds will return there, keeping temperatures across
the CWA in the lower 40s, still above normal for this time in
January.

Strong storm system in the High Plains deepens further Saturday
night before swinging east and northeast into eastern Kansas by late
Sunday afternoon. Increasing isentropic upglide late Saturday night
into Sunday morning will lead to drizzle across southeast Nebraska
and southwest Iowa where temperatures should be below freezing for a
time before temps rise there. Farther north and west, colder air
will be more entrenched as north to northeast low level winds limit
warming. Meanwhile, mid level moisture will be slow to increase,
suggesting a potentially longer period of freezing drizzle is
possible in northeast Nebraska and perhaps west central Iowa into
the afternoon. Moistening mid levels should commence during the
afternoon, providing seeder-feeder ice for a change to snow in
northeast Nebraska. While some accumulation up to an inch or so is
likely by late in the day there, the bulk of the snow will come
later Sunday night as system moves into the Plains.

.LONG TERM...(Sunday night through Thursday)
Issued at 333 AM CST Fri Jan 19 2018

Potential for a winter storm for northeast Nebraska, and
accumulating snows for the rest of eastern Nebraska and southwest
Iowa Sunday night into Monday, are the primary forecast concerns
this period.

Models are in decent agreement this morning in regards to track of
low pressure system and attendant potential for heavy snow. Axis may
have shifted slightly southeast, but still focuses on a central
Nebraska to eastern South Dakota line, including a portion of
northeast Nebraska.

Snow will likely be ongoing in northeast Nebraska to begin Sunday
night, with the changeover to snow gradually working southeast
across the rest of eastern Nebraska and southwest Iowa overnight.
Surface and mid level low centers tracking through northeast Kansas
into southwest then central Iowa places areas north and northwest of
Interstate 80 in favored heavy snow location. Given expected QPF and
Garcia method calculations, snow totals of greater than 6 inches are
possible across northeast Nebraska from Sunday night through Monday
morning. And with the potential for some freezing drizzle initially,
have decided to issue a winter storm watch for that area. Locations
to the south are more uncertain in regards to snow amounts and
potential icing, but certainly a variety of winter weather is
likely, beginning with drizzle or freezing drizzle and ending with
snow Monday afternoon or evening.

There is also some potential for convective showers or snow showers
for a time in southeast Nebraska and southwest Iowa as cold core of
upper low rides across those areas late Sunday night. A tricky
system to deal with now, and hopefully will become more clear with
later forecasts through the next 36 hours.

Beyond Monday, mid level flow flattens out then becomes
southwesterly by Thursday, suggesting a rebound in temperatures by
then. Not a dramatic cooldown to start with on Tuesday as coldest
air follows system to the east quickly. So have highs in the 30s
gradually rising into the 40s Tuesday through Thursday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 506 AM CST Fri Jan 19 2018

VFR conditions will prevail thru the fcst pd.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Watch from Sunday afternoon through Monday morning
     for NEZ011-012-015>018-030>033-042.

IA...None.
&&

$$

SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...DEE


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