Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 160457
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1157 PM CDT Sun Apr 15 2018

.SHORT TERM...(Tonight through Wednesday)
Issued at 323 PM CDT Sun Apr 15 2018

...After some record/near record cold temperatures today and tonight,
attention turns to the next storm system to affect the area
Tuesday night and Wednesday, with thunderstorms, snow, and wind...

Snowfall totals from the Friday night Saturday storm varied from an
inch or less in southeast Nebraska and southwest Iowa to 8 to 10
inches for parts of Antelope, Cedar, and Knox Counties.  Neligh had
10 inches for the most in our CWA.

The OAX 12Z sounding was saturated to around 700mb and the entire
sounding was below -8deg.C The 12Z location of the h5 low was over
southern Iowa and was displaced eastward from the h7 low and the h85
low centers.

Latest radar mosaics continue to show some snow showers in eastern
Nebraska and western Iowa with the cyclonic rotation around the
storm system.  The NamNest/NMM/NAM12 have some patchy flurries and
this seems reasonable give any clouds in the area through the evening
hours.

We currently have record or near records forecast for tonight.   See
the climate section for specifics.  The winds, clouds, clearing
and snowcover will all come into play tonight. The winds will drop
off in the western CWA and the clouds will also be the least
there...so these areas along with snowcovered areas will see the
coldest temperatures in the teens. Highs Monday will be affected
by the cold flow off the surface high pressure system in southeast
South Dakota, however the sun is getting much stronger this time
of year and should see a lot more sun Monday compared to today.
Went below guidance most areas with highs in the 30s where the
deep snowcover is and in the 40s south of the Platte River to near
50 near the Kansas/Missouri borders.

Monday night we have the ridge aloft with southeast flow and
surface low pressure developing over Kansas Tuesday.  Tuesday
night, the 115kt jet is rotating across Colorado into Kansas with
increasing upper level divergence across Nebraska and Iowa which
lasts into Wednesday. Closed h5 low pressure over Alberta has low
pressure extending southward into the Rockies and rotates
negatively into the Plains. There is good model agreement that
there will be low pressure closing off by 12Z Wednesday. There is
poor model agreement related to the latitudinal location with the
12Z GFS over SD/NE, the 00Z EC is over Nebraska, and the 12Z NAM
is over Kansas. The 12Z UKMet is similar to the EC and the CMC is
similar, but a little weaker. The ICON is similar with the
location of the closed low moving into NW Iowa like the EC, but a
little faster. The SREF is in between the EC/GFS. The 12Z EC is
more in line with the NAM, just not quite as far south.

Instability increases in southeast Nebraska Tuesday night as the
surface low tracks into southeast Nebraska. Some strong to severe
storms possible with the high shear, although instability is still
limited. Farther north with the steep lapse rates, showers and
thunderstorms are possible with the rain changing to snow. Based
on the present track, we have accumulating snow in northeast
Nebraska with 1 to 4 inches going. Strong northwest winds in the
advisory level develop for Wednesday as the storm system moves
across Iowa. May need a headline for the snow and wind Tuesday
night into Wednesday and will need to assess the severe threat as
we hone in on the track.

.LONG TERM...(Wednesday night through Sunday)
Issued at 323 PM CDT Sun Apr 15 2018

The extended for Wednesday night and beyond, depending on the
timing of the storm system,we will probably be on the backside of
it with northwest winds with enough wind to keep lows up, but
still dropping back into the 20s to lower 30s. Normal lows are in
the lower 40s and normal highs are in the mid 60s. Mid level
ridging builds in for Thursday with the next storm system over
parts of Nevada, Utah, New Mexico, and southern California.

The storm system over the four corners area Thursday night moves
into the Rockies Friday and precipitation will be breaking out in
western Nebraska, spreading eastward.  Showers will be on the
increase and if there is enough moisture early on, it may begin as a
mix.  As the storm system moves into the Plains, the track of the
closed low is somewhere across Kansas or possible into Oklahoma.
This track will allow cold air to work into the system with
rain/snow for the weekend Friday night into Saturday night.  The
current track takes the more organized thunderstorms from Texas into
Missouri...an enhanced area of rain area in eastern Kansas, and the
potential for some light snow farther north into Nebraska and
Iowa.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1153 PM CDT Sun Apr 15 2018

Clouds wrapping around the low will begin to scatter out as the
low lifts out of the Great Lakes. MVFR ceilings at KOFK is
expected to improve to VFR by 09Z. VFR ceilings will prevail and
beging to scatter out during the day at KOMA and KLNK.

&&

.CLIMATE...
Issued at 323 PM CDT Sun Apr 15 2018

We will likely break the coldest max temperature for today at
Omaha, Lincoln, and Norfolk.

The current records for coldest max temperature are:

Location  Record  Year

Lincoln     41    1945/1917
Omaha       37    1872
Norfolk     34    2000

Tied second coldest average temperature for Omaha from April
1-14. 1881 was the coldest with an average temperature of 31.0.
Both in 1983 and 2018, our average temperatures was 37.9 degrees.

Lincoln also had the second coldest average temperature for April
1-14 with 38.5 and that was behind 1957 with 38.4 degrees.

Norfolk also had the second coldest average temperature for April
1-14 with 34.1 and that was behind 1957 with 34.3 degrees.

Location Forecast Record Year

Lincoln     19      21   1904
Omaha       21      21   1875
Norfolk     15      14   1904

&&

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

$$

SHORT TERM...Zapotocny
LONG TERM...Zapotocny
AVIATION...Smith
CLIMATE...Zapotocny



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