Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 190525

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1125 PM CST Thu Jan 18 2018

.SHORT TERM...(Tonight through Saturday)
Issued at 257 PM CST Thu Jan 18 2018

Quiet weather continues in the short term as a ridge across the
Rockies flattens into a zonal pattern tomorrow. A fairly dense
cirrus shield has topped the ridge overspread the forecast area
this afternoon so skies will be mostly to partly cloudy tonight
with lows in the lower to mid 20s. The cirrus should thin Friday
allowing more sunshine, which will help boost temps into the mid
40s to mid 50s. There is a weak front that settles into the area
Friday night. The Nam and HighRes NMM try and develop some spotty
precip along the boundary along and just north of I80 Friday
night, but other models are dry, so will have to watch it the next
couple of runs. The boundary stalls in the area on Saturday, with
a little cooler highs in the lower to mid 40s.

.LONG TERM...(Sunday through Thursday)
Issued at 257 PM CST Thu Jan 18 2018

...Potentially Strong Winter Storm Still on Track to Impact the
Area Sunday into Monday...

The main concern in the long term forecast remains the the
potential winter storm that moves through the region Sunday into
Monday. Models have continued to target parts of our forecast area
for a variety of wintry weather, including some freezing drizzle
ahead of the storm system, then rain, but changing to snow on the
back side with potentially several inches possible, along with
near blizzard conditions in some areas.

Low level moisture will be increasing Saturday night, with
isentropic lift over the previously mentioned stalled boundary.
This could result in some drizzle developing by daybreak Sunday,
but unfortunately, some of the area will still be below freezing.
Thus, there could be a light glaze of ice develop early Sunday
morning before surface temperatures warm into the mid 30s to upper
40s through the day, while an area of deepening surface low
pressure moves out of southeast Colorado into northeast Kansas or
quite possibly even southeast Nebraska. This essentially splits
our forecast area, with rain becoming snow in northeast Nebraska,
and perhaps even a threat for thunderstorms in southeast NE and
southeast IA for a short period late Sunday afternoon into early
Sunday evening as a dry slot moves into area south of I80.

Deepening of the surface cyclone continues Sunday evening into
early Monday morning as the low moves to northern Iowa. This
places northeast Nebraska in a favored location for heavy snow,
with northwest winds increasing to 25 to 35 mph with higher gusts.
There is some concern that near blizzard conditions could develop
with considerable blowing and drifting snow.

Meanwhile, further south in the I80 corridor and points south,
rain does change to snow, but projected snowfall amounts may be
lower, to possibly not much snow at all in extreme southeast NE
and southwest IA. There still remains some uncertainty on the
highest snowfall amounts, but operational GFS and ECMWF are honing
in on the area from central NE through northeast NE to southwest
SD to northwest IA for the heaviest amounts, coincident where a
noticeable trowal should exist. Present model trends suggest a
wide swath of 6 to 12 inches will be possible there, with lower
amounts along I80 and south. The storm track is pretty consistent,
with the ECMWF just slightly further south then the GFS. The 21
GEFS ensemble members do show a wider range of variability on QPF
and eventual snow amounts, and the impact timeline is still just
outside of our window of snow amount predictability. Models also
continue to show that there is not an arctic surge of air with
this system, so bitter cold is not expected.

Have no doubt that we`ll eventually need a winter storm watch in
the next 24 to 36 hours, but we are still about a day early for
those type of headlines. Obviously, will continue to monitor new
model trends as this storm system which is still in the Pacific
Ocean begins to move onshore.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1124 PM CST Thu Jan 18 2018

VFR conditions are expected through the TAF cycle, with scattered
to broken cirrus and unrestricted visibility. Winds will be light
tonight, ranging from southeasterly to southwesterly. Tomorrow,
southwest winds around 5-10kt are expected, becoming light again
after 00Z.




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