Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 210530

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1130 PM CST Fri Jan 20 2017

Issued at 1123 PM CST Fri Jan 20 2017

Expanded our Dense Fog Advisory for most of eastern Nebraska and
southwest Iowa, in effect until 9 AM. Visibilities will mostly be
near a quarter mile, but will be variable as showers move through
the region and mix up the lower atmosphere at times. Webcams show
dense fog in much of our CWA. We should see some improvement from
west to east, likely before sunrise in western parts of eastern
Nebraska as westerly low level wind component begins to dry things
out there. Will trim advisory when that occurs.


.SHORT TERM...(Tonight through Monday)
Issued at 300 PM CST Fri Jan 20 2017

Main concerns in this period are precipitation chances from
Tonight into Saturday morning, then temperatures through the
period. Fog could become an issue, but will not go with an
advisory at this time.

Primary features of concern from the 12Z upper air charts included
the following. At 300 mb...strong winds were noted in the eastern
Pacific (up to 175 knots) which were punching toward northern Baja.
A secondary jet max of over 100 knots was lifting north/northeast
from western Montana. At 500 mb, one shortwave trough was lifting
northeast from the Dakotas and Minnesota, while another was over
Colorado. 12 hour height falls with the second shortwave were as
high as 120 meters.

That feature will be lifting northeast through the local area
tonight, with measurable precipitation, and also into Saturday
morning. Precipitation type tonight should be mainly rain, but
some snow could mix in. The mix would be mainly across northeast
Nebraska and at this time, no accumulation is expected. Looks for
lows tonight mainly in the 30s.

Clouds should decrease across the area Saturday, with highs
reaching into the mid 40s to lower 50s. If clouds are slower to
clear, it may end up being cooler. North or northwest winds
Saturday night into Sunday should bring some cooler air back into
the area which will last into Monday. At least for now, expect
any precipitation Saturday night would stay south of our area.

.LONG TERM...(Monday night through Friday)
Issued at 300 PM CST Fri Jan 20 2017

We will be watching this period closely. The longer range models
are in decent agreement with the large scale features, but details
vary. Low pressure should intensify over the high plains Monday
night, then track east or northeast through the region Tuesday and
Tuesday night. Warm advection/isentropic upglide, start Monday
night but any saturation appears to stay to our north in that

Highest probabilities for accumulating snow from the 12Z GFS
model are over the northern half of the forecast area. The 12Z
ECMWF is similar, but has higher snow amounts that cover most of
the area. It is too early to get specific or to jump on one model
solution over another. Will bump pops upward slightly and will
have some likely wording for snow.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1123 PM CST Fri Jan 20 2017

Widespread LIFR to VLIFR conditions are forecast overnight, with
gradual improvement between 12Z and 18Z. Surface low pressure
system will continue to infuse low level moisture into eastern
Nebraska, and will trigger scattered showers or drizzle from time
to time. Thus some variability in vsbys is likely, but overall
expect VLIFR cigs/vsbys to dominate. As system moves east in the
morning, westerly surface winds will help dry out lower atmosphere
and scour out low clouds from west to east. Expect VFR conditions
by or shortly after 18Z.


NE...Dense Fog Advisory until 9 AM CST Saturday for NEZ015-030>034-

IA...Dense Fog Advisory until 9 AM CST Saturday for IAZ043-055-056-



LONG TERM...Miller
AVIATION...Dergan is the U.S. government's official web portal to all federal, state and local government web resources and services.