Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 222302

Area Forecast Discussion
National Weather Service Omaha/Valley NE
502 PM CST Sun Jan 22 2017

.SHORT TERM...(Tonight through Wednesday)
Issued at 255 PM CST Sun Jan 22 2017

Our main forecast concern is still the potential for accumulating
snow Tuesday into Wednesday.

Strong jetstream level winds continued from the eastern Pacific into
west Texas with 300 mb winds at 12Z as high as 180 knots. System
that will affect our area Tuesday into Wednesday was just starting
to come onshore this afternoon. Upper air network should sample
things better this evening.

For tonight in our area, low clouds have been lingering over much of
the forecast area through 230 pm, but there has been some erosion
west of Highway 81. RAP low level relative humidity progs were used
as a proxy for expected cloud cover tonight. There could also be some
fog, but will not issue an advisory at this point. Monday could remain
partly to mostly cloudy but allowed highs to reach into the 40s at
all locations.

There is still some model variability in regards to what latitude
the system will move across the plains and produce significant snow
for Tuesday into Wednesday. The general consensus in regards to
the track of the surface low and heaviest QPF has shifted south,
compared to 12 hours ago, although the 12Z GFS suggested things
would remain farther north.

Nevertheless, confidence increased enough and event is now close
enough to issue a winter storm watch. That will be in effect for
our fiver northern counties from 6 am Tuesday to 6 am Wednesday.
Temperatures on Tuesday should reach the 40s in our southern zones
and 30s north. Suspect that accumulations during the daylight
hours of Tuesday should be limited to maybe 2-3 inches northwest
of a line from about Albion to Wayne. Then accumulations should
spread into more of the area Tuesday night.

As mentioned earlier, the track of surface low suggested by a
model blend (except not using the 12Z GFS) would normally put the
heaviest snow across northern Nebraska, southern South Dakota and
then toward northern Iowa/southern Minnesota. That is our thinking
for now. Model forecast soundings were not overly helpful, since
there will probably be dynamic cooling of the column in the
afternoon. North/northwest winds will be increasing across
northeast Nebraska in the afternoon and over all of the area for
Tuesday night. It is the combination of snow and wind that we are
most worried about, and thus the winter storm watch.

.LONG TERM...(Wednesday night through Sunday)
Issued at 255 PM CST Sun Jan 22 2017

The chance for any significant precipitation in this period seems
pretty low at this time. Current timing would end snow before
Wednesday evening, as the system pulls east.

500 mb pattern starts out with a block over southwest Canada and a
trough from Ontario back into the central Plains. That ridge is
expected to strengthen and build slowly east through Saturday.
Highs will start out in the 20s and 30s for Thursday, then
moderate to the 30s or lower 40s by Sunday.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 500 PM CST Sun Jan 22 2017

MVFR cigs finally clear KOMA to the east just before TAF issuance.
Those cigs are forecast to return to eastern Nebraska after 06Z,
reaching KOMA and KOFK by 08Z or so, then to KLNK by 12Z. Cigs
will likely be in the FL010 to FL015 range, with some minor vsbys
restrictions in fog of about 4SM. A gradual erosion of clouds
should bring VFR conditions back to the area before 18Z.


NE...Winter Storm Watch from Tuesday morning through late Tuesday
     night for NEZ011-012-016>018.



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.