Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 220943

Area Forecast Discussion
National Weather Service Omaha/Valley NE
343 AM CST Sun Jan 22 2017

.SHORT TERM...(tonight through Tuesday)
Issued at 343 AM CST Sat Jan 21 2017

...The primary forecast concern is the potential for accumulating
snow Tuesday into Wednesday...

Manual 00z upper-air analysis and early-morning water vapor
imagery indicate a potent subtropical-branch short-wave trough
over the southern Plains with a weaker, polar-branch system over
the upper Great Lakes. The former will evolve into an intense
trough and associated closed low as it translates through the
southeastern States today. In it`s wake, a mid-level ridge will
build over the Rockies today before shifting east into the Great
Plains tonight into Monday. In the low levels, winds will become
decidedly northerly today, allowing for some low clouds and a
cooler air mass to settle into the area, especially along and east
of the MO River. Areas of dense fog present over our western Iowa
counties should dissipate this morning with some light drizzle
possible at these same locations later today. Afternoon highs
should range from around 40 east to lower 40s west.

A weak surface high will build southeast through the mid MO Valley
tonight into Monday while a lee cyclone deepens over the central
High Plains. Strengthening low-level warm advection on the
backside of the high should allow for slight warming of the air
mass with Monday`s highs rebounding into the 40s.

Attention then turns to the evolution of a vigorous mid-level
trough which will shift from the Interior West into the Great
Plains Monday night into Tuesday. There continues to be model
differences in the amplitude and track of this system,
particularly at the surface. The 00z deterministic GFS remains the
most progressive solution with the track of the surface low. The
Canadian/GEM remains the slowest solution, while the ECMWF is a
compromise of the two.

With respect to QPF, the GFS indicates the primary deformation
band of precipitation remaining to our north across SD into west-
central MN. In contrast, the SREF and GEFS mean QPF fields are
more consistent with the ECMWF in suggesting the a swath of higher
precipitation potential over northeast NE/southeast SD/northwest
IA, which is consistent with our conceptual model. Under this
scenario, light snow chances will increase Monday night into
early Tuesday over our northern counties. Precipitation chances will
increase areawide on Tuesday into Tuesday night as large-scale
forcing for ascent strengthens and deepens. Low-level temperature
profiles in forecast soundings indicate all rain or a rain-snow mix
during the day, before a change over to all snow occurs Tuesday

.LONG TERM...(Tuesday night through Saturday)
Issued at 343 AM CST Sat Jan 21 2017

It still appears that several inches of snow will be possible
across northeast Nebraska into west-central Iowa Tuesday night
into Wednesday with lesser amounts with southward extent. Winds
will strengthen from the north Tuesday night with the passage of
the surface low to the east with areas of blowing snow possible.

We will remain in north or northwest flow aloft which will
maintain near or slightly below normal temperatures through the
remainder of the work week. A slight warming trend is anticipated
by next weekend.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1130 PM CST Sat Jan 21 2017

Area of IFR stratus moving south from eastern South Dakota is
expected overspread all eastern Nebraska TAF sites between 09Z and
14Z. IFR cigs will linger through much of the morning, eroding
from west to east, clearing KOFK and KLNK by 18Z, then KOMA
shortly after. Generally MVFR vsbys in fog are forecast along with
the stratus. However ahead of the low clouds, some pockets of IFR
vsbys could affect KOMA and KLNK between 06Z and 12Z.


IA...Dense Fog Advisory until 9 AM CST Sunday for IAZ056-069-080-091.



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