Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 231151
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
551 AM CST Mon Jan 23 2017

.SHORT TERM...(today through Wednesday)
Issued at 323 AM CST Mon Jan 23 2017

...The primary concern in the short term is heavy snow potential
across portions of northeast Nebraska Tuesday into Tuesday
night...

Early-morning water vapor imagery reveals an intense mid-level low
over the southern Appalachians with another potent low off the
WA/OR coasts. The broader trough associated with the latter system
is presently moving onto the West coast and a subsequent
eastward translation through the Interior West will occur today.
Similar to yesterday at this time, a deck of stratus is advancing
south through the forecast area. Deeper mixing on the western edge
of these clouds should promote an eastward erosion through the
afternoon with warmest temperatures again occurring across our
western counties.

By tonight into Tuesday, 00z model guidance has started to
converge on a solution that depicts a mid to upper-level jet
streak and a sizable portion of the western U.S. trough ejecting
into the Great Plains with the attendant surface low tracking from
western KS to southeast NE or northeast KS by 00z Wed.
Strengthening deep-layer forcing for ascent ahead of this
synoptic system will yield an increasing chance of mainly light
snow across northeast NE tonight with categorical to likely PoPs
warranted across the northern two-thirds of the area on Tuesday.
Precipitation type across our northern counties will likely
remain all snow where adiabatic and latent cooling effects will
offset any diurnal warming. Farther south, a rain-snow mix over
our central counties will transition to all rain in the south.

A change over to all snow will occur from northwest-to-southeast
across the area Tuesday night as the cold air deepens with the
passage of the surface cyclone to the east. Northwest winds will
strengthen considerably at this time, resulting in areas of
blowing snow. As mentioned above, we are seeing growing model
consensus in the track and timing of this system, as well as with
the QPF. These data suggest that the southern extent of a heavy
snow band (i.e. greater than four inch accumulations) will likely
impact our northern counties where we will maintain the winter
storm watch for Tuesday into Wednesday.

The ECMWF and more so the Canadian/GEM indicate a more southern
evolution of the heavy snow band than the bulk of available
guidance. Should these solutions ultimately prove more correct,
additional counties will need to be included in any subsequent
warning or advisory. South of Interstate 80, it appears that snow
amounts will remain an inch or less.

Expect snowfall (albeit lighter) to continue Wednesday,
especially across far east NE and west IA. Strong northwest winds
will contribute to areas of blowing snow with highs ranging from
the upper 20s north to mid 30s south.

.LONG TERM...(Wednesday night through Sunday)
Issued at 323 AM CST Mon Jan 23 2017

North to northwest flow aloft will persist through the long-term
forecast period with several embedded vorticity maxima
translating southeast through the region from central Canada. One
of which will move through the mid MO Valley Thursday night with
another on Saturday. Both of these systems will associate with a
surge of colder low-level air into the region, along with the
potential for some flurries. A more substantial clipper-type
system could affect the mid MO Valley next Monday or Monday night
when the chance for some light precipitation would increase.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 551 AM CST Mon Jan 23 2017

IFR/MVFR stratus entrenched across the forecast area this morning.
Diurnal mixing will help to erode western edge of stratus by
late morning, especially as surface ridge moves east into Iowa.
Expect MVFR ceilings to give way to VFR conditions between
19 UTC to 22 UTC. Isentropic ascent in advance of potent
upper/surface system that will affect the area Tuesday into
Wednesday, will bring low VFR ceilings back into KOFK and
perhaps KLNK by 09/10UTC. Could see light precipitation
developing KOFK by pre-dawn hours; however, left precipitation
chances out for the time being.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Watch from Tuesday morning through Wednesday
     morning for NEZ011-012-015>018.

IA...None.
&&

$$

SHORT TERM...Mead
LONG TERM...Mead
AVIATION...Fortin



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