Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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665
FXUS63 KOAX 082311
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
511 PM CST Thu Dec 8 2016

.SHORT TERM...(tonight through Sunday)
Issued at 257 PM CST Thu Dec 8 2016

Early-afternoon water vapor imagery depicted broad cyclonic flow
east of the Rockies with chiefly a zonal regime present across
the Interior West. This quasi-zonal flow pattern will migrate east
into the Great Plains tomorrow (Fri) into Saturday, while in the
low levels, a ridge axis shifts to our east in deference to lee
cyclone formation over the central High Plains.

Tonight, clear skies coupled with light winds attendant to the
transient surface ridge will yield ideal radiational cooling
conditions with lows dipping to near zero across the north and
single digits south. On Friday, strengthening warm advection and
isentropic ascent along the 285-290K surfaces will foster an
increase in clouds with flurries possible across the north. The
cold start to the day and increasing clouds will result in highs
only in the upper teens to lower 20s.

On Saturday, the response to a low-amplitude perturbation
tracking across the northern Plains will result in strengthening
low-level warm advection with temperatures warming into the lower
to mid 30s across central and southern portions of the forecast
area. Over northeast Nebraska and west-central Iowa, the warm
advection in conjunction with frontogenetical forcing will
contribute to an increased chance of accumulating snow.
Variability exists in 12z model guidance with respect to snowfall
totals and where the swath of heaviest snow will develop.
Currently, it appears that up to an inch or two is possible,
mainly across Knox and Cedar counties.

After a brief reprieve Saturday night, the chance of snow will
increase across the entire forecast area on Sunday as large-scale
forcing for ascent strengthens in association with a short-wave
trough amplifying over the mid Missouri Valley. Here too, the
models remain quite dispersive in QPF amounts and distribution
with a dusting to a couple of inches of snow possible Sunday into
Sunday night.

.LONG TERM...(Sunday night through Thursday)
Issued at 257 PM CST Thu Dec 8 2016

An amplifying polar-branch trough in the lee of the Canadian
Rockies will hasten the equatorward surge of another mass of
Arctic air into the mid Missouri Valley Monday night into Tuesday.
A low-probability chance of light snow will exist with the frontal
passage with highs on Tuesday struggling to climb into the teens
to lower 20s. Though some air mass moderation will occur through
the middle of next week, temperatures will remain well below
normal.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 509 PM CST Thu Dec 8 2016

VFR conditions are expected through the TAF period. Winds
will continue to diminish across the region this evening,
becoming light and variable overnight. Winds will turn to the
south, advecting in warmer air and bringing a small chance for flurries
at KOFK late Friday afternoon.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

SHORT TERM...Mead
LONG TERM...Mead
AVIATION...KG



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