Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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508
FXUS63 KOAX 141145
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
545 AM CST Sat Jan 14 2017

.SHORT TERM...(today through Monday)
Issued at 346 AM CST Sat Jan 14 2017

...Significant Ice Storm Still Possible Across Eastern Nebraska
and Western Iowa...

The main focus of the forecast continues to be for the potential
for a winter storm over parts of the area. Little has changed with
respect to forecast reasoning or resulting sensible weather with
this package. Model spread continues to lend to forecaster
uncertainty and thus we will keep the watch headline going for
another cycle.

Models are fairly consistent over the next 24 hours in taking the
closed mid-level cyclone over the Baja into northern Mexico and
then start to eject this northeast late in the weekend. The main
source of uncertainty continues to be the interaction/phasing with
the northern stream shortwave trough late Sunday night and into
the day on Monday. Differences in this phasing leads to below
normal forecaster confidence. The 00Z GFS appeared to strong with
this northern stream system and to suppressed with the closed
cyclone lifting northeast. The EC appeared to be a nice compromise
between the faster more suppressed GFS and more open weaker GEM
for this period.

The highest impacts for this system will certainly come on Sunday
night and Monday, but until then we will start to see some impacts
starting during the day on Sunday. The combination of a lead low-
amplitude wave and an increased in a nocturnal low-level jet over
the southern Plains tonight should lead to a marked increase in
precipitation over the TX panhandle into western KS. This zone of
WAA will likely lift through KS and into the far southern CWA by
daybreak on Sunday, and continue to lift east/northeast through
the morning while weakening in intensity. This will likely provide
the first shot of mixed precipitation, which will likely be in the
form of some light sleet/freezing rain during the day on Sunday.
With the passage of this wave late Sunday we likely see a lull in
precipitation on Sunday evening into the first half of the night.

The main show then looks to start late Sunday night and into the
day on Monday as the closed cyclone lifts northeast through
Kansas. We have a fairly high confidence that this will spread a
shield of precipitation ahead of it into the CWA late on Sunday
night and through the morning on Monday. This is likely when the
highest ice accumulations are likely to occur with widespread
freezing rain expected over the southern 2/3rd of the FA. Over far
southeast NEb and southwest IA /generally up to near I80/ we still
expect temperatures to warm to freezing or just slightly above by
late Monday morning and into the afternoon. Overall we have
cooled the highs on Monday, but this was primarily the result of
the widespread precipitation. In the northwest CWA we are likely
to see a period of freezing rain and sleet, but by afternoon this
should become all snow with some decent 3-5 in accumulations
likely for parts of Antelope/Knox/Boone/Cedar counties.

.LONG TERM...(Monday night through Friday)
Issued at 346 AM CST Sat Jan 14 2017

As we see increased influence by the northern stream shortwave on
Monday evening/night we will see the column cool and potentially
some light snow to mix in for the rest of the CWA, although the
intensity of the precipitation will be light by then with any
remaining snow ending by Tuesday morning. Through the day on
Monday the winds should be fairly light, which will likely help
with impacts to above ground electrical lines, but as Canadian
high pressure builds in on Monday night we will likely see an
increase in northwest winds, with 10 to 20 mph expected and even
though precipitation will be ending this may lead to some impacts
to power lines at this time.

After this system goes by we may be looking at a January thaw for
the middle to late week. Both deterministic and ensemble guidance
indicates very warm temperatures for Wed through at least Friday
with highs/lows 20 degrees above normal possible. Current forecast
may not be warm enough, but little time to diagnose this period of
the forecast tonight.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 545 AM CST Sat Jan 14 2017

VFR conditions will prevail through the period as high pressure
from the northern plains to the upper midwest maintains generally
dry conditions in the lower levels of the atmosphere. Strong upper
level system will begin to lift from northwest Mexico toward
northern Texas after 15/12Z.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Watch from Sunday afternoon through late Monday
     night for NEZ011-012-015>018-030>034-042>045-050>053-
     065>068.

     Winter Storm Watch from Sunday morning through late Monday night
     for NEZ078-088>093.

IA...Winter Storm Watch from Sunday afternoon through late Monday
     night for IAZ043-055-056-069-079-080-090-091.

&&

$$

SHORT TERM...Boustead
LONG TERM...Boustead
AVIATION...Fobert



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