Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Omaha/valley NE
339 PM CST Wednesday Dec 4 2013
Short term...tonight through Friday night.
Forecast concerns tonight will be light snow and flurry potential
and the strong winds and cold wind chills.
At 18z...the 500 mb trough extended from North Dakota west toward Utah.
The bulk of the organized precipitation had shifted into northern
Wisconsin and parts of southern and central Minnesota with a few
flurries and blowing snow in northeast Nebraska. Northwest winds
at 15 to 30 miles per hour with stronger gusts were common across the area
with temperatures only in the teens and 20s.
Tonight...the very cold airmass will continue to deepen with
continued strong northwest winds. Meanwhile...an upper level jet
segment across Colorado will move across Nebraska into northwest
Iowa. The short-range models...18z NAM/12 GFS/4km
WRF/hopwrf/rap/hrrr are indicating that with this feature...middle
level frontogenesis increases along with some upper level support
and a band of light snow may try to develop. There are some
differences in how far north the band may develop...some say bie
to Glenwood south...while others lnk to Oma south. There may be
some saturation issues which could hinder snow. For now...have
increased probability of precipitation in southeast Nebraska and southwest Iowa...with the
best chance south of a line from bie to Red Oak...but still did
include some slight chance probability of precipitation farther north toward Omaha and
flurries elsewhere. Most likely it would be a dusting with amounts
less than a half an inch. Should the band develop...it would band
quickly shift out of the area by 4am.
With the combination of strong northwest winds 15 to 20kts
sustained and cold temperatures...did include a few counties in
northeast Nebraska in a Wind Chill Advisory...mainly after 10pm
through Thursday morning. Temperatures will get even colder
Friday and Saturday morning...however the winds will not be nearly
Cold temperatures continue right through Saturday with highs in
the teens and 20s.
Long term...Saturday night through Wednesday.
Cold temperatures are forecast in the extended period...with slow
moderation towards days 6 and 7. Models are consistent with a deep
middle level trough moving across the plains starting Saturday night
through Monday. This will bring in measurable snow to
Kansas...Nebraska and Iowa starting Saturday night. In addition
another shot of Arctic air will follow the precipitation into next
week. Differences between the European model (ecmwf) and GFS are minimal for the
precipitation event Saturday and Sunday. The 12z European model (ecmwf) has a
sharper amplitude trough versus the GFS...which is broader. In the
Monday through Wednesday time frame...there are only minor
differences in the models. A warm up is forecast from Monday through
Wednesday. High temperatures are currently forecast to rise from
10 to 15 on Monday to the middle 20s by Wednesday.
18z tafs for koma...klnk and kofk.
Current observation indicate areas of -sn along and west of an axis from
about kfsd to khde. -Sn activity was tracking NE in association
with an upper disturbance moving toward the Dakotas. Kofk was
reporting -sn...but radar trends suggest activity is n0t making
much of a push east. Suspect -sn will continue the next couple
hours at kofk thus will maintain tempo group till 21z.
Otherwise...MVFR ceilings extended from eastern Nebraska to over most of Kansas.
However expect VFR ceilings fl050 above ground level currently over central Nebraska will
gradually move east...allowing for improving conditions at all
terminals late this afternoon/early evening time frame. Seems likely at
this point that VFR ceilings will persist then through the rest of the
forecast period at all sites.
NE...Wind Chill Advisory from 10 PM this evening to 11 am CST
Thursday for nez011-012-016-017.