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fxus63 koax 082131 
afdoax 


Area forecast discussion 
National Weather Service Omaha/valley NE 
331 PM CST Thursday Jan 8 2009 




Short term...tonight through Sunday. 
Currently...a broad upper level ridge of high pressure is situated 
over the western Continental U.S....and a deep upper level low is continuing to 
press eastward across the northeast. An upper level shortwave trough 
across the Pacific northwest is currently moving eastward. The timing of this 
wave and associated cold frontal passage through the County Warning Area will be 
the main forecast concern in the short term. The 12z GFS has the 
frontal passage a smidgen faster than the 18z NAM...however both show the 
strongest cold advection swinging through the County Warning Area by 18z. 
Southwest flow into the region tonight will keep temperatures 
rather mild...with temperatures starting tomorrow in the middle 20s 
north to 30s south. Though GFS 850 mb temperatures are generally cooler 
through the day than predicted by the NAM...strong northwest winds 
behind the front will promote temperatures rising to the middle 30s 
along and north of the i80 corridor to middle 40s across the southern County Warning Area 
by 18z before strong cold advection plunges south. In the north 
temperatures are not expected to rise much due to increasing 
clouds and infiltrating cold air. Will maintain a slight chance of 
precipitation tomorrow afternoon and evening as the main upper level trough 
swings through the County Warning Area. Forecast soundings suggest a brief period 
of wintry mix is possible with the initial onset of 
precipitation...but the rapidly cooling atmosphere will lead to a 
rapid change to light snow. 


Relatively quiet weather is expected the remainder of the weekend. 
Sunny but cool conditions will persist on Saturday and Sunday as an 
area of high pressure resides over the forecast area. Sunday should 
be a little warmer than Saturday due to southerly return on the back 
side of the progressing high pressure. 




Long term...Sunday night through Thursday. 
The extended period will be dominated by fast moving weather systems 
and an expanding area of Arctic air by day7. The main snow track 
appears to remain to the northeast of the County Warning Area with bouts of light 
snow and flurries for the local area. 


Sunday night into Monday...a clipper will move through the northern 
plains. The European model (ecmwf)/GFS are still off on their timing by about a 
state...thus big bust potential on temperatures with each system due to 
timing. Warm air ahead of the surface low overnight..then the surface low 
slides southeast. Lows in the teens and 20s and highs in the 
20s/30s. Organized light snow should be northeast of the surface low from 
the Dakotas in Minnesota and Iowa. The County Warning Area is on the western edge of 
the accumulating snow...so have low probability of precipitation east and flurries through 
Monday night. Gusty northwest winds expect late sundy night into Monday 
and winds may be strong enough for a Wind Advisory. The winds 
should drop off by Tuesday morning with single digit lows. 
Snowcover or lack of will also affect temperatures. 


Surface high pressure will build in and then slide east by Tuesday 
afternoon. Again the favored storm track is to the east of the forecast 
area. Still several hundred miles difference in the track of the 
surface low and this will impact temperatures and timing of the push of cold 
air. Highs Tuesday in the teens and 20s. Lows Wednesday single digits 
above and below zero. More light snow and flurries possible Tuesday 
and Tuesday night. Wednesday looks cold and dry. Both the European model (ecmwf) and the 
GFS have a reinforcing push of cold air Wednesday night with bitter cold 
air. Pattern supports highs in the single digits. The 12z European model (ecmwf) 
has backed off to a 1046 high compared to a 1050+ high and both 
GFS/European model (ecmwf) bring return flow into the Western Plains by 00z Friday. 


&& 


Aviation... 
for taf sites kofk/koma/klnk through 09/18z. 


VFR conditions will prevail all sites until cold frontal passage through eastern Nebraska 
by the way 09/09z-18z. MVFR ceilings will accompany wind shift to the 
northwest...around 091100 at kofk/091500 at koma/091600 at klnk. 
Also...there is a threat for ws020/25045kt beginning at 090600 
mainly for koma and klnk. Have opted though not to include until 
next taf issuance due to uncertainties at this time. 


&& 


Oax watches/warnings/advisories... 
NE...none. 
Iowa...none. 
&& 


$$ 


Short term...Kurtz/dergan 
long term...zapotocny 
aviation...Dee