Area forecast discussion 
National Weather Service Omaha/valley NE 
1211 PM CDT sun Sep 21 2014 

Short term...(today through tuesday) 
issued at 311 am CDT sun Sep 21 2014 

..rain chances Monday nt and Tuesday continue to be the primary forecast 

A unique upper flow pattern will determine the weather...and 
specifically the rain chances...through the next several days over 
the forecast area. Water vapor loop and upper air data indicates this 
pattern consists of an upper ridge that currently extends from 
the southern rockies into British Columbia...and a slow-moving 
cutoff upper low that has been lingering on the west side of the 
upper ridge axis...currently sitting over California. The surface 
reflection of the upper ridge was a 1026 mb surface high centered 
over eastern Montana...representing a dry airmass that has worked 
into the forecast area. 

This dry airmass and surface high will keep quiet and dry weather 
in place through Monday. However by Monday evening the upper low 
over California is expected to drift into the upper ridge and make 
its way into the northern High Plains of Wyoming and Montana. 
There is very good model agreement with the position of this 
low...and the run-run consistency is also high. Model trends are 
toward slightly higher heights with the upper low...but generally 
the consistency is quite good. 

With similar model agreement...cyclogenesis over the northern 
High Plains is prognosticated Monday night with the surface high moving 
east of the Mississippi River and strong south flow setting up 
over the plains. Expect any rain Monday night to be confined to 
central Nebraska...with perhaps a few light showers trying to 
overcome the dry air and move as far east as Columbus and Norfolk 
late Monday night. 

On Tuesday the upper low moves into the Dakotas with associated 
upper trough extending into the Southern Plains...the surface low 
deepens to our west...and enough moisture returns to support 
precipitation over all of our forecast area. Instability should be 
limited so we mainly expect rain showers with a few embedded 
thunderstorms. Probability of precipitation range from chance in the east to likely in our 
western counties. Temperatures will be held down a few degrees on 
Tuesday from the rain/clouds...with upper 60s - low 70s common. 

Long term...(tuesday night through saturday) 
issued at 311 am CDT sun Sep 21 2014 

The pattern on Tuesday generally remains in place into 
Wednesday...but model solutions quickly diverge after Wednesday 
night. In addition...subsidence from the upper ridge should be 
overtaking the upper low with an overall weakening of the vertical 
motion associated with it. Models show 500 mb heights at or above 
5880 meters in the upper ridge...with weak upper flow and warming 
aloft. This should suppress convection most areas. Therefore kept 
probability of precipitation Tuesday night into Wednesday night...but have a dry forecast 
for Thursday through Saturday. 

Temperatures under the upper ridge should return to near or 
slightly above normal values in the upper 70s by the end of the 


Aviation...(18z tafs for kofk...klnk and koma.) 
Issued at 1210 PM CDT sun Sep 21 2014 

VFR conditions through the period. Northwest winds around 13 knots 
with gusts up to around 20 knots through about 23-00z...then light 
and variable winds beyond then. 


Oax watches/warnings/advisories... 


Short term...nietfeld 
long term...nietfeld 

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