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Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota 
243 am MST Monday Nov 23 2009 


Discussion...09z surface analysis had weak low over the Black 
Hills with cold front into Colorado and trough into eastern Montana. These 
features a reflection of upper level trough from Montana into Colorado. One 
wave over Montana...but main wave starting to take over in southwest Wyoming 
in response to 90kt jet digging into base of trough. This wave 
will close off as upper low over Kansas tonight. With main forcing now 
further south...have tempered probability of precipitation for today/tonight...especially 
in the south. We/ll see low coverage -shsn today/tonight...with 
mixed -shra this afternoon. Best chances will be along the far 
southern borders of the County Warning Area. Temperatures near guidance. 


Tuesday...transient short wave ridge will bring some 
sunshine...but next fast moving upper level trough will already be 
impacting ND/Montana by evening. Moisture/forcing on tail end of wave 
sufficient for a chance of -shsn Tuesday evening. Breezy spots 
also as cold front brings cold air advection...especially in the 
east. Temperatures near guidance. 


Wednesday...upper trough spins as upper low into Illinois. Upper ridge 
builds over The Rockies...beginning to affect the County Warning Area. Temperatures 
near guidance. 


Extended...an upper level ridge will keep conditions warm and dry 
through Friday afternoon. Next upper wave moves over the West 
Coast Friday and starts pushing east this weekend. This will bring 
cooler temperatures and possibly some precipitation. 


&& 


Aviation...a few areas of -shra or -shsn will be possible today as 
an upper level disturbance moves through. Most areas will remain 
VFR...though some MVFR ceilings may be possible over the Black Hills. 


&& 


Unr watches/warnings/advisories... 
South Dakota...none. 
Wyoming...none. 
&& 


$$ 


Helgeson/schild