362 
fxus63 kunr 202047 
afdunr 


Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota 
247 PM MDT Sat Mar 20 2010 


Discussion...20z analysis shows high pressure and clear skies over 
the northern plains. Dewpoints are in the single digits and teens 
across the forecast area today. Expect to see temperatures fall 
quickly this evening...then possibly warming across northeastern 
Wyoming and and the Black Hills area after midnight. Sunday will be 
mostly sunny and warm. Due to the thermal ridge axis across the area 
temperatures will recover into the middle 50s to middle 60s by afternoon. 


The upper ridge will shift off to the east on Sunday night in 
response to an upper trough approaching from the Pacific northwest. 
A surface cold front will cross the area on Monday afternoon. Most areas 
will see high temperatures in the middle 50s to middle 60s before the cooler air 
moves in. There will be enough instability for some Post frontal 
-shra with an isolated thunderstorm or two on Monday afternoon and 
evening...with a chance of snow showers on Monday night as 
temperatures continue to cool. 


Extended...northern stream shortwave and cold front will slide east 
of the area Tuesday...with some lingering showers possible on the 
backside. Temperatures will be noticeably cooler behind the front on 
Tuesday...with highs in the upper 30s and 40s. Weak upper ridging 
will build in from the west as western Continental U.S. System slides southeast 
across the Southern Plains during the middle part of the week. Dry 
weather and mild temperatures will return for Wednesday and 
Thursday. Some unsettled and cooler weather could return for the end of 
the week and into the weekend...but medium range models remain 
rather unclear at this point. 


&& 


Aviation...VFR conditions can be expected through the forecast 
period. 


&& 


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


$$