393 
fxus63 kunr 061002 rra 
afdunr 


Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota 
401 am MDT sun Jul 6 2008 


Discussion...09z surface analysis shows low pressure over Ontario with 
a trough extending into eastern Colorado. WV imagery shows a 
shortwave currently crossing the area. The shortwave and some weak 
Theta-E advection have combined to produce a couple of areas of 
showers and thunderstorms over western and south central South 
Dakota with isolated -tsra over portions of southeast Montana and northwest South Dakota. 


A stronger shortwave will aprroach this area this afternoon. 
Southeasterly surface winds will provide some upslope oriented flow 
over NE Wyoming with increasing ll moisture pushing ml cape to 
1000-1500j/kg. The capping inversion is expected to errode by middle to 
late afternoon allowing some thunderstorms to develop. There will be 
enough shear over northeastern Wyoming and far southwestern South 
Dakota for the possibility of severe thunderstorms with large hail 
and damaging wind gusts during the afternoon and evening. The 
shortwave will continue eastward across the area tonight...with 
thunderstorms spreading east. Some showers and thunderstorms may 
linger into Monday morning over central South Dakota. Instability 
will increase south and east of a cold front on Monday 
afternoon...leading to another chance of thunderstorms...mainly over 
western and central South Dakota during the afternoon...and over 
southwestern and south central South Dakota during the evening. Upper ridge 
will beging to rebound over the area on Tuesday leading...to a dry 
day with seasonable temperatures. 


Extended...upper ridge builds over the western Continental U.S. Towards the 
middle into the end of the upcoming work week...bringing above 
average temperatures to the area. Dry conditions are expected. 


&& 


Aviation...scattered showers and thunderstorms are expected through this 
evening...bringing some areas of MVFR conditions. Some storms may 
become strong over northeast Wyoming into far western South Dakota 
this afternoon and evening...with gusty winds and hail possible. 
Otherwise...VFR conditions are expected. 


&& 


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


$$