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fxus63 kunr 022124 
afdunr 


Area forecast discussion for western South Dakota and northeastern Wyoming 
National Weather Service Rapid City South Dakota 
224 PM MST Tuesday Dec 2 2008 


Discussion...the cold front has passed through most of South 
Dakota this afternoon as the upper level trough pushes into the 
northern plains. Snow has started across the northern third of the 
County Warning Area already with the precipitation continuing to push southward. 
Northerly winds have increased to around 20 kts and temperatures have 
been falling at most locations this afternoon. As the precipitation moves 
south...most areas will see rain that quickly changes to snow as 
the cold air moves in. 


Strong frontogenesis will move through western South Dakota 
this evening bringing the precipitation right through the County Warning Area. This is a 
fast moving system and many locations may pick up a couple of inches 
rather quickly this evening as it passes through with total snow 
accumulations across the plains at 2 to 4 inches. This snow combined 
with gusty north to northwesterly winds will cause visibilities to 
drop and create some travel problems. The Northern Hills can expect 
an area of upslope snow to develop late this afternoon and evening 
as winds and relative humidity increase. Precipitation should diminish by Wednesday 
morning. 


Another wave moves through Wednesday afternoon producing another 
chance for snow showers. Upslope snows over the Northern Hills are 
expected to continue off and on throughout the day. Additional 
accumulations should be minimal Wednesday. Conditions dry out 
Thursday as cold Canadian high pressure moves into the area...have 
decreased temperatures a bit again as it should be a chilly day. 


Extended...cold high pressure will shift east of our area on 
Friday...and northwest flow aloft will gradually weaken as an upper level 
ridge of high pressure begins building in over the weekend. Latest 
GFS/European model (ecmwf) both show a long wave trough progressing through the plains 
states early next week which could bring additional precipitation to the 
region. Temperatures for the most part should remain near to slightly above 
average. 


&& 


Aviation...IFR conditions will develop across northestern Wyoming and western South Dakota as 
snow spreads across the region...with gusty northwest winds to 40 miles per hour 
creating areas of blowing snow and significantly reduced visibilities. 
Conditions will gradually improve later overnight with mostly VFR 
conditions expected on Wednesday. 


&& 


Unr watches/warnings/advisories... 
South Dakota...Winter Weather Advisory until 5 am MST Wednesday for Butte- 
central Black Hills-Haakon-Harding-northern Black Hills- 
northern foot hills-northern Meade Colorado plains-Pennington Colorado 
plains-Perkins-Rapid City-southern Meade Colorado plains- 
Sturgis/Piedmont foot hills-Ziebach. 


Winter Weather Advisory until 5 am MST /6 am CST/ Wednesday for 
Bennett-Custer Colorado plains-Fall River-Hermosa foot hills- 
Jackson-Mellette-Shannon-southern Black Hills-southern foot 
hills-Todd-Tripp. 


Wyoming...Winter Weather Advisory until 5 am MST Wednesday for 
northeastern Crook-northern Campbell-southern Campbell- 
western Crook-Weston-Wyoming Black Hills. 


&& 


$$