Weather

620 
fxus63 kfsd 071540 
afdfsd 


Area forecast discussion for southeast South Dakota/southwest Minnesota/northwest Iowa 
National Weather Service Sioux Falls South Dakota 
1040 am CDT sun Sep 7 2008 


Discussion... 
only minor changes made to the extended this morning. Band of high 
clouds expanding across the southern half of South Dakota this 
morning will lead to a mostly cloudy if not cloudy day across the 
area. This is all developing in advance of a fairly strong band of 
750-700 mb frontogenesis that sets up across the souther County Warning Area 
tonight. Could see scattered showers move into southwestern corner 
of County Warning Area this afternoon...and then continue to spread east overnight. 
Placement of probability of precipitation was fairly good in previous forecast...but have 
increased probability of precipitation in southern County Warning Area in tonight period. With all the cloud 
cover across the area today...mixing will be reduced and have 
lowered highs a few degrees. /Bt 
&& 


Aviation... 
atmosphere will saturate from aloft as a middle level disturbance moves 
from northeast Wyoming into southern South Dakota. Rain showers 
will develop Sunday night into Monday...mainly south of Interstate 
90. Lower clouds in the lower end of the mfr range to near IFR 
conditions are expected as disturbance moves through. 


&& 


Previous discussion... 
weak short wave generating scattered rain shower- mainly north of i90 and east of James River Erly 
this morning. This should push eastward across eastern County Warning Area Erly this morning and should 
be out of area by 14 or 15z. Areas of fog ahead of this feature across 
SW Minnesota and northwest Iowa should also dissipate Erly this morning with passage of 
short wave. Should see a little sun today before more clouds roll in from the west 
during the afternoon. 


Fairly strong short wave will push eastward across the plains tonight and Monday with strong 
middle level fntrgen along and S of i90. Should see a widespread area of rain 
develop tonight along and S of i90 and spread eastward later tonight into 
Monday. Will go with high probability of precipitation S of a 9v9-fsd-mwm line espec for later 
tonight into Monday morning. Precipitation may have a sharp cutoff further 
north...but hard to pinpoint exactly where...so will keep a small pop across 
the far north tonight into Monday. System should pull away Monday afternoon and will end 
rain from west to east on Monday. Widespread clouds and rain will keep temperatures quite 
cool on Monday...and may not reach 60 across southeastern County Warning Area. Even with some sun 
in the afternoon farther west and northwest...still will not get out of 60s. Pbly will 
see a good soaking rain of at least 1/2 inch S of i90 tonight through 
Monday morning. Surface high will slide southeastward into County Warning Area Monday night and should bring 
some clearing. With light winds and moist ground...will likely see some 
areas of fog late Monday night and Tuesday morning...so did mention in forecast 
eastern County Warning Area. 


Warmup begins Tuesday but did cool temperatures a few degree eastern County Warning Area as low level 
flow will be southeasterly from rain cooled airmass. Better warmup on Wednesday ahead 
of short wave and cold front. Models a little slower on this feature and best chance 
for thunderstorm may hold off until Wednesday night into Thursday morning. So will trim probability of precipitation 
back slightly during the day on Wednesday. 


Later periods will remain unchanged although GFS hinting at a wet Friday night 
and Sat. 




&& 


Fsd watches/warnings/advisories... 
South Dakota...none. 
Minnesota...none 
Iowa...none. 
NE...none. 


&& 


$$