Weather

006 
fxus63 kfsd 070142 
afdfsd 


Area forecast discussion for southeast South Dakota/southwest Minnesota/northwest Iowa 
National Weather Service Sioux Falls South Dakota 
842 PM CDT Sat Sep 6 2008 


Discussion... 
made some changes to the timing of precipitation tonight. Initial 
shortwave that brought the light to occasionally moderate rain to 
the area has pretty much moved out with only some light showers 
around Jackson Minnesota at 830 PM CDT. Expect a period of quiet weather 
after this for about 6 hours before next shortwave moving across 
northern South Dakota swings a cold front aloft through the area. This will 
bring a band of showers...which should decrease in coverage as you 
travel south of the shortwave...through with the best chance for 
additional rainfall over the northern tier of counties. 
Otherwise...lowered evening temperatures a little as temperatures 
did not recover much behind area of precipitation. Will also have to 
watch for fog potential...mainly over northwest Iowa...with light 
winds and a period of clear skies. If the shortwave to the northwest 
is strong enough to bring showers and cloud cover through...this 
threat may be minor and confined mainly to low spots. 


08 


&& 


Aviation... 
mainly VFR through the night with a few showers possible at Hon and 
fsd. Some fog also possible at sux and fsd late tonight. Conditions 
should remain VFR in showers but could fall to IFR in fog. 


&& 


Previous discussion... 
north to south oriented band of showers/isolated thunderstorms will 
continue to work east late this afternoon into the early evening 
hours across the forecast area. This activity has developed in 
response to weak shortwave moving through. Subsidence behind the 
wave appears to be fairly limited...with diurnally driven showers 
developing across central and western portions of the state. Expect 
these showers to remain across mainly west of the James River Valley 
and die with sunset. Remaining showers to the east should become 
more oriented northwest to southeast this evening into the overnight 
as low level boundary interacts with midlevel wave. Have increased 
probability of precipitation through the overnight period...with 0.05-0.15 of moisture 
expected in most locations. Best chances of precipitation appear to 
be in northern and eastern portions of County Warning Area. 


Still very busy pattern through the forecast...with main issues how far 
north the Monday system gets and how fast Wednesday night system moves east. 
Still somewhat unstable for sun as weak trough moves east...with 
main chance rain showers in northestern County Warning Area in the morning...then a nice break for the 
afternoon over the County Warning Area. Models pretty strong with wave for Sun night and 
Monday...but GFS too far north with main quantitative precipitation forecast boundary and also a lit 
on the fast side. Went more with the south bias of the other 
models...but measurable rain still quite possible to the north...with 
a cool rain to the south in the County Warning Area. Certainly expct more flip/flops 
of the models with this system...and next few runs of the GFS will 
most likely revert to the south. Clearing out from northwest to southeast in County Warning Area for Monday 
night with good radiational cooling expected. Nice warming with south 
winds spreading east over the County Warning Area for Tuesday through Wednesday...along with expected 
return of low level moisture for late Tuesday night through Wednesday. So kept the 
probability of precipitation going for southern County Warning Area late Tuesday night and mainly eastern County Warning Area for Wednesday as 
low level southerly jet interacts with dynamic westerly flow aloft. The main 
dynamics and chances thunderstorms excpd with main upper trough and cold front Wednesday 
night...moving off to the east on Thursday. Models look pretty consistent 
bringing return southerly flow of warmer air for Friday afternoon into Sat...and 
went warmer than the previous forecast close to HPC guidance. 


&& 


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


&& 


$$ 
Bt/rsr