329 
fxus63 kfsd 060150 
afdfsd 


Area forecast discussion for southeast South Dakota/southwest Minnesota/northwest Iowa 
National Weather Service Sioux Falls South Dakota 
845 PM CDT Sat Jul 5 2008 


Discussion... 


Low level boundary hung up from near abr to 9v9 to vtn to bff at this time. Broad 
tongue moist air around 850 mb and below pooled either side of boundary 
from eastern to central South Dakota to central NE...capped off in central South Dakota with 700 mb 
temperatures around 14c...explaining why there is nothing going on excpt some 
altocumulus castellanus at this time. Models not much help as NAM going convective into southeastern 
South Dakota early tonight based on low level instability and convergence...and GFS 
having its typical convective feedback bulleyes tonight. However...in 
depth 00z analysis also shows middle level cooling asscd with several thunderstorms 
moving through southeastern Mont towards western South Dakota at this time...with possible right rear quadrant 
of jet maximum moving east towards northern County Warning Area late tonight. This all may at 
some point break cap and light up the boundary in vicinity northwestern County Warning Area after 
midnight tonight...with a possible mesoscale convective system moving east-southeastward through northern and eastern County Warning Area late 
tonight into Sun morning. Chance probability of precipitation may cover it for now as nothing is 
happening...but may have to be uppd quite a bit if cap breaks with 
any convection developing near boundary later this evening. In the meantime... 
basically status quo in zone forecast product with usual fine tuning of grids. 


Ryrholm 


&& 


Aviation... 
VFR conditions will continue through period. Expect scattered thunderstorms and rain 
development around 06z in north central South Dakota and slowly sag 
southeast. Would only expect a brief period of MVFR conditions as 
thunderstorms and rain move through. 


&& 


Previous discussion... 
13 to 14 degree cap in place over much of County Warning Area today and with cloud 
cover over central South Dakota preventing highs from reaching convective 
temperatures...I don't expect any storm development until front and cooler 
air moves into place later this evening. Bought off on GFS solution 
of convection developing in ND and then it back building into South Dakota 
tonight. Mesoscale convective system should form tonight and move into southwestern Minnesota and northwestern Iowa 
towards morning. Southward extent of precipitation is up in the air...but 
don't expect much in southwestern portion of County Warning Area. Severe chances are 
there...but right now I would expect a hail threat early...then 
evolve into a wind and heavy rain event. 


Sun should see remaining convection will be sliding southeastward through northwest Iowa and 
should exit the area by middle morning. Short wave will push fnt into far southern County Warning Area by 
afternoon and may be the focus more more thunderstorm by late middle to late afternoon as 
short wave moves across northern Nebraska. Will go with highest probability of precipitation across the S Sun afternoon 
into Monday morning. Will remain active on Monday as yet another short wave tracks eastward 
across South Dakota. GFS seems to be too far S across Nebraska with model concensus 
further north across South Dakota. So with that in mind will go with scattered thunderstorm across County Warning Area 
Monday afternoon exiting eastern County Warning Area Monday night. This could be a more widespread 
soaker as opposed to the systems tonight into Sun night. Temperatures both 
sun and Monday will greatly be affected by cloud cover. Will pbly see less 
cloud Sun afternoon as opposed to Monday afternoon so will go with warmer temperatures 
sun. 


Cold front will drop southeastward across County Warning Area Tuesday and will bring cooler air into County Warning Area 
for Wednesday. Will keep small probability of precipitation across County Warning Area Tuesday afternoon adn evening with this 
fnt...but instabil is not all that great. 


In the extended...will keep forecast dry through Friday...with another chance thunderstorm 
Sat as next fnt moves through. 


&& 


Fsd watches/warnings/advisories... 


South Dakota...none. 
Minnesota...none. 
Iowa...none. 
NE...none. 


&& 


$$