801 
fxus63 kdmx 282355 aaa 
afddmx 


Area forecast discussion 
National Weather Service Des Moines Iowa 
655 PM CDT Thursday Aug 28 2008 


..updated aviation discussion... 


Discussion... 
primary surface boundary now extends from southeast Iowa through 
northwest Missouri and northern Kansas. Low level moisture remains 
high north of this boundary with dewpoints in the upper 60s to lower 
70s. Secondary boundary advecting the drier air south is over 
northwest Iowa with dewpoints in the 40s in its wake. A fair amount 
of low level instability exists over south central Iowa with 100 mb 
ml convective available potential energy of 2000 to 3000 j/kg reside. Effective deep layer shear of 
> 45 kts is supportive of a few severe storms and 0-3 km convective available potential energy to 
125 j/kg suggests that the low level cin is eroding. Narrow time 
window for severe potential over southern forecast area as this 
region is squeezed by dry push from the north. Much of the area 
should be precipitation free by 00z. Have added fog mention for late 
tonight with light winds and widespread 0.75 to 1.5 inches of rain 
that fell last night. Dry air advecting in may limit this potential 
and will keep it from being widespread. 


High pressure takes control on Friday with pleasantly low dew points 
in place. High pressure dominates through Monday with highs in the 
80s and a fair amount of sun. A frontal boundary is due to arrive 
over the Midwest around middle next week. Timing details likely will 
delay a bit from what current guidance as influence of high pressure 
departing to the east. The high may be delayed pending interference 
from either Tropical Storm Hanna or Gustav to the overall flow. 


&& 


Aviation...29/00z 
the cold front is pushing out of Iowa and drier...cooler air is 
working in. VFR conditions across the County Warning Area through the forecast period with a light 
nwrly wind. Some fog potential south where the recent rain fell... 
especially around kotm so I put a brief period of MVFR visibility due to br. 


&& 


Dmx watches/warnings/advisories...none. 


$$ 


Long term...donavon 
short term...Kinney 
aviation...fab