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Area forecast discussion...updated aviation 
National Weather Service St Louis MO 
604 PM CDT Thursday Aug 28 2008 


Discussion... 
/114 PM CDT Thursday Aug 28 2008/ 
leftovers from mesoscale convective system continue to slowly advect south across extreme 
eastern Missouri and western Illinois early this afternoon. This has 
held temperatures back across west central Illinois and backed 
winds to the east. Believe this area of convection will continue 
to move south across southwest Illinois this afternoon...before 
more convection develops later this afternoon along the cold front 
that is currently positioned to our northwest. 


In fact...atmosphere continues to destabilize across the western 
half of the County Warning Area with dewpoints rising into the lower 70s and 
temperatures near 90 degrees. Deep layer shear of 30kt will keep 
primary Mode of convection multicell...therefore large hail and 
damaging winds will be threats with thunderstorms that become 
severe. Will have to carefully watch storms that interact with the 
outflow boundary layed out across the County Warning Area...enhanced storm 
relative helicity could aid in tornadogenesis. 


Convection should weaken late this evening with loss of diurnal 
instability...as front progresses through the remainder of the County Warning Area. 


A beautiful Holiday weekend looks to be in the offing as high 
pressure builds across the Midwest. Mostly sunny conditions and very 
comfortable temperatures/humidity can be expected as we close out 
another Summer vacation season. 


The center of high pressure will gradually move to the east of the 
area by Monday with temperatures moderating to seasonal normals and 
humidity slowly building back into the area. Temperatures in the 
upper 80s to near 90 degress should be the rule Monday and Tuesday. 


Many questions remain in the extended as Hurricane Gustav will 
surely slow down the mean flow across the United States next week. 
Expect it to delay the progression or stall the shortwave/front that 
approaches our County Warning Area on Wednesday. Current indications are that the 
remnants of the tropical system will then move directly across our 
County Warning Area. Heavy rain and flooding will certainly be possible next 
Thursday/Friday if this scenario is correct. Stay tuned! 


Cvking 


&& 


Aviation... 
/530 PM CDT Thursday Aug 28 2008/ 
for the 00z tafs...cold front currently extending from WI SW through northwestern MO to 
the Texas Panhandle will move southeastward through the County Warning Area tgt. Numerous thunderstorms and rain have 
developed along this fnt from near mkc to near irk at this time. This thunderstorms and rain activity 
will shift southeastward with the cold front. Thunderstorms and rain should move through uin and cou 
from 01-05z...and through stl/sus from 03-07z Friday. The southerly surface winds will 
veer around to a northwesterly direction tgt after passage of the cold front. The 
cold front should make it down to the stl metropolitan area around 06-07z Friday. 
Although the surface dewpoints will be lowering behind the cold front fog may 
develop in uin and cou lt tgt and early Friday morning with a clearing sky and 
saturated ground from Thursday evening rainfall. Cloud cover in stl/sus will 
probably not scattered out until after sunrise Friday morning. Surface winds will be 
northerly on Friday as a surface ridge builds southeastward through the County Warning Area behind the cold front. 


Gks 


&& 


Lsx watches/warnings/advisories... 
MO...none. 
Illinois...none. 
&& 


$$ 


Weather forecast office lsx