Weather

769 
fxus63 klsx 281817 
afdlsx 


Area forecast discussion 
National Weather Service St Louis MO 
117 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... 
/1242 PM CDT Thursday Aug 28 2008/ 
for the 18z tafs... 
main concern for this period is the ongoing convection north of the stl 
metropolitan and timing of afternoon convection that should develop along the 
cold front. The area of thunderstorms north of the stl metropolitan area is 
ongoing from this mornings mesoscale convective system. Original thinking was that it would 
weaken during the middle-morning hours. Obviously it has not and at this 
point do not expect it to. The thunderstorms have continued to move to the southeast 
during the morning and expect this trend to continue. Have added thunderstorms in the vicinity 
to the stl taf to account for the tail end of this cluster passing by 
to the NE. Still expect convection to develop along the cold front over 
northern MO this afternoon in the 20z- 21z time frame. Current thinking 
is that it will develop into a line and push southeast affecting uin and cou 
late this afternoon and early this evening and the stl metropolitan area late 
evening and overnight. With skies clearing overnight..introduced MVFR fog 
during the early morning hours. 


Miller 


&& 


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


$$ 


Weather forecast office lsx