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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Tuesday
• 
• High: 84 °
• Low: 63 °
• T-Storms

• Wednesday
• 
• High: 79 °
• Low: 57 °
• Chance of T-Storms

• Thursday
• 
• High: 72 °
• Low: 48 °
• Chance of a Thunderstorm

• Friday
• 
• High: 77 °
• Low: 45 °
• Partly Cloudy

• Saturday
• 
• High: 73 °
• Low: 54 °
• Partly Cloudy

Area forecast discussion...updated aviation 
National Weather Service St Louis MO 
629 am CDT Tuesday may 21 2013 


Short term...(through tonight) 
issued at 348 am CDT Tuesday may 21 2013 


Focus through this period will be thunderstorms and rain chances. 


Surface analysis at 07z depicts the effective surface bndy across western Iowa 
into northwestern MO...then extending southwestward into eastern Kansas. Believe this is some 
sort of pre-frontal trough/dry line as it appears the actual surface fnt 
is still across eastern Nebraska into western Kansas. This trough/dry line should move 
eastward rather slowly today. 


A number of questions remain about today given the spread among model 
solutions. Expect ongoing precipitation to gradually move eastward out of the County Warning Area 
later this morning. Believe isod to scattered thunderstorms and rain will develop this 
afternoon along the trough/dry line. Setup today does not appear as 
favorable for severe weather today compared to yesterday. 
However...believe the GFS/NAM are underplaying the event today and 
tonight for the County Warning Area. 


Models forecast convection over arklatex region this afternoon/evening lifting 
northeastward tonight into the County Warning Area. This thunderstorms and rain will be driven by a vorticity maximum 
currently over northern nm/southern Colorado region. Models to some degree...except 
for the NAM...develop a surface wave along the surface trough tonight. This 
low should travel northeastward along the surface trough. The European model (ecmwf)/local WRF have a 
more northwestern solution and this seems reasonable as these models have a fairly 
good handle currently on the strength of this system. If this solution 
verifies...this low will provide enhanced shear as well as allow 
steeper lapse rates to advect into the area. Given forecasted hodographs 
and timing...believe thunderstorms and rain will be linear by the time they enter the 
County Warning Area. 


If this northern solution is correct...the day shift may need to consider a 
Flash Flood Watch for eastern portions of the County Warning Area. 


As for temperatures...trended at or above warmest MOS for today and cooler for 
tonight as the actual cold front finally moves through the area. 




Tilly 


Long term...(wednesday through monday) 
issued at 440 am CDT Tuesday may 21 2013 


Focus starts to shift to temperatures as precipitation finally moves east of the 
area. 


With focus on today and tonight...only minor changes were made to 
the previous forecast as much of it still appears to be on track. Models 
are in remarkably good agreement through the period with respect to mass fields. 


Uncertainty remains for temperatures on Wed/thurs. Models suggest temperatures 
will struggle to reach 70s. However...given that it is may...if 
any sun manages to make it through the clouds...would be surprised if 
temperatures did not at least briefly reach upper 70s or into the lower 
80s. With upper ridge building into the area on Sat and 
beyond...temperature forecast becomes more questionable with differing 
solutions at the surface. For now...made only minor changes...but believe 
a trend toward the GFS may be needed with a warmer and drier solution. 


Tilly 


&& 


Aviation...(for the 12z tafs through 12z Wednesday morning) 
issued at 617 am CDT Tuesday may 21 2013 


VFR conditions expected this morning as overnight convection has 
shifted south of the County Warning Area. Next upper level disturbance currently 
crossing the Southern Plains will lead to an increase in showers 
and thunderstorms ahead of a slow moving cold front late this 
afternoon and this evening. Rain chances to finally come to an end 
for terminals around sunrise Wednesday as the cold front moves 
east with winds shifting from the southwest to the west. 


Specifics for kstl... 
VFR conditions expected this morning with thinning cloud cover. 
Showers and thunderstorms expected to increase in coverage once 
again late this afternoon and evening...with cold frontal passage 
between 09z and 12z. 


Cvking 


&& 


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


$$ 


Weather forecast office lsx