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fxus63 keax 211141 
afdeax 


Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO 
541 am CST Sat Nov 21 2009 


..updated aviation discussion... 


Discussion... 


Dense fog will be the short term problem as much of northern MO is 
experiencing visibilities a quarter of a mile or less. Conditions 
will improve by late morning as the fog lifts to form a stratus 
deck. Satellite imagery also shows a low cloud deck tied to deeper 
moisture advecting north from TX/OK/AR. A weak west-east surface ridge 
cutting through the center of the County Warning Area divides dense fog to the north 
and the low clouds to the south. This ridge axis is expected to 
fall apart to day as surface troughing over the High Plains pushes 
east and displaces the ridge...thus allowing the low clouds to 
spread into northern MO. Special fog loop suggests the dense fog is 
rather shallow and likely to burn off by middle morning. By this time 
the low clouds should be working their way into northern MO. The net 
effect is sunshine could be in short supply today. Maximum temperatures 
reflect this idea. 


Latest sref surface visibility probability forecast which correctly 
forecast this mornings dense fog is signaling the potential for 
dense fog for tonight over the northwest 1/4 of the County Warning Area. This would fit 
with the stratus/drizzle now over central OK advecting north-northeast across Kansas 
and eventually northwest MO. 


A couple of shortwaves will pass through the plains and middle MO 
valley during the Sunday-Tuesday time frame. The initial shortwave 
moving into the Central High plains on Sunday will most likely 
weaken as it is caught in between a stronger upstream shortwave 
diving into The Rockies and the upper wave now over eastern Texas. This 
initial shortwave will likely only have some middle/high clouds with it 
so precipitation is not likely to fall in our County Warning Area. 


The second system looks like it will be a different animal as it 
dives southeast with a negative tilt. NAM/GFS/ECMWF/sref/Gem all 
close off the upper circulation Monday night. There is decent model 
consistency in the placement of the upper low and general depiction 
of the upper wave. Earlier GFS runs were too progressive with the 
surface cold front and the 06z model run is now more in line with 
the NAM/ECMWF. With increasing confidence on evolution of this 
system have increased probability of precipitation for Monday night/Tuesday. Another model 
run or two showing this same consistency should allow later shifts 
to raise probability of precipitation to likely. 


Mj 




&& 


Aviation... 
main aviation concerns again focused on the next several hours. 
Regional fog plot satellite imagery showed dense fog across northern 
Missouri with a deck of MVFR/VFR stratus rapidly moving north into 
the Kansas City metropolitan. With this deck expected to impact the metropolitan 
sites during a time when peak fog formation would typically occur the 
dense fog potential at mci looks small right now. Downstream 
observations within this stratus have varied from 2900 feet to greater 
than 3500 feet. So will mention ceilings around 3000 feet. But these could 
really vary from MVFR to VFR through the early morning before 
eventually becoming VFR later this morning. At stj dense fog will 
persist through much of the morning before burning off. All sites are 
expected to be VFR by this afternoon and into the evening hours. 
There is some potential for fog and lower ceilings tonight. Southerly 
winds are expected to advect slightly more moist air into the 
region. Winds are not currently expected to decouple so confidence is 
still somewhat low on just how dense fog may be. 


&& 


Eax watches/warnings/advisories... 
MO...dense fog advisory until 10 am CST this morning for moz001>008- 
011>017-020>024. 


Kansas...dense fog advisory until 10 am CST this morning for ksz025-102. 


&& 


$$