951 
fxus63 keax 211726 
afdeax 


Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO 
1126 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... 


For the 18z tafs...a VFR stratocu cloud deck prevailed acr the terminals 
early this afternoon. However...a MVFR stratus deck was noted in southeastern 
Kansas...ahead of a weak warm front. It is difficult to determine the eastern 
edge of the cloud deck due to the higher stratocu deck. Both the GFS 
and NAM suggest that the MVFR cloud deck may clip the terminals late 
this afternoon. Confidence is not high. Regardless...the MVFR cloud deck 
will shift north tonight and be replaced with a MVFR stratocu/ac scattered- 
broken deck. May see periods of MVFR fog late tonight at the 
terminals...but given cloud cover and modest winds...IFR fog is not 
expected. Otherwise...any MVFR will burn off rapidly after sunrise with 
VFR conditions for Sun morning. 


Db 


Eax watches/warnings/advisories... 
MO...none. Kansas...none. && 


$$