997 
fxus63 keax 212322 
afdeax 


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


..updated aviation discussion... 


Discussion... 
/346 PM CST Sat Nov 21 2009/ 
a weak warm front was located across the southern County Warning Area with low level 
moisture locally pooled near the boundary. The boundary will shift 
quickly north and dissipate. As per forecast soundings suggest...the 
moisture is quite shallow. This appears reasonable given the lower 
dewpoints well to our south...in areas where deeper mixing has 
occurred. Given intervals of cloud cover tonight and stronger southeast 
winds...do not expect widespread dense fog tonight. Given the mixy 
nature of the soundings just above the surface...stratus would likely be 
the result if moisture was deep enough. At the current time...moist 
layer appears insufficient for stratus. The only exception may be 
across the northern grids tonight where low level moisture is a little 
deeper. 


Will introduce patchy fog for the northern grids tonight and let the 
evening shift make any refinements based on current trends. 


Moisture imagery depicts a shortwave moving into the southern and central 
rockies. Models suggest that this shortwave will eject east-northeast into the 
County Warning Area Sun night. Moist is limited with forcing rather weak. Cannot 
rule out a few sprinkles...but will not introduce at this time. 


Otherwise...main concern is late Monday afternoon and Monday night when a strong 
upper level low moves into the plains. The models have a general 
consensus in moving the upper level low near the MO/Iowa bdr Monday night and 
Tuesday with a strong wave moving around the southern periphery of the upper level 
low. Much of the County Warning Area is in the favorable quadrant of a 90kt 300 mb speed maximum 
Monday night with a modest pvu maximum rotating through Missouri. Given the 
low static stability and modest qg forcing...have increased probability of precipitation for 
late Monday afternoon and Monday night. In addition...cannot rule out an isolated 
thunderstorm given the potential for MUCAPES around 100 j/kg. 


Db 


Medium range (tuesday through saturday)... 


Overall decent agreement among ensemble guidance with respect to the 
upper air pattern through the upcoming work week. By the beginning 
of the week...short wave trough is expected dive across the central 
Continental U.S. Bringing increasing precipitation chances to the area. 
Differences in the exact location and timing of this feature is 
evident among various solutions...however the general idea is 
certainly consistent. By Tuesday...upper low will slide across the 
Central Plains and Midwest with location and timing by this time 
frame key in determining where precipitation is most likely and when its 
expected to push east of the County Warning Area. Will keep highest rain chances 
across the northern half of the County Warning Area for Tuesday...sliding activity 
east with time through Tuesday night and Wednesday. 


Upper trough axis appears to be fairly progressive with additional 
short wave energy quick on its heels. Lingering precipitation/cloud cover 
may be evident through midweek as secondary short wave trough dives 
south on the backside of departing system. This will also serve to 
bring some slightly cooler air southward into the midwestern states 
by Wednesday and Thursday. Upper short wave ridging will then 
translate atop the region for the latter part of the week and into 
the week bringing warmer temperatures. 


Deroche 




&& 


Aviation... 


For the 00z tafs...warm front lifting north across the taf sites 
this evening will bring a period of MVFR ceilings and may also have some 
MVFR fog. Once this lifts north between 03 to 04z...pressure 
gradient may be enough to preclude dense fog overnight...but will 
keep the MVFR visibilities from the previous taf given the expected small 
temperature dewpoint spread. VFR conditions expected on Sunday. 


Pc 


&& 


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


&& 


$$