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fxus63 keax 221110 
afdeax 


Area forecast discussion 
National Weather Service Kansas City/Pleasant Hill MO 
510 am CST sun Nov 22 2009 


..updated aviation... 


Discussion... 


Couple of upper level systems will affect the County Warning Area through the middle 
of next week. The lead shortwave as seen in the latest water vapor 
loop has reached the central and southern High Plains. This feature 
will have a minimal impact on the sensible weather as it will be 
lacking a source of deep moisture and will be weakening as it tracks 
eastward today. Increasing isentropic lift on the 300/305k surfaces 
is tapping into middle level moisture left over from an upper system 
now tracking through MS/al. Most of the County Warning Area will be covered by these 
middle clouds for most of today. The far southeastern counties may see 
some afternoon sun. Expect to see a continuation of above normal 
temperatures even with the extensive middle cloud deck mav/NAM MOS 
guidance look pretty reasonable. Radar shows some returns over 
central MO but the sub-cloud layer is so dry that the rain is not 
likely reaching the ground. This may change tonight as increasing 
positive vorticity advection associated with the High Plains shortwave approaches while the 
right rear quadrant of a departing upper level jet segment provide 
some additional lift. Will add slight chance probability of precipitation for the northeast 
County Warning Area for tonight. Later shifts may need to raise probability of precipitation should the very 
dry sub-cloud layer begin to saturate. 


A second and stronger upper system is still slated to reach the 
Central Plains on Monday...and pass through the County Warning Area on Tuesday. The 
models have been fairly consistent on timing...strength and location 
of the upper system. An attendant cold front will move east through 
the Central Plains on Monday and pass through the County Warning Area Monday night. 
Due to good continuity of the model runs have more confidence to 
raise probability of precipitation into the likely category for Monday night. Increasing 
upper level dynamics supplied by a negatively tilted upper trough 
and pronounced upper jet segment in excess of 90kts will interact 
with steepening middle level lapse rates and MUCAPES of 100-200 j/kg to 
allow convective showers and possibly even a few thunderstorms to 
form. 


As the upper system closes off should see warp around cloud cover 
and patchy light rain roll back into the County Warning Area on Tuesday with the 
northern sections most likely to see an precipitation. Prognosticated 
soundings suggest the precipitation should stay liquid although some 
snow could mix in with the rain over far northwest MO. Not much of a 
diurnal range expected as strong cold air advection works in under 
the upper low. 


GFS/European model (ecmwf) depict a third clipper type system will be close on the 
heels of the closed low but confidence low on how this feature will 
play out as clipper systems are difficult to get a handle on this 
far out. 


Mj 


&& 


Aviation... 


VFR 8k-10k feet deck has backfilled into terminal corridor prior to 
12z...and should largely remain in tact through the daylight hours. 
Any sprinkles/light showers should remain to the east over central and 
northestern Missouri...though patches of virga are plausible during the 
late morning and afternoon hours. With medium confidence...have 
stayed on the optimistic side regarding flight categories towards 
the end of the taf period...though some model guidance suggests 
MVFR/IFR ceilings currently over central Kansas reaching terminals after 
midnight. Future taf packages may eventually need to introduce lower 
flight restrictions based on model and observational trends. 


21 


&& 


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


&& 


$$