991 
fxus63 ktop 231315 
afdtop 


Area forecast discussion 
National Weather Service Topeka Kansas 
715 am CST Monday Nov 23 2009 


Update... 


Updated for 12z aviation. 


&& 


Discussion... 


See previous discussion. 


&& 


Aviation... 


Patchy dense fog occasionally bringing down mhk/top visible to 1 mile 
and expect this to continue through 15z. Otherwise VFR conditions 
expected through most of the day with scattered/broken ceilings of 4kft. As 
frontal boundary and boundary layer further moistens by 
evening...low level stratus will develop with MVFR ceilings 
anticipated. Held off mentioning precipitation but could see rain 
at taf sites by 06-09z. Blair 


&& 


Previous discussion... /issued 340 am CST Monday Nov 23 2009/ 


Discussion... 
water vapor shows a shortwave moving out of the northern rockies 
with energy digging southeast into western Colorado. Models continue to 
indicate energy cutting of across the Central Plains by tonight. 
However the NAM continues to be a slow and southern outlier with the 
500mb. Therefore favored a GFS European model (ecmwf) blend for the forecast. With 
good consistency in these models...have increased probability of precipitation for tonight 
and Tuesday to correspond with increasing confidence. 


Initial concern is area observation showing dense fog across north central 
Kansas. After calling around to some of the counties...it looks as 
though dense fog is confined to far western sections of the area. 
RUC forecast soundings indicate the fog will persist through middle 
morning so will issue an advisory for the fog. 


Think the best timing for precipitation will be tonight and Tuesday. Qg 
forcing increases across eastern Kansas through the afternoon...but 
there continues to be some middle level dry air that has to be 
overcome...and higher Theta-E air is slow to advect north until 
towards 00z. There continues to be some steepening of the lapse 
rates as cooler middle level air moves in with the upper low. Because 
of this some weak instability is expected to accompany the storm 
system with the potential for isolated ts. Also noted the lack of 
deep cold air with the system with temperatures in the upper 20 and lower 
30s across Montana at this hour. Models show a modified Pacific airmass 
advecting in behind the system and forecast soundings keep surface temperatures 
at 3c or warmer through the night. Therefore am not to worried about 
snow accumulations. Have cut back the amount of time the snow is in 
the forecast to a six hour window around 12z Tuesday...when temperatures will 
be there coolest. Precipitation should linger through much of the day 
Tuesday as moisture wraps around the low with the deformation zone 
moving across northeast Kansas. Then things should begin to clear out 
Tuesday night as the system lifts east. 


Temperatures should again be mild today...especially across eastern Kansas 
where there should be some sunshine. Temperatures could be a little tricky 
for Tuesday and may be a tad cool if cloud cover and precipitation where to 
diminish early. Next shortwave will dig south on Wednesday...but as 
previous shift mentioned...this front looks to be dry as there is no 
moisture advection in advance of this wave. No changes were made to 
the forecast after Wednesday. 


Wolters 


&& 


Top watches/warnings/advisories...dense fog advisory until 10 am Monday for ksz008-ksz020-ksz034. 


&& 


$$