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Area forecast discussion 
National Weather Service Topeka Kansas 
729 am CST Sat Nov 21 2009 


Update... 


Updated for 12z aviation. 


&& 


Discussion... 


See previous discussion. 


&& 


Aviation... 


Low level stratus has moved across all taf sites...improving fog 
situation. Visibilities will be 5 miles or greater through the 
period. Borderline MVFR ceilings are scattered across the area and 
expect broken ceilings of 2500 to 3500 feet through the majority of 
the taf forecast. 


&& 


Previous discussion... /issued 331 am CST Sat Nov 21 2009/ 


Discussion... 
09z water vapor shows a closed low over central Texas...a shortwave 
moving across the Great Lakes...and a trough moving inland over the 
Pacific northwest. Over Kansas middle level dry air and shortwave ridging 
was in place. Surface observation still show a weak surface ridge in place across 
northeast Kansas. 


In the short term...moisture continues to look marginal for any 
decent chances for precipitation. Really the biggest problem is dealing 
with fog and developing stratus as what moisture there is remains 
trapped with in the boundary layer by a weak eml. Forecast soundings 
keep the boundary layer near saturation through tonight. However 
they do not appear to be ideal for drizzle with a deep stable layer 
and weak lift within the cloud. Think that due to the shallow nature 
of the moisture that stratus is the most likely result of the low 
level moisture and have removed the mention of drizzle for tonight. 
With the stratus this morning and again tonight...temperatures could be a 
little tricky. Think there should be some breaks in the clouds by 
this afternoon. So with some warm air advection on the southerly winds...have highs 
generally in the upper 50s to around 60. The clouds should hold min 
temperatures up in the 40s overnight tonight as stratus redevelops. Models 
no longer bring a front through on Sunday with qg forcing weakening 
as the middle level wave passes overhead. Again with the limited 
moisture...precipitation chances look marginal and have maintained only a 
slight chance pop across north central and northeast Kansas for the 
afternoon because of the wave and to maintain continuity. Temperatures 
should once again be mild with middle 50s to near 60 on Sunday. 


For Monday through Wednesday...have favored the slower and more 
amplified NAM/ECMWF/UKMET which seem to have a better clustering of 
solutions over the GFS. With this solution in mind...expect the 
forecast area to remain in the warm sector for the bulk of the event 
as the surface low tracks just north across Nebraska. Best chance probability of precipitation look 
to be Monday evening as the front passes with decent qg forcing 
lifting across the area as the upper wave closes off. Some wrap 
around precipitation will be possible through Tuesday. However this system 
similar to the last closed low...appears to be lacking a tap into 
deep cold air and 850 temperatures are prognosticated to barley fall below 0c. 
With the better deformation and middle level frontogenesis remaining 
north of the forecast area...would not expect much snow for this 
event. 


A dry northwest flow eventually gives way to middle level ridging 
through the end of the work week. Think cooler temperatures are likely and 
forecast shows this nicely so have not made any changes beyond Wednesday. 
While there may still be some weather going on to the east and 
northeast on Wednesday associated with the closed low...the weather 
looks ideal for Holiday travelers locally and areas to the south and 
west. 


Wolters 


Aviation... 
a few rounds of ground fog already passing over top ASOS...but IFR 
visibilities have struggled to stay persistent. Surface ridge over 
the area with temperatures well beyond crossover levels suggest LIFR fog 
still likely at all sites overnight...at least intermittently. 
Increasing southerly winds will bring increasing moisture above 
would keep limiting ceilings in place for much of 
Saturday...though differences in the level and duration of this is 
in question. Given narrow band of lower ceilings to the 
south...will bring things up to MVFR levels for the afternoon and 
evening. 


65 


&& 


Top watches/warnings/advisories...none. 


&& 


$$ 


99/99/barjenbruch