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fxus63 ktop 211725 
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Area forecast discussion 
National Weather Service Topeka Kansas 
1125 am CST Sat Nov 21 2009 


Update... 
updated for 18 UTC aviation forecast. 


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Discussion... 
see previous forecast discussion below. 


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Aviation... 
current break in the clouds affecting all 3 taf sites will quickly 
pass north while MVFR ceilings advect in from the south. Expect 
MVFR for much of the afternoon. There may be occasional breaks... 
and perhaps even a brief drop to IFR conditions per a few of the 
upstream observation reading below 1k foot ceilings. Forecast gets tricky 
overnight as low level moisture remains in place and it appears 
stratus will be favored with ceilings less than 1k feet for a good 
part of the overnight hours. This seems to be the most likely 
forecast solution at this time but any increase in dry air may 
allow ceilings to break up to VFR overnight. Should be clearing out 
by middle morning regardless. 


Barjenbruch 


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Previous discussion... /issued 729 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 


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Top watches/warnings/advisories...none. 


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$$