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Area forecast discussion 
National Weather Service Topeka Kansas 
1212 PM CST Thursday Dec 4 2008 


Update... 


Updated 18 UTC aviation and first period forecast grids 


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Discussion... 


Lowered highs a few degrees across the western counties of the County Warning Area 
due to increasing high and middle level clouds. See the previous 
discussion below. 


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Aviation... 


Expect VFR conditions during the next 24 hours across the taf 
sites. An upper trough will move southeast across the taf sites 
tonight. The high and middle level clouds will gradually increase 
this afternoon ahead of the 500 mb trough axis. The low-levels look 
too dry for any snow flurries late this afternoon and this evening. 
Skies will gradually clear through the morning hours of Friday. A 
surface ridge will build southeast across eastern Kansas tonight but then 
gradually shift east. Winds will be northwest at 8 to 12 kts this 
afternoon then become light and variable tonight under the ridge 
axis. The winds will shift to the southwest and increase to 8 to 
11 kts through the late morning hours on Friday at all taf sites. 


&& 


Previous discussion... /issued 305 am CST Thursday Dec 4 2008/ 


Discussion... 


Synopsis...00z upper air analysis was active with several shortwave trough 
within larger scale trough over the Pacific northwest and eastern US. Next shortwave of 
interest from our County Warning Area was diving southward through eastern Alberta at 00z. 
Downstream from the wave a low-amplitude shortwave ridge was noted across 
the western hi plains. 08z surface analysis indicated hi pressure across Kansas and western MO. 
A weak cold front extended from southern Minnesota into northern Nebraska. 


Forecast...as next shortwave trough dives into the plains today...weak 
warm air advection will continue to expand clouds from the High Plains eastward into the County Warning Area. 
Very dry low level air will keep any precipitation confined to west of the 
forecast area...but clouds may have some effect on afternoon highs. Going highs 
seemed to account for this and little change was necessary. As the 
shortwave continues to sink southward tonight...some of the precipitation over the western 
hi plains may try to expand eastward...but continued dry nerly low level flow 
shld keep our County Warning Area dry tonight and removed the chance of flurries. Surface 
ridge axis crosses the eastern County Warning Area tonight and this is likely to lead 
to a cold night for the eastern County Warning Area. Have dropped lows a little for 
this area closer to the cooler met guidance. Lows might be a touch 
warmer in the southern/western County Warning Area where clouds are likely to continue 
tonight...and also where warm air advection is expected to kick toward morning. As 
surface ridge pushes southeastward into the MS valley on Friday warm air advection is expected to 
increase ahead of the next shortwave trough diving southeastward in the northwest flow. 
Breezy to windy conds are expected over the western County Warning Area on Friday afternoon as 
low level jet increase. Have warmed going overnight lows on Friday night 
as southwesterly winds are likely to continue through the night. Cold front is 
prognosticated by the GFS/NAM to move through the County Warning Area early Sat morning with 
decent cold air advection through the day. The coldest of the air associated with 
this fnt shld stay to the east of the forecast area though...and thus a quick 
return to normal temperatures /highs in the middle 40s/ is expected by sun. 
NAM/GFS are indicated modestly strong warm air advection late Sat night into sun which 
cloud lead to some saturation and light precipitation...but currently the 
best chance of this shld be north of the forecast area and will keep our dry 
forecast. Next precipitation chance still looks on track for early next week 
and no changes were made here. 


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Top watches/warnings/advisories...none. 


&& 


$$ 


Gargan