172 
fxus63 koax 200753 
afdoax 


Area forecast discussion 
National Weather Service Omaha/valley NE 
253 am CDT Wednesday Aug 20 2008 


Discussion... 
another quiet day in store for today...with more active weather on 
its way for the rest of the week and into the weekend. Subjective 
00z upper air analysis indicates upper trough coming ashore in northwestern 
US...with some heat falls along the northern rockies. Cold pocket of temperatures 
from 850mb to 500mb extended from upper low in OK/Texas northeastward toward the 
northern Great Lakes. Upper low still lingering in the Southern Plains was 
centered in southern OK/northern Texas. Surface high at 06z was centered in 
lower Michigan...with surface low developing in western Montana/northwestern Wyoming. 


Main forecast concerns are in precipitation associated with ejecting upper 
low...as well as cold front later this week. Area will see the last 
in a string of similarly pleasant days today...with highs today 
tempered slightly by increasing clouds...particularly in the southeastern 
County Warning Area...as well as slightly cooler 850mb temperatures. Cloud shield and rain showers 
ahead of weakening/opening upper low will spread into County Warning Area from Kansas/MO 
later this evening...with best chance of precipitation in southeastern Nebraska and much of 
western Iowa through Thursday. 300-305k isentropic lift reaches County Warning Area around 
03-06z...which should help force rain showers once middle-level dry layer is 
overcome. Instability is marginal...thus have leaned heavily toward 
rain showers wording in the 00-18z time frame. Upper wave will be slow to 
pull away as downstream high remains rather Stout aross the northestern 
US...and expect rain showers/isolated ts to linger into Thursday evening in eastern County Warning Area. 


Will see a break Thursday nt/Friday as Southern Plains upper wave pulls away 
and northern stream upper low digs into the northern plains...dragging an 
attendant cold front through the region. Have backed off on probability of precipitation 
during the day Friday...though did keep schc in northern half of County Warning Area. 
NAM/GFS indicate some weak instability building along and ahead of 
the cold front...but precipitation will likely be tied fairly close to 
front. With deepening northern stream upper low...and rather strong cold 
air push behind the front...have leaned toward faster progression of 
the front into the County Warning Area. Kept highest chance probability of precipitation on Friday nt...with probability of precipitation 
lingering in the southern County Warning Area Sat as progression of front slows in KS/MO. 


Made no changes beyond Sat. 


&& 


Aviation... 
for taf sites koma/klnk/kofk through 21/06z. 


Except for a bit more surface wind this afternoon little change expected at taf 
sites from previous few days. Patchy fog possible in 11-14z 
period...especially near MO river...otherwise VFR conds expected. Late 
morning/early afternoon cumulus again should develop with isolated ceilings in 6-7k 
feet range in 20-24z period. Upper low centered over northern Texas that is forecast 
to lift toward southeastern nebr tonight could spread middle cloud ceilings above 10k feet to 
klnk/koma...especially toward 21/06z. 


&& 


Oax watches/warnings/advisories... 
NE...none. 
Iowa...none. 
&& 


$$ 


Mayes/chermok