089 
fxus63 kdmx 081720 aab 
afddmx 


Area forecast discussion...updated 
National Weather Service Des Moines Iowa 
1120 am CST Thursday Jan 8 2009 


..updated aviation discussion... 


Discussion... 
fairly quiet today albeit cold as high pressure sinks southeast 
across central Iowa. Little change from going forecast was made 
today. 


The same cannot be said for tonight through early next week. The 
models have really cranked up the moisture profile from the last 
several days..especially for late tonight north and Friday and 
Friday night central and east. I am understandably suspect of this 
major change however all the models have come on board with this in 
wetter solution. As a result probability of precipitation...quantitative precipitation forecast and snow amounts were 
increased across the north and east. The initial precipitation starts 
tonight in a band of warm advection ahead of the main system as a 
shortwave approaches. The models now strengthen the surface low as 
a strong short wave drops out of Canada. It now appears possible 
for accumulating snow in the far north and east but over several 
periods and for differing reasons. The initial warm advection band 
tonight will produce snow across the north then as warmer air moves 
into mainly the southern half of the state for Friday snow becomes 
mixed with or changes to light rain or drizzle south with a mixed 
bag of precipitation north. Where moisture profiles last night were 
showing a depth of moisture around 100 mb now we are looking at 
saturation levels of several thousand feet. There is not a lot of 
Omega but enough that any drizzle or freezing drizzle may precipitation out 
heavy enough to call it light rain/freezing rain. There is also 
enough of a warm layer for sleet between I-80 and Highway 20. 
Confidence is low ni placement and even ptype as this is a big 
change from the past couple nights. Then for Friday night...def 
zone precipitation hits central and eastern Iowa but by this time enough 
cold air becomes entrenched over central Iowa that ptype should be 
in the form of snow. 


For the weekend...the models are now hinting at another wave pushing 
across late Saturday and Sunday. Light quantitative precipitation forecast is being suggested but 
at this point it doesn't look like more than flurries. A major cold 
push still looks on tap for the first part of next week. Monday 
still looks near normal but temperatures will be plummeting in the 
afternoon and through middle week highs will be in the single digits 
and teens with lows below zero. 


&& 


Aviation...08/18z 
VFR conditions will prevail this afternoon and evening...with west 
northwest breezes becoming light and variable...then coming around 
to southeast by tonight. Middle level clouds are moving in from the 
west and will spread prevailing ceilings across the area before 
00z...but bases will be fl070-fl090 and no MVFR ceilings are 
expected during this time. Low pressure approaching from the 
northwest overnight will result in lowering and thickening 
clouds...especially at the northern sites where snow is also likely 
from about 04-06z Onward. Kfod will be on the edge of the low 
ceilings and snow...whereas kmcw and Kalo will be more significantly 
affected. Prevailing MVFR conditions with periods of IFR 
visibilities are expected at kmcw and Kalo overnight. As a trough 
passes through the area toward midday Friday some lower ceilings are 
possible further south along with a period of br...however it is too 
far out to have degree of certainty in this to include in the 18z 
tafs. 


&& 


Dmx watches/warnings/advisories...none. 


&& 


$$ 


Short term...donavon 
long term...fab 
aviation...Lee