Weather

208 
fxus63 kdmx 131123 aaa 
afddmx 


Area forecast discussion...updated 
National Weather Service Des Moines Iowa 
623 am CDT Monday Oct 13 2008 


..updated aviation discussion... 


Short term /tonight/... 
big story of the day is the cold front moving through northwest Iowa at this time. 
Broad ascent and forcing along and ahead of the front are producing 
a wide swath of rain with embedded showers...which is currently 
affecting eastern portions of South Dakota...NE...KS...and SW Minnesota and northwest Iowa. As 
the front progresses slowly across our County Warning Area today most locations will 
see rainfall and have stuck close to previous forecast in calling 
for likely to definite rain showers spreading across the northwest two thirds of 
the County Warning Area by 00z. There are differences among the models in timing of 
this swath...with the NAM being the slow outlier...but any locations 
in our southeast that do not receive rain by 00z will receive it 
soon thereafter. More problematic forecast regarding the front is 
resultant high temperatures. At 12z the boundary will likely have 
just passed through kest and be near kaxa and kdns. This will result 
in beginning of period maximum temperatures along our northwest edges. Dense cloud 
cover will hold down daytime temperatures across the rest of the 
area...with the progression of the front dictating lower maximum temperatures 
northwest than southeast. Have tried to time this in hourly temperature forecast as well 
in order to get "steadily decreasing temperatures" or similar 
wording in public forecast for the northwest. 


Long term /tonight through Sunday/... 
western trough will continue to elongate overnight as one upper low 
lifts into Canada with a secondary chunk of energy remaining in the 
southern rockies. Frontal boundary will be east of the County Warning Area by tonight 
and with the upper system pulling away from the state...forcing will 
gradually diminish overnight. Expect rain showers activity to slowly 
decrease in coverage and intensity as the area moves to the east. 
Otherwise...much drier air will push into the state on northerly winds 
and overnight with some clearing across the north. This will help 
temperatures end up a good 25 degrees cooler than the past few 
nights across much of the County Warning Area. Models diverge on the handling of the 
system across the SW with the NAM keeping much of the precipitation S of the 
state but the GFS and European model (ecmwf) brining another shot of rain across the 
south half to 2/3rds of the County Warning Area Tuesday night into Wednesday. Sref 
and GFS ensembles indicate that precipitation should impact at least the 
southern half of the area so will keep probability of precipitation for this time. Surface 
ridging will build in quickly Wednesday night into Thursday with drier 
conditions and cool temperatures. Will likely see readings approaching 
freezing in the north on Wednesday night with decent radiational cooling 
and light winds. GFS and European model (ecmwf) still indicating another shortwave 
passing quickly through on Thursday night with weak forcing and 
limited moisture and have maintained low probability of precipitation in the northern third 
of the County Warning Area for some light rainfall. Otherwise...quiet weather into 
the weekend as upper ridging builds into the Midwest. 


&& 


Aviation...13/12z 
cold front will progress through the area from northwest to southeast today and 
into tonight...accompanied by a wide swath of rain showers with mainly MVFR 
visibilities and ceilings. Local IFR conditions are also possible as this swath 
moves through. Most terminals will see several hours of prevailing 
MVFR conditions around frontal passage. Conditions will begin to improve late 
tonight as the front moves away to the south and skies clear out 
behind the system. 


&& 


Dmx watches/warnings/advisories...none. 


&& 


$$ 




Short term/aviation...Lee 
long term...cogil