Weather

021 
fxus63 kdmx 060954 
afddmx 


Area forecast discussion 
National Weather Service Des Moines Iowa 
345 am CST Tuesday Jan 6 2009 


Short term...today 
some forcing is actually passing through Iowa this morning ahead of 
trough but is moisture starved resulting in nothing more than patchy 
middle/high clouds. Trough passage around midday brings US into 
subsidence by afternoon so dry forecast continued. 


Temperatures are the only real concern. 08z surface analysis places low over southeastern 
South Dakota with attendant cold/warm fronts due west and east of feature. Although 
there is a weak trough passage today...little change of airmass is 
noted as this boundary remains to our north. Biggest problem will be 
Snow Field whose effects were rather pronounced yesterday and 
apparent in maximum temperature field. Tried to blend suggestions from 
forecast soundings and what occurred Monday into highs today. 


Long term...tonight-Saturday 
broad trough to move in across the forecast area tonight on a 
northwesterly flow. Soundings indicating very limited and shallow 
low level moisture. There is a weak vorticity maximum that will ride down the 
flow but this feature should stay to the north and east of the County Warning Area 
and with the aforementioned moisture issue I kept tonight dry. I 
did however put some chance probability of precipitation across the far northeast for 
Wednesday as moisture profile a touch better and the vorticity maximum does 
actually brush that portion of the County Warning Area. Any precipitation from this will 
be very light. 


After that we remain entrenched in northwest flow with a series of 
shortwaves pushing through the flow. The problem of these vorticity 
maxes of decent intensity but with limited and shallow moisture will 
remain with US for the rest of the forecast period. Another vorticity 
prognosticated to move southeast across mainly western Iowa Wednesday 
night. The persistence of this feature from model run to run has 
been consistent although some timing and placement issues still 
remain between the models. Again with the lack of moisture I put 
some slight chances in brushing our far west but again very light 
precipitation at best. 


Another clipper type system has been suggested but the Euro is a 
little more aggressive with this feature. Both the GFS and the Euro 
are hinting at placing central Iowa in a split as better energy 
moves north and south of the forecast area. However...ptype will 
become an issue with this system as soundings indicating some pretty 
good warming from about 850mb through 700 mb. The problem once again 
is that the moisture is limited and shallow. A better moisture 
profile is indicated across the northern third or so of the forecast 
area so slight chances were put/expanded in this area. Confidence 
is quite low due to the lack of moisture but for now it bears some 
sort of mention. 


&& 


Aviation...06/06z 
VFR conditions through Tuesday afternoon. Low pressure passing to 
the north of Iowa may bring a band of broken MVFR stratus into the 
fod/mcw areas during the afternoon with little impact farther south. 
Cold front will follow late in the period with gusty northwest winds 
reaching the northwest sections by 06z. 


&& 


Dmx watches/warnings/advisories...none 


&& 


$$ 


Short term/aviation...small 
long term...fab