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000 
FXUS63 KDMX 102132
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
332 PM CST Tue Dec 10 2019

.DISCUSSION.../Tonight through Tuesday/
Issued at 331 PM CST Tue Dec 10 2019

Impressive short burst of snow today due to thin stratus situated
within the dendritic growth zone. This light snow and flurries is
moving off to the southeast with drying occurring into central 
and northwest IA. The next system will quickly sweep into the 
state tonight. A weak area of low pressure will move southeast 
ahead of high pressure overnight with a band snow developing 
mainly just north/northeast of the surface reflection. This band 
will be mainly thermally driven with vigorous forcing within a 
relatively deep dendritic layer of around 5 kft. Supersaturation 
within this layer looks supportive of larger dendrites which would
further support the potential for a short period of intense 
snowfall rates > 1 inch per hour. As of now, these higher snowfall
rates look to be aligned from near Fort Dodge to Marshalltown and
Montezuma with a band of snowfall of 1 to 2 inches possible. Much
of this snow would fall between midnight and 6 am across the area
with the more intense rates lasting an hour or less. Again, the 
greatest threat will be the snow accumulating quickly on roadways.
While the wind is not expected to be a factor, the fluffy nature 
of the snow with snow ratios near 20:1 would be supportive of snow
fog created by vehicles lofting the snow and further reducing 
visibilities. No headlines at this time but will continue to 
monitor and adjust the forecast as needed.

The snow will end quickly from west to east late tonight into early
Wednesday morning as high pressure arrives from the north. The 
system will help drive another round of cold advection into the 
state. High temperatures over northern Iowa will again be in the 
single digits above zero while highs over the south will be in the
low 30s. The combination of the cold temperatures and increasing 
wind Wednesday morning will drop wind chills over far northern 
Iowa into the 10 below to 15 below range. Another chance for light
snow will pass across northern Iowa Wednesday night as warm 
advection lifts through the state. Drier mid level air should 
limit precipitation chances into central Iowa though some 
discrepancies on the amount of low level saturation which could 
impact drizzle chances. Temperatures Thursday will be warmer over 
the central and south with highs in the mid to upper 40s, assuming
the stratus breaks. The mild conditions will persist into Friday 
before the next short wave passes by Friday night into Saturday. 
This system will lead to a transition to a thermal trough dipping 
into the Midwest and colder temperatures. Some light snow is 
possible over the weekend but no significant impacts are 
anticipated. Lower confidence into early next week due to 
uncertainty in the overall evolution of the Hudson Bay low. 

&&

.AVIATION.../For the 18Z TAFS through 18Z Wednesday afternoon/
Issued at 1116 AM CST Tue Dec 10 2019

A few light snow showers will move through Iowa. As of 17z
visibility was down to 1SM at FOD. However, this is very 
localized and visibility reductions are not expected to be 
widespread nor impacting the other terminals. Clouds will be 
patchy. There will be periods where CIGs bounce between MVFR and 
VFR, with bases between 2500 and 3000 feet. Gusty winds will 
continue through the afternoon will diminish into the evening 
hours. Overall, aviation impacts will not be overly harsh through 
period.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

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