National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDMX Received: 2018-01-12 23:39 UTC


137 
FXUS63 KDMX 122339
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
539 PM CST Fri Jan 12 2018

.SHORT TERM.../Tonight through Saturday/
Issued at 339 PM CST Fri Jan 12 2018

Weak short wave energy will drop south through South Dakota and 
Nebraska tonight with some modest vertical ascent within the mid 
level moisture field. Surface flow originating from the large Arctic 
high pressure moving south from the Dakotas will keep profiles quite 
dry below 850 mb. A few flurries are possible west of Interstate 35 
but not much else precipitation wise. Afternoon temperatures remain 
quite cold and generally in the 3 to 12 above range. Main challenges 
for tonight will be increasing clouds from the west northwest then 
timing of clearing over the north. The clouds will provide some 
insulation and will keep temperatures from falling as much as in the 
clearing regions. The northern one third to one half of Iowa should 
be clearing by late tonight into Saturday morning to allow 
temperatures to fall into the 5 to 15 below range and combined with 
northernly winds of 5 to 10 mph, will drop wind chill values into 
the 20 to 30 below range. Will be issuing a wind chill advisory for 
these regions and generally encompasses areas along and north of 
Highway 30. 

The Arctic high pressure will pass across Iowa on Saturday and will 
continue the clearing skies and cold temperatures. High temperatures 
will be near to slightly warmer than today. 

.LONG TERM.../Saturday night through Friday/
Issued at 339 PM CST Fri Jan 12 2018

The short wave that will bring light snow to portions of the Midwest 
Saturday night into early Sunday is tracking more to the southwest 
and will be minimal impact to the area outside light snow potential 
over the far southwest. Any accumulations will be an inch or less. A 
more significant short wave and Arctic boundary will arrive late 
Sunday into Sunday night. The majority of the kinematic forcing 
associated with the upper short wave will move across Minnesota and 
Wisconsin, however, a portion of the energy will move through 
central and northeast Iowa. In addition the exit region of the upper 
level jet will be focused across Iowa and will create additional 
vertical ascent. A deep dendritic layer will develop with this 
system from the surface to near 13 kft and will promote dendritic 
growth. The moisture profiles are a bit unorganized and the 
separation between this system and another moving through western 
Nebraska and Kansas may cause a precipitation split over central and 
southwest Iowa. As of now, snowfall amounts of 1 to 2 inches are 
possible especially over the northeast forecast area and lesser 
amounts elsewhere. The wind cold become a factor as well with wind 
gusts of 35 mph or greater will be possible as the Arctic air 
arrives. 

The arrival of the Arctic air and expected winds will bring 
extremely cold wind chill values to the area by Sunday night through 
Tuesday morning. Wind chill values of 20 to 35 below will be common 
by Monday morning with little improvement through the day. Wind 
chill values may approach 40 below over northern Iowa by Monday 
night into Tuesday morning. Wind chill headlines are anticipated 
through this period. Little to no significant weather is forecast 
through the remainder of the extended. The cold upper trough across 
the region will break around Wednesday followed by a transition to 
more zonal to southwest flow by Friday and should bring high 
temperatures back into the 30s and 40s to end the period. 

&&

.AVIATION.../For the 00Z TAFS through 00Z Saturday evening/
Issued at 539 PM CST Fri Jan 12 2018

System will graze western and southern portions of the forecast
area tonight into Saturday morning. This will spread VFR ceilings
across those locations into Saturday morning, but should only have
limited impact. A few flurries may also occur in the far southwest
but for the most part, visibilities should be unrestricted.
Surface winds will remain from the north to northwest for the
duration of the forecast. 

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory from 9 PM this evening to 10 AM CST Saturday 
for IAZ004>007-015>017-023>028-033>039-047>050.

&&

$$

SHORT TERM...Donavon
LONG TERM...Donavon
AVIATION...Cogil