National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDMX Received: 2017-12-07 17:24 UTC

FXUS63 KDMX 071724

Area Forecast Discussion
National Weather Service Des Moines IA
1124 AM CST Thu Dec 7 2017

.SHORT TERM.../Today through Tonight/
Issued at 345 AM CST Thu Dec 7 2017

CAA will continue throughout the day today with 
mixing to around 900mb developing late this morning into the 
afternoon hours. Current winds are pressure gradient driven with 
shortwave exiting the state before sunrise this morning. Some 
lingering low stratus across the southeast will allow for a few 
flurries prior to 12z.  Otherwise, skies become mostly clear 
throughout the day into the evening. Next shortwave quickly enters 
the north overnight tonight, maybe as early as 06z but more likely 
by around 09z.  Saturation within the dendritic layer begins past 
06z across the northwest and have flurries mentioned through 12z 
Friday. Similar scenario to Thursday with the low stratus deck and 
decent CAA developing causing the flurries. Temperatures today, 
leaned towards the cooler side of guidance.

.LONG TERM.../Friday through Wednesday/
Issued at 345 AM CST Thu Dec 7 2017

An active pattern setting up through the next week as strong 
north/northwest flow dominates through much of the period as the 
highly amplified flow persists. A few flurries or light snow showers 
will be possible Friday morning. An intense short wave will pass 
through Friday night. A short period of light snow is possible over 
the far northeast including the Mason City and Waterloo areas. While 
the mid levels remain mostly dry, the low level moisture will extend 
up into the favorable dendritic growth region temperatures near -
15C. This system will drag a cold front through the state overnight 
with good cold advection differential leading to strong mixing and 
gusty northwest winds.  The momentum transfer efficiency will be 
further aided by good subsidence in the wake of the departing short 
wave along with an increasing pressure gradient. A period of mixed 
layer winds in excess of 40 kts is likely and this may require wind 
headlines. The peak winds are expected to be between 03z-12z then 
gradually diminishing through the day Saturday. Saturday will be 
cold with the thermal trough moving through the state. Wind chill 
values will be near to slightly below zero over the northern half of 
Iowa by late Friday night into Saturday morning. 

Another vigorous short wave will drop southeast into Montana on 
Sunday and this will push warmer temperatures into Iowa. Current 
forecast highs for Sunday are in the upper 30s to upper 40s but may 
very well exceed these highs with westerly winds and good mixing 
through the day. The warm up will be short lived as the short wave 
passes through the state Sunday night and brings another wave of 
cold advection. High temperatures on Monday likely to be early as 
the cold advection arrives. Light snow will be possible during the 
day in addition to another round of gusty northwest winds. Yet 
another strong short wave is expected in the Tuesday night/Wednesday 
period with the next chance for light snow. The entire week next 
week from Monday and just beyond the forecast period will feature 
these fast moving/strong systems. Suspect at least one of these 
systems is being under forecast by model guidance and will be a 
bigger winter weather impact than currently forecast somewhere 
across the Upper Midwest. Trends have continued to push the Monday 
system further west and the Tuesday night/Wednesday system still has 
a lot of noise within the ensemble forecasts, making each of these 
candidates to be stronger than currently forecast.


.AVIATION.../For the 18Z TAFS through 18Z Friday afternoon/
Issued at 1121 AM CST Thu Dec 7 2017

VFR conditions will continue across all of central Iowa through
the remainder of the day. MVFR cigs and a few flurries are 
possible as a stratus deck slides south into the state late
tonight into Friday morning. Model guidance in sound agreement 
with cigs further south toward KDSM and KOTM remaining in VFR 
category as the cloud cover expands south.




SHORT TERM...Podrazik
LONG TERM...Donavon