National Weather Service Raw Text Product

069 
FXUS63 KDMX 031739 CCA
AFDDMX

Area Forecast Discussion...CORRECTED
National Weather Service Des Moines IA
1139 AM CST Wed Jan 3 2018

...Updated Aviation Discussion for 18Z TAFS Below...

.SHORT TERM.../Today through Tonight/
Issued at 400 AM CST Wed Jan 3 2018

Lingering light snow showers/flurries and some patchy blowing 
this morning over the south. The back edge of the stratus looks to
clear the CWA by around 12-13z this morning and thus the snow 
should end by that time across southern Iowa. Certainly some brief
white knuckle driving this morning along and south of Interstate 
80 with the falling snow and blowing snow potential. 

The stout north to northwest winds will persist throughout the day 
today creating a very raw day across the state. Over the far north 
central portions of the forecast area, generally along and north of 
Highway 20, these locations look to dip to the -20F wind chill for a 
few hours b/t 12-17z. Will handle with an SPS for now as an advisory 
seem overkill due to the recent bitter cold snap and the fact that 
conditions were short-lived and improving this morning. 

Now, that being said, tonight into Thursday morning is a different 
story.  Much longer duration, more widespread wind chill values of 
20 below or less, and there are a few locations that could 
experience even 30 below wind chills at times Thursday morning. 
Thus, confident to hoist a Wind Chill Advisory for much of the CWA 
late tonight through mid-morning Thursday. For temperatures, leaned 
closer to the GFS/ECMWF as the NAM was too warm.  Utilized the SREF 
for winds today into tonight which resulted in nudging up winds 
slight this afternoon and during the overnight hours.  The center of 
the surface high pressure really doesn't move into the state until 
after 12z Thursday and the pressure gradient looks to remain strong 
enough overnight across the north and east to keep winds up b/t 5-10 
mph.

.LONG TERM.../Thursday through Tuesday/
Issued at 400 AM CST Wed Jan 3 2018

Next round of arctic air will be in place on Thursday with highs 
struggling into the single digits by afternoon. Wind chills will be 
at or near criteria early in the period although overall wind speeds 
will be marginal as high pressure will be nearby. Still appears that 
a weak wave will move south toward the state later Thursday into 
Thursday night. While not as robust as in previous models runs, 
enough weak forcing and saturation in dendritic zone should be 
sufficient for at least some light snow/flurries into Thursday night 
and have continued this threat in the forecast. Surface ridge 
will then slide through eastern Iowa late Friday into Friday night
with very cold air remaining in the state. 

A system dropping through the intermountain west and into the lower 
Missouri River valley will impact the state this weekend.
Initially, warm advection is expected to intensify on Saturday on
the backside of the departing surface high as thermal ridging 
builds into the Plains. This will persist into Sunday with steady 
or rising temperatures on Saturday night and readings likely 
climbing above freezing across the southern two-thirds or so of 
the state. Both GFS and Euro have the bulk of moisture transport 
and forcing south of Iowa but does bring some weak to moderate 
isentropic lift into the state producing some light precipitation.
It appears temperatures will be warm enough in the far south for 
primarily rain with a rain/snow line somewhere in the middle of 
the state near the I80/Highway 30 corridor, although any 
precipitation that far north will likely be quite light. 
Lingering forcing associated with weak deformation area will 
persist into Sunday night before ending. Cold advection will 
increase by this time on the backside of the system and persist 
into Monday with colder and drier conditions into Tuesday. 

&&

.AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/
Issued at 1127 AM CST Wed Jan 3 2018

VFR conditions are expected at all terminals this period. Several
METARS /e.g. KMCW/ are reporting occasional IFR CIGS associated 
with suspended ice crystals. However webcams and satellite imagery
continue to show clear skies across Iowa. Expect gusty northwest 
winds thru early evening...which could result in some minor 
drifting snow on runways. Winds will diminish in the late evening 
and overnight.

A suspected comms issue is leading to several missing elements at
KOTM. Have included AMD NOT SKED while maintenance/troubleshooting 
is ongoing.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory from 9 PM this evening to 9 AM CST Thursday 
for IAZ004>007-015>017-023>028-033>039-045>050-058>062-071>075-
082>086-093>097.

&&

$$

SHORT TERM...Podrazik
LONG TERM...Cogil
AVIATION...Fowle