National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDMX Received: 2018-10-12 04:30 UTC

FXUS63 KDMX 120434

Area Forecast Discussion
National Weather Service Des Moines IA
1130 PM CDT Thu Oct 11 2018

.DISCUSSION.../Tonight through Thursday/
Issued at 324 PM CDT Thu Oct 11 2018

The cold pattern featuring below to much below normal temperatures
will persist for much of the forecast period. Currently, the 
broad stratus shield is gradually dissipating with the arrival of
drier air and a broadening of temperature/dew point spreads. This
will be short lived though. An upper level short wave will arrive
late tonight and will feature leading theta-e advection. This 
system will first feature increasing mid-level cloudiness followed
by deeper saturation and some precipitation. The initial mid- 
level cloudiness over the central and south in addition to any 
stratus remnants over the north do pose some uncertainty regarding
overnight temperatures and frost/freeze potential. Currently 
already have a Freeze Warning in effect for much of northern Iowa.
High pressure is arriving from the west and will continue to 
erode the stratus. In addition, the system will bring diminishing 
winds and lower surface dew points. Therefore, areas that clear 
should have temperatures fall quickly this evening. With 
uncertainty with cloud cover after midnight, just not enough 
confidence to expand any headlines southward.

Precipitation type is also in question overnight in some areas.
Profiles aloft a plenty cold fro snow therefore, precipitation
type will be reliant on near surface thermodynamic properties. In
these type of situations, a surface wet bulb temperature of 34.5F
or higher typically results in all rain and 33.5F or below is
generally snow. Surface wetbulbs will be close to this range and
do expect a few snow flakes or even a brief period of light snow
to occur in portions of central IA late tonight/early Friday.
Slight warmer temperatures will arrive on Saturday with highs in
the 50s. Another vigorous system will impact the state Saturday
night with a few rain showers possible in the evening followed by
another cold front. Sunday will be cold again with highs in the
upper 30s to mid 40s. A widespread freeze is expected Sunday
night/early Monday morning and this should end the growing season
for much of central and northern Iowa. Temperatures will slowly
warm thorugh next week with 50s and possible a few 60s expected by
mid-week. Little to no precipitation is expected through the
period, therefore, expect everything to continue to dry out!


.AVIATION.../For the 06Z TAFS through 06Z Friday night/
Issued at 1130 PM CDT Thu Oct 11 2018

mid and high level cigs moving back into the state already.  This 
will slow the falling temps. Cigs expected to become MVFR or at 
least patchy coverages of MVFR cigs by 12Z.  Sites out west were 
slow to saturate and start precipitating but soundings show that 
deeper saturation will occur over Iowa a little faster than over the 
Plains.  In any event, only light precip expected.  Soundings vary 
as to precip type.  Should be mostly rain but its very possible a 
rain/snow mix could work in from the west to the KDSM terminal.


Freeze Warning from 1 AM to 8 AM CDT Friday for IAZ004>007-