National Weather Service Raw Text Product

025 
FXUS63 KDMX 200510
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1210 AM CDT Mon Aug 20 2018

...Updated for 06z Aviation Discussion...

.DISCUSSION.../Tonight through Sunday/
Issued at 353 PM CDT Sun Aug 19 2018

Large area of rain has been to the west of the forecast area much
of the day slowly marching toward central Iowa associated with an
upper low spinning across SW NE and NE CO, and an associated 
surface low moving through east central to southeast KS currently.
The upper low and surface low are expected to move into NW MO/SW 
IA overnight and then slowly meander eastward through southern 
IA/northern MO through the day Monday and finally move into 
northern IL Monday night. As this system approaches moisture 
should lift northward through the state with a warm front lifting 
through central Iowa tonight into mid-day Monday. This will allow 
for showers and some thunderstorms to overspread the forecast area
tonight and continue across the area for much of Monday. As the 
surface low tracks across southern Iowa a dry slot will lift into 
south central to east central portions of the forecast area 
through the day Monday. Instability will also increase south of 
the warm front with a potential for some additional convective 
development in dry slot area as the upper low moves overhead and a
pseudo-dry line lifts through the area. The main upper low to 
linger meandering slowly east northeast into Monday night with all
precipitation expected to move out of the area by late Monday 
night. Temperatures with the rain shield and def zone across the 
west to east to be lower Monday with highs struggling to reach the
upper 60s to around 70. Overall severe potential will be low with
this system given the lack of instability expected, but the best 
chance will be an isolated damaging wind gust with the greatest 
potential coming Monday into Monday afternoon in the east central 
to southeast where the dry slot area will be in place. 

Have increased QPF some in the west central to southwest after
getting a better handle on the system and its timing/placement 
and seeing rain totals upstream. Also given the system will likely
pivot in this area with an extended period of rain across the hwy
20 corridor toward the northeast forecast area as the def zone 
moves across and lingers into Monday evening. Therefore have the 
highest QPF in these areas where 1 to 3 inches or more may be 
possible in spots. Remainder of the forecast area will be more 
dependent on convective elements bringing higher rain totals with 
around 0.5 to 1" likely then higher totals of 1-2" where 
thunderstorms or heavier rain rates move through. 

On Tuesday have another small weak wave drop into the backside of
the departing system and may see some increased cloud cover with a
small chance for an isolated shower in the afternoon. Better
chances are to the north and east, so have left it dry for now
with models showing some possibility of lack of moisture with the
system as well. Otherwise high pressure to build into the area for
the remainder of the week with the thermal ridging building in
through Saturday. This should allow temps to warm back into the
80s to even a few 90s as H85 temps warm to around 20C or higher.
The pattern becomes a little more active again into the weekend
with another trough dropping through the area and westerly, near
zonal flow setting up across the central US. 

&&

.AVIATION.../For the 06Z TAFS through 06Z Monday night/
Issued at 1210 AM CDT Sun Aug 19 2018

Showers are widespread over the southwestern half of Iowa with
little if any thunder as low pressure moves near Kansas City at 
midnight. Forecast TAF sites are all VFR at 5z with some MVFR
restrictions over southwest Iowa where there is moderate rain
falling. Expect more MVFR conditions to spread over the terminals
tonight through Monday morning, but have pulled back on IFR 
conditions at this time choosing low end MVFR. There will be a
break in the rain over southeast before redevelopment in the
afternoon. Winds will increase from the northeast and north and 
become gusty on the back side of the low at most terminals by the 
end of the TAF period. 

&&

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

$$

DISCUSSION...Beerends
AVIATION...Ansorge