415 
FXUS63 KDMX 060929
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
429 AM CDT Wed Oct 6 2021

.DISCUSSION.../Today through Tuesday/
Issued at 429 AM CDT Wed Oct 6 2021

Key Message:

-Chances for showers and isolated thunderstorms by later today and
 into Thursday.
-Potentially very warm and windy on Saturday.

An upper low that is drifting north, is located over Arkansas this
morning with Gulf moisture wrapping around it and moving towards
Iowa. At the surface, Iowa remains under the influence of a ridge
of high pressure which is now centered well to the east over the
Great Lakes and southeast Canada. The deep layer flow remains
nearly unidirectional from the east though there is some shift to
the southeast beginning to take place. This flow has left a broad
area of stratus over central and eastern Iowa.

The Gulf moisture will quickly lift northwest into southeast Iowa
this morning and into central Iowa by the afternoon. There are a
few showers along the leading edge of the moisture advection but
much of the precipitation is lagging and awaiting deeper moisture
to be achieved. Expect the greatest chances for showers and
isolated thunderstorms to arrive over the far southeast by mid
afternoon then expanding further north and west overnight and 
into Thursday as the upper low lifts north through Missouri and
into central Illinois by Thursday afternoon. Individual showers
and storms will have relatively slow speeds and it is possible
efficient rain processes develop that could result in locally
heavy rainfall somewhere east of Interstate 35 as the upper low
draws closer and cell motions slow further. PWAT values will be at
or above 1.50 inches which is over 200 percent above climatology.
That said, not expecting heavy rain to be widespread and some
areas could have little to no precipitation in this setup.

Temperatures today and Thursday will be largely dependent on 
cloud cover, much like what occurred on Wednesday. Lean toward the
lower end of guidance for highs on each day though less clouds 
over the far west could lead to warmer conditions there. 

The upper low will lift out of the area Thursday night as a long
wave trough moves east into the western CONUS. This trough will
bring southwest flow aloft to Iowa and warm advection on Friday.
High temperatures on Friday are expected to be in the upper 70s to
low 80s.

The southwest flow will steepen further and the pressure gradient
will tighten on Saturday as even warmer conditions arrive. Deep
mixing is certainly possible, which could lead to windy conditions
by Saturday afternoon. The one catch on Saturday is the potential
for a thickening cirrus shield arriving over Iowa which could
limit heating potential. The increasing southwest flow,
originating over the Baja California, is favorable for cirrus
reaching the state so stay tuned there. Without, clouds, the
mixing and thermodynamic profile is favorable for upper 80s 
temperatures. Have remained less optimistic on temperatures due to
the cloud potential. Wind gusts in excess of 35 mph will be
possible though. A cold front will pass through Saturday night and
Sunday followed by a short wave lifting northeast that could
impact southern Iowa later Sunday and into Sunday night. Showers
and a few thunderstorms will be possible during that time. 

Precipitation chances may linger into Monday as the short wave
continues to lift through Iowa. The forecast for Tuesday and
especially just beyond the 7 day forecast on Wednesday still looks
interesting as closed upper low develops and lifts into the
Midwest. Won't go into too many details at this point since it is
still way out west of Alaska, but it likely will be a severe
weather setup somewhere across the region along with very strong
synoptic winds. Stay tuned!

&&

.AVIATION.../For the 06Z TAFS through 06Z Wednesday night/
Issued at 1159 PM CDT Tue Oct 5 2021

Concerns continue to revolve around ceilings tonight with the
expectation of an MVFR stratus deck expanding into/across much of
the state. Possible IFR may prevail in areas, but kept MVFR for 
the time being with some model struggle in existing cloud cover.
Fog remains a limited concern, mainly in areas that remain cloud
free longest as winds remain light. 


&&

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

$$

DISCUSSION...Donavon
AVIATION...Curtis