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Area forecast discussion 
National Weather Service Des Moines Iowa
630 am CDT Wednesday Sep 17 2014

Short term /today/...
issued at 345 am CDT Wednesday Sep 17 2014

Mostly cloudy skies early this morning will clear out during the day
per forecast soundings...with a pleasant late Summer afternoon
anticipated. Increased forecast high temperatures a degree or two as
ample sunshine and weak warm air advection should allow temperatures
to rise back into the low to middle 70s. Otherwise no sensible weather
to speak of from middle morning Onward.

Long term /tonight through Tuesday/...
issued at 345 am CDT Wednesday Sep 17 2014

The next area of high pressure will be dropping south out of
Canada and into the central Great Lakes tonight and Thursday. This
system will help buffer Iowa from any moisture sources through
Thursday evening while funneling dry air into the state. The
Pacific moisture stream will be following the northwest flow aloft
and remain focused just west of the Missouri River tonight while
the Gulf moisture is shunted to the south. A trough of low
pressure shifting east across the Western Plains combined with a
subtle shift east of the surface high Thursday night will allow good
Theta-E advection to reach western Iowa then move across the state
on Friday. The moisture advection and forcing should be enough to
trigger a few storms during this period. Any precipitation Friday
should be done by the afternoon with warm conditions developing
with highs in the upper 70s to lower 80s.

Precipitation chances with the primary frontal boundary arrival
Friday night and Saturday remain challenging. While precipitable water values do
rise to 1.5 inches or higher...the overall forcing with the system
is not well focused. The best potential should be over the far
north Friday night then south of Interstate 80 Saturday afternoon
during peak heating. The middle level flow by Saturday will be
transitioning northwest and this should hold any tropical
elements just south of the state in Kansas and Missouri.
Overall...have lowered probability of precipitation a bit for Saturday with the potential
for a solid line diminished and more likely resulting scattered to broken
line along the boundary.

Sunday will be a transition day then a return of Canadian high
pressure for Monday and Tuesday. Dry conditions and seasonable
temperatures can be expected during this period.

&&

Aviation...17/12z
issued at 630 am CDT Wednesday Sep 17 2014

VFR conditions will prevail through the taf period with skies
clearing this afternoon. There is some potential for fog early
Thursday morning...especially toward mcw and alo...however
confidence is too low to include in the 12z tafs.

&&

Dmx watches/warnings/advisories...none.

&&

$$

Short term...Lee
long term...donavon
aviation...Lee

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