Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 290827

Area Forecast Discussion
National Weather Service Des Moines IA
327 AM CDT Wed Mar 29 2017

.SHORT TERM.../Today through Tonight/
Issued at 328 AM CDT Wed Mar 29 2017

Several factors coming together for a very soggy period through
tonight for much of the forecast area. Broad area of decent
isentropic lift in Missouri will lift into Iowa today as warm
advection intensifies. In addition, a surge of moisture will
arrive from the south and with the associated lift, will lead to
widespread rainfall overspreading the forecast area from south to
north during the day. Precipitation will take a bit longer to
develop in northern Iowa given the dry easterly flow initially,
but even by later afternoon, the column saturates and
precipitation should push north of the border. Convective
instability will approach southern Iowa by late afternoon with
elevated cape of 250-500 j/kg and have included thunder in
southern Iowa during this time.

The forcing continues into tonight with mid-level kinematics
increasing. This will help to sustain rain/showers across much of
the forecast area overnight. The instability remain in southern
Iowa with precipitation a bit more showery in nature with the warm
sector nearby. Farther north, precipitation is in more of a
deformation area with a more stratiform type of rainfall expected.
Precipitation type concerns appear quite limited at this time and
have gone rain in all locations overnight. Have maximized pops
from 90-100 percent across the area by this afternoon into this
evening given the relatively high QPF. Precipitation values of
1.25-1.75" are expected in the south with around 0.50-0.75" in the
northwest. While decent rises are expected on rivers, the heaviest
rainfall is expected where there have been more significant
deficits of rainfall since late last summer. Therefore, flooding
is expected to be a big problem with this system although a few
locations may approach flood stage.

.LONG TERM.../Thursday through Tuesday/
Issued at 328 AM CDT Wed Mar 29 2017

Will continue to see precipitation linger into Thursday with
mid-level forcing persisting as upper low passes slowly through
Missouri. However, this forcing will be waning with time and
precipitation will become spottier as the day progresses. This
system is expected to eventually push east of the area by Friday
with drier conditions and moderating temperatures into Saturday.
Next system dropping into the Rockies takes a more southern route
through the central United States during the weekend. However,
there will be a period Saturday night into early Sunday where lift
and moisture should be sufficient for some light rainfall,
primarily in southern Iowa where saturation will be deeper. While
some threat of precipitation lingers later Sunday into Monday, it
appears the bulk of the lift and precipitation will remain just
south of Iowa. Temperatures will be holding close to seasonal
normals through the weekend.


.AVIATION.../For the 06Z TAFS through 06Z Wednesday night/
Issued at 1204 AM CDT Wed Mar 29 2017

There has been little change from 00z conditions or thinking
moving forward. MVFR stratus is in place roughly across the
southern half of Iowa at 06z with VFR conditions north. These
conditions should not change much initially, but eventually the
stratus will begin advancing northward after sunrise reaching all
sites with MVFR or IFR stratus. This will be accompanied by
showers crossing the MO River into IA through the morning with
visibility also contributing to restrictions. Confidence is
fairly high for IFR conditions and plenty of showers for the
afternoon and evening hours. The precip will not be continuous
into the evening, but breaks short enough to not attempt to time.
Thunder is also possible, especially south, but confidence in
timing and location is not great enough to include as of yet.





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