Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 162050
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
350 PM CDT Sun Apr 16 2017

.SHORT TERM.../Tonight through Monday/
Issued at 349 PM CDT Sun Apr 16 2017

High pressure will move east of Iowa with ridging aloft that will
provide for another day of plentiful sunshine and very mild
temperatures on Monday. Light and variable winds early in the day
will become from the southeast in the afternoon with highs in the
middle 60s over northern Iowa to the low 70s over southern Iowa.
Clouds will begin to increase Monday night as a shortwave trough
over the Pacific Northwest States moves across the Dakotas with
surface low pressure developing over eastern Montana.

.LONG TERM.../Monday night through Sunday/
Issued at 349 PM CDT Sun Apr 16 2017

By Tuesday morning, the surface low will be nearing the
Dakotas/Minnesota border with a cold front extending southwestward
from it into South Dakota. This cold front will drop southeast
into Iowa Tuesday and Tuesday night. MUCAPE values will peak
between 500 and 1500 J/kg over central Iowa with the highest
values over the southern part of the state and deep layer shear in
the 30 to 40 knot range. However, warm air centered around 700mb
may limit convection to ahead and along the front where a plume of
higher theta-e will reside. The overall trend as noted previously
of less areal coverage continues as the best kinematic forcing is
closer to the surface low tracking across Minnesota into the
western Great Lakes States and the best thermodynamics stays
farther south as noted above.

The cold front will stall out over far southern Iowa and northern
Missouri Tuesday night. Storms that are able to form along this
boundary will have plenty of moisture and fairly unidirectional
shear in the mid-levels that locally heavy rain may be possible as
rounds of storms pass over the same area. NAM/GFS/CMC place 1.5
inches of rain in 12 hours over some part of southern Iowa Tuesday
night.

This stalled boundary will lift northward on Wednesday as a warm
front and be draped from west central to east central Iowa as a
new area of low pressure develops east of the central Rockies and
moves toward Iowa. Soundings are rather impressive at this far out
in time over southern Iowa with MUCAPE approaching 2000 J/kg,
veering low-level hodographs, impressive low level jet dynamics
and SRH. Needless to say, severe weather potential will have to be
monitored for Wednesday afternoon and Wednesday night. Farther
north on the cool side of the front, there will be plenty of
showers. Temperatures may need to be refined on both sides of the
boundary.

As this low pressure pulls away from Iowa, there will be some
residual showers that may linger over eastern Iowa into part of
Thursday. Otherwise, drier and cooler air will arrive on winds from
the north and northwest. Meanwhile, a longwave trough will drop out
of the Northwest into the Rockies with a closed low tracking
through Kansas and Missouri late Friday into Saturday. GFS and
Euro have trended southward, which would brush the state with some
rain showers as best frontogenesis/deformation zone would stay
south of the state. However, the CMC is much farther north
bringing rain to much of the southern 2/3rds of Iowa. May be able
to adjust PoPs downward in coming forecast packages if model
consistency solidifies and remains. While the exact temperatures
will depend on where the clouds and rain setup, temperatures will
remain below normal to end the week and start next weekend.

&&

.AVIATION.../For the 18Z TAFS through 18Z Monday afternoon/
Issued at 1218 PM CDT Sun Apr 16 2017

While there may be times of high level clouds throughout the TAF
period, conditions will remain VFR at all terminals through the
TAF period. Gusty winds from the northwest mainly over the
northern terminals this afternoon will become light and variable
this evening as high pressure moves across the state.

&&

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

$$

SHORT TERM...Ansorge
LONG TERM...Ansorge
AVIATION...Ansorge



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