Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 221956
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
256 PM CDT Sat Apr 22 2017

.SHORT TERM.../Tonight through Sunday/
Issued at 256 PM CDT Sat Apr 22 2017

Weak upper level low circulation evident by the swirl in the
visible satellite data over northwest Missouri. This is responsible
for scattered high level clouds over far southern Iowa. Otherwise,
surface high pressure ridge continues to move slowly south and is
over northern Iowa this afternoon. The ridge will continue to
progress slowly south/southeast through Sunday and will be over the
southeast portion of the state by Sunday afternoon resulting in a
switch to southwest winds and warm advection for much of central
Iowa. Surface dew point temperatures will remain low with the dry
air highly conducive to warming as profiles mix to near 850 mb.
Possible for patchy fog tonight however the dry air in place will
limit potential.

.LONG TERM.../Sunday night through Saturday/
Issued at 256 PM CDT Sat Apr 22 2017

Summary: Another week, another active weather pattern with multiple
opportunities for showers and thunderstorms. There will be
fleeting times of dry weather. Temperatures will tend to be below
normal from Tuesday through the end of the week.

Winds will become strong and gusty as a tight pressure gradient sets
up over the state as an area of low pressure moves through South
Dakota toward Minnesota. Wind gusts approaching 40 mph will be
possible. Within the warm air advection ahead of the cold front, a
few showers or thunderstorms may occur later Monday and Monday night
with the best chance over northern Iowa. Severe weather does not
look like with meager instability to work with and stout inversion
around 700mb per forecast soundings.

As the low pulls away from the state, a new area of low pressure
will already be forming east of the central Rockies and track from
the central Plains Tuesday morning to eastern Iowa late
Tuesday/early Wednesday along a boundary draped over Iowa. To the
south of this boundary, good theta-e advection will occur with
strong frontogenesis north of the boundary. Expect many of the
showers and storms along and north of this boundary, but still a
bit of uncertainty in the position of the boundary and the surface
low at this time. Drier air will arrive by late Wednesday and
offer a break from the showers into early Thursday.

Models continue to diverge beyond Thursday with the GFS farther
north compared to the Euro and CMC. The Euro/CMC would have mainly
dry weather from Thursday through early Saturday whereas the GFS
would offer many more chances for rain. What confidence there is is
that southern Iowa would have a better chance of showers and
thunderstorms vs northern Iowa so slightly trended down PoPs over
northern Iowa as did our offices covering Minnesota.

&&

.AVIATION.../For the 18Z TAFS through 18Z Sunday afternoon/
Issued at 1226 PM CDT Sat Apr 22 2017

VFR conditions through the period. High pressure moving southeast
through the area during the period will cause a wind shift from
northeast to southwest.

&&

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

$$

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



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