Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 220827
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
327 AM CDT Tue Aug 22 2017

.SHORT TERM.../Today through Tonight/
Issued at 327 AM CDT Tue Aug 22 2017

A small area of rain still over the far southeastern counties, and
should continue to push ESE and exit the area within the next few
hours. High clouds shield also working on exiting the forecast area
with some brief low sct-bkn decks showing up just as the high clouds
clear out. Otherwise drier air pushing in from the northwest fast
with dewpoints already in the upper 50s in NW IA, and into the
lower/mid 50s across SE SD and SW MN. Dewpoints should drop some
still through the day, with dry conditions expected into tonight.
Temperatures to warm into the 70s to around 80, but breezy northwest
winds also expected. Otherwise high pressure from the northern high
plains will build southeastward through the day to dominate the
forecast area tonight. This will result in clear skies, light winds
and temperatures dropping into the lower to mid 50s for lows.

.LONG TERM.../Wednesday through Monday/
Issued at 327 AM CDT Tue Aug 22 2017

Overall the long term forecast is fairly quiet, with steady
temperatures just a bit below normal for the season. From
Wednesday through Thursday night Iowa will remain beneath the
cyclonic influence of a 500 mb gyre located over eastern Canada.
At the surface a cool high pressure area will dominate the region
on Wednesday before sliding southeastward. On Wednesday night into
Thursday a shortwave impulse rounding the cyclonic flow aloft will
provide some modest forcing and some prognostic models depict
small blotches of light rain, however, forecast soundings indicate
a distinct lack of moisture or instability and have maintained a
dry forecast for now.

On Thursday the eastern Canada/northeastern U.S. 500 mb trough
will finally eject eastward, allowing for a return of a nebulous
zonal/weak ridging flow aloft. A broad, weak shortwave will then
move through the light flow over the Upper Midwest from Friday
into Saturday, providing for a return of rain chances at times.
However, there is no small-scale focus mechanism for convection
and instability will remain very limited. A likely solution for
sensible weather during this time will be increasing clouds,
showers, and possibly a few thunderstorms in our northwestern
counties closer to the mid-level trough.

In the latter half of the weekend and into early next week, the
modest shortwave described above will gradually carve out a broad
cyclonic flow region over the mid-southeastern U.S., resulting in
lingering rain chances across Iowa. The details of this large-
scale evolution will be somewhat dependent on the interaction
between this broad trough and the remnants of a potential
tropical cyclone being resolved by the ECMWF and GFS lifting out
of Texas during this time. In any event, no real weather impacts
or hazardous weather are expected in our forecast area for the
next seven days, other than intermittent light showers and a few
benign thunderstorms.

&&

.AVIATION.../For the 06Z TAFS through 06Z Tuesday night/
Issued at 1130 PM CDT Mon Aug 21 2017

Lingering storms south of I 80 with light rain/lower MVFR cigs at
times for KALO/KMCW/KDSM/KOTM between 06-12z then generally VFR
mid to high level as clouds depart. Winds to pick up from NW
gusting up to 22 kts during peak heating 14-23z then relaxing.
High level sct clouds aft 15z...then generally sct-skc aft 18z.
/rev

&&

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

&&

$$

SHORT TERM...Beerends
LONG TERM...Lee
AVIATION...REV



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