Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 261743

Area Forecast Discussion
National Weather Service Des Moines IA
1242 PM CDT Fri Aug 26 2016

...Updated for 26/18Z Aviation Discussion...

.SHORT TERM.../Today/
Issued at 342 AM CDT Fri Aug 26 2016

High pressure moving into northwest Iowa has brought cooler
temperatures and lower dew points to that region with each dropping
into the low to mid 50s. A broad area of cirrus shield continues to
stream north as moisture transport is ongoing over the drier air
below. A few patches of fog have begun to develop along the northern
periphery of the cirrus including near Waterloo and Mason City and
actually a few reports farther south under the high clouds.
Potential for local reduced visibilities to one quarter mile due to
the fog over the next several hours.

A few showers and thunderstorms have develop over northern Missouri
along ribbon of theta-e advection. CAMs being aggressive lifting
precipitation into central Iowa this morning. The initial push north
should be slowed by dry air as the area of high pressure slides east
across northern Iowa. Proximity soundings at Des Moines show a
moistening profile becoming saturated down to 8-10 kft toward noon
then saturation lowering to around 5 kft by mid to late
afternoon. May be a bit low on pops over the south this morning
then precipitation should lift into the Interstate 80 to Highway
30 corridor mid to late afternoon. Clouds will again have an
impact on high temperatures.

.LONG TERM.../Tonight through Thursday/
Issued at 342 AM CDT Fri Aug 26 2016

For tonight...a broad ribbon of theta-e advection will lift from
roughly the I-80 corridor Northward across the forecast area.
Showers and thunderstorms should develop/spread Northward
overnight tied to that and aided by some decent forcing.

On Saturday a shortwave will sweep the Northern Plains and upper
midwest and a warm front across Northern/Eastern Iowa will linger
through mid afternoon. Showers/storms should be ongoing across
much of central Iowa Saturday morning then be confined to the
North and East later in the day.

For Sunday in the wake of the passing shortwave we will be in
broad Southwest flow with a surface low over the Northern Plains
and a frontal boundary setting up across the Dakotas and Minnesota
into Iowa by later in the day. Instability will increase later in
the day with a chance for showers and storms in the afternoon into
Sunday night. Then for Monday into Tuesday ridging will develop
over the Rockies but as the ridge develops...a trough will set up
over Eastern portions of the upper midwest with a frontal boundary
somewhere across the region and models indicate some instability
so there will be additional chances for showers and storms into
Monday and Monday night. Tuesday into Thursday the aforementioned
upper ridge pushes into the central plains then the upper midwest
and this should warm us up going into mid to late week.
Instability along the fringe of the ridge will mean at least some
isolated storms across Northern/Eastern portions of the forecast
area but models are pretty divergent by this point so I kept the
slight chance/chance pops we had going in the longer term at this


.AVIATION.../For the 18Z TAFS through 18Z Saturday afternoon/
1242 PM CDT Fri Aug 26 2016

Ceilings will gradually lower at all TAF sites as an area of
SHRA/TSRA overspreads the state tonight from southwest to northeast.
Have gone MVFR at all TAF sites...but would not be surprised to see
at least a brief period of IFR conditions due mainly to ceilings
overnight especially after 08Z and lasting through approximately 12Z
Saturday. Precipitation will gradually end from southwest to
northeast during the day on Saturday.




SHORT TERM...Donavon
AVIATION...Zogg is the U.S. government's official web portal to all federal, state and local government web resources and services.