Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 280907
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
407 AM CDT Sun Aug 28 2016

.SHORT TERM.../Today/
Issued at 404 AM CDT Sun Aug 28 2016

Surface high pressure is centered to the east of the state but
remains ridged into central Iowa. Areas of fog has developed due
to the calm winds and mostly clear skies with the exception of
some high cirrus. A few locations have dropped down to one quarter
mile visibility including Mason City, Ames and Carroll. Expect
will need a dense fog advisory for portions of the north, mainly
along and north of Highway 30 through mid morning.

Farther south a few isolated thunderstorms have developed over
northern Missouri and far south central Iowa. This is a region of
deeper moisture just south of the ridge axis and an area of
theta-e advection. The high pressure will gradually shift
further east today allowing the return flow to lift north. The
deeper moisture will move towards the Interstate 80 corridor by
the afternoon and wrap around into western IA while drier air
lingers north and east. Surface dew points will rise back into the
low 70s for much of central Iowa this afternoon. This will help
lower convective temperatures and increase instability. The modest
forcing associated with the theta-e advection will be enough to
overcome the weak convective inhibition for a few showers and
thunderstorms to initiate within the region of deeper moisture.
High temperatures are expected to be in the low to mid 80s.

.LONG TERM.../Tonight through Saturday/
Issued at 404 AM CDT Sun Aug 28 2016

Generally a quiet weather pattern and thus low impact weather in
store throughout the week and into next weekend. The main concern
was focused on periodic thunderstorm chances tonight through
Tuesday. Models are in decent agreement with the overall synoptic
pattern and utilized a blend this week.

Tonight into Tuesday...a large ridge continues to control the
weather pattern over the southern two-thirds of the CONUS with
zonal flow aloft further north into Canada. Several weak impulses
will ride the upper level ridge and potentially impact the
forecast area during this time frame. Surface high pressure is
expected to remain over the Great Lakes and Cornbelt and provide
plenty of subsidence and dry air over the state. Low confidence
with any widespread thunderstorm activity, let alone any severe
weather. Very weak shear, if any at all, and any forcing and
moisture is limited tonight into Tuesday. Atmosphere does
destabilize enough during the afternoon Monday, so kept low chance
pops going during this time into the evening. Tuesday, a weak
boundary meanders across the state and may provide a little better
focus or organization for thunderstorm development, but still low
confidence with anything widespread due to the lack of significant
moisture and forcing with this system.

Wednesday through Saturday...Large upper level ridge builds into the
region and provides relatively dry conditions and cooler weather.
The next potential for significant thunderstorm activity looks to be
Friday night into Saturday with a decent vort max cutting across
Kansas into Missouri.

&&

.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1052 PM CDT Sat Aug 27 2016

Fog development is expected across the area tonight with good
radiational cooling and ample low level moisture. Anticipate
widespread MVFR to IFR conditions during the early morning hours
until mid morning when the fog burns off. Will see VFR conditions
by midday tomorrow through the end of the forecast period. Surface
winds will be light and variable overnight becoming light from the
southeast on Sunday.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

SHORT TERM...Donavon
LONG TERM...Podrazik
AVIATION...Cogil


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