Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 281735

National Weather Service Des Moines IA
1135 AM CST Mon Nov 28 2016

.SHORT TERM.../Today through Tonight/
Issued at 402 AM CST Mon Nov 28 2016

There are a few things to consider in this short term period.  We
have a large upper low that will sit over the Dakotas and West
central MN through the forecast period.  At the surface will be a
surface low lifting from Northeast SD into roughly the same location
of the upper low by 12Z Tuesday.  There will be a cold front that
will push across the state today.  By 12Z the front should make it
into Western Iowa then by 18Z the front should be into the Eastern
portion of our forecast area.  The rest of the afternoon the front
will make it into Western Illinois.  Coincident with the frontal
passage will be a pretty good area of forcing...mainly over the
Eastern quarter of the state but certainly clipping our far
Southeast.  Instability isn`t much but should be enough for an
isolated storm across our far East and locations over Eastern Iowa.

There was a dry push of air coming into the state overnight which
cleared skies and led to some pretty strong wind gusts...around 50-
55mph at times.  Through the night the wind was diminishing but
still quite gusty.  This will persist into the morning hours and we
may also see some gusty winds with the frontal passage. Temperatures
today will be in the 50`s which is some 15 degrees above normal.

For tonight we will see some clearing behind the front and slightly
cooler low temps tonight but winds will become Southwest and stay
around 10kts so I am not looking for a particularly cold night. With
the low still around it won`t be very clear either.  There will be a
fair amount of mid and high clouds.

.LONG TERM.../Tuesday through Sunday/
Issued at 402 AM CST Mon Nov 28 2016

The forecast challenge early in the period remains the closed
upper low over the Dakotas and Minnesota Tuesday and Wednesday the
the evolution of a closed low over the southwest CONUS late in the
week and into the weekend. Minor adjustments to the upper low
track as it will remain over the eastern Dakotas on Tuesday
however will dip a bit farther south Tuesday night and move near
the IA/MN border. This track will wrap short wave energy deeper
into Iowa on Wednesday with precipitation chances down to
Interstate 80. The NAM is the weakest and driest solution for
Wednesday with other solutions including the GFS more robust with
forcing by the afternoon. Given the developing cyclonic curvature
and amount of short wave energy rotating around the upper...should
have at least some light precipitation develop. Very cold
profiles aloft will mean precipitation type will rely on surface
temperatures and dew points. Wetbulb temperatures will be in the
low to mid 30s will yield a mix of rain or snow north. Minor snow
accumulations are possible.

Thursday and Friday will be quiet and remaining cool with highs in
the 30s to low 40s. Strong short wave energy will begin to drop
south through the inter-mountain west and be near the Four Corners
region by Friday. The ECMWF is an outlier with the evolution of
this system as it closes off and shifts it quickly northeast with
a major system developing towards next Sunday. The GFS/GFS
Ensembles/Canadian and the 12z ECMWF ensembles close this system
off over northern Mexico and thus much less active next weekend.
Favor the consensus solution and have continued the dry trend
through is period.


.AVIATION.../For the 18Z TAFS through 18Z Tuesday afternoon/
Issued at 1135 AM CST Mon Nov 28 2016

Main concerns are early thunder and winds today...followed by
lowering cigs northwest/north aft 12z Tuesday. Dry slot making
its way through region now...with iso thunder along the dryline.
Confined any thunder chances to KMCW...KALO and KOTM though line
over the southeast may have been chance of affecting apt at KOTM.
Otherwise mixing winds through 23z will give way to less wind
overnight...then aft 15z Tuesday winds again mix up from the west
southwest as cigs lower northwest to MVFR conditions between
12-18z. /rev




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