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fxus63 kdmx 152338 

Area forecast discussion
National Weather Service Des Moines Iowa
638 PM CDT sun Sep 15 2019

..aviation update...

Discussion.../tonight through Sunday/
issued at 225 PM CDT sun Sep 15 2019

Primary concerns this forecast will be fog potential over eastern
Iowa tonight, early week warmth, and then thunderstorm chances
midweek into this weekend. With a mainly clear sky tonight and
winds becoming light, this should be a good setup for at least
areas of fog. The favored locations will be over eastern Iowa
where the lightest winds are expected. Otherwise, upper level
ridging and ridge axis will build through Iowa tonight into Monday
and then transition to southwest flow aloft into at least early
next weekend. With 850mb temperatures in the low 20 celsius range
on Monday and Tuesday, surface temperatures will rise into the
middle and upper 80s, which is about 10 degrees above normal for
the middle of September. Combined with the above normal dewpoints,
heat index values will be in the low to middle 90s on both days
with Tuesday also having a breezy wind from the south.

As the transition to southwest flow begins Monday, this will open
the door for shortwave troughs to move through the region and bring
periodic chances for storms. One period will be late Tuesday night
into early Thursday as a shortwave trough moves northwest of Iowa.
At the surface, a cold front will advance into the state with qg
convergence aloft supporting development of storms. Cips
experimental analog-based severe probability guidance does show a
stripe of 15% probability of severe over much of Iowa. While there
could be some strong storms with moderate instability, deep layer
shear is lacking and may limit the overall severe risk.

The aforementioned front never makes it through Iowa as it retreats
northward into Minnesota on Thursday into Friday in response to a
long wave trough deepening over the western US. As this trough
ejects over the Dakotas next Saturday and a new cold front
approaches the area, it could be a rather active day. Depending on
the timing of this front, there does look to be the potential for
strong to perhaps severe weather sometime around the Saturday


Aviation.../for the 00z tafs through 00z Monday evening/
issued at 633 PM CDT sun Sep 15 2019

Main concern during the period will be potential for IFR/LIFR fog
development at sites Kalo/kotm. Growing confidence in fog
development overnight across eastern Iowa underneath mostly clear
skies, light winds, and ample moisture abound as surface high
continues to slide across. Have introduced IFR conditions at both
sites for the time being. Elsewhere, VFR conditions forecast to
prevail at kfod/kmcw/kdsm as southeast winds also set in across
the area overnight.


Dmx watches/warnings/advisories...

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