Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 160000
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
700 PM CDT Wed Mar 15 2017

.SHORT TERM.../Tonight through Thursday/
Issued at 342 PM CDT Wed Mar 15 2017

Large area of high pressure will continue to settle southeast
tonight from the lower Ohio Valley and into the southeastern CONUS
by Thursday morning. This will allow for strong warm advection to
lift back into Iowa. Currently there is a tight 850 mb thermal
gradient from central Iowa into central Nebraska of -10C to +10C.
A ribbon of cloud cover currently exists within this gradient and
in response to the warm advection moving slowly east. The
warm/theta-e advection will gain momentum east overnight and it is
possible that a few sprinkles or flurries develop in response
though potential is low enough to exclude from the forecast at
this point.

Temperatures are expected to be warmer on Thursday though some of
the warm advection will be negated by the snow pack over northern
Iowa. Temperatures should reach the 50s to near 60 south but
linger in the 30s to low 40s north where the deepest snow pack
exists. Light remains possible over the far north and far east
where the better saturation exists.

.LONG TERM.../Thursday night through Wednesday/
Issued at 342 PM CDT Wed Mar 15 2017

Low level gulf moisture arrives Thursday night with good southerly
flow developing ahead of an approaching low pressure trough. Dew
points in the 30s and 40s will be lifting into Iowa. Areas of fog
likely will develop especially over the snow pack regions as the
high dew points move over the colder surface. In addition, some
drizzle could develop within the moist layer considering it is a
warm advection regime leading to vertical ascent which would help
force collision coalescence. The fog and drizzle should diminish
as the boundary passes through from west to east late Thursday
night into Friday morning. Temperatures are expected to be even
more mild on Friday with highs in the low to mid 40s north to the
low 60s south as good mixing develops by the afternoon in the wake
of the boundary.

Weak ridging builds into the Midwest this weekend and while
Saturday will be a bit cooler, mild conditions will generally
persist into Monday with little to no precipitation expected. A
boundary will move through the region late Monday into Monday
night as a strong short wave passes to the northeast. This will
usher in another round of cold advection into Iowa and cooler
weather by Tuesday. Mid next week still features ridging following
for Wednesday in advance of a deepening system over the southwest
CONUS that will impact the region toward the end of next week.

&&

.AVIATION.../For the 00Z TAFS through 00Z Thursday afternoon/
Issued at 700 PM CDT Wed Mar 15 2017

A band of lower clouds which are borderline MVFR will advance across
TAF locations tonight bringing a 3 to 4 hour period of lower cigs.
Otherwise VFR conditions expected until towards the end of the
period when low level moisture significantly increases bringing in
MVFR cigs and some drizzle and fog which may also bring reduced
vsbys.

&&

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

$$

SHORT TERM...Donavon
LONG TERM...Donavon
AVIATION...FAB



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