Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 231140
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
540 AM CST Fri Feb 23 2018

.SHORT TERM.../Today through Tonight/
Issued at 337 AM CST Fri Feb 23 2018

Precipitation has ended across the forecast area pushing off to
the northeast quickly as the sfc low has lifted into SE MN. The
associated cold front has moved into western portions of the
forecast area, with winds picking up a bit and temperatures
falling into the mid 20s. As the colder drier air moves into the
area today, skies expected to clear some and winds remain a bit
gusty this morning. High pressure to nudge into the state, and
quickly have WAA kicking back in with return flow setting up ahead
of the next system into tonight. Therefore still see fairly mild
temps across the state today, with nearly steady temps across the
north and slight warming into the southeast. With clear to partly
cloudy skies across the state this evening expect temps to fall
fairly quickly before seeing them steady off or warm late tonight.
Theta-e advection to lift into the southern forecast area late
tonight toward 09-12z Saturday. Soundings moistening, with some
light precip possibly spreading into the far south early Saturday
morning. Could initially have some ice introduction and light
snow, but overall soundings showing a quick loss of ice
introduction as warmer air moves in aloft and a change to freezing
rain expected. This cold result in a dusting of snow, followed by
a light glazing in the far south through the early morning hours.

.LONG TERM.../Saturday through Thursday/
Issued at 337 AM CST Fri Feb 23 2018

Main concern during the long term period remains the winter storm
to affect the area on Saturday. 00Z run of the GFS has fallen
more in line with the ECMWF solution of an open wave. As with
previous runs, the GFS and ECMWF transition to a closed upper-
level low north of Iowa. Kinematic and thermodynamic forcing are
still ample enough to result in good vertical ascent while the
system is over Iowa, resulting in higher precipitation rates and
possibly some convection.

The precipitation will begin as a mix of freezing rain or snow
over southern Iowa as a warm nose lifts into the state. The
precipitation will eventually orient as mostly snow northwest with
a wintry mix possible near the surface low track and rain to the
southeast.

The wind will increase during the period and should become gusty
from the west northwest by Saturday night. This would create some
blowing snow issues over the northwest. Have a 4 to 8 inch swath
of snow mainly along and north of a line through Carroll, Fort
Dodge and Mason City due to expected higher rates. Some light
freezing rain may occur along the southern fringe of this line.
The precipitation should end by midnight for most locations
followed by high pressure ridging by Sunday morning.

The upper level flow will transition to more zonal by Monday then
become southwesterly Tuesday night into Wednesday. Do expect
precipitation mid-week, however exact track of the system will
determine precipitation type due to warmer air lifting north. At
this time best chances for snow are in the northern CWA and a
transition to rain across the southern CWA.

&&

.AVIATION.../For the 12Z TAFS through 12Z Saturday morning/
Issued at 540 AM CST Fri Feb 23 2018

Tricky cloud forecast today with an area of clearing moving into
the western portion of the forecast area and expected to continue
to spread across the southern half of the state. Band of low
clouds behind the cold front up north expected to allow low clouds
to linger across the north through the morning hours. Otherwise
clouds to increase again tonight ahead of another weather system,
with the chance of a wintry mix moving into KOTM toward 09-12z
Saturday. Westerly to northwesterly winds to then become more
northeasterly tonight.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Saturday morning through late Saturday
night for IAZ004>007-015>017-023>025-033>035-044-045.

&&

$$

SHORT TERM...Beerends
LONG TERM...Zogg
AVIATION...Beerends



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