Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 040924
AFDDMX

AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
324 AM CST Sun Dec 4 2016

.SHORT TERM.../Today through Tonight/
Issued at 324 AM CST Sun Dec 4 2016

Precipitation is currently widespread across much of the forecast
area except for far northwest portions. The precipitation will
persist for the next several hours in the east with the strongest
forcing from the system passing through Iowa from now through
around 15Z. Overall progression has slowed slightly from earlier
runs and have lingered precipitation in the east until midday.
Precipitation type has been the biggest issue as a wedge of higher
dewpoints and wetbulbs have extended from southwest into central
Iowa near Des Moines. This has maintained a triangle of rain
across the south with the apex at Des Moines. Models have been
indicating that this wedge of higher wetbulbs gradually dissipates
with some transition from rain to either a mix or even all snow
for a period this morning. However, accumulations in the south
will be hard to come by given the existing warmth of ground
surface temperatures. Farther north, from about I80 northward,
precipitation type has been primarily snow overnight although
accumulations have been spotty as surface temperatures started
warm. Snowfall rates have also remained light with visibilities of
1 to 3 miles and melting has generally kept up with the falling
snow. However recently, as the forcing has increased this morning,
visibilities have come down to a mile or below in the northeast
quarter of the forecast areas, primarily where the advisory is
out.

Given the strongest forcing will be passing through over the next
few hours, anticipate the snow to persist across the north and
east with some expansion farther south as well. Advisory area
looks good and will leave as is for now. The system will pass east
by midday with strong subsidence across the area by this afternoon
and some clearing as well. There is no cold air on the backside of
the system with warm advection actually continuing as thermal
ridge builds toward the state. Temperatures will be warm tonight
and will have to make some consideration for fog given the recent
moisture, light south winds and relatively clear skies.

.LONG TERM.../Monday through Saturday/
Issued at 324 AM CST Sun Dec 4 2016

Temperatures will climb well above normal on Monday with thermal
ridge approaching the state from the west. This will be the last
warm day for much of the rest of the forecast ahead of an
approaching cold front which will arrive Monday night. There may
be some light precipitation associated with this boundary, however
the bulk of moisture will be well to the southeast and despite a
decent amount of forcing, only light rain/snow is expected Monday
night in northern Iowa. Colder air will arrive on Tuesday with
continued cold advection through Thursday as a Polar airmass
advects southward into the state. Any precipitation threat on
Wednesday and Thursday continues to be limited and any potential
snowfall would be very light. There will be some moderation into
next weekend with the potential for snowfall on Saturday as a
shortwave moves rapidly through the Midwest.

&&

.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1201 AM CST Sun Dec 4 2016

Confidence has increased somewhat since 00z. Widespread IFR/LIFR
conditions continue along and west of an KAIO-KAMW-KMIW-KALO line
at 06z...and these conditions are expected to spread eastward into
KDSM and KOTM early this morning. All TAF sites will likely see a
period of IFR visibility restrictions due to snow or a rain/snow
mix. Conditions should then increase sharply toward midday as the
precip departs with VFR conditions returning through the rest of
the period.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 AM CST this morning for IAZ017-
026>028-037>039-050.

&&

$$

SHORT TERM...Cogil
LONG TERM...Cogil
AVIATION...Small


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