Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 111601

Area Forecast Discussion
National Weather Service Des Moines IA
1001 AM CST Mon Dec 11 2017

Issued at 1001 AM CST Mon Dec 11 2017

Updated to include Decatur and Clarke Counties in the wind
advisory. Stronger winds aloft and soundings suggest winds may
advance farther east this afternoon. Will monitor for additional
updates through day.  /rev


.SHORT TERM.../Today through Tonight/
Issued at 332 AM CST Mon Dec 11 2017

The forecast concern is focused on the clipper system anticipated
to bring blustery winds later this morning and into the afternoon
hours. The biggest change to the forecast was increased winds
several knots across the western half of the forecast area as the
strong PV anomaly punches into the state by around 15z this
morning. Should see some stout initial gusts exceeding 40 knots
across the west and can expect the blustery winds to persist into
the afternoon hours with the strong mixing developing. Winds atop
the mix layer range from 35-45 knots. Utilized the ARW but the
latest NAM, RAP, and HRRR are in fairly good agreement with the
winds coming in stronger than previously anticipated. With the
increase in winds and wind gusts today, issued a wind advisory for
western portions of the forecast area. Cannot rule out some gusts
to 45 mph at locations east of this advisory area, but seems to
be a limited time frame if they do occur. The other concern was
precipitation chances but this system lacks any significant depth
of moisture as the strong PV anomaly pushes south across Iowa
today. Have mainly rain mentioned today with no ice introduction
into the column and surface temperatures warming to above freezing
by the time the mainly forcing moves through the area.

.LONG TERM.../Tuesday through Sunday/
Issued at 332 AM CST Mon Dec 11 2017

Large amplified trof over the eastern United States will persist for
the rest of the week as several short waves drop into the backside
of the trof.  The first of these will arrive on Wednesday with a
cold front diving through the state during the day.  Winds will pick
up in the wake of the front with cold advection and tight pressure
gradient aiding the strong winds.  In addition, near surface mixing
will also help in momentum transfer of the stronger winds aloft.
Strongest forcing will remain to the northeast of the state with
precipitation likely staying in Minnesota and Wisconsin.  Thermal
ridging ahead of the front will be across the state to start the day
with unseasonably mild temperatures, especially in the south before
the cold air arrives by later in the day.  The colder air will
remain across the state on Thursday with a weak reinforcing
shortwave passing through the state later in the day.

The upper pattern tries to become a bit more zonal toward next
weekend as the eastern trof become much less amplified.  This should
allow warmer air into the state by next weekend with temperatures
above normal.  However, there remains a decent amount of uncertainty
with models having a difficult time resolving the numerous
shortwaves in the flow both spatially and temporally into the


.AVIATION.../For the 12Z TAFS through 12Z Tuesday morning/
Issued at 526 AM CST Mon Dec 11 2017

Winds look to quickly increase b/t 15-18z today from north to
south across the TAF area. With the winds will be MVFR ceilings
moving through the state. Hires models are in great agreement with
the timing of the stratus moving through later this morning and
into the afternoon. The very strong wind gusts decouple by around
00z, but pressure gradient winds continue through the end of the
forecast period. The MVFR stratus is likely to exit by around
00-02z tonight.


Wind Advisory until 6 PM CST this evening for IAZ004-005-015-023-



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