Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 240855
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
355 AM CDT Tue Oct 24 2017

.SHORT TERM.../Today through Tonight/
Issued at 355 AM CDT Tue Oct 24 2017

The main concern in the short term was focused on the winds this
morning into the afternoon hours. Models are not capturing current
(as of 03z) winds/gusts across northern Iowa into southern
Minnesota and utilized an adjusted MAV/MET guidance to start with
winds today. Evident on WV, strong PV anomaly punching into
northwestern Iowa providing plenty of wind gusts over 40 mph
across the far northern with EST and SPW topping 50 mph. Expecting
these wind gusts to continue to occur and filter even further
south as the strong PV anomaly pushes south this morning. Mixing
only looks to persist this morning through around midday before
the pressure gradient begins to relax this afternoon. Still
expecting gusty winds this afternoon, but the strongest gusts will
occur from now until the late morning hours as the strong PV
anomaly pushes through state. The winds atop the mixed layer range
in the 40-45 knot through around 17-18z before gradually
weakening during the remainder of the afternoon. NAM is a bit more
representative of current winds across northern Iowa, but still
are a tad too low wrt to gusts. Nudged up wind gusts this morning
across the advisory area into southwest portions of the forecast
area. Added three more counties across the southwest to reflect
this change. Certainly confident in the widespread wind advisory
and cannot rule out several gusts over 50 mph this morning. Lower
confidence in seeing wind gusts over 58 mph, but then it wouldn`t
be too surprising given the current wind trends and with the
expected mixing to increase with the sunrise.

.LONG TERM.../Wednesday through Monday/
Issued at 355 AM CDT Tue Oct 24 2017

Warm advection will be ongoing at the start of the period as a
thermal ridge crosses the Plains. With this ridge approaching the
state, westerly surface flow and some sunshine, temperatures are
expected to be seasonably warm for highs on Wednesday. The warmth
will continue overnight into Thursday morning prior to arrival of
the next cold front. This front will be associated with a
deepening trof across the central United States. The frontal
passage will be uneventful as moisture will be lacking as the
associated forcing passes through the state. Strong cold advection
on the backside of the front along with subsidence will lead to
strong northwest winds by later in the afternoon into the evening.

Both GFS and EC models indicate the deformation precipitation may
skim northern portions of the state on by Thursday night and push
farther south into Iowa on Friday. At this point, any
precipitation would be patchy and light as bulk of forcing and
activity will be well east of the state. However, thermal trof
will be building into the state with much colder air. The
combination of the brisk northwest winds, cloudy skies and patchy
precipitation on Friday will lead to a very raw day. The threat of
any precipitation should come to an end by Friday night as the
system begins to depart. Temperatures on Friday night and Saturday
night are likely to be well below freezing effectively ending the
growing season for whatever vegetation remains active at this
point. Moderation is expected into early next week but with timing
difference between the models on timing of any precipitation
threat.

&&

.AVIATION.../For the 06Z TAFS through 06Z Tuesday night/
Issued at 1203 AM CDT Tue Oct 24 2017

Strong winds remain the theme for this TAF package. High
confidence in widespread 25 to 30 kt sustained winds, with gusts
of 35 to 45kts. Slight chance of MVFR remains at KMCW and KALO.
Winds should die down after sunset tonight.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM CDT this evening for IAZ004>007-015>017-
023>028-033>039-044>050-057>061-070>073-081>083-092-093.

&&

$$

SHORT TERM...Podrazik
LONG TERM...Cogil
AVIATION...Kotenberg



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