Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 261129
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
629 AM CDT Tue Mar 26 2024

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

* Precipitation intensity eases, transitions to snow as it
  pushes east today. Light accumulations, greatest north up to
  around an inch or two.

* Small window for wintry mix before transition to all snow,
  freezing rain chances lessened, but freeze/refreeze on some
  roads may be possible.

* Much colder and breezy NW winds today. Highs 20s/30s, wind chills
  single digits to 20s.

* Moderation/warming mid-late week peaks Friday, eases weekend
  into early next week.

&&

.DISCUSSION...
Issued at 247 AM CDT Tue Mar 26 2024

Surface low early this morning has crossed central Iowa and
continues to track slowly northeastward. This has allowed a cold
frontal boundary to continue to drop through western Iowa and
central Iowa and bring with it markedly colder temperatures, below
freezing temperatures, and the return of wintry precipitation.

As noted in previous forecast iterations, there may be a period of
some wintry mix before fully transitioning from rain to snow. What
has changed though is that the risk for freezing rain during that
transition has broadly lessened/been eliminated with the low to mid
level pressure centers becoming more vertically stacked/aligned.
While HRRR/RAP point soundings do continue to show a subtle warm
nose at/just above 850mb, it is not as pronounced and in almost all
cases falls below freezing just before the surface. Still may be a
brief wintry mix transition, but more sleety in nature. Northern
areas remain on track to see light snowfall accumulations, mainly
around an inch or less. A couple spots near Minnesota border could
approach 2 inches.

A sneaky hazard with this too may be the freezing of rain/snow melt
on roadways as it is unlikely any roads will be treated given
antecedent rainy conditions. This is not/will not be a traditional
flash freeze type of event as the cold front is not remarkably
sharp, but more of a slow burn/freeze so to speak as road temps
trail/react to the colder temperatures moving in. Something to keep
in mind, and could warrant some expansion of the Winter Weather
Advisory across portions of the western CWA early this morning. Do
not currently anticipate prominent issues in/around the Des Moines
and Ames metros for the morning rush as precipitation will be
fading as the system and better lift continues to push
northeast. A secondary area of precipitation will move across
southeast Iowa this morning in/around the surface front, but
should not pose much hazard with temperatures remaining above
freezing much of the time and occurrence post sunrise.

Through the daytime today, breezy northwest winds, gusting into the
30s mph and strongest west, and the colder temperatures will combine
for a quick return to winter and wind chills as cold as the single
digits through the day today in northwest areas and down into the
20s for much of the rest of the area. Will pretty short lived cold
though as moderation/warming will bring back temperatures in the
50s/60s by Thursday/Friday as ridging traverses the central CONUS.

Some uncertainly in precipitation chances late this week into the
weekend with understandable discrepancies in shortwave handling
amongst the synoptic guidance. Suffice it to say that the next
potential window for precipitation may be later Friday into
Saturday, but is far from robust. Into next week, there is fair
agreement in the large scale pattern, placing the region under SW
upper level flow. This would also provide us another fair
opportunity at precipitation, but timing and details vary widely.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 623 AM CDT Tue Mar 26 2024

TAF period will see gradual return to VFR conditions, but toward
the latter portions of the TAF period in most cases. The worst
conditions, IFR to low MVFR, will continue to take place over
the next 6 to 9 hours as the parent weather system continues to
slowly depart NE. As a result, KFOD/KMCW/KALO will combat
ceilings in/around 1kft and periods of snowfall that may reduce
visibilities to around 2 miles at times. KOTM will see
predominantly rain, but may see brief light snow before
precipitation exits around 18z. KDMX, splitting the middle
between the areas of precipitation may not see much more than a
handful of flurries through the day, but will still be IFR to
low MVFR due to ceilings. All sites will battle strong northwest
winds gusting 25 to around 30 kts through the day, easing after
00z.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 AM CDT this morning for
IAZ004>006-015-016-023-024-033-034-044.

&&

$$

DISCUSSION...Curtis
AVIATION...Curtis


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