798
FXUS63 KDMX 191143
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
643 AM CDT Wed Mar 19 2025

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

.KEY MESSAGES...

- Heavy snow band with blizzard conditions today from north
  central to west central Iowa. Roads will become impassable and
  power outages are possible.

- High winds expected today with wind gusts of 55 to 65 mph.
  Will reach the southeast this afternoon.

- A few severe storms possible today. A tornado is also possible
  over the southeast.

&&

.DISCUSSION...
Issued at 418 AM CDT Wed Mar 19 2025

Surface low pressure (986 mb) is moving into eastern Kansas at 08z
this morning. An impressive 80 kt low level jet has developed to the
east of the low near the KS/MO border and pointing into far northern
MO and into southern Iowa where the best speed convergence exists.
Strong theta-e advection is ongoing into Iowa and increasing mid-
level lapse rates near 9 C/km and MUCAPES over 1000 J/kg have
developed as well. A few thunderstorms are developing as well from
near the Omaha metro and east to near Audubon and southeast to
Osceola. These storms will be capable of near severe criteria hail
and potentially storms over west central Iowa could mix 60 mph winds
to the surface ahead of the strong synoptic scale winds later today.


Outside of the elevated thunderstorm chances this morning and the
potential for surface based convection south central mid-morning
into the early afternoon, the forecast focus is still on the
Blizzard and High Wind event today. A slight shift southeast in the
primary heavy snow band has occurred the past 24 hours. however, it
is slight enough that no changes to the current headlines is
required. It is possible that parts of Emmet county has less snow
than previously expected but still enough snow that blizzard
conditions are still likely. Convective snow due to elevated
instability and the potential for slantwise convection remains and
that is a driving factor into why the HREF probs for 1 and 2 inch
per hour snowfall rates are so high through this region. Still
expecting these snowfall rates and there could be brief periods of
2+ inch per hour rates for brief periods. Still expecting good
dendritic growth and the aggregate growth process is likely shortly
after the transition to snow. This combined with temperatures in the
low 30s and there will be a period of wet/sticky snow that combined
with the high winds, will lead to potential power outages. The cold
advection aloft will lead to a more fluffy and mobile snow during
the event however did keep the snow to liquid ratios at less than
12:1 due to the expected significant fragmentation of snow crystals.
Travel will become nearly impossible across this snow band area
today with many roads becoming impassable. Do not travel in this
area today! Still expecting at least light snow to occur across the
rest of the forecast area not within the heavy snow band. Some CAMs
suggest that 1-3 inches could occur across parts of southeast Iowa
late this afternoon/early evening and if that occurs, winter
headlines may be required.

The high wind event is mostly on track. With the systems overall
slight shift southeast, the main high wind dynamics have shifted
slightly south. The system still has a 60-75 ubar/km pressure
gradient across the northwest half of Iowa today along good pressure
height rises following the surface low pressure. Mixed layer winds
remain impressive with 50+ kts at 925 mb and 65 to 70 kts at 850 mb.
The mixed layer depth will be somewhere between that range. Wind
gusts of 55 to 65 mph are expected. The strongest winds will not
reach the Ames and Des Moines areas until this afternoon then the
southeast into mid afternoon and therefore have kept the timing of
the current wind headlines as well.

There still remains the potential for surface based storms along the
warm from over south central into southeast Iowa from mid morning
into the early afternoon. Conditions are favorable for a few
supercells that will have the potential for a tornado or two. That
potential will be short lived in the NWS DMX forecast area
before moving out of the area. Damaging wind gusts and large
hail will also be possible.

Generally quiet weather after today outside of another short wave
passing through the area Friday and Friday evening. Currently have
rain in the forecast with that system and some gusty winds. There is
a chance for a switch to light snow before ending. High temperatures
will generally be in the 40s and 50s with the coolest conditions
generally over the snow covered region.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 639 AM CDT Wed Mar 19 2025

Conditions will deteriorate quickly this morning at KFOD/KMCW as
rain/storms transition to heavy snow and then blizzard
conditions as strong northwest winds develop. Showers and storms
are expected at the other sites and eventually a transition to
light snow before ending. Strong winds with gusts over 50s kts
likely at most sites. Conditions will gradually improve tonight.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning until 10 PM CDT this evening for IAZ004>007-
015>017-023>026-033>036-044>046-057.
High Wind Warning until 7 PM CDT this evening for IAZ004>007-
015>017-023>025-033>035-044>046-057-058-070.
High Wind Warning from 1 PM this afternoon to 10 PM CDT this
evening for IAZ026>028-036>039-047>050-059>062-071>074-081>084-
092>095.
Winter Weather Advisory until 10 PM CDT this evening for
IAZ027-037-047-058-070.
High Wind Warning from 4 PM this afternoon to 10 PM CDT this
evening for IAZ075-085-086-096-097.

&&

$$

DISCUSSION...Donavon
AVIATION...Donavon