Severe Thunderstorm Warning 25, NWS Des Moines, IA

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

.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 /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1203 AM CDT Wed Mar 19 2025

Challenging aviation forecast with degrading aviation conditions
overnight through the day Wednesday as a high impact storm brings
rain, thunderstorms, some even strong to severe overnight into
Wednesday morning especially south, and then rain changing to
snow and becoming quite heavy especially for KFOD and KMCW
dropping visibilities significantly. In addition, winds become
exceptionally strong Wednesday with winds out of the north
gusting to around 50 knots or more by the afternoon. The wind
will just intensify the poor conditions where snow is ongoing
creating blizzard conditions at times. Although impacts will be
worst at KMCW/KFOD, other sites also have at least MVFR
visibilities and fall towards or into IFR ceilings with the
exception of KOTM at this time. Timing and impacts may still
need adjustments at all sites as storms move into the area and
rain changes to snow.

&&

.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...KCM

Hazardous Weather Outlook
National Weather Service Des Moines IA
314 PM CDT Tue Mar 18 2025

IAZ004>007-015>017-023>026-033>036-044>046-057-191200-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Sac-Calhoun-Webster-Hamilton-
Crawford-Carroll-Greene-Audubon-
314 PM CDT Tue Mar 18 2025

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Tonight

There is a marginal risk for severe weather for the area late
tonight. The primary threat is large hail.

A Blizzard Warning is in effect for starting very late tonight.
Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

A Blizzard Warning is in effect for much of the area Wednesday.
Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

A High Wind Warning is in effect for the area Wednesday. Please
refer to the National Weather Service website at
weather.gov/desmoines for further details.

There is a marginal risk for severe weather for the area
Wednesday, mainly in the morning. The primary threats are large
hail and damaging winds. Thundersnow is also possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed for severe weather reports.
Reports of snow depth and adverse winter conditions are also
appreciated.

IAZ027-037-047-058-070-191200-
Butler-Hardin-Boone-Guthrie-Cass-
314 PM CDT Tue Mar 18 2025

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Tonight

There is a marginal risk for severe weather for the area late
tonight. The primary threat is large hail.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

A Winter Weather Advisory is in effect for the area Wednesday.
Please refer to the National Weather Service website at
weather.gov/desmoines for further details.

A High Wind Warning is in effect for the area Wednesday. Please
refer to the National Weather Service website at
weather.gov/desmoines for further details.

There is a marginal risk for severe weather for the area
Wednesday, mainly in the morning. The primary threats are large
hail and damaging winds. Thundersnow is also possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed for severe weather reports.
Reports of snow depth and adverse winter conditions are also
appreciated.

IAZ028-038-039-048>050-059>062-071>075-081>086-092>097-191200-
Bremer-Grundy-Black Hawk-Story-Marshall-Tama-Dallas-Polk-Jasper-
Poweshiek-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-Clarke-
Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-Appanoose-
Davis-
314 PM CDT Tue Mar 18 2025

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Tonight

There is a marginal risk for severe weather for the area late
tonight. The primary threat is large hail.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

A High Wind Warning is in effect for the area Wednesday. Please
refer to the National Weather Service website at
weather.gov/desmoines for further details.

There is a marginal risk for severe weather for the area Wednesday.
The primary threats are large hail and damaging winds. Thundersnow
is also possible.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed for severe weather reports.
Reports of snow depth and adverse winter conditions are also
appreciated.

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