Alert archive / Iowa / Severe Thunderstorm Warnings in 2018

Severe Thunderstorm Warning 81, NWS Des Moines, IA

May 29, 2018Boone County, Story County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at May 29, 2018, 6:50 PM CDT for Boone County, Story County, Iowa. It was in force for 15 min. 2 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: May 29, 2018, 6:50 PM CDT (23:50 UTC)
Expired: May 29, 2018, 7:05 PM CDT
In force: 15 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Boone County, IA, Story County, IA

The radar

The Des Moines radar (KDMX), 37 km from the middle of the area, began a volume at 23:51 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

What was reported inside it

Time	Report	Where	Remark
May 29, 6:50 PM CDT	TSTM WND GST 58	3 E Ames, IA	RAMI4 RWIS STATION REPORTS.
May 29, 6:55 PM CDT	HAIL 0.25	Ames, IA

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

Did it verify

Verified. The Iowa Environmental Mesonet's Cow matched one storm report to this severe thunderstorm warning; the first came 0 minutes after it went out.

Cow counts a report within 15 km of the polygon while the warning was in force: a tornado for a tornado warning; hail of 1 inch or more, a gust of 58 mph or more or wind damage for a severe thunderstorm warning; a flash flood report for a flash flood warning.

The watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
May 29, 1:43 PM CDT	Severe Thunderstorm Watch	SPC	6 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 11.8 hours before the alert went out and 244 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1666 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 140 m²/s²
0-3 km storm-relative helicity: 153 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

398 
WUUS53 KDMX 292350
SVRDMX
IAC015-169-300030-
/O.NEW.KDMX.SV.W.0081.180529T2350Z-180530T0030Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Des Moines IA
650 PM CDT TUE MAY 29 2018

The National Weather Service in Des Moines  has issued a

* Severe Thunderstorm Warning for...
  Western Story County in central Iowa...
  East central Boone County in central Iowa...

* Until 730 PM CDT.

* At 649 PM CDT, a severe thunderstorm was located over Ames, moving
  northwest at 30 mph.

  HAZARD...60 mph wind gusts and penny size hail.

  SOURCE...Radar indicated.

  IMPACT...Expect damage to roofs, siding, and trees.

* Locations impacted include...
  Ames, Nevada, Gilbert, Iowa State Center, Kelley and Ames Municipal
  Airport.

This includes Interstate 35 between mile markers 108 and 119.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4202 9344 4192 9361 4209 9385 4221 9365
TIME...MOT...LOC 2349Z 134DEG 26KT 4202 9361 

HAIL...0.75IN
WIND...60MPH
 
$$

Martin

2 follow-up statements

558 
WWUS53 KDMX 292359
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
659 PM CDT TUE MAY 29 2018

IAC015-169-300030-
/O.CON.KDMX.SV.W.0081.000000T0000Z-180530T0030Z/
Story IA-Boone IA-
659 PM CDT TUE MAY 29 2018

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 730 PM CDT
FOR NORTHWESTERN STORY AND EAST CENTRAL BOONE COUNTIES...

At 659 PM CDT, a severe thunderstorm was located near Gilbert, or
near Ames, moving northwest at 30 mph.

HAZARD...60 mph wind gusts and penny size hail.

SOURCE...Trained weather spotters and local mesonet site.

IMPACT...Expect damage to roofs, siding, and trees.

Locations impacted include...
Ames, Gilbert, Iowa State Center and Ames Municipal Airport. 

This includes Interstate 35 between mile markers 114 and 119.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4207 9350 4196 9367 4209 9385 4221 9365
TIME...MOT...LOC 2359Z 134DEG 26KT 4207 9368 

HAIL...0.75IN
WIND...60MPH
 
$$

Martin

933 
WWUS53 KDMX 300005
SVSDMX

Severe Weather Statement
National Weather Service Des Moines IA
705 PM CDT TUE MAY 29 2018

IAC015-169-300015-
/O.CAN.KDMX.SV.W.0081.000000T0000Z-180530T0030Z/
Story IA-Boone IA-
705 PM CDT TUE MAY 29 2018

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN STORY AND EAST
CENTRAL BOONE COUNTIES IS CANCELLED...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been cancelled.  However gusty winds and
heavy rain are still possible with this thunderstorm.

A Severe Thunderstorm Watch remains in effect until 800 PM CDT for
central Iowa.

LAT...LON 4207 9350 4196 9367 4209 9385 4221 9365
TIME...MOT...LOC 0004Z 134DEG 26KT 4210 9373 

$$

Martin

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Des Moines, IA wrote its last area forecast discussion before this severe thunderstorm warning went out at May 29, 4:13 PM CDT, 2 hours 37 minutes earlier.

Area forecast discussion, May 29, 4:13 PM CDT, 2 hours 37 minutes before

Area Forecast Discussion
National Weather Service Des Moines IA
413 PM CDT Tue May 29 2018

.DISCUSSION.../Tonight through Tuesday/
Issued at 413 PM CDT Tue May 29 2018

Primary focus on current storms with a short wave lifting
northwest from the Alberto system and another shortwave
approaching from the west. Two areas of storms have developed in
response. Similar to Monday, large hail, damaging winds and a few
landspouts are all possible. Strong winds thus far have been more
prominent than Monday with 0-3km theta-e differences of 25-30K and
downdraft CAPE around 1500 J/kg. The two regions should converge
just west of Interstate 35 in a few hours and should be the focus
for a few stronger updrafts before the entire area then begins to
move to the east. Possible that zone could have locally heavy
rainfall before storms diminish. Another area of storms over
Nebraska and Kansas will move into western Iowa round midnight or
after in a weakened state.

Most of Wednesday should be dry though additional storms are
possible as the boundary moves across central Iowa as it moves
east in the afternoon. The best chance will be over the far
northeast by mid afternoon. Wednesday will finally be cooler with
highs only in the 80s! The upper ridge will build back into the
area Thursday and Friday with highs back into the upper 80s to mid
90s. The next strong upper level system will arrive Friday night
into early Saturday. This will bring additional thunderstorm
chances to the region. A few could be severe. This will bring
cooler and more seasonal temperatures to the area for the
weekend. More zonal flow arrives to begin next week and will bring
slightly warmer temperatures and a few spot chances for additional
thunderstorms.

&&

.AVIATION.../For the 18Z TAFS through 18Z Wednesday afternoon/
Issued at 1230 PM CDT Tue May 29 2018

Scattered thunderstorms possible again later this afternoon and
evening. The main risk with these storms will be local microbursts
and thunderstorm outflow winds. The predominant wind will be from
the southeast today then gradually transitioning to southwest on
Wednesday. Any MVFR or lower cigs and vsbys will be in vicinity of
thunderstorms otherwise VFR conditions are forecast.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

DISCUSSION...Donavon
AVIATION...Donavon

Hazardous weather outlook, May 29, 3:14 PM CDT, 3 hours 36 minutes before

Hazardous Weather Outlook
National Weather Service Des Moines IA
314 PM CDT Tue May 29 2018

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-301100-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
314 PM CDT Tue May 29 2018

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Scattered thunderstorms are expected this afternoon through the
evening, and at times overnight. Some of the storms this afternoon
and evening may be severe, mainly west of Interstate 35, with
strong winds and large hail the main threats.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Thunderstorm chances will persist on Wednesday, then return from
Friday night into Saturday. Severe weather may be possible at
times.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed this afternoon and evening.

In the hours before

Local storm report, May 29, 6:25 PM CDT, 25 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
625 PM CDT TUE MAY 29 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0624 PM     TSTM WND DMG     4 N EARLHAM             41.55N 94.12W
05/29/2018                   DALLAS             IA   PUBLIC

            2 FEET DIAMETER TREE FELL ON I AVE.

&&

AK

Local storm report, May 29, 6:27 PM CDT, 23 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
627 PM CDT TUE MAY 29 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0626 PM     TSTM WND DMG     DES MOINES              41.58N 93.62W
05/29/2018                   POLK               IA   PUBLIC

            4-6" TREE BRANCHES DOWN. (DELAYED REPORT).

&&

AK

Local storm report, May 29, 6:30 PM CDT, 20 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
630 PM CDT TUE MAY 29 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0630 PM     TSTM WND GST     WAUKEE                  41.61N 93.86W
05/29/2018  E65 MPH          DALLAS             IA   PUBLIC

            VIA SOCIAL MEDIA.

&&

AK

Local storm report, May 29, 6:38 PM CDT, 12 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
638 PM CDT TUE MAY 29 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0634 PM     TSTM WND DMG     4 W RINGSTED            43.30N 94.59W
05/29/2018                   EMMET              IA   PUBLIC

            A FEW 1 INCH TREE BRANCHES ARE DOWN. PEA
            SIZE HAIL ALSO REPORTED. HEAVY RAIN.

&&

AK

Local storm report, May 29, 6:40 PM CDT, 10 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
640 PM CDT TUE MAY 29 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0639 PM     TSTM WND DMG     2 ESE DES MOINES INT AI 41.52N 93.63W
05/29/2018                   POLK               IA   BROADCAST MEDIA

            REPORTED AT BURNHAM AVE DES MOINES, IA. TREE
            UPROOTED, FELL ON HOUSE.

&&

AK

Local storm report, May 29, 6:46 PM CDT, 4 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
646 PM CDT TUE MAY 29 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0646 PM     TSTM WND DMG     1 SE DES MOINES INT AIR 41.52N 93.64W
05/29/2018                   POLK               IA   BROADCAST MEDIA

            MULTIPLE TREES DOWN ALONG FLEUR DRIVE IN DES
            MOINES.

&&

AK

The office that day

Everything else NWS Des Moines, IA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 29, 3:30 PM CDT	Severe Thunderstorm Warning	DMX	Polk, Story	18 min
May 29, 3:36 PM CDT	Severe Thunderstorm Warning	DMX	Story	24 min
May 29, 3:49 PM CDT	Severe Thunderstorm Warning	DMX	Crawford	41 min
May 29, 3:59 PM CDT	Severe Thunderstorm Warning	DMX	Hamilton, Story	16 min
May 29, 5:15 PM CDT	Severe Thunderstorm Warning	DMX	Audubon, Cass	45 min
May 29, 5:26 PM CDT	Severe Thunderstorm Warning	DMX	Polk, Warren	34 min
May 29, 5:37 PM CDT	Severe Thunderstorm Warning	DMX	Polk	23 min
May 29, 6:00 PM CDT	Severe Thunderstorm Warning	DMX	Dallas, Guthrie, Madison	30 min
May 29, 6:12 PM CDT	Severe Thunderstorm Warning	DMX	Dallas	33 min
May 29, 6:14 PM CDT	Severe Thunderstorm Warning	DMX	Emmet, Palo Alto	46 min
May 29, 6:24 PM CDT	Severe Thunderstorm Warning	DMX	Worth	21 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2018 Every severe thunderstorm warning in 2018

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.