Alert archive / Iowa / Special Weather Statements in 2017

Special Weather Statement, NWS Des Moines, IA

August 21, 2017Humboldt County, Pocahontas County, Iowa

NWS Des Moines, IA issued this special weather statement at Aug 21, 2017, 11:23 AM CDT for Humboldt County, Pocahontas County, Iowa. It was in force for 52 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued
Aug 21, 2017, 11:23 AM CDT (16:23 UTC)
Expired
Aug 21, 2017, 12:15 PM CDT
In force
52 min
Issued by
NWS Des Moines, IA

Counties Humboldt County, IA, Pocahontas County, IA

The radar

The Des Moines radar (KDMX), 138 km from the middle of the area, began a volume at 16:26 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.

The nearest sounding before it

Minneapolis, MN (KMPX), launched 12:00Z, 4.4 hours before the alert went out and 227 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-pSkew-T log-p diagram, Minneapolis, MN at 12:00Z on 2017-08-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Minneapolis, MN at 12:00Z on 2017-08-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 74 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
1321 m above ground
0-6 km bulk shear
40 kt
0-1 km storm-relative helicity
74 m²/s²
0-3 km storm-relative helicity
98 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.5

Open this sounding in Storm Lab

The text

As transmitted.

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What forecasters said that day

The local office's own words before this special weather statement 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 special weather statement went out at Aug 21, 7:05 AM CDT, 4 hours 18 minutes earlier.

Area forecast discussion, Aug 21, 7:05 AM CDT, 4 hours 18 minutes before
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Hazardous weather outlook, Aug 21, 4:03 AM CDT, 7 hours 20 minutes before
Hazardous Weather Outlook
National Weather Service Des Moines IA
403 AM CDT Mon Aug 21 2017

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-220915-
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-
403 AM CDT Mon Aug 21 2017

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Periods of thunderstorms will occur today and tonight. There is a
marginal risk for hail and strong wind with the storms this
morning, along with heavy rainfall that could lead to localized
flooding.

There is a slight risk for severe storms late this afternoon and
tonight. All modes of severe weather is possible along with heavy
rainfall which could lead to localized flooding. Very large hail
is possible across much of central Iowa especially north of
Interstate 80 and west of Interstate 35. Damaging wind and a few
tornadoes are possible across all of central Iowa.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening.

FAB

In the hours before

Special weather statement, Aug 21, 9:34 AM CDT, 1 hour 49 minutes before
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Special weather statement, Aug 21, 9:43 AM CDT, 1 hour 40 minutes before
Special Weather Statement
National Weather Service Des Moines IA
943 AM CDT MON AUG 21 2017

IAZ023-024-034-035-211545-
Humboldt IA-Calhoun IA-Webster IA-Pocahontas IA-
943 AM CDT MON AUG 21 2017

...Gusty Winds and Hail Possible over Northwest Iowa...

At 940 AM CDT, Doppler radar was tracking a strong thunderstorm near
Rockwell City, moving northeast at 20 mph with another strong storm
exiting Buena Vista County into Pocahontas County.

Nickel size hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Fort Dodge, Pocahontas, Rockwell City, Dakota City, Humboldt, Lake
City, Manson, Laurens, Gowrie, North Twin Lake, Fort Dodge Regional
Airport, South Twin Lake, Dayton, Stratford, Pomeroy, Fonda,
Coalville, Rolfe, Badger and Otho.

LAT...LON 4290 9397 4247 9397 4247 9394 4222 9393
      4221 9485 4247 9486 4248 9488 4290 9492
TIME...MOT...LOC 1440Z 243DEG 15KT 4244 9453

Small
Local storm report, Aug 21, 9:57 AM CDT, 1 hour 26 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
957 AM CDT MON AUG 21 2017

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

0913 AM     HEAVY RAIN       1 NE AUDUBON            41.72N 94.92W
08/21/2017  M5.30 INCH       AUDUBON            IA   FIRE DEPT/RESCUE

&&

BSS
Local storm report, Aug 21, 10:28 AM CDT, 55 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1028 AM CDT MON AUG 21 2017

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

0700 AM     HEAVY RAIN       5 NW WALL LAKE          42.31N 95.16W
08/21/2017  M3.30 INCH       SAC                IA   COCORAHS

            COCORAHS OBSERVER REPORTED 3.30 INCHES OVER
            THE LAST 24 HOURS.

&&
Local storm report, Aug 21, 10:30 AM CDT, 53 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1030 AM CDT MON AUG 21 2017

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

0655 AM     HEAVY RAIN       1 SE AUDUBON            41.71N 94.92W
08/21/2017  M3.17 INCH       AUDUBON            IA   AWOS

            AUDUBON AWOS RECORDED 3.17 INCHES OVER THE
            LAST 24 HOURS.

&&
Special weather statement, Aug 21, 11:23 AM CDT, 0 minutes before
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The office that day

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

IssuedProductOfficeCountiesLasted
Aug 20, 11:03 PM CDTSpecial Weather StatementDMXCrawford27 min
Aug 20, 11:05 PM CDTSevere Thunderstorm WarningDMXCarroll, Crawford, Sac40 min
Aug 21, 12:32 AM CDTFlash Flood WarningDMXCrawford6 hr
Aug 21, 1:27 AM CDTSpecial Weather StatementDMXAudubon, Guthrie33 min
Aug 21, 1:31 AM CDTFlash Flood WarningDMXAudubon, Carroll, Crawford, Guthrie6 hr
Aug 21, 1:53 AM CDTSpecial Weather StatementDMXCass22 min
Aug 21, 1:55 AM CDTSevere Thunderstorm WarningDMXEmmet, Palo Alto35 min
Aug 21, 2:07 AM CDTSevere Thunderstorm WarningDMXAdair, Adams, Audubon, Cass, Guthrie53 min
Aug 21, 2:46 AM CDTSevere Thunderstorm WarningDMXAdair, Adams, Cass, Guthrie, Madison, Union44 min
Aug 21, 3:02 AM CDTSpecial Weather StatementDMXKossuth43 min
Aug 21, 3:30 AM CDTSevere Thunderstorm WarningDMXAdair, Adams, Ringgold, Taylor, Union32 min
Aug 21, 9:43 AM CDTSpecial Weather StatementDMXCalhoun, Humboldt, Pocahontas, Webster62 min
Aug 21, 1:39 PM CDTSpecial Weather StatementDMXEmmet, Kossuth, Palo Alto66 min
Aug 21, 2:02 PM CDTSevere Thunderstorm WarningDMXEmmet, Kossuth, Palo Alto29 min
Aug 21, 3:43 PM CDTSpecial Weather StatementDMXCalhoun, Carroll, Crawford, Emmet, Humboldt, Kossuth and 4 more77 min
Aug 21, 5:03 PM CDTSpecial Weather StatementDMXAudubon, Boone, Cass, Dallas, Greene, Guthrie and 4 more57 min
Aug 21, 5:37 PM CDTSpecial Weather StatementDMXBoone, Grundy, Hamilton, Hardin, Story53 min
Aug 21, 6:04 PM CDTSpecial Weather StatementDMXJasper, Polk41 min
Aug 21, 6:16 PM CDTSpecial Weather StatementDMXMadison, Warren44 min
Aug 21, 6:26 PM CDTSpecial Weather StatementDMXBlack Hawk, Grundy, Marshall, Tama64 min
Aug 21, 6:38 PM CDTSpecial Weather StatementDMXJasper, Mahaska, Marion52 min
Aug 21, 6:52 PM CDTSpecial Weather StatementDMXClarke, Lucas, Madison, Union, Warren68 min
Aug 21, 6:58 PM CDTSpecial Weather StatementDMXPoweshiek47 min

Nearby

Special Weather Statements in Iowa, 2017Every special weather statement in 2017

Sources

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