Alert archive / Iowa / Severe Thunderstorm Warnings in 2014

Severe Thunderstorm Warning 260, NWS Des Moines, IA

August 20, 2014Jasper County, Polk County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Aug 20, 2014, 4:59 AM CDT for Jasper County, Polk County, Iowa. It was in force for 31 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 20, 2014, 4:59 AM CDT (09:59 UTC)
Expired: Aug 20, 2014, 5:30 AM CDT
In force: 31 min
Issued by: NWS Des Moines, IA
Area: Storm-based polygon
Hail: 1.0 in
Wind: 50.0 mph

Counties Jasper County, IA, Polk County, IA

The radar

The Des Moines radar (KDMX), 35 km from the middle of the area, began a volume at 10:00 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.

Did it verify

Not verified. The Iowa Environmental Mesonet's Cow found no qualifying storm report inside this severe thunderstorm warning while it was in force. That is not proof nothing happened: reports are thin where few people live.

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 nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 10.0 hours before the alert went out and 242 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: 544 J/kg
Mixed-layer CIN: -7 J/kg
Mixed-layer LCL: 1473 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 43 m²/s²
0-3 km storm-relative helicity: 90 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 1.1

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

456 
WUUS53 KDMX 200959
SVRDMX
IAC099-153-201030-
/O.NEW.KDMX.SV.W.0260.140820T0959Z-140820T1030Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE DES MOINES IA
459 AM CDT WED AUG 20 2014

THE NATIONAL WEATHER SERVICE IN DES MOINES  HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  SOUTHWESTERN JASPER COUNTY IN CENTRAL IOWA...
  SOUTHEASTERN POLK COUNTY IN CENTRAL IOWA...

* UNTIL 530 AM CDT

* AT 459 AM CDT...A SEVERE THUNDERSTORM WAS LOCATED OVER SOUTHRIDGE
  MALL...OR NEAR DES MOINES...MOVING EAST AT 35 MPH.

  HAZARD...QUARTER SIZE HAIL. 

  SOURCE...TRAINED WEATHER SPOTTERS. 

  IMPACT...DAMAGE TO VEHICLES IS EXPECTED. 

* LOCATIONS IMPACTED INCLUDE...
  DES MOINES...ALTOONA...PLEASANT HILL...CARLISLE...MITCHELLVILLE...
  PRAIRIE CITY...DES MOINES INT'L AIRPORT...PRINCIPAL PARK...IOWA
  STATE FAIRGROUNDS...SOUTHRIDGE MALL AND RUNNELLS.

THIS INCLUDES INTERSTATE 235 NEAR MILE MARKER 10.
 
PRECAUTIONARY/PREPAREDNESS ACTIONS...

FOR YOUR PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
BUILDING.

&&

LAT...LON 4151 9333 4149 9333 4150 9335 4149 9340
      4150 9340 4149 9341 4149 9342 4151 9342
      4150 9344 4151 9349 4151 9366 4157 9367
      4168 9326 4151 9324
TIME...MOT...LOC 0959Z 262DEG 29KT 4154 9358 

HAIL...1.00IN
WIND...<50MPH

$$

LEE

3 follow-up statements

581 
WWUS53 KDMX 201010
SVSDMX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
510 AM CDT WED AUG 20 2014

IAC099-153-201030-
/O.CON.KDMX.SV.W.0260.000000T0000Z-140820T1030Z/
JASPER IA-POLK IA-
510 AM CDT WED AUG 20 2014

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 530 AM CDT
FOR SOUTHWESTERN JASPER AND SOUTHEASTERN POLK COUNTIES...

AT 509 AM CDT...A SEVERE THUNDERSTORM WAS LOCATED OVER PLEASANT
HILL...MOVING EAST AT 35 MPH.

HAZARD...QUARTER SIZE HAIL. 

SOURCE...TRAINED WEATHER SPOTTERS. 

IMPACT...DAMAGE TO VEHICLES IS EXPECTED. 

LOCATIONS IMPACTED INCLUDE...
DES MOINES...ALTOONA...PLEASANT HILL...CARLISLE...MITCHELLVILLE...
PRAIRIE CITY...IOWA STATE FAIRGROUNDS AND RUNNELLS.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FOR YOUR PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
BUILDING.

&&

LAT...LON 4151 9333 4149 9333 4150 9335 4149 9340
      4150 9340 4149 9341 4149 9342 4151 9342
      4150 9344 4151 9349 4151 9357 4159 9358
      4168 9326 4151 9324
TIME...MOT...LOC 1009Z 262DEG 29KT 4155 9347 

HAIL...1.00IN
WIND...<50MPH

$$

LEE

451 
WWUS53 KDMX 201020
SVSDMX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
520 AM CDT WED AUG 20 2014

IAC099-153-201030-
/O.CON.KDMX.SV.W.0260.000000T0000Z-140820T1030Z/
JASPER IA-POLK IA-
520 AM CDT WED AUG 20 2014

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 530 AM CDT
FOR SOUTHWESTERN JASPER AND SOUTHEASTERN POLK COUNTIES...

AT 520 AM CDT...A SEVERE THUNDERSTORM WAS LOCATED 6 MILES WEST OF
PRAIRIE CITY...OR 7 MILES EAST OF PLEASANT HILL...MOVING EAST AT 35
MPH.

HAZARD...QUARTER SIZE HAIL. 

SOURCE...RADAR INDICATED. 

IMPACT...DAMAGE TO VEHICLES IS EXPECTED. 

LOCATIONS IMPACTED INCLUDE...
ALTOONA...PLEASANT HILL...MITCHELLVILLE...PRAIRIE CITY AND RUNNELLS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

FOR YOUR PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
BUILDING.

&&

LAT...LON 4151 9333 4149 9333 4150 9335 4149 9340
      4150 9340 4149 9341 4149 9342 4151 9342
      4150 9344 4150 9346 4162 9348 4168 9326
      4151 9324
TIME...MOT...LOC 1020Z 262DEG 29KT 4156 9335 

HAIL...1.00IN
WIND...<50MPH

$$

LEE

223 
WWUS53 KDMX 201027
SVSDMX

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
527 AM CDT WED AUG 20 2014

IAC099-153-201037-
/O.EXP.KDMX.SV.W.0260.000000T0000Z-140820T1030Z/
JASPER IA-POLK IA-
527 AM CDT WED AUG 20 2014

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHWESTERN JASPER AND
SOUTHEASTERN POLK COUNTIES WILL EXPIRE AT 530 AM CDT...
                
THE STORM WHICH PROMPTED THE WARNING HAS WEAKENED BELOW SEVERE
LIMITS...AND NO LONGER POSE AN IMMEDIATE THREAT TO LIFE OR PROPERTY.
THEREFORE THE WARNING WILL BE ALLOWED TO EXPIRE.

LAT...LON 4151 9333 4149 9333 4150 9335 4149 9340
      4150 9340 4149 9341 4149 9342 4151 9342
      4150 9344 4150 9346 4162 9348 4168 9326
      4151 9324
TIME...MOT...LOC 1023Z 262DEG 29KT 4156 9335 

$$

LEE

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 Aug 20, 4:09 AM CDT, 50 minutes earlier.

Area forecast discussion, Aug 20, 4:09 AM CDT, 50 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
409 AM CDT WED AUG 20 2014

.SHORT TERM /TODAY/...
ISSUED AT 405 AM CDT WED AUG 20 2014

AS ANTICIPATED ELEVATED THUNDERSTORMS HAVE FORMED IN A BROKEN BAND
ACROSS SOUTHERN/SOUTHWESTERN IOWA EARLY THIS MORNING...ALONG THE
NOSE OF THE VEERING LOW LEVEL JET AND WITHIN A REGION OF THETA E
ADVECTION ALOFT. A FEW STORMS WILL LIKELY PRODUCE SOME HAIL BUT NO
ORGANIZED SEVERE WEATHER IS EXPECTED. THIS ACTIVITY WILL PERSIST FOR
THE NEXT SEVERAL HOURS AS IT SLOWLY DRIFTS NORTHEAST TOWARD CENTRAL
IOWA...THEN GRADUALLY FADE LATER THIS MORNING WITH MOSTLY DRY
CONDITIONS ANTICIPATED BY THE AFTERNOON. CONCURRENTLY...AN EFFECTIVE
WARM FRONT IN THE FORM OF A SURGE OF WARMER AND MORE MOIST AIR WILL
MOVE IN FROM THE SOUTHWEST TODAY...RESULTING IN SULTRY CONDITIONS
ACROSS MUCH OF OUR AREA BY LATER TODAY. HEAT INDEX VALUES WILL TOP
OUT NEAR 100 DEGREES FROM AROUND THE I-80 CORRIDOR SOUTHWARD THUS NO
ADVISORY IS WARRANTED AT THIS TIME.

.LONG TERM /TONIGHT THROUGH TUESDAY/...
ISSUED AT 405 AM CDT WED AUG 20 2014

PRECIP TRENDS WILL BE THE PRIMARY FORECAST CONCERN RIGHT ON INTO
NEXT WEEK...BUT UNFORTUNATELY DETAILS WILL BE HARD TO COME BY.
GENERAL PATTERN CHANGES LITTLE WITH PERSISTENT WRN CONUS TROUGH/ERN
RIDGE SCENARIO AS PNA INDEX CONTINUES TO LOWER. THIS LEAVES IA IN
PROLONGED SW FLOW ALOFT WITH SURFACE FEATURES REACHING THE STATE
LATER THIS WEEK AND MOVING LITTLE INTO NEXT WEEK.  CONVECTION FOR
THE NEXT FEW DAYS WILL MAINLY BE NOCTURNAL WITH LITTLE CONVERGENCE
OR LARGER SCALE FORCING.  WARM/THETA-E ADVECTION SURGE WILL PUSH
THROUGH TONIGHT WITH WEAKER THERMODYNAMIC FORCING THU NIGHT. WITH
BAROCLINIC ZONE ADVANCING NE...THIS WILL LEAVE IA IN A VERY WARM AND
HUMID AIRMASS WITH HIGHS IN THE UPPER 80S/LOWER 90S. PEAK HEAT
INDICES WILL BE PUSHING ADVISORY CRITERIA...JUST OVER 100F...BUT NOT
QUITE THERE SO WILL CONTINUE MENTION IN THE HWO.

BY THE WEEKEND AND EARLY NEXT WEEK SURFACE BOUNDARY SHOULD ADVANCE
MORE SOUTH AND EAST INCREASING THE POTENTIAL FOR PEAK
HEATING/SURFACE BASED CONVECTION. SURFACE FEATURES SHOULD LINGER
THROUGH THE END OF THE VALID PERIOD WITH A PROLONGED MENTION OF
POPS. BETTER SYNOPTIC FORCING WITH WRN TROUGH FINALLY ADVANCES FAR
ENOUGH EAST TO INCREASE POPS AND PRECIP COVERAGE BY TUE...BUT BEST
SENSIBLE WEATHER REFLECTION SEEMS JUST BEYOND THE CURRENT VALID
PERIOD TUE NIGHT INTO WED.

THE AIRMASS WILL BE FAVORABLE FOR LOCALLY HEAVY RAINS THROUGH THE
ENTIRE PERIOD WITH QUITE FAVORABLE ELEVATED K INDICES...WARM CLOUD
DEPTHS AND PWS.  HAVE STARTED WITH HEAVY RAIN MENTION NORTH
TONIGHT...BUT ADDITIONAL WORDING MAY NEED TO BE ADDED WITH LATER
PACKAGES. NE HALF OF THE FORECAST AREA REMAINS QUITE DRY...SO NO
HEADLINES FOR NOW UNTIL CONFIDENCE OF HEAVY RAIN LOCATIONS AND
MORE FAVORABLE ANTECEDENT MOISTURE CONDITIONS BECOME BETTER
PHASED. SEVERE POTENTIAL WILL REMAIN ELEVATED AS WELL DUE TO THE
DEGREE OF INSTABILITY AND AT LEAST MARGINAL EFFECT SHEAR...BUT
THERE DOES NOT APPEAR TO BE ANY PARTICULAR PERIOD TO FOCUS ON
BESIDE MARGINAL INCREASE FROM THE WEEKEND ON DUE TO BOUNDARY
INTERACTIONS. WILL KEEP BROAD MENTION OF BOTH THREATS GOING IN
THE HWO.

&&

.AVIATION...20/06Z
ISSUED AT 1134 PM CDT TUE AUG 19 2014

BOUNDARY WILL LIFT ACROSS IOWA THROUGH WEDNESDAY...THIS WILL BRING
CHANCES FOR SHRA/TSRA TO SITES...PRIMARILY SOUTHERN SITES
THROUGHOUT THE PERIOD. BEST CHANCES WILL COME BEFORE 12Z...BEFORE
DECREASING. HAVE INCLUDED VC MENTION AT KFOD/KDSM/KOTM. NORTHERN
SITES WILL LIKELY SEE BR/FG NEAR 12Z GIVEN AMPLE LOW LEVEL
MOISTURE. MVFR...IFR OR LOWER CEILINGS AND VISIBILITIES WILL BE
POSSIBLE AT TIMES AT SITES THROUGH 12Z BEFORE IMPROVING QUICKLY
AFTER 12Z. WINDS WILL BECOME SOUTHERLY AND CONDITIONS WILL REMAIN
VFR THROUGH REMAINDER OF PERIOD.

&&

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

&&

SHORT TERM...LEE
LONG TERM...SMALL
AVIATION...AWB

Hazardous weather outlook, Aug 19, 3:27 PM CDT, 13 hours 32 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
327 PM CDT TUE AUG 19 2014

IAZ004>007-015>017-023>028-035>039-049-050-062-202030-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-WEBSTER-
HAMILTON-HARDIN-GRUNDY-BLACK HAWK-MARSHALL-TAMA-POWESHIEK-
327 PM CDT TUE AUG 19 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TONIGHT

AREAS OF FOG ARE LIKELY TO DEVELOP TONIGHT. THE FOG MAY BECOME
LOCALLY DENSE WITH VISIBILITIES LESS THAN ONE QUARTER MILE AT
TIMES.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

PERIODIC THUNDERSTORMS ARE ANTICIPATED WEDNESDAY THROUGH MONDAY.
LOCALLY HEAVY RAINFALL IS POSSIBLE. THE PROBABILITY OF SEVERE
WEATHER IS LOW...HOWEVER THE BEST CHANCES WILL BE WEDNESDAY NIGHT
AND AGAIN OVER THE WEEKEND. LOCALLY HEAVY RAINFALL IS POSSIBLE
WITH AN OF THE THUNDERSTORMS.

HEAT INDICES WILL RISE INTO THE LOW TO MID 90S
TUESDAY...WEDNESDAY...AND THURSDAY AFTERNOON.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

IAZ033-034-044>048-057>061-070>075-081>086-092>097-202030-
SAC-CALHOUN-CRAWFORD-CARROLL-GREENE-BOONE-STORY-AUDUBON-GUTHRIE-
DALLAS-POLK-JASPER-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-
UNION-CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-
APPANOOSE-DAVIS-
327 PM CDT TUE AUG 19 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TONIGHT

SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP OVERNIGHT TONIGHT.
AN ISOLATED SEVERE STORM WITH QUARTER SIZED HAIL IS POSSIBLE.
LOCALLY HEAVY RAINFALL MAY OCCUR AS WELL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

PERIODIC THUNDERSTORMS ARE ANTICIPATED WEDNESDAY THROUGH MONDAY.
LOCALLY HEAVY RAINFALL IS POSSIBLE. THE PROBABILITY OF SEVERE
WEATHER IS LOW...HOWERVER THE BEST CHANCES WILL BE WEDNESDAY
NIGHT AND AGAIN OVER THE WEEKEND. LOCALLY HEAVY RAINFALL IS
POSSIBLE WITH AN OF THE THUNDERSTORMS.

HEAT INDICES WILL RISE INTO THE UPPER 90S TO JUST OVER 100 DEGREES
TUESDAY...WEDNESDAY...AND THURSDAY AFTERNOON.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

In the hours before

Special weather statement, Aug 20, 3:35 AM CDT, 1 hour 24 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
335 AM CDT WED AUG 20 2014

IAZ057>059-070>072-082-083-201000-
AUDUBON-GUTHRIE-DALLAS-CASS-ADAIR-MADISON-UNION-CLARKE-
INCLUDING THE CITIES OF...AUDUBON...EXIRA...GUTHRIE CENTER...
PANORA...BAYARD...CASEY...PERRY...WAUKEE...ADEL...ATLANTIC...
GREENFIELD...STUART...ADAIR...FONTANELLE...WINTERSET...EARLHAM...
CRESTON...OSCEOLA
335 AM CDT WED AUG 20 2014

...SCATTERED THUNDERSTORMS PRODUCING HEAVY RAIN AND HAIL...

SCATTERED THUNDERSTORMS HAVE DEVELOPED EARLY THIS MORNING AND WILL
PERSIST THROUGH SUNRISE. A FEW OF THESE STORMS WILL PRODUCE PENNY
TO NICKEL SIZED HAIL...ALONG WITH LOCALLY HEAVY RAIN THAT COULD
RESULT IN PONDING OF WATER AND MINOR FLOODING OF LOW LYING AREAS.

LEE

Local storm report, Aug 20, 4:30 AM CDT, 29 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
430 AM CDT WED AUG 20 2014

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

0420 AM     HAIL             DE SOTO                 41.53N 94.01W
08/20/2014  E1.25 INCH       DALLAS             IA   PUBLIC

&&

BSS

Special weather statement, Aug 20, 4:39 AM CDT, 20 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DES MOINES IA
439 AM CDT WED AUG 20 2014

IAZ059>061-071>074-082>085-201100-
DALLAS-POLK-JASPER-ADAIR-MADISON-WARREN-MARION-UNION-CLARKE-LUCAS-
MONROE-
INCLUDING THE CITIES OF...PERRY...WAUKEE...ADEL...DES MOINES...
NEWTON...GREENFIELD...STUART...ADAIR...FONTANELLE...WINTERSET...
EARLHAM...INDIANOLA...NORWALK...CARLISLE...PELLA...KNOXVILLE...
CRESTON...OSCEOLA...CHARITON...ALBIA
439 AM CDT WED AUG 20 2014

...SCATTERED THUNDERSTORMS PRODUCING HAIL EARLY THIS MORNING...

SCATTERED THUNDERSTORMS WILL AFFECT THE AREA EARLY THIS MORNING
THROUGH SUNRISE. SOME OF THE STORMS WILL PRODUCE HAIL OF PENNY
SIZE OR LARGER...ALONG WITH LOCALLY HEAVY DOWNPOURS.

LEE

Local storm report, Aug 20, 4:59 AM CDT, 0 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
459 AM CDT WED AUG 20 2014

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

0452 AM     HAIL             DES MOINES INT AIRPORT  41.53N 93.66W
08/20/2014  E1.00 INCH       POLK               IA   CO-OP OBSERVER

            FROM AIRPORT WEATHER OBSERVER

&&

BSS

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 20, 4:34 AM CDT	Severe Thunderstorm Warning	DMX	Adair, Madison	41 min
Aug 20, 6:10 AM CDT	Severe Thunderstorm Warning	DMX	Appanoose, Lucas, Monroe, Wayne	50 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2014 Every severe thunderstorm warning in 2014

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.