Alert archive / Iowa / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 177, NWS Des Moines, IA

August 9, 2009Dallas County, Iowa

NWS Des Moines, IA issued this severe thunderstorm warning at Aug 9, 2009, 5:06 PM CDT for Dallas County, Iowa. It was in force for 39 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Aug 9, 2009, 5:06 PM CDT (22:06 UTC)
Expired
Aug 9, 2009, 5:45 PM CDT
In force
39 min
Issued by
NWS Des Moines, IA
Area
Storm-based polygon

County Dallas County, IA

The radar

The Des Moines radar (KDMX), 27 km from the middle of the area, began a volume at 22:09 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 watch it was issued in

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

IssuedProductOfficeLasted
Aug 9, 3:44 PM CDTSevere Thunderstorm WatchSPC6 hr

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 10.1 hours before the alert went out and 198 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, Omaha, NE at 12:00Z on 2009-08-09Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1138 joules per kilogram.LCLLFCEL10008507005003002001001 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, Omaha, NE at 12:00Z on 2009-08-09The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 113 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
1138 J/kg
Mixed-layer CIN
-213 J/kg
Mixed-layer LCL
726 m above ground
0-6 km bulk shear
45 kt
0-1 km storm-relative helicity
113 m²/s²
0-3 km storm-relative helicity
135 m²/s²
Significant tornado parameter
0.0
Supercell composite
3.9

Open this sounding in Storm Lab

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 9, 3:24 PM CDT, 1 hour 42 minutes earlier.

Area forecast discussion, Aug 9, 3:24 PM CDT, 1 hour 42 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
324 PM CDT SUN AUG 9 2009

.DISCUSSION...
FOCUS OF SEVEN DAY FORECAST IS ON CONVECITVE POTENTIAL REST OF TODAY
AND TONIGHT. IN WAKE OF MORNING SEVERE STORMS GOOD INSTABILITY
REMAINS ACROSS SOUTHERN HALF OR TWO THIRDS OF CWA WITH NEBULOUS
SURFACE FRONT/OUTFLOW BOUNDARY DRAPED NW-SE ACROSS CENTRAL IOWA.
DISORGANIZED STORMS CONTINUE TO FIRE UP WITHN BROAD PSEUDO-FRONTAL
ZONE. SECONDARY MID-LEVEL IMPULSE ASSOCIATED WITH BROAD TROUGH OVER
KS/NE APPROACHING AND SHOULD INITIATE STRONGER CONVECTION LATE THIS
AFTERNOON INTO TONIGHT...WITH THE ENVIRONMENT CONTINUING TO SUPPORT
ADDITIONAL SEVERE WEATHER. HAVE INCLUDED NUMEROUS TS AND SEVERE
WORDING ACROSS ABOUT SOUTHERN HALF/TWO THIRDS OF AREA TONIGHT. IN
ADDITION TO LARGE HAIL/HIGH WIND THREAT...THERE IS THE POTENTIAL FOR
TRAINING STORMS WITH STEERING FLOW TAKING THEM NORTHEAST THIS
EVENING ALONG THE FRONTAL ZONE...RESULTING IN LOCALLY HEAVY RAIN. IN
MOST OF OUR AREA FFG VALUES ARE QUITE HIGH AFTER A DRY MONTH OR
SO...HOWEVER THE SEVERE THUNDERSTORM THAT STRUCK NORTHEASTERN IOWA
THIS MORNING DROPPED A VERY QUICK INCH OR TWO OF RAIN ALONG THE
TRACK FROM EASTERN HARDIN THROUGH BLACK HAWK COUNTY. IN LIGHT OF
THESE FACTORS HAVE OPTED TO ISSUE A FLASH FLOOD WATCH FOR FIVE
COUNTIES AROUND THIS SWATH...TO RUN THROUGH 12Z TOMORROW MORNING.

FROM MONDAY THROUGH SATURDAY THE FORECAST REMAINS QUIET. KEPT A FEW
SLIGHT POPS MONDAY/MONDAY NIGHT WITH A SECONDARY SHORTWAVE MOVING
OVERHEAD IN THE MID-LEVEL FLOW...HOWEVER MOISTURE WILL BE VERY
LIMITED PRECLUDING ANY HIGHER POPS. HIGH PRESSURE WILL DOMINATE
TUESDAY THROUGH THURSDAY PRODUCING DRY...MILD...AND PLEASANT
WEATHER. TOWARD THE WEEKEND LONG-RANGE MODELS CONTINUE TO INDICATE A
MID-LEVEL TROUGH AND SURFACE FRONT TRAVERSING THE AREA. DISAGREEMENT
ON TIMING AND EVOLUTION OF THIS SYSTEM BETWEEN THE MODELS
PERSISTS...HOWEVER IT IS BEGINNING TO APPEAR A BIT MORE LIKELY THAT
A FRONT WILL APPROACH ON SUNDAY OR SUNDAY NIGHT SO HAVE UPPED THE
POPS A BIT TO LOW CHANCE CATEGORY AT THE END OF THE FORECAST PERIOD.

&&

.AVIATION...09/18Z
ELEVATED CONVECTION STILL DEVELOPING BEHIND COLD FRONTAL BOUNDARY
ACROSS STATE. POST-FRONTAL TAF SITES ARE OCCASIONALLY MVFR. CIGS ARE
TRENDING TO VFR THROUGHOUT THE DAY EXCEPT NEAR TS. AS THE FRONTAL
BOUNDARY MOVES SOUTHEAST TONIGHT...SITES SHOULD SEE SOME CLEARING
AND THERE WILL BE A POTENTIAL FOR RADIATIONAL FOG DEVELOPMENT.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...FLASH FLOOD WATCH THROUGH MONDAY
MORNING FOR BACLK HAWK-BREMER-GRUNDY-HARDIN-TAMA.

&&

SHORT TERM/LONG TERM...LEE
AVIATION...HINSBERGER
Hazardous weather outlook, Aug 9, 2:37 PM CDT, 2 hours 29 minutes before
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In the hours before

Local storm report, Aug 9, 2:48 PM CDT, 2 hours 18 minutes before
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Local storm report, Aug 9, 3:45 PM CDT, 1 hour 21 minutes before
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Local storm report, Aug 9, 4:05 PM CDT, 1 hour 1 minute before
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Local storm report, Aug 9, 4:22 PM CDT, 44 minutes before
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Local storm report, Aug 9, 4:27 PM CDT, 39 minutes before
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Local storm report, Aug 9, 4:33 PM CDT, 33 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
433 PM CDT SUN AUG 09 2009

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

0431 PM     TSTM WND DMG     CUMBERLAND              41.27N 94.87W
08/09/2009                   CASS               IA   TRAINED SPOTTER

            TREE LIMBS UP TO 12 INCH DIAMETER ARE DOWN.

&&

JH

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 9, 7:32 AM CDTSevere Thunderstorm WarningDMXCrawford, Sac43 min
Aug 9, 8:10 AM CDTSevere Thunderstorm WarningDMXCalhoun, Carroll, Crawford, Greene, Sac50 min
Aug 9, 8:50 AM CDTSevere Thunderstorm WarningDMXCalhoun, Webster55 min
Aug 9, 9:30 AM CDTSevere Thunderstorm WarningDMXHamilton, Webster, Wright60 min
Aug 9, 9:45 AM CDTSevere Thunderstorm WarningDMXBoone, Hamilton, Story45 min
Aug 9, 10:07 AM CDTSevere Thunderstorm WarningDMXFranklin, Grundy, Hamilton, Hardin, Marshall, Story53 min
Aug 9, 10:38 AM CDTSevere Thunderstorm WarningDMXBlack Hawk, Butler, Grundy, Marshall, Tama67 min
Aug 9, 11:05 AM CDTTornado WarningDMXBlack Hawk, Grundy40 min
Aug 9, 11:46 AM CDTSevere Thunderstorm WarningDMXBlack Hawk18 min
Aug 9, 3:35 PM CDTFlash Flood WatchDMXBlack Hawk, Bremer, Grundy, Hardin, Tama5 hr
Aug 9, 4:00 PM CDTSevere Thunderstorm WarningDMXCass45 min
Aug 9, 4:24 PM CDTSevere Thunderstorm WarningDMXAdair36 min
Aug 9, 5:18 PM CDTSevere Thunderstorm WarningDMXAdair, Clarke, Madison, Union, Warren57 min
Aug 9, 5:26 PM CDTSevere Thunderstorm WarningDMXPolk49 min
Aug 9, 5:49 PM CDTSevere Thunderstorm WarningDMXMarion, Warren41 min
Aug 9, 5:52 PM CDTSevere Thunderstorm WarningDMXAdams, Taylor38 min
Aug 9, 5:53 PM CDTSevere Thunderstorm WarningDMXJasper, Marshall, Polk52 min
Aug 9, 6:04 PM CDTAreal Flood AdvisoryDMXPolk, Warren2 hr
Aug 9, 6:15 PM CDTSevere Thunderstorm WarningDMXClarke, Lucas, Warren45 min
Aug 9, 6:17 PM CDTSevere Thunderstorm WarningDMXClarke, Decatur, Ringgold, Union43 min
Aug 9, 6:25 PM CDTSevere Thunderstorm WarningDMXMahaska, Marion, Poweshiek50 min
Aug 9, 6:28 PM CDTSevere Thunderstorm WarningDMXRinggold, Taylor47 min
Aug 9, 6:33 PM CDTSevere Thunderstorm WarningDMXJasper, Marshall, Poweshiek, Tama57 min
Aug 9, 6:54 PM CDTSevere Thunderstorm WarningDMXMarshall, Tama51 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2009Every severe thunderstorm warning in 2009

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.