Alert archive / Iowa / Severe Thunderstorm Warnings in 2002

Severe Thunderstorm Warning 389, NWS Sioux Falls, SD

October 1, 2002Lyon County, Iowa

NWS Sioux Falls, SD issued this severe thunderstorm warning at Oct 1, 2002, 2:35 PM CDT for Lyon County, Iowa. It was in force for 40 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: Oct 1, 2002, 2:35 PM CDT (19:35 UTC)
Expired: Oct 1, 2002, 3:15 PM CDT
In force: 40 min
Issued by: NWS Sioux Falls, SD
Area: Counties, with a storm outline in the text

County Lyon County, IA

What was reported inside it

Time	Report	Where	Remark
Oct 1, 3:07 PM CDT	Hail 0.75	Alvord, IA
Oct 1, 3:17 PM CDT	Hail 0.88	Alvord, IA

NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in.

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

Omaha, NE (KOAX), launched 12:00Z, 7.6 hours before the alert went out and 232 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: 976 J/kg
Mixed-layer CIN: -220 J/kg
Mixed-layer LCL: 1127 m above ground
0-6 km bulk shear: 43 kt
0-1 km storm-relative helicity: 43 m²/s²
0-3 km storm-relative helicity: 111 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.7

Open this sounding in Storm Lab

The text

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

570 
WUUS53 KFSD 011935
SVRFSD
IAC119-012015-

BULLETIN - EAS ACTIVATION REQUESTED
SEVERE THUNDERSTORM WARNING
NATIONAL WEATHER SERVICE SIOUX FALLS SD
235 PM CDT TUE OCT 1 2002

THE NATIONAL WEATHER SERVICE IN SIOUX FALLS HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
  WESTERN LYON COUNTY IN NORTHWEST IOWA

* UNTIL 315 PM CDT

* AT 235 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
  SEVERE THUNDERSTORM 10 MILES WEST OF LARCHWOOD...OR ABOUT 9 MILES
  NORTH OF CANTON...MOVING NORTHEAST AT 35 MPH.

* THE SEVERE THUNDERSTORM WILL BE NEAR...
  INWOOD AROUND 240 PM CDT
  LARCHWOOD AROUND 245 PM CDT
  ALVORD AROUND 250 PM CDT
  LESTER...DOON AROUND 255 PM CDT
  ROCK RAPIDS AROUND 305 PM CDT

THIS STORM HAS A HISTORY OF PRODUCING LARGE HAIL AND DAMAGING WIND.
GO INSIDE A STURDY BUILDING AND STAY AWAY FROM WINDOWS.

LAT...LON 4349 9654 4328 9651 4326 9609 4350 9617

BOUSTEAD

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 Sioux Falls, SD wrote its last area forecast discussion before this severe thunderstorm warning went out at Oct 1, 10:45 AM CDT, 3 hours 50 minutes earlier.

Area forecast discussion, Oct 1, 10:45 AM CDT, 3 hours 50 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1045 AM CDT TUE OCT 1 2002

SFC BNDRY HAS NOW SLOWED TO A CRAWL ALG FAR SERN CWA BRDR...AND
AWAITING FIRST WAVE ACRS NRN KS/SWRN NEBRASKA TO DO MUCH MORE
MOVING. NLG PROF SHOWS OFF SFC FLOW IS FAR FROM FAVORABLE FOR
PROPAGATION.  AREA OF ELEVATED TSRA IN ECNTRL NE WITH LIFT LEADING
INITIAL WAVE...AND VERY GOOD LAPSE RATES ALFT OVR BNDRY. SFC REMAINS
CAPPED INTO EARLY AFTN...BUT IF TMPS REACH LOWER TO MID 80S AS LOW
LVL MSTR GATHERS VIA LOW LVL CONVERGENCE...APPEARS MORE THAN FAVORABLE
FOR SCT TSRA TO BECOME SFC BASED...AND WL THREATEN TO BECOME SEVERE
ACRS FAR SE...MAINLY HAIL THREAT WHEN SLIGHTLY ELEVATED N OF BNDRY.

SHOULD BE TWO DISTINCT AREAS OF PCPN THRU AFTN...WITH SECONDARY AREA
OF SHRA DEVELOPING MID MORNING BACK IN COLDER AND MORE STABLE AIR
WHERE STG FRONTOGENESIS. WL WATCH ENHANCEMENT INTO MIDDAY...WANING A
BIT EARLY AFTN...BUT WITH BETTER PV FORCING BY LTR AFTN...WL SEE
INCREASING COVERAGE ONCE AGAIN.

TEST OF IFPS UPGRADE SUCCESSFUL. UPDATES OUT BY 1600Z.

.FSD...NONE
CHAPMAN

Hazardous weather outlook, Oct 1, 11:30 AM CDT, 3 hours 5 minutes before

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-IAZ001>003-
012>014-020>022-031-032-NEZ013-014-021200-

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1130 AM CDT TUE OCT 1 2002

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST SOUTH DAKOTA...
SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND NORTHEAST NEBRASKA.

.DAY ONE...

SCATTERED SHOWERS AND THUNDERSTORMS WILL PREVAIL ACROSS MUCH OF
NORTHWEST IOWA THIS AFTERNOON.  ISOLATED THUNDERSTORMS MAY BECOME
SEVERE MID TO LATE AFTERNOON...GENERALLY ALONG AND SOUTHEAST OF A
LINE FROM STORM LAKE TO HORNICK.  THE GREATEST THREAT WOULD BE HAIL
UP TO QUARTER SIZE...ALONG WITH SPOTTY HEAVY RAINFALL ONE TO TWO
INCHES.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED FROM 200 PM THROUGH 700 PM
SOUTHEAST OF A LINE FROM SPENCER TO SIOUX CITY.

.DAYS TWO THROUGH SEVEN...

AN UNSETTLED AND COOL WEATHER PATTERN WILL AFFECT SOUTHEAST SOUTH
DAKOTA...SOUTHWEST MINNESOTA...NORTHWEST IOWA...AND FAR NORTHEAST
NEBRASKA THE REMAINDER OF THE WEEK INTO THE WEEKEND. THERE IS A
CHANCE OF LIGHT RAIN WEDNESDAY ASSOCIATED WITH AN UPPER LEVEL
DISTURBANCE. HOWEVER...A POTENTIALLY STRONG LOW PRESSURE SYSTEM WILL
DEVELOP IN THE ROCKIES BY THURSDAY...AND MOVE OVER THE AREA THURSDAY
NIGHT AND FRIDAY. SIGNFICANT RAINFALL MAY BE ASSOCIATED WITH THIS
SYSTEM...ESPECIALLY IN NORTHWEST IOWA...FAR SOUTHEAST SOUTH
DAKOTA...AND PARTS OF SOUTHWEST MINNESOTA THURSDAY NIGHT INTO FRIDAY.
ANOTHER PROBABLY WEAKER SYSTEM WILL AFFECT THE AREA BY LATE
SATURDAY...WITH A CHANCE OF A COLD RAIN.

In the hours before

Local storm report, Oct 1, 2:09 PM CDT, 26 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
209 PM CDT TUE OCT 01 2002

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0118 PM    6 N TABOR                 SD   .88 INCH HAIL
10/01/02   BON HOMME                      REPORTED BY PUBLIC.

0125 PM    1 S LESTERVILLE           SD   .88 INCH HAIL
10/01/02   YANKTON                        REPORTED BY STORM
                                          SPOTTER.

0126 PM    3 NE LESTERVILLE          SD   .75 INCH HAIL
10/01/02   YANKTON                        REPORTED BY PUBLIC.

0128 PM    12 SW HURLEY              SD   .75 INCH HAIL
10/01/02   TURNER                         REPORTED BY PUBLIC.

0137 PM    8 NE UTICA                SD   1 INCH HAIL
10/01/02   YANKTON

0150 PM    HURLEY                    SD   1.75 INCH HAIL
10/01/02   TURNER

0150 PM    3 W HURLEY                SD   1.25 INCH HAIL
10/01/02   TURNER

The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 1, 2:41 PM CDT	Severe Thunderstorm Warning	FSD	Sioux	39 min
Oct 1, 3:16 PM CDT	Severe Thunderstorm Warning	FSD	Lyon	44 min
Oct 1, 3:19 PM CDT	Severe Thunderstorm Warning	FSD	Sioux	26 min
Oct 1, 3:34 PM CDT	Severe Thunderstorm Warning	FSD	O'Brien	41 min
Oct 1, 4:20 PM CDT	Severe Thunderstorm Warning	FSD	Clay	40 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2002 Every severe thunderstorm warning in 2002

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive.