A weak frontal boundary moved southwest across Iowa during the day on the 9th into the evening hours. During the late afternoon, the airmass became unstable with CAPE around near 3500 J/kg.
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The episode as NWS DMX wrote it up.
A weak frontal boundary moved southwest across Iowa during the day on the 9th into the evening hours. During the late afternoon, the airmass became unstable with CAPE around near 3500 J/kg. Moderate shear was available, at 35 to 40 kts. Thunderstorms developed in a northwest to southeast line across central into northwest Iowa. Numerous funnel clouds were produced from the storm cells. A cluster of cells produced two landspouts northwest of the Fort Dodge area. They were quite weak and only touched down briefly.
The local office's own words before the first event, 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 the first event at Aug 9, 5:30 PM CST, 26 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE DES MOINES IA 630 PM CDT SAT AUG 9 2008 UPDATED AVIATION DISCUSSION .DISCUSSION... FEW ISOLATED CELLS HAVE GONE UP ON TWO WEAK BOUNDARIES STRETCH ACROSS THE AREA SO FAR THIS AFTERNOON...AND STARTING TO GET A FEW CELLS ON MORE DEFINED WEAK COLD FRONT BOUNDARY STRETCHING FROM SW MN INTO NC/NE IOWA...SOUTHEASTWARD INTO EASTERN IOWA. OTHER WEAK BOUNDARY STRETCHING MORE NORTH TO SOUTH NEAR JEFFERSON TO PERRY TO CHARITON...WITH SOME MOISTURE POOLING IN THAT AREA AS DEWPOINTS INTO THE LOWER 70S IN THAT AREA. CONVERGENCE ALONG BOTH FRONTS IS RATHER WEAK...BUT LOW LEVEL LAPSE RATES ARE QUITE STEEP AND SPC MESOANALYSIS INDICATING AROUND 1000-1500 J/KG OF SBCAPE. HOWEVER CELLS HAVING A TOUGH TIME SUSTAINING THEMSELVES/GROWING WITH MID LEVEL LAPSE RATES INDICATING A RELATIVELY STABLE LAYER ALOFT. THEREFORE KEPT MAINLY SLIGHT CHANCE/LOW CHANCE POPS ACROSS THE CWA INTO THE EVENING HOURS. AS BOUNDARY SAGS SOUTHWARD...AND DAYTIME HEATING SUBSIDES...INSTABILITY DECREASES WITH AN AREA OF SFC HIGH PRESSURE SINKING SOUTHWARD FROM ONTARIO/ERN MN. THEREFORE HAVE DRY CONDITIONS LATE TONIGHT...INTO SUNDAY. HIGH PRESSURE TO PUSH EASTWARD INTO SUNDAY NIGHT WITH WAA/SOUTHERLY FLOW RETURNING TO WESTERN IOWA...WHICH MAY KICK OFF A FEW STORMS JUST TO THE WEST OF THE CWA WITH MOISTURE TRANSPORT/LLJ ORIENTED MORE INTO NE NEBRASKA AND SW MINNESOTA. MOISTURE FLOW INCREASES INTO THE CWA LATER MONDAY INTO TUESDAY...AS A SFC TROUGH PASSES THROUGH THE STATE ASSOCIATED WITH A WEAK SHORTWAVE EJECTING OUT AHEAD OF THE MAIN PARENT TROUGH/CLOSED LOW OVER THE PRAIRIE PROVINCES OF CANADA. LONG RANGE MODELS THEN DIVERGE ON THE SOLUTION INTO THE MIDDLE TO END OF THE WEEK...WITH HOW THEY HANDLE THE MOVEMENT OF THE CLOSED UPPER LOW. 12Z GFS A LITTLE FASTER THAN THE PREVIOUS RUN...BUT STILL MUCH SLOWER THAN THE ECMWF. FOR NOW TRENDED TOWARD THE EC...WHICH HAS BEEN MORE CONSISTENT THE PAST FEW DAYS WITH THIS SYSTEM. MAINLY LED TO SOME BROADBRUSHING OF POPS INTO THE END OF THE WEEK/EARLY UPCOMING WEEKEND. MAINLY LEFT AT SLIGHT CHANCE THOUGH...DUE TO THE UNCERTAINTY. && .AVIATION...10/00Z WEAK COLD FRONT FROM NEAR KSPW TO JUST NORTH OF KALO WILL CONTINUE MOVING SOUTH OVERNIGHT. SCATTERED THUNDERSTORMS ALONG AND AHEAD OF THIS FRONT WILL CONTINUE TO PERCOLATE OVER THE NEXT COUPLE OF HOURS IN A MODERATELY UNSTABLE LOW LEVEL AIRMASS. HOWEVER...MID LEVEL LAPSE RATES WILL KEEP THE STORMS SUB SEVERE. OUTSIDE OF TSRA CHANCES THIS EVENING AND A LOW CONFIDENCE THREAT OF FOG LATE TONIGHT...VFR CONDITIONS ARE EXPECTED. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && PUBLIC...MJA/JOHNSON AVIATION...MOYER
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DES MOINES IA 528 AM CDT SAT AUG 9 2008 IAZ004>007-016-017-025>028-036>039-049-050-062-101100- EMMET-KOSSUTH-WINNEBAGO-WORTH-HANCOCK-CERRO GORDO-WRIGHT-FRANKLIN- BUTLER-BREMER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-MARSHALL-TAMA- POWESHIEK- 528 AM CDT SAT AUG 9 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA ALONG AND EAST OF A LINE FROM ESTHERVILLE TO CLARION AND GRINNELL. .DAY ONE...TODAY AND TONIGHT ISOLATED TO SCATTERED THUNDERSTORMS NON SEVERE THUNDERSTORMS ARE EXPECTED THROUGH EARLY EVENING. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY THERE IS A CHANCE OF THUNDERSTORMS OFF AND ON FROM MONDAY NIGHT THROUGH EARLY WEDNESDAY. THE SEVERE WEATHER THREAT APPEARS TO BE LOW AT THIS TIME. ANOTHER THREAT FOR THUNDERSTORMS IS EXPECTED FROM THURSDAY INTO FRIDAY WITH SOME SEVERE THREAT POSSIBLE. .SPOTTER INFORMATION STATEMENT... THE POTENTIAL FOR SPOTTER ACTIVATION IS MINIMAL THROUGH WEDNESDAY. IAZ015-023-024-033>035-044>048-057>061-070>075-081>086-092>097- 101100- PALO ALTO-POCAHONTAS-HUMBOLDT-SAC-CALHOUN-WEBSTER-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- 528 AM CDT SAT AUG 9 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA WEST OF A LINE FROM EMMETSBURG TO WEBSTER CITY AND OSKALOOSA. .DAY ONE...TODAY AND TONIGHT ISOLATED NON SEVERE THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON INTO THIS EVENING. .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY THERE IS A CHANCE OF THUNDERSTORMS OFF AND ON FROM MONDAY NIGHT THROUGH EARLY WEDNESDAY. THE SEVERE WEATHER THREAT APPEARS TO BE LOW AT THIS TIME. ANOTHER THREAT FOR THUNDERSTORMS IS EXPECTED FROM THURSDAY INTO FRIDAY WITH SOME SEVERE THREAT POSSIBLE. .SPOTTER INFORMATION STATEMENT... THE POTENTIAL FOR SPOTTER ACTIVATION IS MINIMAL THROUGH WEDNESDAY. CC
The Des Moines radar (KDMX), 109 km away, was scanning. The volume nearest the first event began at 23:55 UTC.
2 tornado. Local standard time, as filed.
Brief touchdown with no damage.
Two seperate spotters reported a brief tornado between Clare and Barnum.
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