Severe Thunderstorm Warning 229, NWS Sioux Falls, SD

000 
WWUS53 KFSD 250501
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1201 AM CDT TUE AUG 25 2009

IAC149-193-NEC043-051-SDC127-250515-
/O.CON.KFSD.SV.W.0229.000000T0000Z-090825T0515Z/
PLYMOUTH IA-WOODBURY IA-DAKOTA NE-DIXON NE-UNION SD-
1201 AM CDT TUE AUG 25 2009

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 1215 AM CDT
FOR SOUTHEASTERN UNION...EXTREME EASTERN DIXON...DAKOTA...
NORTHWESTERN WOODBURY AND SOUTHERN PLYMOUTH COUNTIES...

AT 1156 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE 
HAIL...AND DAMAGING WINDS NEAR 60 MPH. THIS STORM WAS LOCATED NEAR 
DAKOTA CITY...OR 6 MILES SOUTHWEST OF SIOUX CITY...MOVING EAST AT 30 
MPH.

THE SEVERE THUNDERSTORM WILL BE NEAR...SOUTH SIOUX CITY...SERGEANT 
BLUFF AND SIOUX CITY AROUND 1205 AM CDT...

OVERALL...THE STORM HAS SHOWN SIGNS OF WEAKENING IN INTENSITY OVER 
THE PAST TEN MINUTES. HOWEVER SOME WIND CIRCULATIONS EXIST ON RADAR 
NEAR THE SIOUX CITY METRO AREA ITSELF...WHICH MAY CAUSE LOCALIZED 
WET MICROBURST WINDS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

SEVERE THUNDERSTORMS PRODUCE DAMAGING WIND IN EXCESS OF 60 MPH...
DESTRUCTIVE HAIL...DEADLY LIGHTNING...AND VERY HEAVY RAIN. FOR YOUR
PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF YOUR HOME
OR BUSINESS. HEAVY RAINS FLOOD ROADS QUICKLY SO DO NOT DRIVE INTO
AREAS WHERE WATER COVERS THE ROAD.

&&

LAT...LON 4227 9667 4256 9670 4270 9633 4233 9619
TIME...MOT...LOC 0459Z 256DEG 25KT 4243 9643

$$

MJF

000 
WWUS53 KFSD 250514
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1214 AM CDT TUE AUG 25 2009

IAC149-193-NEC043-051-SDC127-250524-
/O.EXP.KFSD.SV.W.0229.000000T0000Z-090825T0515Z/
PLYMOUTH IA-WOODBURY IA-DAKOTA NE-DIXON NE-UNION SD-
1214 AM CDT TUE AUG 25 2009

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN UNION...EXTREME
EASTERN DIXON...DAKOTA...NORTHWESTERN WOODBURY AND SOUTHERN PLYMOUTH
COUNTIES EXPIRES AT 1215 AM CDT...

THE STORM WHICH PROMPTED THE WARNING HAS WEAKENED AND NO LONGER 
APPEARED TO BE SEVERE. HOWEVER GUSTY WINDS AND CERTAINLY HEAVY RAIN 
ARE STILL POSSIBLE WITH THIS THUNDERSTORM. A FLASH FLOOD WARNING 
WILL REMAIN IN EFFECT OVERNIGHT.

LAT...LON 4227 9667 4256 9670 4270 9633 4233 9619
TIME...MOT...LOC 0514Z 256DEG 25KT 4245 9629

$$

MJF

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
924 PM CDT MON AUG 24 2009

.DISCUSSION...
CAP CONTINUES TO HOLD ACROSS NORTHERN PARTS OF THE AREA AND THIS
LOOKS LIKE IT WILL HOLD AS BETTER UPPER LEVEL SUPPORT MOVES INTO
NEBRASKA. SO...WITH THUNDERSTORM ACTIVITY FIRING UP OVER CENTRAL
INTO NORTHEAST NEBRASKA THE ATTENTION TURNS TO THE SOUTHERN
COUNTIES. THE NEW 0Z NAM WILL BE DISREGARDED AT THIS TIME AS IT
SEEMS UNLIKELY THAT THE CONVECTIVE CLUSTER IN CENTRAL NEBRASKA WILL
MOVE EAST-SOUTHEAST. SO...HAVE BUMPED UP POPS IN NE NEB AND NW IA
AND INCREASED QPF AMOUNTS AS WELL. MAY NEED TO FURTHER BOLSTER QPF
AMOUNTS AND ACTUALLY A LITTLE CONCERNED ABOUT SOME POTENTIAL FLASH
FLOODING FROM ABOUT DIXON TO SIOUX CITY LATER TONIGHT. PWAT VALUES
RUNNING ABOUT 2 INCHES AND WARM CLOUD DEPTH ABOUT 14-15 KFT. WITH
0.5 KM CAPE VALUES AROUND 3000 J/KG...UPDRAFTS WILL BE STRONG AND
PRECIPITATION EFFICIENCY WILL BE VERY GOOD. SO...AN INCH OF RAIN IN
20 MINUTES A DEFINITE POSSIBILITY. /08

&&

.PREV DISCUSSION...
BATCH OF ACCAS DEVELOPING NEAR KHON-KBKX AS LEADING SHORTWAVE LIFT
LIFTS NORTHEAST ACROSS FORECAST AREA.  AT THE SURFACE...WEAK
PREFRONTAL TROUGH LOCATED ACROSS CENTRAL SOUTH DAKOTA. ATMOSPHERE
REMAINS CAPPED HOWEVER SO AM NOT EXPECTING MUCH IN THE WAY OF
CONVECTION OTHER THAT ELEVATED SHOWERS ACROSS FAR NORTHWESTERN
CORNER THROUGH EARLY EVENING.  MODELS SUGGESTING SHORT WAVE OVER
PANHANDLE OF NEBRASKA WILL LIFT NORTHEAST...HOWEVER...DUE TO THE
WEALTH OF HIGH CLOUDS ACROSS WESTERN NEBRASKA HAVE BEEN UNABLE TO
IDENTIFY THIS FEATURE ON WATER VAPOR. SEVERE THREAT IS SOMEWHAT
MARGINAL WITH WEAK SHEAR. FOR HAIL...50 DBZ CORE NEEDS TO APPROACH
40K. WITH ATMOSPHERIC SOUNDINGS FAIRLY WATER LOADED...SOME STORMS
MAY BE ABLE TO PRODUCE SOME DECENT RAINFALL ACROSS THE AREA. FAVORED
AREA FOR STORM DEVELOPMENT REMAINS ALONG AND WEST OF A LINE FROM
TYNDALL TO BROOKINGS. AS COLD FRONT SHIFTS SOUTH AND EAST...IT
BECOMES MORE WEST TO EAST ORIENTED POTENTIALLY KEEPING KSLB AND KSUX
SOUTH OF THE FRONT.  HAVE RAISED FORECAST LOWS WITH EXPECTED CLOUD
COVER...BUT ESPECIALLY IN THESE AREAS ACROSS NORTHWEST IOWA.

SHWRS AND TSTMS SHUD DCRS VERY SLWLY SWD TUE MRNG...BUT ANOTHER
APPCHG SHRTWV FROM THE SW IN SPLIT FLOW SHUD CAUSE SOME INCRS AGN
LATE TUE OR TUE EVE, BIG QSTN IS HOW EXTENSIVE AND HOW FAR N THIS
RESURGENCE WILL BE. FOR NOW WILL ALLOW IT TO AFFECT MAINLY SERN PART
OF FCST AREA MAINLY S AND E OF FSD...DCRS LATE TUE NGT WITH A SLGT
CHC FAR SE WED MRNG. THIS IS AN INCRS OVER WHAT WE HAD ERYR AND WITH
THE OSCILLATING NATURE OF MODEL SOLNS WILL NOT GO TOO WILD WITH THE
TUE NGT/WED MRNG CHANGE...BUT IF EVE SOLNS COME IN AND KEEP THE
RIPENING TREND...WE WUD HAVE TO MAKE TUE NGT WETTER OVER SRN FCST
AREA AND EXTEND SOME PCPN FRTHR N. OTHER MODELS SUCH AS THE GFS AND
ECMWF ARE WEAKER AND A LTL FRTHR S ON THIS LTL SYS.

TEMPS WILL SHOW A SLOW COOLING TREND WITH CLOUD COVER TUE A FACTOR
ESPLY S. LOW LEVEL COOLER AIR SHUD CONT TO FLOW INTO FCST AREA TUE
THRU WED.

EXPECT IN ANY EVENT FOR THE SHWRS/TSTMS TO BE GONE BY WED NOON...THO
HAVE KEPT A SLGT CHC AFTN/EVE TSTMS IN OUR EXTRM SW WED. AS INSTBLTY
INCREASES A LTL NEAR THAT AREA AND HALF DECENT HEATG EXPECTED. THU
SHUD THEN BE DRY AND MILD WITH MID 70S EAST TO LOW 80S W.

FIRST QSTN ON FRI THRU MON PERIOD IS CDFNT SLIPPING THRU THU/FRI AS
UPPER LOW HEADS FOR A GREATLKS DIGGING. CLOSE CALL ON MENTIONING
TSTMS OR NOT...ESPLY AS FAST AS SOME MODELS ARE NOR BRINGING IT
THRU. WITH TIMING QSTNS HAVE LEFT OUT MENTN...SO THE ONLY PCPN
MENTNION THIS FOUR DAY PD WILL BE A LSGT CHC SHWRS FAR E SAT ON BACK
END OF COOL UPPER LOW. DESPITE THE COOL AIR THIS WILL BRING
IN...GUIDNCE SEEMS A LTL TOO COOL ON HIGHS FOR THE PERIOD...FOR NOW
JUST EDGED THEM UP A CPL DEGS.

&&

.AVIATION...
CONDS ARE EXPECTED TO BE PRIMARILY VFR THOUGH MAY SEE SOME BRIEF
MVFR PERIODS THIS EVENING AS SCATTERED THUNDERSTORMS DEVELOP ALONG A
COLD FRONT MOVING THROUGH THE AREA. BEST CHANCES FOR STORMS WILL BE
ALONG AND NORTH OF HIGHWAY 60. FRONT WILL SLOW AS IT IS SHIFTING
SOUTH AND BECOME MORE ORIENTED EAST WEST TOWARDS TUESDAY MORNING.
MAY HAVE SOME MVFR CEILINGS JUST NORTH OF THE FRONT...WITH THE
POTENTIAL FOR SHOWERS LINGERING INTO TUESDAY MAINLY ALONG AND SOUTH
OF A LINE FROM YANKTON TO WINDOM.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...

SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&

WILLIAMS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1135 AM CDT MON AUG 24 2009

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-
IAZ001>003-012>014-020>022-031-032-NEZ013-014-251200-
AURORA-BEADLE-BON HOMME-BROOKINGS-BRULE-BUENA VISTA IA-
CHARLES MIX-CHEROKEE IA-CLAY-CLAY IA-COTTONWOOD MN-DAKOTA NE-
DAVISON-DICKINSON IA-DIXON NE-DOUGLAS-GREGORY-HANSON-HUTCHINSON-
IDA IA-JACKSON MN-JERAULD-KINGSBURY-LAKE-LINCOLN-LINCOLN MN-
LYON IA-LYON MN-MCCOOK-MINER-MINNEHAHA-MOODY-MURRAY MN-NOBLES MN-
OBRIEN IA-OSCEOLA IA-PIPESTONE MN-PLYMOUTH IA-ROCK MN-SANBORN-
SIOUX IA-TURNER-UNION-WOODBURY IA-YANKTON-
1135 AM CDT MON AUG 24 2009

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

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS...
THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG A COLD FRONT MOVING
THROUGH THE REGION THIS EVENING. WHILE WIDESPREAD AND ORGANIZED
SEVERE WEATHER IS NOT EXPECTED...AN ISOLATED THUNDERSTORM THIS
EVENING FROM SOUTH CENTRAL SOUTH DAKOTA AND ACROSS AREAS NORTH OF
INTERSTATE 90 MAY PRODUCE HAIL UP TO QUARTER SIZE AND WINDS UP TO
60 MPH. ADDITIONAL THUNDERSTORMS ARE LIKELY TO DEVELOP LATER
TONIGHT FROM NORTHEAST NEBRASKA INTO NORTHWEST IOWA...BUT SEVERE
STORMS ARE NOT EXPECTED.

WIND AND FOG...
PATCHY DENSE FOG OVER PORTIONS OF SOUTHWEST MINNESOTA AND
NORTHWEST IOWA WILL SLOWLY DISSIPATE BY EARLY THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THE THREAT FOR THUNDERSTORMS WILL GRADUALLY END AND SHIFT
SOUTHWARD TUESDAY INTO TUESDAY NIGHT. SEVERE STORMS ARE NOT
EXPECTED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE POSSIBLE AFTER 7 PM CDT.

&&

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.WEATHER.GOV/SIOUXFALLS. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.

BT