Severe Thunderstorm Warning 218, NWS Sioux Falls, SD

000 
WWUS53 KFSD 270626
SVSFSD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE SIOUX FALLS SD
126 AM CDT SUN JUL 27 2008

SDC003-005-015-035-073-111-270645-
/O.CON.KFSD.SV.W.0218.000000T0000Z-080727T0645Z/
JERAULD SD-SANBORN SD-AURORA SD-BEADLE SD-DAVISON SD-BRULE SD-
125 AM CDT SUN JUL 27 2008

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 145 AM CDT
FOR NORTHERN BRULE...EXTREME NORTHWESTERN DAVISON...BEADLE...
AURORA...WESTERN SANBORN AND JERAULD COUNTIES...

AT 125 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO
INDICATE A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING
DESTRUCTIVE WINDS IN EXCESS OF 70 MPH.  THESE STORMS WERE LOCATED
ALONG A LINE EXTENDING FROM BROADLAND TO 6 MILES SOUTHWEST OF LANE TO
5 MILES EAST OF KIMBALL...OR ALONG A LINE EXTENDING FROM 8 MILES
NORTHWEST OF HURON TO 28 MILES SOUTHWEST OF HURON TO 24 MILES EAST OF
CHAMBERLAIN...MOVING SOUTHEAST AT 51 MPH.

SEVERE THUNDERSTORMS WILL BE NEAR...
   WESSINGTON SPRINGS...WHITE LAKE AROUND 130 AM CDT...
   WOONSOCKET...HURON AROUND 140 AM CDT...
   CAVOUR...YALE...PLANKINTON AROUND 145 AM CDT...

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

LAT...LON 4462 9785 4384 9807 4384 9833 4365 9833
      4352 9854 4387 9932 4393 9937 4394 9894
      4420 9894 4421 9871 4464 9870
TIME...MOT...LOC 0625Z 302DEG 44KT 4446 9830 4399 9847
          4375 9884

$$
WILLIAMS

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
835 PM CDT SAT JUL 26 2008

.DISCUSSION...
SFC BNDRY ACRS NRN SD ATTM. S/W MOVG THRU ERN MT/ERN WY HELPING TO
TRIGGER SCT STORMS ACRS THE WESTERN HIGH PLAINS. THIS S/W SHUD AID
IN TRW DEVELOPING LATER TONIGHT ACRS NRN CWA NR FNT AND THEN TRACK
SEWD. LLJ SHUD BEGIN TO KICK IN TOWARDS 06Z AND WUD EXPECT TRW TO
THEN DEVELOP. THE WRN SD STORMS CUD HOLD TOGETHER AND THIS CUD BE
THE ACTIVITY THAT AFFECTS CWA TONIGHT IF COMPLEX GETS MORE
ORGANIZED. SO 2 PSBLTYS FOR STORMS...SO SEE NO REASON TO CHANGE
POPS...EXCEPT TO PUSH BACK TIMING SOMEWHAT TO MAINLY AFTER 06Z. SVR
THREAT STILL PSBL AND CUD SEE A WIND EVENT IF WRN SD STORMS HOLD
TOGETHER. IF STORMS DEVELOP MORE ALONG BOUNDARY WHEN LLJ KICKS
IN...THEY WUD TEND TO BE MORE ELEVATED AND THUS THAT THREAT WUD BE
HAIL.

&&

.AVIATION...

VFR EXPECTED AT TAF SITES THROUGH 06Z...THEN CONVECTION ACROSS WRN
SD THIS EVENING COULD BEGIN TO IMPACT THE SD TAFS...WITH KHON HAVING
THE BEST CHANCE FOR VCTS/TS DUE TO VICINITY OF EAST-WEST SFC AND
85OMB BOUNDARY JUST NORTH OF KHON...AND AXIS OF DECENT INSTABLITY
ALSO IN THIS AREA. THUNDERSTORMS THAT GET GOING ALONG THIS BOUNDARY
MAY TEND TO TURN SOUTHEAST TOWARD KFSD LATE TONIGHT...AFTER 08Z...
AS LLJ CRANKS UP. EXPECT MOST OF THE OVERNIGHT TSTRM ACTIVITY TO
STAY NORTH AND EAST OF KSUX. ANOTHER ROUND OF THUNDERSTORMS POSSIBLE
AFTER 18Z SUNDAY.  LOCAL MVFR ACCOMPANIED BY GUSTY WINDS VICINITY OF
ANY THUNDERSTORM LATE TONIGHT AND SUNDAY AFTERNOON.

&&

.PREVIOUS DISCUSSION...
FOR TONIGHT...MAIN CONCERNS WILL BE CONVECTIVE CHANCES. SHOULD BE
TWO AREAS OF CONCERN. ONE AN ELEVATED THREAT IN MAINLY THE
800-700MB LAYER. A MID LEVEL BOUNDARY IS EXPECTED TO BE ACROSS
NORTHERN SOUTH DAKOTA WITH A PORTION OF THIS BOUNDARY POSSIBLY
SNEAKING AS FAR SOUTH AS A DE SMET TO ABOUT WINDOM LINE. WILL LEAN A
LITTLE CLOSER TO THE NAM/RUC INSTABILITY AND WIND OUTPUT VS THE GFS
WHICH SEEMS TO QUICK TO SHIFT THE INSTABILITY EAST LATE THIS
AFTERNOON AND EARLY THIS EVENING GIVEN BACKING WINDS OVER THE
WESTERN HIGH PLAINS. ALSO...OUTSIDE OF MID LEVEL BOUNDARY...THERE IS
REALLY NO FOCUSING MECHANISM NEARBY TO GET GOING...OUTSIDE OF WHAT
APPEARS TO BE A LITTLE MOISTURE DISCONTINUITY IN NORTHEAST NEBRASKA.
IF THE 18Z SUX ACARS SOUNDING IS CORRECT THROUGH THE TEMPERATURES
WILL NEED TO CLIMB TO AROUND 90 WITH MID 60 DEW POINTS TO GET THINGS
GOING. THE NELIGH PROFILER IS BECOMING MORE FAVORABLE IN THE LOW
LEVELS SO WILL NEED TO MONITOR THIS AREA IN CASE DEVELOPMENT OCCURS.
UNFORTUNATELY THE MERRIMAN PROFILER IS STILL UNAVAILABLE SO
DETERMINING THE WIND FIELD CLOSER TO POTENTIAL CONVECTIVE INITIATION
FOR LATER TONIGHT IS LEFT TO THE IMAGINATION.

THE SECOND THREAT SHOULD BE LATE TONIGHT INTO SUNDAY AS UPPER LEVEL
SUPPORT SWINGS AROUND THE UPPER LEVEL RIDGE AND DIVES THROUGH THE
CWA. PLENTY OF MOISTURE AND INSTABILITY AROUND TO SUPPORT A HEAVY
RAIN AND SEVERE THREAT WITH MIXED LAYER CAPE VALUES IN EXCESS OF
3500 J/KG...THE EFFECTIVE BULK SHEAR AROUND 45 KNOTS AND ABOUT 25-30
ON THE SFC DELTA THETA E DIFFERENCE. THIS MAY BE WHERE THIS MOISTURE
DISCONTINUITY IN NEBRASKA CAN PLAY A ROLE AS A FOCUSING MECHANISM
FOR A POSSIBLE LINEAR SYSTEM ON SUNDAY.

AS FOR TEMPERATURES...WILL LEAN TOWARDS LOWS MAINLY IN THE 60S
TONIGHT AND WILL STILL GO WITH THE IDEA FOR LOWER 80S OVER MUCH OF
SW MN AND NW IA WITH POTENTIAL DAYTIME THUNDERSTORMS AND CLOUD
COVER. SOUTH CENTRAL SD COULD GET DOWNRIGHT HOT AND WILL SHOOT FOR
MID 90S.

MONDAY SHOULD PROVE TO HAVE LESS ACTIVITY BEFORE THE LLJ KICKS IN ON
MONDAY NIGHT AND OUR CHANCES FOR THUNDERSTORMS INCREASES. THE CHANCE
FOR THUNDERSTORMS WILL LINGER INTO MAINLY TUESDAY MORNING.
TEMPERATURES ON MONDAY AND TUESDAY SHOULD BE PRETTY CLOSE TO
CLIMATOLOGY WITH HIGHS IN THE MID 80S TO LOW 90S AND LOWS IN THE
60S.

IN THE LATTER PERIODS(WED-SAT)...AGREEMENT AMONGST THE EXTENDED
MODELS CONTINUES TO BE AVERAGE AT BEST. SO...TENDING TO STICK CLOSE
TO CLIMATOLOGY FOR WEDNESDAY AND THURSDAY...WHERE THERE IS A BETTER
CHANCE FOR A FEW THUNDERSTORMS IN NORTHWEST FLOW...THEN TRANSITION
TO A LITTLE ABOVE CLIMO FOR FRIDAY INTO SATURDAY AS AN UPPER LEVEL
RIDGE BUILDS INTO THE AREA. WITH THIS DEVELOPING RIDGE...WILL KEEP
POPS AT 10 OR LESS THURSDAY NIGHT INTO SATURDAY. A DECENT WAVE
PROJECTED TO MOVE ACROSS THE NORTHERN PLAINS FROM WEDNESDAY INTO
THURSDAY MORNING AND THIS SHOULD BE THE BEST CHANCE FOR
PRECIPITATION DURING THIS TIME FRAME. OTHERWISE...THE ECMWF AND THE
GFS ENSEMBLE MEAN HINTING THAT THE FASTER JET LEVEL FLOW WILL SHIFT
NORTH AND THE RIDGE/INCREASING SUMMERTIME HEAT COULD SETTLE IN
THROUGH NEXT WEEK.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
423 PM CDT SAT JUL 26 2008

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-
IAZ001>003-012>014-020>022-031-032-NEZ013-014-271200-
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-
423 PM CDT SAT JUL 26 2008

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

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS...
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER NORTHWEST
SOUTH DAKOTA LATE THIS AFTERNOON OR EVENING...AND THEN SPREAD
SOUTHEAST DURING THE NIGHT. THESE STORMS WILL BE CAPABLE OF
PRODUCING UP TO QUARTER SIZE HAIL AND WIND GUSTS TO 60 MPH MAINLY
ALONG AND WEST OF THE JAMES RIVER. FURTHER EAST...THE THREAT OF
SEVERE WEATHER WILL DIMINISH AS THE STORMS MOVE EAST OF
INTERSTATE 29.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

THERE IS A CHANCE OF THUNDERSTORMS SUNDAY AFTERNOON AND NIGHT AND
AGAIN ON MONDAY NIGHT.	SOME OF THESE STORMS COULD BE SEVERE WITH
LARGE HAIL AND DAMAGING WINDS.

THUNDERSTORMS WILL AGAIN BE POSSIBLE WEDNESDAY EVENING AND NIGHT.
THE BEST CHANCES FOR STORMS WILL BE ALONG AND EAST OF I-29.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE POSSIBLE AFTER 8 PM WEST OF THE JAMES
RIVER.

&&

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