Severe Thunderstorm Warning 185, NWS Sioux Falls, SD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA
NATIONAL WEATHER SERVICE SIOUX FALLS SD
440 PM CDT FRI SEP 15 2006

.DISCUSSION...
FAIRLY MESSY FORECAST FOR TONIGHT WITH A PAIR OF WAVES TO DEAL WITH.
FIRST IS THE EXITING SYSTEM OVER THE EASTERN CWA...WHICH SHOULD
PROVIDE SOME SHOWERS AND ISOLATED THUNDERSTORMS FOR PARTS OF
SOUTHWEST MN INTO NORTHWEST IA EARLY IN THE EVENING. THE SECOND IS A
STRONGER SYSTEM THAT IS MOVING ONTO THE WESTERN HIGH PLAINS THIS
AFTERNOON. SCATTERED THUNDERSTORMS HAVE ALREADY BEGUN TO DEVELOP IN
CENTRAL NEBRASKA WITH THIS FEATURE AND SHOULD WORK INTO THE AREA
THROUGHOUT THE EVENING HOURS. DRY SLOT WILL WORK INTO THE SOUTHERN
CWA BY LATE TONIGHT AND SHOULD AID IN ADDITIONAL SHOWER AND
THUNDERSTORM DEVELOPMENT AHEAD OF IT. TROP HEIGHTS ALSO SUGGEST
BETTER CHANCE FOR PRECIPITATION AFTER ABOUT 03Z. NO MAJOR DEVIATIONS
FROM GUIDANCE LOWS TONIGHT.

STRONG SURFACE TROUGH WILL BE THE MAIN PLAYER TOMORROW CREATING THE
POTENTIAL FOR SEVERE WEATHER. DRY SLOT WILL WORK INTO THE WESTERN
CWA IN THE MORNING HOURS.  ATMOSPHERE WILL DESTABILIZE ALONG AND
AHEAD OF DRY LINE RESULTING IN THUNDERSTORM DEVELOPMENT IN THE MID
AFTERNOON HOURS ALONG AND EAST OF THE JAMES RIVER VALLEY. STRONG
WIND SHEAR WILL RESULT IN RAPID CELL MOVEMENT. WITH FAIRLY STRONG
DIRECTIONAL AND SPEED SHEAR ALONG AND AHEAD OF THE COLD
FRONT...POTENTIAL EXISTS FOR  A TORNADO OR TWO MAINLY WITH INITIAL
CELL DEVELOPMENT. EXPECT CELLS TO RAPIDLY EVOLVE INTO A SQUALLINE
WITH THE MAIN THREAT BEING STRONG DAMAGING WINDS...THOUGH COULD HAVE
SOME HAILERS IN THERE AS WELL.

WRAP AROUND STRATUS AND INSTABILITY SHOWERS WORKS INTO THE NORTHERN
2/3 OF THE CWA ON SUNDAY...KEEPING TEMPERATURES DOWN IN THE NORTH.
FURTHER SOUTH...LIMITED AMOUNTS OF CLOUDS COUPLED WITH COLD AIR
ADVECTION SHOULD RESULT IN SIGNIFICANT MIXING...AND HAVE KEPT
FORECASTED HIGHS ON SUNDAY IN NW IOWA IN THE UPPER 60S TO NEAR 70.

THAT WILL BE THE LAST OF MILD TEMPERATURES FOR A WHILE AS THE COLD
AIR CONTINUES TO POUR INTO THE REGION ON THE BACKSIDE OF OF TROUGH.
HIGH PRESSURE BUILDS INTO THE REGION AND BY WEDNESDAY
MORNING...CLEAR SKIES AND LIGHT WINDS SHOULD RESULT IN A FAIRLY COOL
CRISP  EARLY AUTUMN MORNING. TEMPERATURES WILL REBOUND SOME ON
WEDNESDAY AHEAD OF THE NEXT WAVE MOVING IN FROM THE WEST.  MODELS
HAVE BEEN CONSISTENTLY INCONSISTENT WITH THE PATH OF THIS WAVE...BUT
HAVE SIDED MORE WITH A SOUTHERN TRACK WHICH KEEPS THE BULK OF THE
FORCING SOUTH OF THE CWA. HAVE ADDED SOME SLIGHT CHANCE POPS ON
THURSDAY...MAINLY SOUTH OF I-90...BUT WILL LIKELY HAVE TO BE REFINED
AS THE PATH OF THE WAVE BECOMES MORE CLEAR.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WIND ADVY ALL OF SD CWA EXCEPT UNION CO. 16Z-23Z.
MN...WIND ADVY ALL OF SW MN EXCEPT COTTONWOOD AND JACKSON COS.
16Z-23Z.
IA...WIND ADVY LYON CO. 16Z-23Z.
NE...NONE.

&&

08/BT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1046 AM CDT FRI SEP 15 2006

SDZ038>040-050-052>071-MNZ071-072-080-081-089-090-097-098-
IAZ001>003-012>014-020>022-031-032-NEZ013-014-161200-
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-
1046 AM CDT FRI SEP 15 2006

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

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS...
SCATTERED THUNDERSTORMS WILL MOVE NORTHEAST THROUGH EXTREME
SOUTHEAST SOUTH DAKOTA INTO NORTHWEST IOWA AND SOUTHWEST
MINNESOTA THROUGHOUT THE DAY. THESE STORMS ARE NOT EXPECTED TO BE
SEVERE BUT COULD PRODUCE BRIEF HEAVY RAINFALL AND LIGHTNING.

A FEW THUNDERSTORMS COULD ALSO DEVELOP WEST OF THE JAMES RIVER
VALLEY LATE THIS AFTERNOON INTO THIS EVENING. SOME OF THESE
STORMS COULD PRODUCE HAIL TO DIME SIZE. THUNDERSTORMS WILL
INCREASE IN COVERAGE AFTER MIDNIGHT AND SHIFT NORTHEAST. A FEW OF
THESE COULD ALSO PRODUCE HAIL TO THE SIZE OF NICKELS.

WIND AND FOG...
SOUTHERLY WINDS OF 25 TO 35 MPH WITH GUSTS AROUND 40 MPH WILL
SPREAD FROM SOUTH DAKOTA INTO SOUTHWEST MINNESOTA AND NORTHWEST
IOWA THIS AFTERNOON AND EARLY TONIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING THE AFTERNOON ALONG
AND EAST OF A DE SMET TO YANKTON LINE...THEN RACE RAPIDLY EAST
INTO SOUTHWEST MINNESOTA AND NORTHWEST IOWA BY EARLY EVENING.
THESE THUNDERSTORMS WILL HAVE A GOOD CHANCE OF BECOMING SEVERE
AND A MODERATE RISK OF SEVERE WEATHER IS LIKELY. THE
THUNDERSTORMS ARE EXPECTED TO DEVELOP INTO A LINE WITH EMBEDDED
SUPERCELLS POSSIBLE. THE MAIN THREAT FROM THESE STORMS WILL BE
WIND GUSTS TO 80 MPH AND HALF DOLLAR SIZED HAIL...WITH A FEW
TORNADOES ALSO POSSIBLE.

STRONG WEST TO NORTHWEST WINDS AND MUCH COOLER WEATHER SHOULD
AFFECT THE AREA SUNDAY INTO MONDAY. GENERALLY 20 TO 35 MPH WINDS
ARE EXPECTED...MAINLY DURING THE AFTERNOON HOURS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL BE POSSIBLE AFTER 500 PM CDT MAINLY WEST
OF THE JAMES VALLEY.

&&

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

08