Tornadoes and Flash Flood in South Dakota, September 1 to 2, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
312 PM CDT WED SEP 1 2010

.SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT
FORECAST CHALLENGES WILL BE PRECIPITATION CHANCES TONIGHT THROUGH
THURSDAY...AND TEMPERATURES THROUGHOUT THE SHORT TERM.

AS OF 19Z AN AREA OF LOW PRESSURE IS SLOWLY MOVING ENE ACROSS
WESTERN SOUTH DAKOTA. SOUTHERLY WINDS AHEAD OF THE LOW IS BRINGING
MOISTURE BACK INTO THE REGION WITH DEW POINTS IN THE MID 50S. IT
APPEARS AS THROUGH THE HIGHER DEW POINTS WILL REMAIN JUST SOUTH OF
THIS CWA. THE NAM12 IS HANDLING THE MOISTURE RETURN THE BEST SO
WILL USE THIS MODEL FOR THE TRACK AND PLACEMENT FOR PRECIPITATION
CHANCES. AS THE LOW MOVES ENE...SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP ALONG THE MISSOURI RIVER BETWEEN 22-01Z THIS
EVENING. THERE IS MORE THEN ENOUGH SHEAR...WEAK INSTABILITY THAT
STRONG TO POSSIBLY SEVERE STORMS COULD DEVELOP. NOT FULLY
CONVINCED WITH THE OVERALL SEVERE THREAT SO WILL LEAVE SEVERE OUT
OF THE FORECAST.

THE NORTHERN PLAINS WILL BE ON THE BACK SIDE OF THE SURFACE
LOW/UPPER LEVEL TROF ON THURSDAY. STRONG NORTHWEST WINDS WILL
DEVELOP ACROSS THE WESTERN DAKOTAS...WITH NAM BUFKIT SOUNDING
SUGGESTING NEAR WIND ADV. CRITERIA ALONG AND WEST OF THE MISSOURI
RIVER. WILL LET THE EVENING SHIFT DECIDE IF A WIND ADV IS NEEDED.
ALSO ON THURSDAY...THE COMBINATION OF COLD AIR ALOFT AND STEEP LOW
LEVEL LAPSE RATES SHOULD RESULT IN INSTABILITY SHOWERS...ESPECIALLY
ALONG AND EAST OF THE JAMES RIVER. BEYOND THURSDAY...THE REGION
WILL BE DOMINATED BY A COOL CANADIAN HIGH PRESSURE.

.LONG TERM...SATURDAY THROUGH WEDNESDAY

MODERATE FORECASTER CONFIDENCE FOUND WITH THE 00Z AND 12Z SET OF
MEDIUM RANGE MODEL SOLUTIONS. OVER THE WEEKEND...TEMPERATURES WILL
TREND WARMER WITH A LONGWAVE RIDGE OF HIGH PRESSURE BUILDING UP
OVER THE NORTHERN PLAINS STATES. THAT IS A SHORT-LIVED PERIOD OF
WARM AND DRY WEATHER...THOUGH...AS ENERGY LIFTS OUT OF A WESTERN
CONUS LONGWAVE TROF AND ONTO THE NORTHERN PLAINS LATE SUNDAY NIGHT
THROUGH MONDAY NIGHT. PRECIPITATION CHANCES LOOK PRETTY GOOD
HEADING INTO MONDAY OF NEXT WEEK...SO THIS IS THE FORECAST PERIOD
WITH THE HIGHEST POPS AT THIS TIME.

&&

.AVIATION...
18Z TAFS FOR THE KABR...KATY...KPIR AND KMBG TERMINALS

VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT FOR ALL TAF LOCATIONS.
INCREASING LIFT AND MID LEVEL CLOUDS WILL LEAD TO THE DEVELOPMENT
OF SCATTERED SHRAS/TSRAS ACROSS THE REGION BY 00Z...PERSISTING
THROUGH THE OVERNIGHT HOURS AS PRECIPITATION SHIFTS NORTH AND
EAST. IFR CONDITIONS CAN BE EXPECTED WITH THUNDERSTORMS. THERE
WILL ALSO BE A WIND SHIFT OVERNIGHT...WITH SOUTH WINDS CHANGING TO
NORTHWEST WINDS.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
&&

SHORT TERM...SD
LONG TERM...DORN
AVIATION...DORN

WEATHER.GOV/ABERDEEN

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ABERDEEN SD
408 AM CDT WED SEP 1 2010

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-020915-
TRAVERSE-BIG STONE-CORSON-CAMPBELL-MCPHERSON-BROWN-MARSHALL-
ROBERTS-WALWORTH-EDMUNDS-DAY-DEWEY-POTTER-FAULK-SPINK-CLARK-
CODINGTON-GRANT-HAMLIN-DEUEL-STANLEY-SULLY-HUGHES-HYDE-HAND-JONES-
LYMAN-BUFFALO-
408 AM CDT WED SEP 1 2010 /308 AM MDT WED SEP 1 2010/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WEST CENTRAL
MINNESOTA...CENTRAL SOUTH DAKOTA...NORTH CENTRAL SOUTH DAKOTA AND
NORTHEAST SOUTH DAKOTA.

.DAY ONE...TODAY AND TONIGHT

RANGELAND FIRE INDEX WILL REACH THE HIGH TO VERY HIGH CATEGORY FOR
WEST RIVER COUNTIES IN THE FORECAST AREA.

THUNDERSTORMS WILL BE POSSIBLE THROUGH THE DAY AND OVERNIGHT. THE
RISK FOR SEVERE WEATHER WILL STRETCH FROM THE MISSOURI VALLEY THIS
AFTERNOON...INTO THE JAMES VALLEY THIS EVENING...AND FURTHER EAST
OVERNIGHT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY OR TONIGHT.

CONNELLY