Hail and Damaging Winds in South Dakota, August 11, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
246 PM CDT THU AUG 11 2011

.SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
SHORTWAVE IMPULSE AHEAD OF THE MAIN UPPER LOW IS MOVING EAST
ACROSS THE NORTHERN PLAINS. MID LEVEL JET STREAK ALSO PASSING
THROUGH THE AREA. THIS HAD LET TO SHOWER AND THUNDERSTORM ACTIVITY
ALREADY ACROSS WESTERN/CENTRAL DAKOTAS. AS CAP CONTINUES TO WEAKEN
LATER THIS AFTERNOON AND INSTABILITY INCREASES...EXPECTING
ADDITIONAL STORM DEVELOPMENT WITH SVR STORMS LIKELY AS WELL. CAPE
VALUES IN EXCESS OF 2000 J/KG AND SHEAR FROM 30 TO 40 KNOTS WILL
ALLOW FOR THIS TO HAPPEN. ACTIVITY WILL SHIFT EAST/SOUTHEAST
THROUGH THE EVENING HOURS WITH A CONTINUED THREAT FOR HAIL AND
STRONG WINDS AND STORMS CONGEAL/FORM A CLUSTER. THERE SHOULD BE A
BREAK IN THE ACTION FRIDAY MORNING BEFORE THE MAIN UPPER LOW
SWINGS SOUTHEAST OVER THE NORTHERN PLAINS. WITH THE COOLER TEMPS
ALOFT AND AFTERNOON SFC HEATING...WILL SEE ADDITIONAL SHOWER AND
THUNDERSTORM ACTIVITY DEVELOP...ESPECIALLY OVER THE EASTERN CWA.
THE UPPER WAVE EXITS THE AREA FRIDAY NIGHT AS SFC HIGH FOLLOWS FOR
THE WEEKEND. LOOKING LIKE A PLEASANT START TO THE WEEKEND WITH DRY
CONDITIONS AND SEASONABLE TEMPERATURES.

.LONG TERM...SUNDAY THROUGH THURSDAY
PERIOD STARTS WITH UPPER LEVEL RIDGING AND RISING HEIGHTS OVER
THE CENTRAL US. MEANWHILE...A LOW PRESSURE SYSTEM DEVELOPS AND
MOVES INTO THE PACIFIC NORTHWEST. AS THIS SYSTEM MOVES EAST
SEVERAL SHORTWAVES WILL EJECT OUT AHEAD OF THE TROUGH AND RIDE
OVER THE RIDGE. AS USUAL MODELS HAVE SLIGHT TIMING DIFFERENCES
WITH THESE SHORT WAVES...AND THUS THE BLANKETING OF LOW POPS
CONTINUES THROUGH THE EXTENDED. THE MAIN LOW IS EXPECTED TO TRACK
EAST ACROSS CANADA...HOWEVER MODELS DIFFER SIGNIFICANTLY ON
TIMING. THE ECMWF DEVELOPS A CLOSED UPPER LOW AND TRACKS IT ACROSS
CANADA FLATTENING THE RIDGE ON WEDNESDAY...ABOUT 24 HOURS FASTER
THAN THE GFS AND GEM. THE GFS ALSO SWINGS THE LOW FURTHER
SOUTH...WITH A MUCH MORE PRONOUNCED 700 MB BAROCLINIC ZONE. DUE TO
THE LARGE DIFFERENCES...STUCK WITH A MODEL BLEND FOR MUCH OF THE
EXTENDED.

&&

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

VFR CONDITIONS WILL PREVAIL THROUGH EARLY AFTERNOON. THE EXCEPTION
WILL BE KMBG WHICH COULD SEE BRIEF PERIODS OF LIGHT RAIN ASSOCIATED
WITH A CLUSTER OF SHOWERS AND THUNDERSTORMS LEFT OVER FROM
ELEVATED CONVECTION THAT DEVELOPED IN EASTERN MONTANA THIS
MORNING. LATER IN THE AFTERNOON AND TONIGHT THE MAIN WAVE OF
ENERGY WILL MAKE ITS WAY INTO THE REGION AND MORE ORGANIZED STORMS
WILL TAKE SHAPE AND DEVELOP FROM WEST TO EAST ACROSS THE STATE.
PERIODS OF IFR/MVFR CONDITIONS WILL BE POSSIBLE UNDER STRONGER
THUNDERSTORMS.

&&

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

SHORT TERM...TMT
LONG TERM...SERR
AVIATION...SERR

WEATHER.GOV/ABERDEEN

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ABERDEEN SD
433 AM CDT THU AUG 11 2011

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-120945-
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-
433 AM CDT THU AUG 11 2011 /333 AM MDT THU AUG 11 2011/

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

THUNDERSTORM CHANCES WILL BE INCREASING AS AN UPPER LEVEL LOW
PRESSURE TROUGH MOVES INTO THE REGION THIS AFTERNOON AND TONIGHT.
THERE IS A SLIGHT RISK THAT SOME OF THE STORMS WILL BE SEVERE WITH
LARGE HAIL AND DAMAGING WINDS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

OFF AND ON CHANCES OF THUNDERSTORMS ARE EXPECTED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NECESSARY THIS AFTERNOON AND TONIGHT.

MOHR