Severe Thunderstorm Warning 192, NWS Aberdeen, SD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ABERDEEN SD
320 PM CDT THU SEP 16 2004

.SHORT TERM...TONITE THROUGH SUNDAY NITE
MAIN CONCERN THROUGH SHORT RANGE WILL BE TEMPS.  BUT FIRST THINGS
FIRST.  WILL KEEP SLIGHT MENTION OF SHOWERS ACROSS NORTHEAST CWA
THIS EVENING AS S/W TRACKS ACROSS STATE AND LLJ FOCUSES THIS EVENING
ACROSS THIS REGION.  INSTABILITY IS WEAK AND MOISTURE FAIRLY LOW SO
ISOLATED COVERAGE SHOULD SUFFICE.  AFTER TONIGHT IMPRESSIVE MID
LEVEL RIDGE BEGINS BUILDING ACROSS NATIONS HEARTLAND AS DEEP TROF
DEVELOPS JUST INLAND OF WEST COAST.  ON FRIDAY THERE IS SOME HINT AT
POSSIBILITY OF SHOWERS AGAIN IN FAR EAST CWA BUT AGAIN MOISTURE
SCANT AND MID LEVEL FORCING LOOKS MINIMAL THUS WILL MAINTAIN DRY
FORECAST.  ONCE WE HEAD INTO SATURDAY VERY WARM H7 THERMAL RIDGE
EXPECTED TO EXPAND OUT INTO THE PLAINS.  FULLY ANTICIPATE SATURDAY
THROUGH SUNDAY TO BE CAPPED AND RATHER WARM...ESPECIALLY SUNDAY.  ON
SUNDAY LOW LEVEL LAPSE RATES ARE PRETTY STEEP WHICH SHOULD SUPPORT
PLENTY OF WARMTH AND WIND.  WITH WINDS PERHAPS FAVORING A SOUTHWEST
DIRECTION TRENDED ABOVE GUIDANCE ON SUNDAY SINCE H85 TEMPS ARE
EXPECTED TO CLIMB WELL ABOVE 20C.  FOR SUNDAY NIGHT DECIDED TO SIDE
WITH SLOWER ETA AND CUT POPS BACK TO SLIGHT ACROSS WESTERN CWA.
HAVE A FEELING THAT GFS IS TOO FAST KNOCKING DOWN CAPPING MID LEVEL
THERMAL RIDGE OVER WESTERN PLAINS.

.LONG TERM...MONDAY THROUGH THURSDAY
DGEX AND GFS SIMILAR OVERALL BUT WITH TIMING DIFFERENCES.  ECMWF
STARTS SIMILAR TO THE OTHERS BUT QUICKLY DIVERGES ITS SOLUTION BY
KEEPING A BROADER WESTERN TROUGH THAT LIFTS NORTHEAST OVER THE
EASTERN RIDGE.  ECMWF DOES NOT APPEAR TO HANDLE ENERGY FROM THE NEXT
TROPICAL SYSTEM TO MOVE INTO THE SOUTHERN US VERY WELL...IT BRINGS
THE TROPICAL SYSTEM ONSHORE THROUGH THE GULF STATES WHEREAS THE DGEX
AND GFS BRING THE SYSTEM ONSHORE OVER THE CAROLINAS.  PREFERRED A
BLEND OF THE DGEX AND GFS FOR THE OVERALL EXTENDED SOLUTION.  TIMING
OF UPPER LEVEL SHORTWAVES AND ASSOCIATED SURFACE FEATURES WILL
LIKELY CHANGE SEVERAL TIMES OVER THE NEXT FEW DAYS.

BASIC PATTERN IS A DIGGING WESTERN TROUGH WHICH MOVES ONSHORE INTO
THE GREAT BASIN MONDAY.  SOUTHWEST FLOW ALOFT DOMINATES THE EASTERN
ROCKIES AND CENTRAL AND NORTHERN PLAINS.  A COLD FRONT MOVES OUT OF
THE ROCKIES BY EARLY TUESDAY BUT EVENTUALLY STALLS JUST EAST OF THE
CWA.  DGEX AND GFS BOTH BRING ENERGY FROM THE EASTERN PACIFIC
HURRICANE JAVIER INTO THE BASE OF THE WESTERN TROUGH EARLY IN THE
EXTENDED PERIOD...AND EJECT THAT ENERGY IN THE SOUTHWEST FLOW ACROSS
THE PLAINS.  AN UPPER LEVEL RIDGE AND SURFACE HIGH PRESSURE PERSIST
OVER THE EASTERN STATES IN A BLOCKING PATTERN SIMILAR TO THAT SEEN
WITH THE PAST FORECAST CYCLES.  RESULT IS A SERIES OF WAVES ALONG A
NEARLY STATIONARY SURFACE BOUNDARY THE FORMS OVER THE PLAINS SINCE
THE BLOCKING HIGH PREVENTS THE SYSTEMS FURTHER PROGRESSION.

MAIN CHALLENGE IN DETERMINING THE STRENGTH OF THE BLOCK AND THE RATE
OF PROGRESSION FOR SHORTWAVES MOVING OUT OF THE WESTERN TROUGH IS
THE PATH AND STRENGTH OF TROPICAL SYSTEMS WHICH TEND TO STRENGTHEN
THE BLOCKING RIDGE.  AN ADDITIONAL CHALLENGE IS TIMING PRECIPITATION
ASSOCIATED WITH EACH WAVE MOVING PARALLEL TO THE STATIONARY
BOUNDARY.  UPPER LEVEL FLOW WILL PARALLEL THE SURFACE BOUNDARY
...FURTHER SLOWING THE SYSTEM PROGRESSION.  HOWEVER EXPECT THE
PRECIPITATION TO BE MOST CLOSELY ALIGNED WITH THE 700 TROUGH.
CONFIDENCE IN PRECIP FORECAST IS VERY LOW GIVEN UNCERTAINTY OF
SYSTEM MOVEMENT.

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

TDK/BM

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ABERDEEN SD
501 AM CDT THU SEP 16 2004

MNZ039-046-SDZ003>011-015>023-033>037-045-048-051-171000-
BIG STONE-BROWN-BUFFALO-CAMPBELL-CLARK-CODINGTON-CORSON-DAY-DEUEL-
DEWEY-EDMUNDS-FAULK-GRANT-HAMLIN-HAND-HUGHES-HYDE-JONES-LYMAN-
MARSHALL-MCPHERSON-POTTER-ROBERTS-SPINK-STANLEY-SULLY-TRAVERSE-
WALWORTH-
501 AM CDT THU SEP 16 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF CENTRAL...NORTH
CENTRAL AND NORTHEAST SOUTH DAKOTA...AS WELL AS BIG STONE
AND TRAVERSE COUNTIES IN MINNESOTA.

.DAY ONE...TODAY AND TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY OR TONIGHT.

ALBRECHT