Severe Thunderstorm Warning 55, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA
NATIONAL WEATHER SERVICE ABERDEEN SD
300 PM CDT WED JUN 13 2001

INTERESTING PACKAGE TODAY AS WE SIT BETWEEN RAIN EVENTS.  WITH THE
WET GROUND...TIMING AND LOCATION OF FUTURE EVENTS IS THE FOCUS FOR
THIS PACKAGE.  FOR TONIGHT SURFACE LOW IS CURRENTLY IN SOUTHERN
SOUTH DAKOTA WITH AN INVERTED TROUGH EXTENDING NORTHEAST INTO THIS
COUNTY WARNING AREA.  LAPS ANALYSIS DEPICTS A WARM FRONTAL BOUNDARY
THROUGH THE EAST PART OF OUR AREA.  THE SURFACE LOW WILL WEAKEN AS
THE UPPER LOW CENTER NOW OVER THE ROCKIES SWEEPS ACROSS THE PLAINS
INDUCING A STRONGER SURFACE LOW TO OUR SOUTHWEST.  IN THE INTERIM
THE INVERTED TROUGH WILL REMAIN ROUGHLY STATIONARY OVER OUR EASTERN
AREA.  CURRENT WSR-88D LOOP IS SHOWING SHOWERS FORMING ALONG THE
MISSOURI RIVER AND FILLING IN ALONG THE TROUGH IN THE EAST.  CURRENT
LAPS ANALYSIS DEPICTS CAPE VALUES OVER 5K J/KG IN SOUTHEAST SOUTH
DAKOTA. 30 KT LOW LEVEL JET IS PUSHING INTO THE SOUTH EAST PART OF
THE STATE BRINGING FAIRLY STRONG WARM ADVECTION TO THE EAST.  COLD
ADVECTION IN THE MID LEVELS HAS STARTED IN THE WEST PART OF THE
CWA.  EXPECT THUNDERSTORMS TO FORM AND DRIFT ALONG BOUNDARY IN
EASTERN PART OF THE STATE.  CURRENT FLASH FLOOD GUIDANCE VALUES ARE
QUITE LOW SO WILL ISSUE A FLASH FLOOD WATCH WITH THIS PACKAGE FOR
THE EASTERN PART OF THE CWA FOR TONIGHT.  RAIN WILL CONTINUE ALONG
INVERTED TROUGH THROUGH TOMORROW UNTIL UPPER LOW PUSHES THROUGH WITH
SURFACE LOW CAPTURED IN ITS CIRCULATION.  TEMPERATURES WILL BE
MODIFIED BECAUSE OF THE RAIN BUT MOS SEEMS TO HAVE A REASONABLE
HANDLE ON THIS.

.EXTENDED FORECAST DISCUSSION...
EXTENDED MODELS ARE NOT IN VERY GOOD AGREEMENT THIS AFTERNOON.
AFTER ANALYZING THE MODELS AND THE ENSEMBLES A LITTLE MORE...I
HAVE DECIDED TO GO WITH THE A BLEND OF THE MRF AND ECMWF FOR THE
FORECAST PACKAGE. SOME RIDGING WILL BEGIN IN THE ZONAL FLOW OVER
THE STATE BY TUESDAY. WEAK SHORT WAVES WILL MOVE WITH THIS UPPER
FLOW SUNDAY THROUGH WEDNESDAY. THE TIMING OF THESE SHORT WAVES
STILL REMAINS TRICKY. NEVER-THE-LESS THE CHANCE OF SOME SHOWERS
AND THUNDERSTORMS WILL CONTINUE THROUGH THIS TIME. THE MRF MOS
TEMPERATURES LOOKS TO BE ON THE COOL SIDE DO TO THE LACK OF
DEVELOPING THE EXPECTED RIDGE. THEREFORE WILL DO SOME ADJUSTING
TO THE TEMPS MAINLY TOWARD THE END OF THE FORECAST PERIOD.

.ABR...FLASH FLOOD WATCH EASTERN CWA.

KEEFE/SALMONS