Severe Thunderstorm Warning 36, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA
NATIONAL WEATHER SERVICE ABERDEEN SD
310 PM CDT SUN JUN 11 2000

ANOTHER INTERESTING AFTERNOON AND EVENING IS TAKING SHAPE ACROSS THE
CWA. CURRENT KABR AND KUNR 88D IMAGES INDICATED SCATTERED SHOWERS
AND THUNDERSTORMS WERE DEVELOPING FROM FAULK COUNTY SOUTH AND
SOUTHWESTWARD INTO CHERRY COUNTY NEBRASKA WITH OTHER WIDELY
SCATTERED SHOWERS AND STORMS IN THE RAPID CITY CWA. 19Z MSAS
ANALYSIS INDICATED THE BEST AREA FOR STORMS TO FORM WAS WEST OF
MOBRIDGE AND PIERRE. THE FACTORS INCLUDE: 60 DEGREE SURFACE
DEWPOINTS POOLING...THETA E RIDGE...GREATEST MOISTURE
CONVERGENCE...GREATEST PRESSURE FALLS AND LIFTED INDICIES OF -6 TO
-9 AHEAD OF COLD FRONT IN EXTREME WESTERN SOUTH DAKOTA.

LIKE THE PREVIOUS RUN...THERE IS SOME SIGNIFICANT DIFFERENCES WITH
EACH MODEL. THE ETA AND AVN MODEL DO INDICATE MOST OF THE SHOWERS
AND THUNDERSTORMS WILL STAY ON THE SOUTH DAKOTA SIDE OF OUR CWA AND
WAS CONCENTRATED TO TONIGHT AND THEN AGAIN LATE TOMORROW AFTERNOON
AND EVENING. WILL FOLLOW THE ETA/AVN ON THIS PACKAGE AS NGM SEEMS
WAY TOO AGRESSIVE WITH THE MOISTURE...ESPECIALLY BEING IN THE WARM
SECTOR TOMORROW. LATEST SURFACE MAP INDICATED THE MAIN WARM FRONT
WAS NORTH OF US AND WAS JUST NORTH OF THE NORTH DAKOTA/SOUTH DAKOTA
BORDER. TEMPERATURES IN NORTHERN MINNESOTA AND NORTHERN NORTH DAKOTA
WERE ONLY IN THE 60S AND 70S WHILE MOST STATIONS IN SOUTH DAKOTA
WERE IN THE MID TO UPPER 80S THIS AFTERNOON.

FOR TONIGHT...SURFACE DEWPOINTS WILL CONTINUE TO RISE AS THE
SOUTHERLY FLOW CONTINUES. KABR/KUDX RADAR IMAGES MAY DICTATE THE
WORDING OF THE THUNDERSTORM ACTIVITY FOR CENTRAL AND NORTH CENTRAL
SOUTH DAKOTA. FOR ABERDEEN AND WATERTOWN...BELIEVE MOST OF THE
ACTIVITY WILL BE AFTER 7 OR 8 PM. CURRENT WORK PACKAGE HAS 50 POPS
FOR THESE TWO GROUPS...BUT MAY UP THEM JUST BEFORE ISSUANCE.
PERUSAL OF GUIDANCE WERE VERY SIMILIAR FOR LOW TONIGHT AND WILL
FOLLOW.

THE ETA/AVN MODEL BRINGS THE LOW OUT INTO WESTERN DAKOTAS TOMORROW.
BEING IN THE WARM SECTOR...WILL TREND TOWARD THE FWC GUIDANCE THAN
REST OF THE GUIDANCE WHICH WAS A FEW DEGREES COOLER. JUST LIKE
YESTERDAY...LIFTED VALUES DROP TO (-3 TO -8)C AND CAPES CLIMB TO
OVER 3000 ACROSS MUCH OF THE CWA TOMORROW AFTERNOON(ETA). BELIEVE
THUNDERSTORM ACTIVITY WILL KICK OFF ALONG THE COLD FRONT TOMORROW
AFTERNOON...AND THEN MOVE EAST ACROSS THE CWA LATE TOMORROW
AFTERNOON AND TOMORROW NIGHT. ETA/AVN MODEL QPF OUTPUT HITS THE CWA
THE HARDEST BETWEEN 00Z AND 06Z TUESDAY WITH AMOUNTS OF 0.25 TO 0.75
OF AN INCH.

WILL CONTINUE POPS ON TUESDAY AS THE LOW PULLS AWAY. THE ETA/AVN
MODELS DO SHOW SOME WRAP AROUND PRECIPITATION...ESPECIALLY ACROSS
THE NORTH AND EAST. IT WILL BE DEFINITELY COOLER ON TUESDAY.
GUIDANCE WAS EXTREMELY CLOSE FOR LOWS MONDAY NIGHT WITH SOME
DIFFERENCE IN THE GUIDANCE FOR HIGHS ON TUESDAY AND WILL TAKE A
MAJORITY OF THE GUIDANCE VALUES FOR HIGHS.

.EXTENDED FORECAST...
MEDIUM RANGE MODELS SIMILAR AT DAY THREE AND DIVERGE BY DAY FIVE.
THE EXTENDED FORECAST PERIOD STARTS WITH H5 TROUGH DIGGING OVER
CENTRAL UNITED STATES.  SURFACE LOW MOVES THROUGH FORECAST AREA
EARLY WEDNESDAY WITH UPPER FEATURE MOVING THROUGH LATE IN THE DAY
WEDNESDAY.  FROM HERE ON MODELS DIVERGE WITH ECMWF FASTER AND NCEP
PROGS TAKING A SOMEWHAT SLOWER TRACK WITH THE MRF BEING THE SLOWEST.
WILL USE A POSITION SIMILAR TO NCEP WHICH IS A BLEND OF MEDIUM RANGE
POSITIONS.  WILL KEEP WEDNESDAY DRY COUNTING ON THE MRF TO BE
SLIGHTLY SLOW.  THIS WILL ALLOW THE SURFACE FEATURE TO MOVE EAST ON
TUESDAY.  WILL INCLUDE A TUESDAY NIGHT PERIOD OF A CHANCE OF
THUNDERSTORMS.  THURSDAY WILL SEE OLD PACIFIC LOW MOVE ACROSS
SOUTHERN CANADA PUSHING NEXT WEAK SURFACE LOW WITH AN ASSOCIATED
COLD FRONT.  FRONT WILL MOVE ACROSS THE AREA THURSDAY AND BRING THE
NEXT CHANCE OF PRECIPITATION.  BY FRIDAY NEXT MAJOR UPPER WAVE IS TO
OUR WEST AND SHOULD NOT REACH EASTERN SOUTH DAKOTA UNTIL THE WEEK
END.  OVERALL THICKNESS PATTERN WOULD INDICATE COOLER TEMPERATURES
AND FMR GUIDANCE TEMPERATURES% WOULD REFLECT THIS AS THEY ARE WELL
BELOW CLIMO ON DAY FIVE IN SPITE OF THE INCREASING BIAS TOWARD
CLIMO. WILL STAY CLOSE TO THEM.

.ABR...NONE.

ECKBERG/KEEFE

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