Severe Thunderstorm Warning 47, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA
NATIONAL WEATHER SERVICE ABERDEEN SD
315 PM CDT TUE JUN 12 2001

THE MODELS ARE IN FAIR AGREEMENT INITIALLY BUT THESE DIFFERENCES
GROWS AS TIME MOVES OUT TO 48HRS. THE ETA AND AVN SEEM TO AGREE
THE BEST THROUGH THE TWO DAY FORECAST PERIOD WITH THE NGM BEING
MUCH MORE IN DISAGREEMENT WITH THE REST OF THE MODELS BY 48HRS.
HAVE DECIDED TO USE A COMBINATIONS OF THE ETA AND AVN BUT LEAN
MORE TOWARD THE ETA. THERE ARE A FEW CONCERNS WITH THIS FCST.
ONE IS THE POSITIONING AND TIMING OF FRONT AND OTHER BOUNDARIES.
THE NEW ETA SEEM TO BE A LITTLE SLOWER THAN THE PREVIOUS MODEL.
THIS PUTS THE MOISTURE AND LIFT LATER TONIGHT AND EARLY TOMORROW.
BUT THE BETTER NUMBERS OR CONVECTION IS WEDNESDAY AFTERNOON.
ANOTHER CONCERN IS JUST WHEN WILL THE SEVERE CONVECTION START THIS
EVENING. CONVECTION IS ALL AROUND US AT THIS TIME. STILL HAVE A
GOOD CAP OVER US BUT IT IS WEAKENING. AND FINELY HOW MUCH RAIN WITH
THEY GENERATE. THE AMS IS QUITE MOIST AND FLASH FLOOD GUIDANCE HAS
SOME LOW READING. BUT STILL WILL HOLD OFF ON A FLASH FLOOD WATCH.
NOW FOR DAY TWO...THE UPPER LOW THAT IS DIGGING SOUTH OVER WESTERN
U.S. WILL SLIDE EAST OVER THE STATE BY THURSDAY. THE PRECIP SHOULD
BE MORE IN THE FORM OF RAIN TO SHOWERS THAN THUNDERSTORMS AS THE AMS
WILL BE A LITTLE MORE STABLE BEHIND THE FRONT. NGM/AVN GUIDANCE
TEMPS SEEM TO CLOSE BUT WILL TAKE A BLEND OF THE TWO FOR THE FCST.
.EXTENDED FORECAST DISCUSSION...
MODELS ARE IN FAIR AGREEMENT THIS PERIOD.  HOWEVER THEY AGREE ON THE
DEVELOPMENT OF ZONAL FLOW OVER THIS AREA IN THE NEAR TERM WHICH WILL
HAVE EMBEDDED WAVES IN THE FLOW MAKING TIMING VERY TRICKY AT BEST.
TOWARD THE END OF THE PERIOD THE MID CONTINENT RIDGE STARTS TO
REBUILD RETURNING AN UPPER FLOW FROM THE SOUTHWEST WHICH WILL HELP
TO USHER IN WARMER TEMPERATURES.  FIRST UPPER WAVE WITH ASSOCIATED
SURFACE LOW AND FRONTAL BOUNDARY MOVES THROUGH THE AREA FRIDAY AS IT
MOVES EAST A WEAK BAROCLINIC BOUNDARY PERSISTS THROUGH TUESDAY AND
FINALLY PUSHES THROUGH AHEAD OF H5 CLOSED LOW MOVING THROUGH
SOUTHERN CANADA.  WILL START WITH CHANCE OF SHOWERS AND
THUNDERSTORMS FRIDAY AND AGAIN FROM AROUND SUNDAY INTO TUESDAY.  MOS
TEMPERATURES LOOK REASONABLE AND WILL GO CLOSE TO THEM.

.ABR...NONE.