Severe Thunderstorm Warning 93, NWS Aberdeen, SD

AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST
SOUTH DAKOTA AND WEST CENTRAL MINNESOTA
NATIONAL WEATHER SERVICE ABERDEEN SD
300 AM CDT MON JUL 24 2000

MODELS ARE SIMILAR WITH MAIN FEATURES BUT HANDLE H5 LOW MOVING
THROUGH THE RIDGE DIFFERENTLY.  AVN IS VERY CONSISTENT WITH PREVIOUS
RUN ALTHOUGH ETA SEEMS TO HAVE A GOOD HANDLE ON CURRENT SITUATION.
WILL USE A BLEND OF AVN/ETA.  NGM SEEMS TOO FAST IN THIS CASE.  MAIN
CONCERN FOR TODAY IS TIMING OF CONVECTION.  SPC HAS MDT RISK TO OUR
SOUTHEAST AND SLIGHT RISK OVR MUCH OF THE CWA.  LATEST IR SATELLITE
SHOWING CONVECTION IS CURRENTLY ONGOING CLOSE TO STRENGTHENING
SURFACE LOW MOVING OUT OF MONTANA.  WARM FRONT ALSO HAS AN AREA OF
CONVECTION ASSOCIATED WITH IT.  AT THIS TIME CONVECTION IS
DISSIPATING AS IT MOVES EAST TOWARD ABERDEEN COUNTY WARNING AREA.
LAPS DATA SHOWING HIGHEST DEWPOINTS AND MOST UNSTABLE AIR TO OUR
SOUTHWEST.  ETA AND AVN SIMILAR IN MOVING THIS LOW INTO NEBRASKA AND
SETTING UP WARM FRONT ALONG SOUTHERN SOUTH DAKOTA BORDER.  STRONG
LOW LEVEL FEED INTO WARM FRONT FOR MOST OF TODAY.  ETA DEPICTS 35+
KTS THROUGH NEBRASKA.  GOOD H25 DIVERGENCE BULLS EYE FORMS ALSO TO
OUR SOUTH LATER THIS AFTERNOON.  SO EXPECT BEST CHANCE FOR
CONVECTION WILL OCCUR ALONG WARM FRONT TO OUR SOUTH.  DO LIKE NCEP
DEPICTION OF SEPERATE AND TRAILING COLD FRONT FROM NORTHERN LOW AND
EXPECT OUR BEST CHANCE OF CONVECTION HERE WILL BE ASSOCIATED WITH
IT.  BOTH MODELS DEPICT COOLING OF THE LAYER BELOW H70.  ETA TIME
HEIGHT CROSS SECTION THEN SHOWS AREA OF LOW LAYER LIFT ASSOCIATED
WITH PASSING COLD FRONT LATE IN THE EVENING.  MODEL SOUNDINGS DEPICT
LIFTED INDEX VALUES FALLING TO -3C TO -7C BY THIS AFTERNOON WITH
CAPES FROM AROUND 1200 J/KG TO 3000 J/KG WITH THE ETA HAVING THE
MOST UNSTABLE VALUES. THE AVN BRINGS COOLER AIR INTO LOW LEVELS IN
THE EAST FASTER THAN ETA.  WILL KEEP POPS IN ALL AREAS BUT FEEL
ENOUGH UNCERTAINTY ABOUT LOCATION AND TIMING THAT WILL NOT UP POPS
MUCH FROM CURRENT VALUES AND WILL NOT MENTION SEVERE IN THIS AREA.
TONIGHT WILL KEEP CHANCE OF CONVECTION ALONG FRONT WHICH WILL NOT
CLEAR OUR AREA UNTIL MORNING.  ETA ESPE\CIALLY HOLDS IN MID LEVEL
MOISTURE THROUGH TUESDAY SO WILL BE IN NO HURRY TO CLEAR SKIES.

.ABR...NONE

KEEFE
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