MESOSCALE DISCUSSION 1996
   NWS STORM PREDICTION CENTER NORMAN OK
   0329 AM CDT FRI SEP 21 2007
   
   AREAS AFFECTED...PORTIONS SERN AND EXTREME E-CENTRAL ND...NERN
   SD...CENTRAL/W-CENTRAL/NWRN MN.
   
   CONCERNING...TORNADO WATCH 677...
   
   VALID 210829Z - 211030Z
   
   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 677 CONTINUES.
   
   CONVECTIVE COVERAGE IS INCREASING ACROSS MUCH OF N-CENTRAL/NERN MN
   AND EXTREME E-CENTRAL SD...WITH ACTIVITY LIKELY TO MOVE ENEWD-NEWD
   ACROSS NRN PORTION WW 677 INTO WW 676.  LARGE HAIL WILL BE PRIMARY
   CONCERN.  HAIL UP TO ABOUT 1.75 INCH DIAMETER HAS BEEN REPORTED OVER
   FAR AREA ON BOTH SIDES OF RED RIVER DURING PAST HALF HOUR FROM
   STRONGEST STORM...WHICH HAS BEEN PERSISTENT/ELEVATED SUPERCELL.
   
   SFC MESOANALYSIS SHOWS CYCLONE OVER CENTRAL SD N PIR...WITH WARM
   FRONT ENEWD TOO NEAR ABR...AXN...40 N MSP...EAU.  PRIND WARM FRONT
   WILL CONTINUE TO DRIFT NWD...WITH GREAT MAJORITY OF CONVECTION
   REMAINING ROOTED IN ELEVATED BUT STILL FAVORABLY BUOYANT LAYER TO
   ITS N.  ELEVATED MUCAPES 1500-2500 J/KG ARE EVIDENT JUST N OF FRONT
   BASED ON MODIFIED RUC SOUNDINGS...DIMINISHING GRADUALLY WITH NWD
   EXTENT.  FAVORABLE KINEMATIC PROFILES WILL CONTINUE ALOFT WITH 
   EFFECTIVE SHEAR MAGNITUDES GENERALLY 50-60 KT.  ISENTROPIC ASCENT N
   OF MOIST/45-55 KT LLJ WILL CONTINUE TO BOOST PARCELS TO LFC. 
   INCREASE IN COVERAGE WITH MCS DEVELOPMENT IS POSSIBLE.  VERY STABLE
   NEAR-SFC LAYER -- WITH TEMPS MID 50S TO LOW 60S -- SHOULD NARROW SVR
   THREAT TO HAIL.
   
   ALONG AND S OF WARM FRONT...SBCINH IN 150-250 J/KG RANGE MAY
   INCREASE EVEN FURTHER...AS DIABATIC SFC COOLING CONTINUES BENEATH
   BASE OF ELEVATED MIXED LAYER.  ANY TSTMS MOVING OVER THIS AIR MASS
   -- SUCH AS THOSE NOW EVIDENT NE FSD -- ALSO MAY REMAIN ELEVATED. 
   RELATIVELY HIGHER THETAE OF NEAR-SFC AIR S OF FRONT INDICATES SOME
   POTENTIAL FOR STG GUSTS GENERATED ALOFT TO PENETRATE STABLE LAYER TO
   GROUND...THOUGH LARGE HAIL IS MORE PROBABLE IN THIS REGIME AS WELL.
   
   ..EDWARDS.. 09/21/2007
   
   
   ATTN...WFO...DLH...MPX...FGF...FSD...ABR...
   
   44589539 44629643 44959640 44959682 45119679 45129785
   46609796 46609770 47659737 47609682 48049704 47989551
   48469562 48509519 48369510 48269431 47359445 46419479
   46099436 46079307 45409304 45399344 44979380 44969441
   44909546