MESOSCALE DISCUSSION 1369
NWS STORM PREDICTION CENTER NORMAN OK
0917 PM CDT MON JUL 02 2012
AREAS AFFECTED...PORTIONS NERN MN...WRN LS...NRN WI...WRN-CENTRAL
UPPER MI.
CONCERNING...SEVERE THUNDERSTORM WATCH 455...
VALID 030217Z - 030415Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 455
CONTINUES.
SUMMARY...CONTINUE WW ALONG/AHEAD OF SVR BOW/MCS INITIALLY OVER NERN
MN. ADDITIONAL WW APPEARS PROBABLE OVER PORTIONS NERN WI/UPPER MI.
ACTIVITY OVER NERN ND HAS DISSIPATED BEHIND ITS OWN GUST FRONT.
FURTHER CONVECTIVE DEVELOPMENT CANNOT BE RULED OUT OVER WRN PORTIONS
WW...WHETHER IN POCKETS OF UNDISTURBED BOUNDARY-LAYER AIR OVER RED
RIVER REGION...OR IN ELEVATED WAA REGIME ATOP EXPANDING MCS OUTFLOW.
HOWEVER...BEST-ORGANIZED SVR THREAT BY FAR SHOULD REMAIN WITH MAIN
MCS.
DISCUSSION...DAMAGING BOW ECHO WILL CONTINUE TO POSE SVR WIND RISK
FROM DLH AREA ESEWD ACROSS ADJOINING PORTIONS LS/WI...DESPITE
PRESENCE OF SHALLOW MARINE LAYER. SVR POTENTIAL THEREAFTER IS
SOMEWHAT MORE UNCERTAIN...BASED ON IMPACT OF MCS INTERACTION WITH
THAT LAYER...HOWEVER SURVIVING PORTION OF COMPLEX AGAIN WILL HAVE
ACCESS TO FAVORABLY MOIST/UNSTABLE AIR S OF LS. COLD POOL AND
ATTENDANT ISALLOBARIC PERTURBATION ALREADY APPEARS SUFFICIENTLY
WELL-ORGANIZED THAT SVR GUSTS MAY BE FORCED DOWN THROUGH MARINE
LAYER OVER LAKE AND LAKE SHORE AS WELL. SFC DEW POINTS 70S F S OF
LAKE-BREEZE FRONT WILL RESULT IN ONLY GRADUAL INCREASE IN
MLCINH...WHILE SUPPORTING MLCAPE 2500-4000 J/KG...BASED ON MODIFIED
MPX/GRB RAOBS AND MODEL SOUNDINGS. TO EXTENT MEAN MOTION FOR PAST
COUPLE HOURS IS VALID...APEX OF BOW WOULD START TO EXIT ERN PORTIONS
WW AND REACH WRN UPPER MI AROUND 330Z. SOME EWD TURN ALSO IS
POSSIBLE OVER UPPER MI BASED ON BACKING OF FORWARD-PROPAGATIONAL MCS
MOTION VECTORS IN BETWEEN LM-LS...INDICATED BY NEW NAM-BASED
GUIDANCE.
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