MESOSCALE DISCUSSION 1366
NWS STORM PREDICTION CENTER NORMAN OK
0640 PM CDT MON JUL 02 2012
AREAS AFFECTED...PORTIONS ERN ND...NRN MN...WRN LS...NRN WI.
CONCERNING...SEVERE THUNDERSTORM WATCH 454...
VALID 022340Z - 030045Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 454
CONTINUES.
SUMMARY...ANOTHER WW WILL BE ISSUED BEFORE SCHEDULED 00Z EXPIRATION
OF WW 454...FOR AREAS ALONG AND E OF UPSCALE CONVECTIVE GROWTH NOW
UNDERWAY OVER NRN MN. NEW WW LIKELY WILL GO FARTHER E TO COVER
PARTS OF WRN ARROWHEAD OF MN...WRN LS AND NRN WI...IN PROJECTED
TRACKS OF PROBABLE MCS.
DISCUSSION...WELL-DEFINED CONVECTIVE/OUTFLOW BOUNDARY WAS EVIDENT IN
SFC MESOANALYSIS AND VIS/RADAR IMAGERY AT 23Z...FROM
BELTRAMI-TRAVERSE COUNTIES MN...AND MOVING EWD. THIS BOUNDARY NOW
IS BEING REINFORCED BY AGGREGATING SVR TSTMS THAT SHOULD BUILD COLD
POOL...LEADING TO FORWARD-PROPAGATIONAL ACCELERATION. OTHER
CONVECTION WAS DEVELOPING/INTENSIFYING ALONG MORE ZONALLY
ALIGNED...COMBINED OUTFLOW/DIFFERENTIAL-HEATING BOUNDARY OVER
PORTIONS BELTRAMI/ITASCA/ST. LOUIS COUNTIES MN. AIR MASS ACROSS NRN
MN S OF LATTER BOUNDARY IS FAVORABLE...WITH SFC DEW POINTS 70S F
CONTRIBUTING TO NEGLIGIBLE MLCINH AND 2500-3500 J/KG MLCAPE.
FARTHER E...LAKE-BREEZE BOUNDARY WAS DRAWN OVER PARTS OF ST. LOUIS
COUNTY THEN WRAPPING SWD/SEWD AROUND WRN END OF LS...INTO PORTIONS
DOUGLAS/BAYFIELD COUNTIES WI THEN GENERALLY EWD PARALLEL TO LS SRN
SHORE. THIS BOUNDARY WILL ACT AS ERN/NRN BOUND FOR SFC-BASED TSTM
INFLOW AND GREATEST DAMAGING-WIND POTENTIAL FOR CONVECTION MOVING
INTO THAT REGION. EXTENT TO WHICH ANY COLD-POOL DRIVEN MCS WILL
PENETRATE SVR GUSTS THROUGH SHALLOW MARINE LAYER WILL DEPEND
STRONGLY ON STORM-SCALE EFFECTS...SUCH AS PRESSURE PERTURBATIONS
GENERATED BY COMPLEX SHORTLY BEFORE IT ENCOUNTERS THAT LAYER.
HOWEVER...SOME DAMAGING-WIND POTENTIAL MAY EXTEND OVER LAKE AS WELL.
MEANWHILE...ISOLATED STG-SVR CONVECTION DEVELOPING NW GFK WILL MOVE
THROUGH POCKET OF FAVORABLY HIGH-THETAE BOUNDARY-LAYER AIR OVER RED
RIVER VALLEY REGION...THEN ULTIMATELY INTO NWRN MN AIR MASS
STABILIZED BY LARGER CONVECTIVE COMPLEX.
MEANWHILE...HOWEVER,,,MLCAPE 3000-4000 J/KG AND 30-40 KT EFFECTIVE
SHEAR MAGNITUDES WILL AID STORM ORGANIZATION.
..EDWARDS.. 07/02/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
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