MESO: Mesoscale Discussion 1798

ACUS11 KWNS 292104
SWOMCD
SPC MCD 292103
WIZ000-MNZ000-292300-

MESOSCALE DISCUSSION 1798
NWS STORM PREDICTION CENTER NORMAN OK
0403 PM CDT THU AUG 29 2013

AREAS AFFECTED...PORTIONS CENTRAL/NRN MN...NWRN WI.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 292103Z - 292300Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...ENVIRONMENT MAY BECOME MORE FAVORABLE FOR SVR THROUGH
REMAINDER AFTN...INVOF OUTFLOW BOUNDARY THAT ARCS ACROSS NRN MN
BEHIND INITIAL MCS. SUPERCELLS ARE POSSIBLE WITH LARGE HAIL AND
DAMAGING GUSTS...AND A TORNADO CANNOT BE RULED OUT.

DISCUSSION...SFC MESOANALYSIS SHOWED OUTFLOW BOUNDARY EXTENDING FROM
TAIL END OF WI/MI BORDER MCS WNWWD ACROSS NRN WI AND MN NEAR HYR-BRD
LINE...THEN ARCHING NWWD BETWEEN PKD-BJI AND NWD TO SFC LOW OVER
NWRN BELTRAMI COUNTY. WRN PORTION OF THIS BOUNDARY HAS BEN
RETREATING NEWD AHEAD OF SFC COLD FRONT THAT WAS ANALYZED FROM LOW
SSWWD ACROSS EXTREME SERN ND. A FEW HOURS OF SUSTAINED INSOLATION
BEHIND MCS CLOUD COVER HAS LED TO FAVORABLE DESTABILIZATION ALONG
AND SSW OF OUTFLOW BOUNDARY.

WARM SECTOR IS VERY NARROW FOR ABOUT 100 NM S OF SFC LOW...THEN IS
CHARACTERIZED BY POCKETS OF SUFFICIENTLY STG MIXING FOR MID-60S F
SFC DEW POINTS FARTHER S OVER CENTRAL MN...AROUND LXL.
HOWEVER...DEEPER/SOMEWHAT CONVERGENT BOUNDARY LAYER NEAR OUTFLOW
BOUNDARY IS MAINTAINING UPPER-60S TO MID-70S F SFC DEW
POINTS...CONTRIBUTING TO MLCAPE 2000-3000 J/KG ALONG NERN EDGE OF
EML AND RELATED STEEP LAPSE RATE PLUME. THIS SEGMENT OF OUTFLOW
BOUNDARY ALSO RESIDES BENEATH 35-50 KT EFFECTIVE SHEAR MAGNITUDE.
LOW-LEVEL SRH AND LOW-MIDDLE LEVEL SHEAR EACH INCREASE WITH EWD
EXTENT INTO OUTFLOW AIR...WHERE FLOW IS MORE BACKED NEAR
SFC...HOWEVER BUOYANCY DECREASES AND CINH STRENGTHENS...WITH BILLOW
CLOUDS SEEN IN VIS IMAGERY OVER ITASCA COUNTY. ACTIVITY THAT HAS
FORMED ON BOUNDARY OVER BELTRAMI COUNTY MAY HAVE NARROW CORRIDOR OF
SFC-BASED EFFECTIVE INFLOW...BUT SHOULD OUTPACE FAVORABLE
DESTABILIZATION AS IT MOVES EWD INTO OUTFLOW AIR. MORE SUBSTANTIAL
SVR POTENTIAL MAY BE FARTHER S FROM LXL/BRD AREA EWD INTO NWRN
WI...WHERE INITIALLY ELEVATED CONVECTION ROOTED IN ACCAS LAYER MAY
EVOLVE INTO SFC-BASED TSTMS. EFFECTIVE SRH DECREASES SHARPLY S OF
BOUNDARY...SO ANY SUSTAINED SUPERCELL POTENTIAL APPEARS TO BE
CONFINED TO BOUNDARY ITSELF AND 30-50 NM BAND TO ITS N.

..EDWARDS/THOMPSON.. 08/29/2013

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...DLH...MPX...FGF...

LAT...LON 47929428 47309430 46789385 46249207 45799178 45119231
45489468 45699574 45929613 46949542 47749496 47929428

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.