MESO: Mesoscale Discussion 1113

ACUS11 KWNS 121740
SWOMCD
SPC MCD 121740
NDZ000-SDZ000-121945-

MESOSCALE DISCUSSION 1113
NWS STORM PREDICTION CENTER NORMAN OK
1240 PM CDT TUE JUN 12 2007

AREAS AFFECTED...WRN/CENTRAL ND...WRN/CENTRAL SD

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 121740Z - 121945Z

TSTMS WILL CONTINUE TO DEVELOP AND INTENSIFY OVER WRN ND...AND
NWRN/CENTRAL SD DURING THE NEXT FEW HOURS. A FEW OF THESE TSTMS ARE
EXPECTED TO BEGIN POSING A MARGINAL SVR THREAT BY 20Z...AND A WW MAY
BE NEEDED BEFORE THEN. VERY HVY RAINFALL RATES IN EXCESS OF 2 IN/HR
WILL ALSO BE POSSIBLE SPCLY WHERE CELL TRAINING OCCURS.

DESPITE COPIOUS CLOUD COVER MOVING INTO THE AREA...SUFFICIENTLY
STRONG AND DEEP LAYER CONVERGENCE AHEAD OF AN MCV AND WEAKENING CINH
HAS AIDED IN A NEW ROUND OF TSTMS TO DEVELOP RECENTLY OVER SWRN
ND/NWRN SD WITH ADDITIONAL TSTMS DEVELOPING OVER CENTRAL SD IN THE
WAKE OF THIS MCV. 17Z SURFACE ANALYSIS INDICATED A CORRIDOR OF
HIGHER INSTABILITY /MLCAPES FROM 1500-2500 J/KG EXTENDING FROM
CENTRAL SD NWWD INTO WCENTRAL/SWRN ND. MID LEVEL FLOW WAS ADEQUATE
FOR ROTATING SUPERCELLS /30-40 KTS AT 6 KM PER BISMARCK/RAPID CITY
VWP DATA/ ALONG THE WRN PORTION OF THIS INSTABILITY AXIS /WHERE
CONVECTION WAS BEGINNING TO DEVELOP/. GIVEN INCREASING UPPER FORCING
AHEAD OF APPROACHING VORT MAX OVER CENTRAL MT...AND A VERY MOIST AND
WEAKLY CAPPED ATMOSPHERE /SFC TEMPERATURES NEAR 80 F...EXPECT AT
LEAST ISOLATED SVR TSTMS WITHIN THE NEXT FEW HOURS. ANY SVR TSTMS
THAT DO DEVELOP WILL BE CAPABLE OF PRODUCING LARGE HAIL/DMGG WINDS
ALONG WITH VERY HVY RAIN. AN INCREASING LOW LEVEL JET EARLY THIS
EVENING OVER CENTRAL ND/NCENTRAL SD SUGGESTS THAT AN ISOLATED
TORNADO OR TWO IS ALSO POSSIBLE TOWARD EVENING IF ANY DISCRETE
SUPERCELLS FORM. THE AMOUNT OF MID/HIGH CLOUD COVER MOVING NWD OUT
OF SD AND IT/S EFFECTS ON INSOLATION AND INSTABILITY MAY BE
SUFFICIENT TO PRECLUDE A GREATER COVERAGE OF SVR THREAT OVER ND.

.CROSBIE.. 06/12/2007

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

ATTN...WFO...FGF...ABR...BIS...UNR...

43169996 43350189 46020270 46770265 47350279 47910272
48350210 48590125 48650080 48780041 48830007 48779954
48659976 48109910 44439938

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