MESO: Mesoscale Discussion 1807

ACUS11 KWNS 250053
SWOMCD
SPC MCD 250052
NDZ000-SDZ000-250145-

MESOSCALE DISCUSSION 1807
NWS STORM PREDICTION CENTER NORMAN OK
0752 PM CDT FRI AUG 24 2012

AREAS AFFECTED...CENTRAL AND ERN ND

CONCERNING...SEVERE THUNDERSTORM WATCH 588...

VALID 250052Z - 250145Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 588
CONTINUES.

SUMMARY...A MIX OF MULTICELL AND SUPERCELL STORM STRUCTURES WILL
PERSIST THIS EVENING AS A PRIMARY BROKEN LINE OF STORMS ADVANCES EWD
FROM CENTRAL INTO ERN ND...WITH THE POTENTIAL FOR ADDITIONAL ND
COUNTIES TO BE LOCALLY ADDED TO WW 588. MEANWHILE...COUNTIES IN THE
WRN EXTENT OF THIS WATCH CAN BE CANCELLED ONCE THE PRIMARY N-S WIND
SHIFT MOVES THROUGH A GIVEN COUNTY.

DISCUSSION...AT 00Z...TRENDS IN REGIONAL RADAR IMAGERY AND SURFACE
OBSERVATIONS INDICATED A SYNOPTIC LOW HAD MOVED EWD INTO SRN MCLEAN
AND OLIVER COUNTIES ND /BETWEEN N60 AND BIS/. A N-S WIND SHIFT
EXTENDED FROM THE LOW SWD TO THE WEST OF BIS TO CENTRAL SIOUX COUNTY
ND INTO NORTH CENTRAL TO SWRN SD. MOST OF THE STORMS IN ND HAVE
MOVED OFF THE N-S ORIENTED BOUNDARY...WITH THE STRONGEST STORM /A
SUPERCELL/ LOCATED IN SWRN WELLS/FAR NRN KIDDER COUNTIES AT 0025Z.
THIS LATTER STORM HAS TENDED TO MOVE WITH A MORE EWD TRAJECTORY AND
THUS MAINTAINING SUPERCELL MODE. MEANWHILE...A WARM FRONT EXTENDING
EWD FROM THE ND SURFACE LOW HAS CONTINUED TO MOVE NWD THROUGH ERN
ND...AND NOW RESIDES N OF GFK...AIDING IN FURTHER DESTABILIZATION
/MLCAPE 1000-1500 J PER KG/ ACROSS THE WARM SECTOR. THIS COMBINED
WITH FORCING FOR ASCENT SPREADING ACROSS CENTRAL INTO ERN ND THIS
EVENING WILL ALLOW STRONG TO SEVERE STORMS TO REMAIN POSSIBLE TO AT
LEAST THE ND/MN BORDER. THIS SUPPORTS THE ADDITION OF ND COUNTIES
ON THE ERN PERIPHERY OF WW 588.

A COUPLE OF STRONG TO SEVERE STORMS WILL REMAIN POSSIBLE ACROSS
NORTH CENTRAL SD THIS EVENING AS N-S WIND SHIFT ADVANCES EWD INTO A
MODERATELY UNSTABLE AIR MASS. THE SRN EXTENT OF STRONGER BULK SHEAR
RESIDES IN THIS REGION AND WILL SUPPORT SOME STORM ORGANIZATION...
BUT THE LIMITED COVERAGE FOR SEVERE STORMS IN NRN SD SUGGESTS A NEW
WW IS NOT WARRANTED.

..PETERS.. 08/25/2012

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

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

LAT...LON 45430109 46380091 47430035 48530011 48749740 47439699
46439724 45719846 45299944 45240032 45430109

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