MESO: Mesoscale Discussion 1772

ACUS11 KWNS 252254
SWOMCD
SPC MCD 252253
SDZ000-NDZ000-260030-

MESOSCALE DISCUSSION 1772
NWS STORM PREDICTION CENTER NORMAN OK
0553 PM CDT SUN AUG 25 2013

AREAS AFFECTED...PARTS OF NW INTO N CNTRL SOUTH DAKOTA AND ADJACENT
S CNTRL/SERN NORTH DAKOTA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 252253Z - 260030Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...SOME INCREASE IN SEVERE STORM POTENTIAL APPEARS POSSIBLE
ACROSS AT LEAST A SMALL AREA OF NORTH CENTRAL SOUTH DAKOTA DURING
THE NEXT FEW HOURS. IT DOES NOT SEEM PROBABLE THAT A WATCH WILL BE
NEEDED AT THE PRESENT TIME...BUT TRENDS WILL CONTINUED TO BE
MONITORED FOR THE POSSIBILITY OF AN INCREASING THREAT THAT COULD
REQUIRE ONE.

DISCUSSION...SOME INCREASE IN CONVECTIVE DEVELOPMENT IS ONGOING
NORTH OF THE BLACK HILLS INTO AREAS NORTHWEST THROUGH NORTH OF FAITH
SD. THIS MAY BE IN RESPONSE TO FORCING FOR ASCENT AND WEAKENING OF
MID-LEVEL INHIBITION ASSOCIATED WITH A WEAK PERTURBATION MIGRATING
NORTHEAST OF THE ROCKIES. THIS IS WITHIN BROADER SCALE ANTICYCLONIC
FLOW AROUND THE NORTHWESTERN PERIPHERY OF THE STRONG LOWER CENTRAL
PLAINS SUBTROPICAL HIGH CENTER. UNCERTAINTY EXISTS CONCERNING
STRENGTH OF THIS FORCING...AND HOW LONG IT WILL PERSIST...BUT THERE
APPEARS SOME SUGGESTION IN MODEL DATA THAT IT COULD CONTRIBUTE TO
MAINTENANCE OF THUNDERSTORM ACTIVITY INTO THE 00-03Z TIME
FRAME...WHILE CONTINUING NORTHEASTWARD INTO THE CENTRAL DAKOTAS.

WHILE CONVECTION APPEARS POSSIBLE AS FAR NORTH AS CENTRAL NORTH
DAKOTA...POTENTIAL FOR STRONGEST STORM DEVELOPMENT SEEMS TO EXIST
ACROSS NORTH CENTRAL SOUTH DAKOTA...AROUND THE MOBRIDGE AREA...WHERE
LOW-LEVEL CONVERGENCE APPEARS FOCUSED. IF CONVECTION DOES INDEED
PERSIST INTO THIS AREA...INFLOW OF INCREASINGLY MOIST AND UNSTABLE
BOUNDARY LAYER AIR CHARACTERIZED BY CAPE IN EXCESS OF 2000 J/KG
PROBABLY WILL SUPPORT AN INCREASING SEVERE THREAT. DEEP LAYER SHEAR
BENEATH 30+ KT WESTERLY 500 MB FLOW IS SUPPORTIVE OF SUPERCELLS
CAPABLE OF PRODUCING LARGE HAIL AND LOCALLY DAMAGING WIND GUSTS.

..KERR/HART.. 08/25/2013

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

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

LAT...LON 45810148 46519830 45459864 44640044 44970202 45810148

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