MESO: Mesoscale Discussion 0781

ACUS11 KWNS 131949
SWOMCD
SPC MCD 131949
MTZ000-WYZ000-IDZ000-132045-

MESOSCALE DISCUSSION 0781
NWS STORM PREDICTION CENTER NORMAN OK
0249 PM CDT SUN MAY 13 2007

AREAS AFFECTED...SWRN AND S CNTRL THROUGH ERN MT AND EXTREME NRN WY

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 131949Z - 132045Z

STORMS ARE EXPECTED TO DEVELOP OVER THE HIGHER TERRAIN OF SWRN MT
AND NWRN WY AND INTENSIFY AS THEY MOVE NEWD INTO S CNTRL AND ERN MT.
ISOLATED LARGE HAIL AND DAMAGING WIND WILL BE THE MAIN THREATS. WW
WILL LIKELY BE NEEDED ONCE SURFACE BASED INITIATION APPEARS
IMMINENT.

A COLD FRONT EXTENDS FROM NERN MT NEAR GLASGOW SWWD INTO ERN ID. AN
OUTFLOW BOUNDARY WAS SETTLING SLOWLY SWD JUST N OF BILLINGS. NELY
LOW LEVEL FLOW WITHIN PRE-FRONTAL WARM SECTOR IS HELPING TO MAINTAIN
SURFACE DEWPOINTS IN THE LOW TO MID 50S ACROSS SRN AND ERN MT
BENEATH 7.5-8 C/KM 700-500 MB LAPSE RATES. THIS ALONG WITH STRONG
SURFACE HEATING IS RESULTING IN DESTABILIZATION WITH MLCAPE FROM
1000 TO 1500 J/KG IN THIS REGION. VISIBLE IMAGERY SHOWS CUMULUS
DEVELOPING OVER THE HIGHER TERRAIN OF SWRN MT AND NERN ID. THE
CONVECTIVE POTENTIAL SHOULD CONTINUE TO INCREASE AS THE CAP WEAKENS
AND LARGE SCALE ASCENT ASSOCIATED WITH EWD ADVANCING SHORTWAVE
TROUGH SPREADS EWD THROUGH THIS AREA. STORMS WILL LIKELY DEVELOP
INITIALLY OVER THE HIGHER TERRAIN THEN SPREAD NEWD THROUGH THE WARM
SECTOR. A 40 TO 50 KT MID LEVEL JET ALONG ERN PERIPHERY OF THE
SHORTWAVE TROUGH ABOVE WEAK ELY BOUNDARY LAYER FLOW IS RESULTING IN
FAVORABLE VERTICAL SHEAR FOR INITIAL STORMS TO DEVELOP SUPERCELL
STRUCTURES. PRIMARY THREATS WILL BE ISOLATED DAMAGING WIND AND LARGE
HAIL. HOWEVER...AN ISOLATED TORNADO OR TWO MAY ALSO BE
POSSIBLE...MAINLY WITH ANY STORMS ADVANCING NEWD AND INTERACTING
WITH THE OUTFLOW BOUNDARY.

.DIAL.. 05/13/2007

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

ATTN...WFO...BYZ...GGW...RIW...TFX...PIH...

46370500 45000609 44730997 44631114 44901223 45861156
47130811 47960600 47430507

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