MESO: Mesoscale Discussion 0844

ACUS11 KWNS 210403
SWOMCD
SPC MCD 210403
MTZ000-210530-

MESOSCALE DISCUSSION 0844
NWS STORM PREDICTION CENTER NORMAN OK
1103 PM CDT SUN MAY 20 2007

AREAS AFFECTED...SERN MT THROUGH EXTREME NERN WY AND WRN SD

CONCERNING...SEVERE THUNDERSTORM WATCH 281...

VALID 210403Z - 210530Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 281
CONTINUES.

PRIMARY SEVERE THREAT IS EXPECTED TO PERSIST WITH EWD ADVANCING LINE
OF STORMS ACROSS E CNTRL MT NEXT HOUR OR TWO. SEVERE THREAT ACROSS
NERN WY AND WRN SD APPEARS INCREASINGLY MARGINAL.

LINE OF STORMS ACROSS E CNTRL MT IS MOVING EWD AT AROUND 30 KT. THIS
LINE HAD DEVELOPED BOW ECHO CHARACTERISTICS DURING THE PAST HOUR BUT
HAS SINCE SHOWN SIGNS OF WEAKENING. ACTIVITY SHOULD CONTINUE EWD
ALONG INSTABILITY GRADIENT THROUGH ERN MT AS A FORWARD PROPAGATING
SYSTEM WHERE CONVERGENCE AND STORM RELATIVE INFLOW IS BEING ENHANCED
BY A SELY LOW LEVEL JET. HOWEVER...LATEST OBJECTIVE ANALYSIS SHOWS
WEAKER INSTABILITY TOWARD THE ND BORDER...AND THE STABILIZING
EFFECTS OF THE COOLING BOUNDARY LAYER WILL ALSO LIKELY SERVE AS A
LIMITING FACTOR FOR A SUSTAINED SEVERE THREAT. CURRENT THINKING IS
THAT THE THREAT OF SEVERE WEATHER WILL PERSIST FOR ANOTHER COUPLE
HOURS...FOLLOWED BY A GRADUAL WEAKENING TREND.

.DIAL.. 05/21/2007

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

ATTN...WFO...BYZ...GGW...

46570409 46150516 46140667 46640659 47450635 47640431

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