MESO: Mesoscale Discussion 1889

ACUS11 KWNS 180016
SWOMCD
SPC MCD 180016
COZ000-WYZ000-MTZ000-UTZ000-IDZ000-180145-

MESOSCALE DISCUSSION 1889
NWS STORM PREDICTION CENTER NORMAN OK
0716 PM CDT TUE SEP 17 2013

AREAS AFFECTED...PARTS OF THE ERN GREAT BASIN AND CNTRL ROCKIES

CONCERNING...SEVERE THUNDERSTORM WATCH 526...

VALID 180016Z - 180145Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 526
CONTINUES.

SUMMARY...OVERALL SEVERE THREAT APPEARS TO HAVE PEAKED WITHIN MOST
OF WW 526 AS CONVECTIVE OUTFLOWS HAVE AIDED IN INCREASED
SURFACE-BASED STABILIZATION. GREATEST SHORT-TERM POTENTIAL FOR
SEVERE HAIL/WIND APPEARS PRIMARILY NEAR THE UT/CO/WY BORDER...BUT
THIS CONVECTION SHOULD WEAKEN AS IT SHIFTS EWD THIS EVENING.

DISCUSSION...MID-LEVEL REFLECTIVITY CORES HAVE WEAKENED WITH MUCH OF
THE CONVECTION WITHIN/NEAR WW 526. STRONGER CELLS HAVE BECOME
CONFINED TO NEAR THE UT/CO/WY BORDER AREA. HOWEVER...WITH DOWNSTREAM
AIR MASS HAVING BEEN COOLED BY EARLIER CONVECTION /SURFACE
TEMPERATURES LARGELY NOW IN THE 60S/...THESE STORMS WILL LIKELY
WEAKEN GIVEN ONLY PERIPHERAL INFLUENCE OF LARGE-SCALE ASCENT.

FARTHER N...MORE WIDESPREAD CONVECTION AND OVERTURNING HAS YIELDED
SUBSTANTIAL STABILIZATION IN THE PAST HOUR...WITH THIS TREND LIKELY
CONTINUING THIS EVENING. STRONGER FORCING FOR ASCENT SHOULD STILL
SUSTAIN CONVECTION FOR SEVERAL MORE HOURS...BUT THE LACK OF GREATER
BUOYANCY/INSTABILITY WILL LIKELY HAMPER SEVERE POTENTIAL BEYOND A
MARGINAL/LOCALIZED THREAT.

..GRAMS.. 09/18/2013

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

ATTN...WFO...BOU...CYS...BYZ...RIW...GJT...SLC...PIH...

LAT...LON 41650629 40320695 40070829 39990981 40201045 40451084
40931178 41171248 41441270 41861268 43041207 44181127
44811053 45280980 45390906 45240777 44390653 41650629

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