MESO: Mesoscale Discussion 1789

ACUS11 KWNS 292246
SWOMCD
SPC MCD 292246
NEZ000-SDZ000-NDZ000-MTZ000-WYZ000-292345-

MESOSCALE DISCUSSION 1789
NWS STORM PREDICTION CENTER NORMAN OK
0546 PM CDT FRI JUL 29 2011

AREAS AFFECTED...ERN MT...FAR ERN WY...WRN SD...WRN ND...WRN NEB
PANHANDLE

CONCERNING...SEVERE THUNDERSTORM WATCH 700...

VALID 292246Z - 292345Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 700
CONTINUES.

COVERAGE OF DISCRETE TSTMS HAS BEEN INCREASING OVER THE PAST 1-2 HRS
ACROSS WW 699...ALONG A NEARLY STATIONARY SFC TROUGH/CONFLUENCE
LINE...AND PERHAPS AIDED BY A WEAK UPPER IMPULSE EVIDENT IN RECENT
WATER VAPOR IMAGERY. THE DOWNSTREAM ENVIRONMENT SHOULD CONTINUE TO
REMAIN FAVORABLE FOR MAINTAINING TSTM INTENSITY...AS LOW-LEVEL MOIST
AXIS /DEW POINTS IN THE MID 60S/ IS POSITIONED FROM S-CNTRL SD INTO
SWRN ND...ALTHOUGH NET EFFECT ON POTENTIAL INSTABILITY MAY BE OFFSET
BY LOSS OF DIABATIC HEATING OVER THE NEXT SEVERAL HRS. ALTHOUGH
STILL SOMEWHAT UNCERTAIN...ONGOING TSTM ACTIVITY MAY GROW UPSCALE
INTO A SMALL CLUSTER/MCS AND REMAIN FOCUSED ALONG LOCAL MAXIMUM OF
FORCED ASCENT IN RESPONSE TO THE EWD MOVING UPPER IMPULSE. SHOULD
THIS OCCUR...A DOWNSTREAM THREAT OF DMGG WIND GUSTS MAY MATERIALIZE
ACROSS NWRN SD AND SWRN ND.

FARTHER N ACROSS NERN MT...RECENT VISIBLE SATELLITE IMAGERY
INDICATES TCU FIELD HAS BEEN GROWING IN VERTICAL EXTENT RECENTLY
ALONG THE WEAKLY CONFLUENT SFC TROUGH. THE ENVIRONMENT IS
SUFFICIENTLY UNSTABLE /MLCAPE VALUES NEAR 2000 J/KG/ TO SUPPORT
CONTINUED DEVELOPMENT OF TSTMS ACROSS NERN MT. GIVEN MODERATELY
STRONG WLY MIDLEVEL FLOW /E.G. 30 KTS AT 500 MB/ ATOP S-SELY
LOW-LEVEL FLOW...EFFECTIVE SHEAR WILL BE FAVORABLE FOR ORGANIZED
STORM STRUCTURES CAPABLE OF PRODUCING DMGG WIND GUSTS AND LARGE
HAIL. CONVECTIVE TRENDS ARE BEING MONITORED FOR A POSSIBLE WW.

..ROGERS.. 07/29/2011

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

ATTN...WFO...BIS...LBF...UNR...CYS...BYZ...GGW...

LAT...LON 41450443 46500574 48930649 48990279 47950266 45180209
41480208 41450443

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