Wednesday, June 20, 2007

MESO: Mesoscale Discussion 1218

ACUS11 KWNS 202002
SWOMCD
SPC MCD 202002
WYZ000-MTZ000-IDZ000-202100-

MESOSCALE DISCUSSION 1218
NWS STORM PREDICTION CENTER NORMAN OK
0302 PM CDT WED JUN 20 2007

AREAS AFFECTED...PORTIONS OF CNTRL ID...SWRN MT

CONCERNING...SEVERE POTENTIAL...SEVERE THUNDERSTORM WATCH LIKELY

VALID 202002Z - 202100Z

CLUSTERS OF STRONG TO SEVERE TSTMS ARE EXPECTED TO DEVELOP THIS
AFTERNOON IN ASSOCIATION WITH A MID-LEVEL IMPULSE IMPINGING UPON THE
WRN CONUS RIDGE. ALTHOUGH INSTABILITY SHOULD REMAIN MODEST...STRONG
DEEP-LAYER SHEAR SHOULD RESULT IN SOME SUPERCELLS WITH LARGE HAIL
AND GUSTY OUTFLOW WINDS AS THE PRIMARY THREATS. A SEVERE TSTM WATCH
ISSUANCE IS LIKELY BY 21Z.

A MID-LEVEL IMPULSE /EVIDENT IN WATER VAPOR IMAGERY/ HAS NOW REACHED
THE NRN GREAT BASIN. 12Z MODEL GUIDANCE RESOLVED THIS FEATURE QUITE
WELL AND TRACK IT ATOP THE WRN CONUS RIDGE AXIS TOWARDS THE NRN
ROCKIES BY THIS EVENING. LIFT ASSOCIATED WITH THIS IMPULSE HAS AIDED
IN SMALL CB/TCU DEVELOPMENT ACROSS THE ID SAWTOOTHS AND MT SWRN MTNS
/PER RECENT VISIBLE SATELLITE AND LIGHTNING IMAGERY/. LATEST RUC
OBJECTIVE ANALYSIS INDICATES MODEST SURFACE-BASED INSTABILITY WITH
SBCAPES APPROACHING 1000 J/KG. THIS IN COMBINATION WITH 30 TO 40 KTS
OF SWLY MID-LEVEL FLOW WILL SUPPORT SUPERCELL DEVELOPMENT. IN
ADDITION TO A LARGE HAIL THREAT...STEEP LOW-LEVEL LAPSE RATES WILL
AID IN GUSTY DOWNDRAFT WINDS.

.GRAMS.. 06/20/2007

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

ATTN...WFO...BYZ...RIW...TFX...PIH...MSO...BOI...

46311540 47011470 47281352 47141184 46441074 45101058
44371274 44191344 44471439 45111539

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