SWOMCD
SPC MCD 121903
NDZ000-SDZ000-MTZ000-WYZ000-122030-
MESOSCALE DISCUSSION 1266
NWS STORM PREDICTION CENTER NORMAN OK
0203 PM CDT MON JUL 12 2010
AREAS AFFECTED...ERN MT
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 121903Z - 122030Z
THREAT FOR LARGE HAIL AND DAMAGING WIND GUSTS IS EXPECTED TO
INCREASE BY MID AFTERNOON AS STORMS DEVELOP/SPREAD EWD ACROSS MUCH
OF ERN MT. AREA IS BEING MONITORED FOR A WW.
STRONG MID-LEVEL HEIGHT FALLS ARE BEGINNING TO SPREAD ACROSS MT IN
ADVANCE OF POTENT UPPER DISTURBANCE CURRENTLY DIGGING SEWD ACROSS
THE STATE OF WA. LARGE SCALE ASCENT/DESTABILIZATION ASSOCIATED WITH
THIS FEATURE...IN ADDITION TO STRONG SURFACE HEATING/STEEPENING
LOW-LEVEL LAPSE RATES WILL LIKELY LEAD TO THUNDERSTORM DEVELOPMENT
BY MID AFTERNOON ALONG/AHEAD OF SURFACE FRONT LOCATED FROM 25 NE OF
HVR TO 50 N OF SHR AT 18Z...WHICH IS SUPPORTED BY INCREASING
ENHANCEMENT TO CUMULUS FIELD OVER CENTRAL/N-CENTRAL MT.
WITH UPPER 50S F DEWPOINTS RESIDING ACROSS MUCH OF ERN MT...AND
MODESTLY STEEP MID-LEVEL LAPSE RATES /AROUND 7 C PER KM IN THE
700-500 MB LAYER/...MLCAPE VALUES WILL CONTINUE TO CLIMB TO AROUND
1000 J/KG BY PEAK HEATING. IN ADDITION...50+ KT MID-LEVEL SPEED MAX
WILL CONTINUE TO APPROACH THE REGION THROUGH THE REMAINDER OF THE
AFTERNOON/INTO THE EVENING...WHICH WILL CONTRIBUTE TOWARD EFFECTIVE
BULK SHEAR VALUES AOA 40 KT. GIVEN THE COMBINATION OF STRONG
FORCING...STEEPENING LAPSE RATES...AND STRENGTHENING DEEP LAYER WLY
FLOW...LINE SEGMENTS AND SUPERCELLS WILL BE POSSIBLE...POSING A
THREAT OF LARGE HAIL AND DAMAGING WIND GUSTS.
..GARNER.. 07/12/2010
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...BIS...UNR...BYZ...GGW...TFX...
LAT...LON 48340934 49280763 49380503 48490382 45330399 44990657
46140802 48340934
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