Wednesday, April 18, 2007

MESO: Mesoscale Discussion 0515

ACUS11 KWNS 182051
SWOMCD
SPC MCD 182051
WYZ000-MTZ000-182215-

MESOSCALE DISCUSSION 0515
NWS STORM PREDICTION CENTER NORMAN OK
0351 PM CDT WED APR 18 2007

AREAS AFFECTED...NRN WY AND SRN MT

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 182051Z - 182215Z

A SEVERE THREAT WILL LIKELY DEVELOP OVER NRN WY AND SRN MT OVER THE
NEXT FEW HOURS. LARGE HAIL WILL BE THE PRIMARY THREAT ALTHOUGH
ISOLATED WIND DAMAGE WILL ALSO BE POSSIBLE. A WW MAY BECOME
NECESSARY LATE THIS AFTERNOON ACROSS THE REGION.

LATEST SFC ANALYSIS SHOWS A SFC LOW NEAR RIVERTON WY WITH A COLD
FRONT EXTENDING SWD ACROSS SW WY INTO ERN UT. A LOW-LEVEL MOIST AXIS
EXISTS ACROSS WRN SD...ERN MT AND NE WY WHERE SFC DEWPOINTS RANGE
FROM THE 30S F TO THE LOWER 40S F. SFC HEATING ALONG THE MOIST AXIS
IS RESULTING IN INSTABILITY WITH MLCAPE VALUES GENERALLY AROUND 500
J/KG. IN ADDITION...RUC ANALYSIS AND WATER VAPOR IMAGERY SHOW A
SERIES OF SUBTLE SHORTWAVE TROUGHS EMBEDDED IN A LARGER WRN U.S.
UPPER-LEVEL TROUGH. AS THESE FEATURES MOVE NNEWD ACROSS THE REGION
WILL INCREASE LARGE-SCALE ASCENT PROVIDING A FOCUS FOR SCATTERED
THUNDERSTORM DEVELOPMENT OVER THE NEXT FEW HOURS. AS THUNDERSTORMS
INCREASE IN COVERAGE AND MATURE...MODERATE VERTICAL SHEAR AND LAPSE
RATES EXCEEDING 9.0 C/KM SHOWN ON FORECAST SOUNDINGS SHOULD BE
SUFFICIENT FOR ISOLATED SUPERCELLS WITH LARGE HAIL. WIND DAMAGE
SHOULD BE MORE ISOLATED BUT MAY ALSO ACCOMPANY ANY SUPERCELLS THAT
DEVELOP.

.BROYLES.. 04/18/2007

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

ATTN...WFO...UNR...CYS...BYZ...RIW...

43330757 43790910 44171040 44661072 45381067 45980996
46120879 45640682 45100554 44160444 42920478 42730615

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