MESO: Mesoscale Discussion 0638

ACUS11 KWNS 140019
SWOMCD
SPC MCD 140018
MTZ000-IDZ000-ORZ000-WAZ000-140145-

MESOSCALE DISCUSSION 0638
NWS STORM PREDICTION CENTER NORMAN OK
0718 PM CDT MON MAY 13 2013

AREAS AFFECTED...NRN/WRN MT...CENTRAL ID...FAR NERN ORE...AND FAR
SERN WA

CONCERNING...SEVERE THUNDERSTORM WATCH 159...

VALID 140018Z - 140145Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 159
CONTINUES.

SUMMARY...THE GREATEST SEVERE WEATHER THREAT ACROSS WW 159 INTO THE
EVENING WILL BE IN CENTRAL ID TO WRN MT. MEANWHILE...ADDITIONAL
HIGH BASED STORMS HAVE DEVELOPED E OF WW 159...WITH THE POTENTIAL TO
PRODUCE DAMAGING WINDS AND A HAIL THREAT. THE OVERALL COVERAGE OF
THIS LATTER AREA IS UNCERTAIN...AND PRECLUDES THE NEED FOR A NEW
WATCH AT THIS TIME.

DISCUSSION...A STRONG NEGATIVELY-TILTED SHORTWAVE TROUGH CONTINUES
TO PROGRESS EWD ACROSS WA/ORE...WITH A FURTHER INCREASE IN
DOWNSTREAM WSWLY MIDLEVEL WINDS EXPECTED ACROSS WW 159 INTO
CENTRAL/ERN MT THIS EVENING. THIS WILL MAINTAIN STRONG BULK
SHEAR...SUPPORTING STORM ORGANIZATION. DESPITE RELATIVELY MODEST
INSTABILITY /MUCAPE 500-1000 J PER KG/ TENDING TO LIMIT THE COVERAGE
OF STRONGER CELLS THUS FAR...HEIGHT FALLS/ASCENT SPREADING ACROSS
CENTRAL ID/WRN MT ARE EXPECTED TO COMPENSATE...RESULTING IN
ADDITIONAL TSTM DEVELOPMENT.

TO THE EAST OF WW 159...REGIONAL RADAR IMAGERY SHOWED A FEW STORMS
HAVE DEVELOPED ALONG A ZONE OF LOW LEVEL CONVERGENCE AND WITHIN A
DEEPLY MIXED BOUNDARY LAYER WHERE LOW LEVEL AND MID LEVEL LAPSE
RATES ARE QUITE STEEP. ONE PARTICULAR STORM IN FERGUS COUNTY MT /45
NE KLWT/ HAS BECOME ROBUST WITH SUSTAINED REFLECTIVITY AT 7 KM AND 9
KM PER WDSS-II CAPPI. STEEP MIDLEVEL LAPSE RATES EXCEEDING 8
C/KM...LARGE DEWPOINT DEPRESSIONS PER 00Z GTF/GGW SOUNDINGS AND
STRENGTHENING BULK SHEAR SUGGEST DAMAGING WINDS AND HAIL WILL BE A
THREAT WITH THIS STORM AND OTHERS THAT DEVELOP. GIVEN DEWPOINTS
ONLY IN THE LOWER 40S LIMITING STRONGER INSTABILITY...THE COVERAGE
OF INTENSE STORMS SHOULD REMAIN LOW AND WILL LIKELY PRECLUDE THE
NEED FOR A WATCH.

..PETERS.. 05/14/2013

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

ATTN...WFO...BYZ...GGW...TFX...MSO...BOI...OTX...PDT...

LAT...LON 45251861 45901788 46331730 46591658 46941594 46961545
47211495 47371449 47671454 48041463 48781439 48581356
48211299 48481214 48351158 48241085 48341012 48420851
48420717 48300607 47500534 47020542 46610631 46570949
46541003 46641036 46941137 46431178 46191249 45761313
45131466 45101566 44471627 44611697 44291729 44301787
44271848 45251861

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