MESO: Mesoscale Discussion 1306

ACUS11 KWNS 291934
SWOMCD
SPC MCD 291934
WYZ000-MTZ000-IDZ000-292200-

MESOSCALE DISCUSSION 1306
NWS STORM PREDICTION CENTER NORMAN OK
0234 PM CDT SAT JUN 29 2013

AREAS AFFECTED...PORTIONS OF CNTRL/WRN/SRN MT...ERN/CNTRL ID...FAR
NWRN WY

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 291934Z - 292200Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...THE AREA IS BEING MONITORED FOR AN INCREASING POTENTIAL
FOR SVR THUNDERSTORMS THIS AFTERNOON...BUT THE ISSUANCE OF A WW IS
CURRENTLY UNLIKELY.

DISCUSSION...RECENT VISIBLE SATELLITE IMAGES INDICATE CUMULUS
BUILDUPS BECOMING MORE ABUNDANT FROM PARTS OF THE SALMON RIVER
MOUNTAINS IN CNTRL ID EWD TO THE ABSAROKA RANGE INCLUDING THE
BITTERROOT RANGE...WITH 7- AND 9-KM CAPPI RADAR DATA IN THESE AREAS
INDICATING DEEPER CONVECTIVE CORES BEGINNING TO BLOSSOM FROM THIS
ACTIVITY. CONTINUED DIURNAL/DIABATIC SFC HEATING S/E OF A
MULTI-LAYERED CLOUD SHIELD OVERLYING PARTS OF W-CNTRL MT AND FAR
E-CNTRL ID WILL ALLOW OROGRAPHIC CIRCULATIONS TO FURTHER
DEEPEN/STRENGTHEN THROUGH THE DAY. THIS WILL ENCOURAGE AN INCREASE
IN CONVECTIVE COVERAGE/INTENSITY THROUGH THE AFTERNOON...ESPECIALLY
AS THE SRN FRINGES OF A LOBE OF ASCENT TRACKING FROM THE PACIFIC NW
TO SRN BRITISH COLUMBIA GLANCE THE AREA.

WITH RELATIVELY RICH TROPOSPHERIC MOISTURE CONTENT IN PLACE -- E.G.
PW VALUES OF 0.75-1.20 INCHES PER GPS DATA AND SFC DEWPOINTS HOLDING
IN THE 50S TO THE LOWER 60S -- AMIDST THE NWD EXTENSION OF A PLUME
OF STEEP MID-LEVEL LAPSE RATES...MLCAPE VALUES OF 500-2000 J/KG WILL
BECOME COMMON ACROSS THE AREA THROUGH THE AFTERNOON. THIS...COMBINED
WITH 20-35 KT OF EFFECTIVE BULK SHEAR...WILL SUPPORT A FEW
ORGANIZED/INTENSE STORMS AND POSSIBLE SUPERCELLS WITH ISOLATED
INSTANCES OF SVR WINDS/LARGE HAIL. LARGE DCAPE ACCOMPANYING STEEP
LOW-LEVEL LAPSE RATES WILL ALSO CONTRIBUTE TO THE SVR-WIND
POTENTIAL. THE GREATEST INSOLATION/BUOYANCY WILL EXTEND FROM CNTRL
MT TO SWRN MT AND INTO ADJACENT ERN ID...WHERE THE STRONGEST STORMS
ARE EXPECTED.

HOWEVER...AT THIS TIME...LIMITED DEEP-LAYER FORCING FOR ASCENT AND
THE ABSENCE OF STRONGER DEEP SHEAR MAY SUPPRESS CONVECTIVE
ORGANIZATION/SVR POTENTIAL. FURTHERMORE...WEAK BACKGROUND FLOW IN
THE LOW LEVELS PER REGIONAL VWP DATA WILL REDUCE THE STRENGTH OF
VERTICAL TRANSPORT OF HORIZONTAL MOMENTUM IN DOWNDRAFTS. IN
TURN...ANY SVR WIND POTENTIAL MAY ONLY BE SPORADIC. AS SUCH...THE
ISSUANCE OF A SEVERE THUNDERSTORM WATCH IS CURRENTLY UNLIKELY...BUT
THE AREA WILL CONTINUE TO BE MONITORED FOR INCREASING SVR TRENDS
THROUGH THE AFTERNOON.

..COHEN/MEAD.. 06/29/2013

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

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

LAT...LON 45831632 46621592 47551431 47971296 47991102 47201011
46310982 44960991 43961085 43551292 43911425 44761566
45831632

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