MESO: Mesoscale Discussion 1487

ACUS11 KWNS 032041
SWOMCD
SPC MCD 032040
AZZ000-032315-

MESOSCALE DISCUSSION 1487
NWS STORM PREDICTION CENTER NORMAN OK
0340 PM CDT SUN JUL 03 2011

AREAS AFFECTED...CNTRL/SCNTRL AZ

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 032040Z - 032315Z

STRONG TO POSSIBLY SEVERE THUNDERSTORMS WILL IMPACT CNTRL/SCNTRL AZ
THROUGH MID-EVENING...INCLUDING THE GREATER PHX AREA. A SEVERE
THUNDERSTORM WATCH IS POSSIBLE...ROUGHLY 50 PERCENT PROBABILITY.
PRIMARY IMPACTS WILL BE DAMAGING MACROBURST WINDS.

BOUNDARY LAYER MOISTURE INCREASE...OWING TO BOTH OUTFLOW FROM
YESTERDAY/S SONORA MCS AND AN EARLY MORNING GULF OF CA SURGE...HAS
RESULTED IN A RESERVOIR OF MLCAPES OF 1000-1500 J/KG FROM KTUS-KPHX
W INTO THE LWR DESERTS. WHILE SOME MIXING/DRYING WILL LIKELY OCCUR
/PARTICULARLY KTUS EWD/...EXPECT THAT CONSIDERABLE CAPE WILL BE
AVAILABLE THROUGH EVENING.

TAIL-END OF A MID-LEVEL WAVE APPEARS TO BE MOVING ACROSS NRN SONORA
AND SERN AZ AT 19Z AND THIS WILL LIKELY MAINTAIN A FAVORABLE UPPER
LEVEL DIVERGENT PATTERN OVER CNTRL/SCNTRL AZ THROUGH PEAK HEATING.
STORMS HAVE ALREADY FORMED OVER THE RIM COUNTRY EARLY THIS AFTN AND
HIGH-BASED STORMS MAY ALSO DEVELOP OVER THE HIGHER TERRAIN OF
SCNTRL/SERN AZ WITH TIME. THESE STORMS MAY PRODUCE GUSTY WINDS.

CONCERN IS THAT AS OUTFLOW BOUNDARIES CONSOLIDATE AND MOVE
WWD...STORMS WILL EASILY INITIATE ACROSS THE LOWER DESERTS BY LATE
AFTN/EARLY EVENING. HERE...INSOLATION WILL BE AT A PREMIUM AS
EARLIER HIGH-ELEVATION STORM DEBRIS REMAINS CLEAR OF THE DESERTS.
NUMEROUS CONVECTION-ALLOWING MODELS SUGGEST AN UPTICK IN STORM
DEVELOPMENT AFTER 00Z OVER THE GREATER PHX AREA AND POINTS WSW AND
THIS SEEMS REASONABLE.

UPSLOPE FLOW HAS WEAKENED IN THE PHX AREA RECENTLY...WITH A
DOWNSLOPE FLOW AT KTUS. WHILE THIS WILL REDUCE OVERALL SHEAR...IT
WILL BE SUFFICIENT FOR ORGANIZED STORMS...PRIMARILY LINEAR...WWD
PROPAGATING MODES GIVING SCATTERED MACROBURSTS. SVR THREAT WILL
PROBABLY PERSIST WELL INTO THE EVENING OVER SWRN AZ WITH A CONTINUED
WIND THREAT.

..RACY.. 07/03/2011

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

ATTN...WFO...TWC...FGZ...PSR...VEF...

LAT...LON 32381437 33621436 34641391 35111219 34841142 34090961
33441043 33161088 32111093 31351112 31581188 32381437

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