MESO: Mesoscale Discussion 1791

ACUS11 KWNS 282141
SWOMCD
SPC MCD 282141
AZZ000-CAZ000-290015-

MESOSCALE DISCUSSION 1791
NWS STORM PREDICTION CENTER NORMAN OK
0441 PM CDT WED AUG 28 2013

AREAS AFFECTED...PORTIONS OF SRN AZ AND FAR SERN CA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 282141Z - 290015Z

PROBABILITY OF WATCH ISSUANCE...5 PERCENT

SUMMARY...AN ISOLATED MARGINALLY SVR WIND GUST CANNOT BE RULED OUT
INTO THE EVENING HOURS.

DISCUSSION...GPS PW DATA INDICATE THAT TROPOSPHERIC MOISTENING HAS
TAKEN PLACE ACROSS THE AREA DURING THE PAST DAY...WITH 24-HOUR PW
INCREASES RANGING FROM AROUND 0.10 INCH IN FAR SERN CA TO 0.50 INCH
IN SERN AZ. THIS MOISTENING IS ACCOMPANIED BY MODERATE TO LOCALLY
STRONG INSTABILITY...WITH SFC TEMPERATURES IN THE UPPER 90S TO
AROUND 105 DEGREES. ISOLATED TO WIDELY SCATTERED THUNDERSTORMS HAVE
BEEN DEVELOPING IN RESPONSE TO TERRAIN-DRIVEN CIRCULATIONS ACROSS
THE MOGOLLON RIM AND THE SERN AZ MOUNTAINS...WITH A COUPLE OF
CONVECTIVE CLUSTERS INVOF THE LOWER CO RIVER VALLEY IN FAR SWRN AZ.
IWA/EMX VWP DATA INDICATE AROUND 10-15 KT OF FLOW AOB 5 KM AGL WITH
SOME MEAN ELY COMPONENT. THIS SHOULD ALLOW COLD POOLS TO MOVE OFF
THE HIGHER TERRAIN AND POTENTIALLY FOCUS LATER GENERATIONS OF
CONVECTION OVER THE DESERT FLOORS LATER THIS AFTERNOON INTO THE
EVENING.

DEEP INVERTED-VEE THERMODYNAMIC PROFILES ASSOCIATED WITH SFC
TEMPERATURE-DEWPOINT SPREADS EXCEEDING 40F AND DCAPE AOA 1000 J/KG
IN MANY AREAS MAY SUPPORT A FEW STRONG DOWNBURSTS...AIDED BY WATER
LOADING OWING TO PW VALUES BETWEEN 1.5 AND 1.8 INCHES. AN ISOLATED
MARGINALLY SVR WIND GUST CANNOT BE RULED OUT. HOWEVER...WEAK
TROPOSPHERIC FLOW SHOULD INHIBIT ANY SUBSTANTIAL CONVECTIVE
ORGANIZATION FROM ENSUING...THUS PREVENTING A GREATER SVR POTENTIAL.

..COHEN/CORFIDI.. 08/28/2013

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

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

LAT...LON 33141512 34151501 34881426 35091308 34651187 33501042
32261035 31541135 31661221 32301442 33141512

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