MESOSCALE PRECIPITATION DISCUSSION 0453
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1122 PM EDT SAT JUL 14 2018

AREAS AFFECTED...SRN NEVADA INCLUDING LAS VEGAS METRO AREA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 150321Z - 150615Z

SUMMARY...SOUTHERN NEVADA (INCLUDING THE LAS VEGAS METRO AREA)
WILL BE A FOCUSED AREA OF GREATER FLASH FLOOD CHANCES THIS EVENING
AS A CONCENTRATED AREA OF THUNDERSTORMS DEVELOPS. RAIN RATES OF
1-2 IN/HR WILL BE POSSIBLE.

DISCUSSION...KESX RADAR SHOWED A WESTERLY PROPAGATING OUTFLOW
BOUNDARY MOVING FROM NEAR LAKE MEAD AROUND 0030Z... TO THE LAS
VEGAS METRO AREA AROUND 03Z. RECENT OBSERVATIONS FROM BOTH KLAS
AND KVGT SHOWED BREEZY EASTERLY WINDS OVER 15 KNOTS BEHIND THIS
OUTFLOW BOUNDARY WITH 7-8 DEGREE JUMPS IN SURFACE DEWPOINTS
RELATIVE TO THE PREVIOUS HOUR OBSERVATION. THE INCREASE IN
LOW-LEVEL MOISTURE COINCIDING WITH EASTERLY WINDS SHOULD LEAD TO
AN HOUR OR TWO OF FOCUSED OROGRAPHIC ASCENT IN AN UNSTABLE AIR
MASS IN THE VICINITY OF THE SPRING MOUNTAINS AND SHEEP RANGE. KESX
RADAR SHOWED NEW UPDRAFTS DEVELOPING OVER THE PAST HALF HOUR...AND
THIS CONVECTION MAY GROW AND THEN DRIFT OVER THE LAS VEGAS METRO
AREA BETWEEN 03Z AND 05Z. ELSEWHERE... SRN NEVADA WAS A REGIONAL
MAX IN INSTABILITY WITH MLCAPE VALUES AROUND 1500 J/KG NORTH OF
LAS VEGAS. DESPITE INCREASING CINH... THIS MAY SUSTAIN ADDITIONAL
AREAS OF CONVECTION INTO NORTHERN CLARK COUNTY... SOUTHERN LINCOLN
COUNTY... AND SOUTHERN NYE COUNTIES.

CONVECTION WAS STILL OF A SINGLE-CELL NATURE... AND ALTHOUGH IT
MAY CONGEAL INTO SMALL CLUSTERS WITH TIME... THIS MAY LIMIT FLASH
FLOODING TO LOCALIZED AREAS. HOWEVER... GIVEN THE ONGOING AND
EXPECTED INCREASE IN CONVECTION IN THE VICINITY OF LAS VEGAS...
AND THE POTENTIAL FOR A STATIONARY FOCUSING MECHANISM (TERRAIN
FEATURES NEARBY)... THERE DOES APPEAR TO BE SOME CHANCE OF FLASH
FLOODING THIS EVENING. AS THE BOUNDARY LAYER CONTINUES TO
STABILIZE AFTER SUNSET... CONVECTION SHOULD GRADUALLY DIMINISH
WITH A DECREASING THREAT OF FLASH FLOODING AROUND 06Z.

LAMERS

ATTN...WFO...VEF...

ATTN...RFC...CBRFC...CNRFC...

LAT...LON   37511475 37171415 36271405 35671429 35311514
            35851599 36541631 37341560