MESOSCALE PRECIPITATION DISCUSSION 0588
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
834 PM EDT SUN OCT 18 2015
 
AREAS AFFECTED...S NEVADA...SE CALIFORNIA...SW UTAH...NW ARIZONA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 190045Z - 190545Z
 
SUMMARY...CONTINUED FLASH FLOOD THREAT THOUGH STARTING TO DIMINISH
IN INTENSITY AND SCALE THROUGH THE EARLY OVERNIGHT HOURS.

DISCUSSION...STRONG LINE OF CONVECTION SEEN IN RADAR/VIS/IR
CROSSING SE NEVADA INTO SW UT/NW AZ CONTINUES TO BE A FLASH FLOOD
THREAT WITH RAIN RATES IN THE 1.0-1.5"/HR WITHIN THE STRONGEST
CORES/OVERSHOOTING TOP REGIONS.  CURRENTLY THE LINE IS COINCIDENT
WITH TPW AXIS ACROSS THE COLORADO RIVER VALLEY...WITH VALUES IN
THE 1.0-1.25" RANGE. 00Z VEF SOUNDING INDICATES DECREASING LOW
LEVEL SUPPORT WITH INCREASING DEWPOINT DEPRESSIONS FROM SURFACE TO
ABOUT 7H.  STILL MID-LEVEL LAPSE RATES ARE STEEP ENOUGH AHEAD OF
THE CONVECTIVE LINE TO SUPPORT MUCAPES IN THE 1500-2500 J/KG RANGE
(HIGHER FURTHER SOUTH TOWARD E CALIFORNIA).  INSTABILITIES WILL
CONTINUE TO DIMINISH...THOUGH SYNOPTIC SETUP WITH BROAD DIFFLUENCE
AHEAD OF APPROACHING S/W AS WELL AS INCREASING PVA SHOULD ALLOW
FOR THE ELEVATED UPDRAFTS TO CONTINUE REMAIN OVER THE NEXT 4-5
HOURS AS THEY PROGRESS INTO UT/AZ...GIVEN WORSENING LOW LEVEL
DRIER ENVIRONMENT...MUCH OF THE RAINFALL WILL BE LOST TO PROFILE
MOISTENING ALSO REDUCING THE HIGHER RAIN RATES SEEN OVER THE LAST
FEW HOURS.  STILL TOTALS MAY CONTINUE TO SUPPORT ISOLATED FLASH
FLOODING PARTICULARLY OVER INCREASED TERRAIN OF S UT.

FURTHER NORTHWEST IN SW ESMERALDA/S NYE CONTINUES...A SMALL LOBE
OF VORTICITY AND INCREASED MOISTURE CONSOLIDATED AROUND
IT...CONTINUES TO REMAIN IN DIFFLUENT FLOW FOR CONTINUED REPEAT
DEVELOPMENT WITH TOPS NEARING -50C STILL SUPPORTIVE OF MODERATE
RAIN RATES...SLOW SOUTH-SOUTHEASTWARD DRIFT WILL TRACK OVER AREAS
ALREADY AFFECTED EARLIER TONIGHT...POTENTIALLY REAGGRAVATING
FLOODING CONDITIONS.

GALLINA 

ATTN...WFO...FGZ...SLC...VEF...

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

LAT...LON   38801253 38201183 37421175 36801210 36301254 
            35601318 34951383 34471453 34421542 35211558 
            36191581 36511596 36651672 36981721 37561725 
            38031660 37591584 37251530 37861444 38771324