MESOSCALE PRECIPITATION DISCUSSION 0557
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1008 AM EDT MON OCT 05 2015
 
AREAS AFFECTED...EASTERN CA/SOUTHERN NV/NORTHWESTERN AZ... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 051407Z - 052007Z
 
SUMMARY...EARLY MORNING CONVECTION CONTINUES TO DEVELOP IN CLOSE
PROXIMITY TO A STRONG UPPER LOW SPINNING OVER THE CA HIGH DESERTS.
STEEP MID-LEVEL LAPSE RATES SAMPLED OVER SOUTHERN NV SUGGESTS
ADDITIONAL DEVELOPMENT IS LIKELY...PARTICULARLY AS SOLAR HEATING
COMMENCES. UNIDIRECTIONAL FLOW SUPPORTS A THREAT FOR TRAINING
CONVECTION ALONG A NORTH/SOUTH AXIS.

DISCUSSION...IN SPITE OF THE EARLY HOUR...IMPRESSIVE INSTABILITY
IS IN PLACE WITH MUCAPES APPROACHING 1000 J/KG VIA THE 12Z VEF
RAOB. FAIRLY STEEP LAPSE RATES IN THE 900-650 MB LAYER WITH
UNIDIRECTIONAL FLOW SPANNING MUCH OF THE TROPOSPHERE. RADAR AND
LIGHTNING DATA THIS MORNING SUPPORT BOTH OF THESE ARTIFACTS WITH
ABUNDANT LIGHTNING OCCURRING ALONG A NORTH/SOUTH AXIS ACROSS
SOUTHERN NV. RECENT OBSERVATIONS SUPPORT APPROXIMATELY 0.25 TO
0.50 INCHES OF RAINFALL IN 3 HOURS. THE MORNING SOUNDING SHOWED A
BIT OF DRY AIR FROM THE SURFACE TO 800-MB WHICH COULD BE
DECREASING THE PRECIPITATION EFFICIENCY OVER THE REGION.

OVER THE COURSE OF THE NEXT SEVERAL HOURS...EXPECT THE COVERAGE OF
CONVECTION TO EXPAND AS SOLAR INSOLATION CONTINUES. DIFFERENTIAL
HEATING ZONES WILL ALSO BECOME ADDITIONAL FOCI FOR CONVECTIVE
DEVELOPMENT WITH HEAVY DOWNPOURS AND TRAINING POSSIBLE GIVEN THE
FAVORABLE VERTICAL WIND PROFILES. ADDITIONAL AREAS OF CONCERNS
WOULD BE THE USUAL LOCATIONS OF STEEP TERRAIN AS WELL AS ACROSS
URBANIZED LOCALES. 

MESOSCALE MODELS SEEM TO FAVOR A LOOSELY ORGANIZED CONVECTIVE
EVENT WITH PULSE THUNDERSTORMS FIRING AMIDST THE INCREASINGLY
UNSTABLE ATMOSPHERE. THERE IS PLENTY OF MOISTURE SUPPORT FROM THE
SEA OF CORTEZ WITH +3 SIGMA 850-700 MB MOISTURE FLUX ANOMALIES.
FLASH FLOODING WILL REMAIN POSSIBLE THROUGH THE EARLY AFTERNOON
AND WILL LET THE NEXT SHIFT RE-ASSESS THE SITUATION. PLEASE VIEW
THE LATEST SPE FROM NESDIS/SAB FOR ADDITIONAL INFORMATION.


RUBIN-OSTER

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

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

LAT...LON   37551511 37021397 36031344 34991329 34341406 
            34421520 35261623 36491673 37271646