Graphic for MPD #0557

MESOSCALE PRECIPITATION DISCUSSION 0557
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 AM EDT TUE JUL 25 2017

AREAS AFFECTED...FAR SERN NV INTO SWRN UT/NWRN AZ

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

VALID 250636Z - 251230Z

SUMMARY...SLOW MOVING CORES OF HEAVY RAIN WITH FLASH FLOOD
POTENTIAL ARE EXPECTED TO CONTINUE TO IMPACT PORTIONS OF FAR SERN
NV INTO SWRN UT AND NWRN AZ OVER THE NEXT SEVERAL HOURS. RAINFALL
RATES OF 1 TO 1.5 IN/HR WILL BE FOUND IN THE STRONGER CORES.

DISCUSSION...A 24 HOUR LOOP OF CIRA LAYERED PW IMAGERY SHOWED DEEP
LAYERED MOISTURE ADVECTING NORTH INTO THE SOUTHWEST U.S. FROM THE
TROPICAL EAST PACIFIC RESULTING IN A 2.24 INCH PRECIPITABLE WATER
VALUE AT YUM FOR 00Z...A NEAR RECORD ACCORDING TO THE SPC SOUNDING
CLIMATOLOGY. ANOMALOUS MOISTURE...3+ STANDARDIZED ANOMALIES...WAS
IN PLACE FROM PORTIONS OF ERN CA INTO SRN NV AND PORTIONS OF UT AS
OF 06Z. KICX RADAR IMAGERY AND EXPERIMENTAL GOES 16 INFRARED
IMAGERY SHOWED A SMALL CLUSTER OF ONGOING CONVECTION OVER
WASHINGTON AND NRN MOHAVE COUNTIES WITH RECENT SPC MESOANALYSIS
PAGE MUCAPE VALUES OF 500 TO 1000+ J/KG ACROSS THE REGION.

THE NV/UT/AZ TRI-STATE REGION WAS CAUGHT IN BETWEEN A WELL DEFINED
MID-LEVEL LOW ON THE NRN CA COAST AND RIDGE OVER NEW MEXICO. A
COMBINATION OF RAP ANALYSES...700 MB VAD WIND PLOTS AND 3.9 MICRON
SATELLITE IMAGERY SHOWED A LOW-MID LEVEL CIRCULATION/VORTICITY
MAXIMUM OVER NWRN AZ ALONG WITH AN INVERTED TROUGH AXIS EXTENDING
NEWD INTO CNTRL UT AT 06Z...LIKELY RESPONSIBLE FOR ONGOING
NOCTURNAL CONVECTION ALONG THE WRN UT/AZ BORDER...AMID GENERALLY
WEAK LOW-MID LEVEL FLOW. IN THE UPPER TROPOSPHERE...GOES HD WIND
VECTORS ALIGNED WELL WITH RAP ANALYSES SHOWING 30-50 KT OF FLOW
OVER WRN UT...RESULTING IN SOME DEGREE OF SPEED DIVERGENCE ALOFT
GIVEN WEAKER WIND SPEEDS TO THE SOUTH.

GIVEN THE FORECAST CONTINUED ADVECTION OF DEEP MOISTURE TO THE
NORTH THROUGH THE OVERNIGHT HOURS...AND LINGERING WEAK INSTABILITY
ALOFT...THE EXPECTATION IS FOR CONVECTION TO CONTINUE OR NEW CELLS
TO DEVELOP IN AND AROUND THE WRN UT/AZ BORDER. SLOW MOVEMENT AND
BRIEF TRAINING OF RAINFALL RATES 1-1.5 IN/HR MAY CONTINUE TO POSE
A FLASH FLOOD THREAT THROUGH 12Z. THIS SCENARIO IS SUPPORTED IN
SIMULATED REFLECTIVITY FROM THE 00Z NAM CONUS NEST AND RECENT RUNS
OF THE ESRL EXPERIMENTAL HRRR.

OTTO

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

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

LAT...LON   39121171 38941103 38431075 37391072 36621144
            36311287 36081429 36131476 36351532 36771552
            37361538 37861437 38571305 38951226


Last Updated: 237 AM EDT TUE JUL 25 2017