MESOSCALE PRECIPITATION DISCUSSION 0438
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
216 PM EDT THU JUL 12 2018

AREAS AFFECTED...EAST CENTRAL NV...SOUTHWEST UT

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

VALID 121815Z - 130000Z

SUMMARY...MTN CONVECTION TO SPAWN A SW MOVING COMPLEX OVER SW
UT/SE NV.  SLOW/STATIONARY CONVECTION ALONG SOUTHERN GREAT BASIN
RANGES...BOTH POSING PSBL FF RISK THROUGH 00Z.

DISCUSSION...CIRA LPW/TPW ALONG WITH GPS NETWORK DEPICT A
FUNNELING OF LOW LEVEL MOISTURE UP THROUGH THE LOWER CO RIVER
VALLEY INTO THE MEADOW VALLEY/VIRGIN RIVER VALLEYS WITH VALUES
REACHING INTO THE 1.25" RANGE WHICH IS ABOUT 200% OF NORMAL.  THE
MID TO UPPER LEVEL PW LAYERS SUGGEST SOME MODERATE CONNECTION
STILL TO THE NORTHERN STREAM WITH 5-3H LAYER ORIENTED ACROSS S NV
AND CENTRAL UT TO CENTRAL WY.  SURFACE ANALYSIS SUGGESTS THE
FRONTAL BOUNDARY IS FAIRLY DEEP ALONG THE NW EDGE OF THIS MOISTURE
PLUME WHICH CAN BE DELINEATED BY THE CU/TCU GROWTH ON THE GREAT
BASIN RANGES. 

FURTHER SOUTHEAST INTO CENTRAL ANS SW UT MOUNTAIN RANGES GIVEN
CLEAR SKIES AND GOOD INSOLATION THIS MORNING BUT ALSO THE
INCREASING MOISTURE...AS ALREADY SPARKED TCU INTO SOME ISOLATED
CBS.  RAP FORECAST SUGGEST THE LL FLOW WILL INCREASE SLOWLY
USHERING IN INCREASED MST AND THEREFORE INSTABILITY REACHING
2500-3000 J/KG TOWARD LATE AFTERNOON.  AS SUCH CONVECTION ALONG
THE SPINE IS EXPECTED TO CONTINUE TO DEVELOP AND WITH LIMITING
FLOW ALOFT WILL BE SLOW MOVING WITH HOURLY TOTALS OF .75-1"
POSSIBLE.  HOWEVER AS THE FLOW INCREASES AND COLD POOLS GENERATE
OUTFLOW BOUNDARIES SHOULD FOCUS CONVECTION THAT WILL PROPAGATE TO
THE INFLOW WITH INCREASING UPDRAFT STRENGTH/MST FLUX TO SUPPORT
INCREASED RATES OF 1-1.5"/HR PSBL (HIGHEST WITH CELL MERGERS) AS
THERE IS A GOOD POTENTIAL FOR A COMPLEX TO GROW UPSCALE MOVING
SOUTH SUPPORTED BY THE 12Z ARW/NSSL WRF AND NAM CONEST.
HOWEVER...SINCE HI-RES CAMS ARE SLOW ON CONVECTIVE
INITIATION...WOULD EXPECT AN HOUR OR SO EARLIER WITH THE COMPLEX
EVOLUTION TOO.

WHILE THERE IS GREATER UNCERTAINTY FURTHER WEST INTO CENTRAL
NV...BEING SW OF THE FRONTAL ZONE THERE IS AT LEAST SOME THREAT
FOR TERRAIN LOCKED CONVECTION TO POSE A PSBL FLASH FLOOD THREAT
HERE AS WELL (UP TO 1" IN LESS THAN 1 HR)...AND HAVE INCLUDED IT
IN THE AREA OF CONCERN FOR PSBL FLASH FLOODING THROUGH 00Z.

GALLINA

ATTN...WFO...LKN...SLC...VEF...

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

LAT...LON   39951045 39321024 38781072 37691112 37061254
            36831323 36821421 36981486 37371568 38381737
            39161709 39351463 39071399 38871379 38831291
            39401200 39881140