MESOSCALE PRECIPITATION DISCUSSION 0584
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
229 PM EDT FRI JUL 28 2017

AREAS AFFECTED...UTAH

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

VALID 281830Z - 282230Z

SUMMARY...SLOW MOVING/TERRAIN LOCKED CONVECTION WITH INCREASING
MOISTURE PROFILES MAY SUPPORT LOCALIZED FLASH FLOODING CONDITIONS
ESPECIALLY GIVEN WET PAST WEEK.

DISCUSSION...GOES MOSAIC SHOWS STRONGER/BROADER SHORTWAVE LIFTING
OUT OF NE NV WITH AN ARCHED MID-LEVEL TROF CURVING BACK NEARING
PARALLEL TO THE SOUTHERN WASATCH WITH LESS THAN 10KT EASTWARD
PROGRESSION.  CONFLUENT UPPER LEVEL FLOW ACROSS N UT ACCELERATES
TO A 50KT JET WITH WEAK ANTICYCLONIC TURNING TO SUPPORT FAVORABLE
RIGHT ENTRANCE ASCENT DYNAMICS.  THE EXITING HEIGHT FALLS ALLOWS
FOR LOW TO MID-LEVEL SOUTHWESTERLY MOISTURE FLUX FROM THE N SEA OF
CORTEZ. PER CIRA LAYERED PW THE MOISTURE IS QUITE HEALTHY BUT
THERE IS A DISTINCT DRY GRADIENT COINCIDENT WITH THE
AFOREMENTIONED MID-LEVEL TROF PASSAGE. 

TO AID MOISTURE TRANSPORT A WEAK S/W RETURNING FROM THE EAST UNDER
THE MEAN UL RIDGE IS ALSO ADVECTING SOME OF THE HIGHLY ANOMALOUS
MOISTURE THAT WAS ACROSS THE SOUTHWEST EARLIER THIS WEEK.  WHILE
NOT VERY STRONG 8-7H EASTERLY/NORTHEASTERLY FLOW IS CONVERGENT
WITH THE RETURN FLOW EAST OF THE CHANNEL BROADENING THE OVERALL
AREA OF POTENTIAL ASCENT ACROSS SOUTHERN UT AT THIS TIME.  THIS
COMBINES FOR OVERALL TPWS OF 1.2-1.3".

IN ADDITION THIS CONFLUENCE OF LOW-LEVEL STREAMS SUPPORTS A WEAK
CLOUD BEARING FLOW 7-4H BETWEEN THE TWO SHORTWAVE SYSTEMS.  THIS
SHOULD ALLOW FOR VERY SLOW CELL MOTION TOWARD THE NORTHEAST WITH
UPSTREAM REDEVELOPMENT POTENTIALLY SUPPORTING REPEAT CELLS.  GIVEN
WET GROUND CONDITIONS OVER THE LAST WEEK OR SO ONLY SERVES TO
ENHANCE POTENTIAL FOR LOCALIZED FLASH FLOODING CONCERNS.

GALLINA

ATTN...WFO...GJT...SLC...

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

LAT...LON   40261016 39620987 38331033 37331111 37261223
            37411297 38011284 39311186 40081119