MESOSCALE PRECIPITATION DISCUSSION 0499...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 PM EDT SAT JUL 21 2018

CORRECTED FOR ADD NV TO AREA AFFECTED

AREAS AFFECTED...NORTHWEST AZ...EXT SOUTHWEST UT...EXT SOUTHEAST
NV

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

VALID 211745Z - 212215Z

SUMMARY...SLOW CELL MOTIONS/MODERATE MOISTURE AND WET ANTECEDENT
CONDITIONS POSE POSSIBLE SCATTERED FLASH FLOODING CONDITIONS THIS
AFTERNOON

DISCUSSION...GOES-16 IMAGERY SUITE SHOWS DECAYING MCS WITH WELL
DEFINED MCV LIFTING NNW ACROSS LA PAZ COUNTY.  EARLY MORNING
CONVECTION HAS WANED AND KICKED FAST MOVING OUTFLOW BOUNDARY
TOWARD THE LAS VEGAS METRO AT THIS TIME...AND THOUGH THIS AREA HAS
BEEN CLOUDED OVER THROUGH THE BULK OF EARLY MORNING INSOLATION
THERE ARE A FEW REMAINING NEW CELLS DEVELOPING BUT THEY ARE FAIRLY
NARROW CORE AND MOVING RAPIDLY ENOUGH TO NOT POSE MUCH OF A FF
THREAT AT THIS TIME INDIVIDUALLY SPEAKING.  HOWEVER...IT IS THE
STRENGTHENING OF LOW TO MID-LEVEL FLOW AS THE MCV LIFTS NORTH AND
TIGHTENS HEIGHT FIELDS WITH THE TIGHTLY CURVED 7-5H SYNOPTIC RIDGE
ORIENTED ALONG THE UT/AZ BORDER THAT HAS PROVIDED MODERATE DPVA
AND MID-LEVEL MOISTURE CONVERGENCE TO ENHANCE BAND AND DEVELOPED
ELEVATED CBS ACROSS SOUTHERN MOJAVE INTO YAVAPAI COUNTY. CURRENTLY
CELL MOTIONS ARE SUFFICIENT BUT THERE MAY BE SOME REPEAT TRACKS TO
COMPOUND TOTALS FROM .5-1" TO 1-1.5" OVER THE NEXT 1-3 HOURS.

OF GREATER CONCERN IS CONVECTIVE INITIATION IN THE AREAS NOT
AFFECTED BY CLOUD COVER ACROSS SOUTHWEST UT/NW AZ AND INTO THE
CENTRAL MOGOLLON RIM REGION WHERE TEMPS HAVE RISEN INTO THE 80S
WITH TDS IN THE MID 50S...THOUGH LOWER ELEVATIONS IN SE NV NEAR
THE ARROW CANYON, MORMON AND VIRGIN RANGES HAVE SEEN TEMPS TO THE
UPPER 90S AND TDS IN THE UPPER 50S TO 60S.  AS SUCH INSTABILITY
HAS RISEN OVER 2000 J/KG BUT REMAINS SLIGHTLY CAPPED BUT IS
ERODING.  FURTHER EAST INTO THE COLORADO TO KAIBAB PLATEAU HAS
SEEN SOME TCU WHERE THE CAP IS A BIT LESS THOUGH INSTABILITY IS
ALSO A BIT WEAKER TOO.  WHILE THE LOW LEVELS SHOW INVERTED V IN
THE RAOBS...MODEST MID-LEVEL MOISTURE REMAINS FOR TPWS OVER .9"
AND UP TO 1.2" FURTHER WEST...PROVIDING SUFFICIENT IF ONLY ABOUT
150 TO 175% OFF NORMAL FOR CELLS TO PRODUCE HEAVY RAIN.  LOWER TPW
AREAS ARE ALSO CLOSER TO THE RIDGE AXIS AND HAVE GREATER
ANTICYCLONIC MST CONVERGENCE AS WELL AS LIMITED CELL MOTIONS AND
PROPAGATION VECTORS.  THIS SHOULD ALLOW FOR INCREASED TOTALS
ESPECIALLY OVER N MOJAVE TO NW COCONINO COUNTIES OVER THE NEXT 3-4
HRS.  TOTALS OF 1-2" ARE LIKELY IN THIS AREA WITH SOME POSSIBLE
3"+ OR EVEN GREATER.

THOUGH A BIT LESS CERTAIN WITH REDUCED MID-LEVEL CONVERGENCE BUT
STRONG MTN UPSLOPE CIRCULATION WILL EXIST OVER SW UT AND HAVE
INCLUDED THE REGION IN THE AREA OF CONCERN BUT BELIEVE FF THREAT
WILL INCREASE IN THE 21-00Z TIME FRAME.

GALLINA

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

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

LAT...LON   38331189 38211142 37691163 37331182 36501191
            35821157 35131100 34731060 34361075 34351124
            34111297 34301373 34761437 35251476 36151511
            37081509 37741466 37651354 38021278