539
AWUS01 KWNH 010025
FFGMPD
AZZ000-UTZ000-NVZ000-010600-

Mesoscale Precipitation Discussion 1163
NWS Weather Prediction Center College Park MD
824 PM EDT Mon Aug 31 2026

Areas affected...Southwest Utah...Northwest Arizona...Ext
Southeast Nevada...

Concerning...Heavy rainfall...Flash flooding likely

Valid 010030Z - 010600Z

SUMMARY...Flash flooding risk likely to continue into early
overnight period as lingering cells track through areas already
affected with ongoing flooding.  Additional 1-2" in spots as
convective lines still show some repeating potential in the near
term.

DISCUSSION...Current fading visible, 3.9um SWIR loops from GOES-E
and RADAR mosaic continue to show SW to NE bands of thunderstorms
across SW UT and far NW AZ tracking eastward under the influence
of the exiting compact shortwave and negative tilt trof currently
analyzed along the central NV/UT border.  This places the
convection generally behind the strongest dPVA/forcing; however,
low level flow continues to respond out of the Lower Colorado
river Valley through SW UT toward the core of the height-falls
across central UT.  Higher theta-E air continued to replenish the
mixed air with pool of remaining conditionally unstable air
centered along the corner of NV/AZ/UT with 2000 J/kg of MLCAPE
though there is some building capping with loss of solar
heating... as noted with diminishing cu field.  Still, the
15-20kts of flow from the unstable air intersecting with the
ongoing convection will support some back-building and perhaps
isolated new development along the convergent upstream edge
through the Grand Canyon region of northwest AZ into the Kaibab
Forest Plateau.

Given total Pwats remain in the 1.5" range, mostly fed below
700mb, efficient cells currently near 1.25-1.5" will slowly weaken
toward 1" and less with time and distance from remaining
unstable/moist air.  Still, favorable WSW to ENE propagation/cell
motions will support possible repeating in the short-term while
also tracking through areas already heavily affected by earlier
round today as well as multiple rounds over the weekend.  As such,
spots of additional 1-2" will likely result in a more widely
scattered reaggrivation of flash flooding across S UT and N AZ,
with some lower potential further north and east as the forcing
wave continues to exit the region.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

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

ATTN...RFC...RSA...STR...NWC...

LAT...LON   39571205 39311059 38461044 37361079 36501160
            35901260 35961397 36931503 37811509 38681398