Mesoscale Precipitation Discussion 0587
NWS Weather Prediction Center College Park MD
844 PM EDT Thu Aug 02 2018

Areas affected...Southwest UT...Southern NV...Northwest AZ...

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

Valid 030043Z - 030630Z

SUMMARY...Ongoing convection seeking out remaining instability
within favorable upper level ascent region but will deminish with
loss of daytime heating.

DISCUSSION...Goes-W Visible/IR imagery show numerous clusters of
convective development with small core overshooting tops
throughout, especially across Mohave county, AZ into SW UT where
deepest/coolest tops reside in the range of -65 to -70C.  Blended
TPW and GPS network also depicts slowly increasing moisture from
the Lower Colorado River Basin lifting into the Vegas metro and
northeastward into SW UT.  This is in response to the advancement
of a subtle/flat shortwave feature crossing out of the Central
Sierra into the Range/Basin area of central NV.

In addition to the DPVA from the wave, highly anticyclonically
curved jet and outflow channel exists especially further north
into UT/Central NV, where some organizational/deforamtion
zone/baroclinic leaf pattern is starting to emerge suggesting a
bit of training/increased moisture pooling from N Nye to White
Pine to Juab county...while deepest moisture remains in the lower
valley, GPS indicates increases to near 1" (00z SLC sounding to
1.03")which is in the 175-200% or in the 90-95th percentiles,
providing increased efficiency to cells along the deformation
band.  While instability is a bit less than further south, values
in the 500-1000 J/kg range should be sufficient to maintain heavy
rainfall threat.   HRRR suggests this band will advance westward
but will also build south into S NV, and with slower deep cloud
bearing flow, may align favorably into SW UT for some additional
training after 03z as well.  Deeper moisture to 1.5" and
instaiblity over 1500 J/kg, are more likely to support deeper and
more efficent rainfall production making flash flooding to
continue and be likely through the evening and early overnight
hours. 

Gallina

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

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

LAT...LON   40421275 40001213 39191202 37821234 37091250
            36091286 35011353 35371489 36601578 37251637
            38581745 39671534 40221409