Mesoscale Precipitation Discussion 0577
NWS Weather Prediction Center College Park MD
519 PM EDT Wed Aug 01 2018

Areas affected...SW Utah into Mogollon Rim of Arizona, and SW New
Mexico

Concerning...Heavy rainfall...Flash flooding possible

Valid 012117Z - 020240Z

Summary...Nearly stationary thunderstorms along areas of elevated
terrain in the Desert Southwest may cause localized heavy rainfall
and flash flooding. Rain rates of 1-2 in/hr will be possible.

Discussion...GOES-15 visible and IR satellite channels show a
concentrated area of convective development from southwest Utah,
arcing back to the southeast along the Mogollon Rim in Arizona,
and into mountainous regions of west-central and southwest New
Mexico. These thunderstorms were developing in a modestly unstable
and moist environment, but these values as analyzed by the RAP (PW
around 0.8-1.0 inches; MLCAPE around 500 j/kg) are not
exceptionally high. The PW values are closer to the 60-70th
percentile for this time of year. However, they are high enough to
support locally heavy rainfall. The primary driving factor for
flash flood risk will be very slow storm motions. A large
mid-upper level anticyclone is centered on central Arizona, and
there is a weakness in the deep layer mean flow right over the
outlined region. Therefore, storms are likely to be nearly
stationary and could remained tied to terrain features for a few
hours with only a slow drift. This could lead to rain rates of 1-2
in/hr and localized flash flooding. The threat should wane with a
loss of daytime heating around 03Z.

Lamers

ATTN...WFO...ABQ...EPZ...FGZ...GJT...PSR...SLC...TWC...VEF...

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

LAT...LON   37981183 37111088 35851062 34770989 34720886
            35140777 34220668 32550761 32640912 33631102
            35021275 36811358 37931313