Mesoscale Precipitation Discussion 0681
NWS Weather Prediction Center College Park MD
225 PM EDT Fri Aug 17 2018

Areas affected...Central/Northern AZ...Western NM

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

Valid 171823Z - 180023Z

Summary...Slow-moving showers and thunderstorms with heavy
rainfall rates are expected this afternoon. Some flash flooding
will be possible.

Discussion...The latest GOES-16 visible satellite imagery is
showing some convective initiation locally over the higher terrain
of central/northern AZ, especially over the Mogollon Rim, as well
as areas of western NM. Over the next few hours, as strong diurnal
heating continues and boundary layer instability increases, expect
more coverage of showers and thunderstorms with a focus on the
orographically favored areas. However, the expectation for this
afternoon is that the coverage will not be quite as robust as
yesterday owing to the fact that the thermodynamic profiles are
overall a tad weaker by comparison.

Nevertheless, the PWATS across the region remain rather high and
are generally a solid 1.5 to 2 standard deviations above normal.
This will be conducive to driving enhanced rainfall rates that may
approach 2 inches/hr. The steering flow across the region is quite
weak, and so all of the convective cells should be very
slow-moving which will be capable of enhancing the storm totals on
a very small scale. On the other hand, it should be noted that
with such weak shear profiles/mid level flow, the convection will
be highly disorganized and of a pulse type where individual cells
will not be sustainable for an extended period of time.

A consensus of the 12Z hires guidance and recent HRRR runs support
the potential for as much as 2 to 3 inches locally through 00Z.
This may result in some flash flooding. Will continue to monitor
through the afternoon.

Orrison

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

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

LAT...LON   36941178 36931023 36720919 36260816 35550733
            34500706 33710716 32890751 32500826 33120953
            33531047 33791159 33981249 34271333 35051417
            36071408 36651359 36871277