Mesoscale Precipitation Discussion 0992
NWS Weather Prediction Center College Park MD
636 AM EDT Sun Oct 21 2018

Areas affected...In and near southern NV

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

Valid 211035Z - 211635Z

Summary...Showers and thunderstorms have expanded in coverage in
and near Las Vegas NV.  Hourly rain totals of 0.5-1" and local
amounts of 1-2" are expected over the next several hours.

Discussion...Showers and thunderstorms are thriving to the
northeast of an upper level low located over southern CA. 
Precipitable water values are 0.5-1" per recent GPS data, with
surface dew points rising into the low to mid 50s.  MU CAPE values
are 500-1500 J/kg have been pushing northward from western AZ and
southeast CA near and south of a 700 hPa trough moving northward
into the area.  Effective bulk shear of 20-45 kts lies across the
area per SPC mesoanalyses.

With the expansion of showers and thunderstorms, expect
precipitable water values to rise another 0.25" and for rainfall
efficiency to slightly increase.  Radar estimates have advertised
localized areas of 0.5"+ so far, which could enhance further,
particularly if any mesocyclones form within this environment,
which is supported by the available bulk shear.  Short periods of
training could also lead to these rain rates/totals.  Hourly rain
totals of 0.5"+ should continue, with local amounts of 1-2"
expected over the next several hours as activity spreads northward
ahead of the upper low and 700 hPa trough.

Roth

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

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

LAT...LON   38061458 37781357 37021318 35391319 35021329
            35061444 34811532 35801603 35851612 37191643
            37951562