Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Aug 25 2025 00:32:53

AWUS01 KWNH 250032
FFGMPD
NVZ000-CAZ000-ORZ000-250600-

Mesoscale Precipitation Discussion 0996
NWS Weather Prediction Center College Park MD
831 PM EDT Sun Aug 24 2025

Areas affected...Sierra Nevada...Western and Central NV

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

Valid 250030Z - 250600Z

SUMMARY...Monsoonal showers and thunderstorms will continue
through the evening hours across the Sierra Nevada and portions of
the Great Basin. Additional areas of flash flooding will still be
likely with localized burn scar impacts still a concern over the
next few hours.

DISCUSSION...The late-day visible satellite imagery shows an
expansive area of monsoonal showers and thunderstorms impacting
the Sierra Nevada and interior portions of the Great Basin
including central and western NV.

A fair amount of surface-based instability remains in place across
central NV in particular, with an axis of instability extending
westward back into the northern Sierra Nevada. SBCAPE values are
on the order of 1000 to 2000+ J/kg, and there are some 3-hour
SBCAPE differentials across central NV of +800 to +1000 J/kg which
suggests that there are corridors of untapped instability that
will help sustain the ongoing convective threat for at least a few
more hours.

Deep monsoonal moisture remains in place as evidenced by the
latest CIRA-ALPW data which shows significant concentrations of
moisture in the mid to upper levels of the vertical column. The
00Z RAOB sounding from KREV depicted a PW of 0.96 which is again
near a daily record.

This moisture and instability coupled with upslope flow into the
terrain along with localized outflow boundary collisions over the
plateau areas of central and western NV favor clusters of
monsoonal convection persisting through the evening hours.

Given the high moisture environment, rainfall rates up to 1.5
inches/hour will still be possible, with some additional isolated
rainfall amounts of 2 to 3 inches possible which is supported by
recent runs of the experimental WoFS guidance. Generally these
additional rains are likely to foster some additional scattered
areas of flash flooding over the next few hours, and there will
continue to be concerns for localized burn scar impacts.

Orrison

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!6nixlvhIh_I9jdS5427KRxaRq7kuX1VCkuKYunDEDak_uiH_xxLUbjJCLFgMieSFnEYN=
fADW2bw8vIMgwXfOvgvT0Sk$  for graphic product...

ATTN...WFO...EKA...HNX...LKN...MFR...REV...STO...VEF...

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

LAT...LON   42022197 41862065 40971920 40761788 40971643=20
            40831473 40151416 39351460 38141624 37101747=20
            36721851 37021921 37641975 38442030 39622075=20
            39862096 40302126 40892193 41132253 41122298=20
            41502321 41922278=20

=3D =3D =3D
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