Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Aug 26 2025 14:55:20

AWUS01 KWNH 261455
FFGMPD
CAZ000-261850-

Mesoscale Precipitation Discussion 1006
NWS Weather Prediction Center College Park MD
1054 AM EDT Tue Aug 26 2025

Areas affected...San Joaquin Valley into Sierra Nevada foothills

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

Valid 261450Z - 261850Z

SUMMARY...Slow moving thunderstorms will pose a threat for
isolated flash flooding across portions of the San Joaquin Valley
into the Sierra Nevada foothills over the next 2-4 hours. Rainfall
rates of 1-2 in/hr will be possible.

DISCUSSION...GOES West infrared satellite imagery and GLM data
showed scattered thunderstorms expanding in coverage over the San
Joaquin Valley and Sierra Nevada foothills as of 1430Z, within
about 50 miles of Madera. Cells were located along a weak
mid-level shear axis inferred on water vapor imagery, emanating
from a vorticity maximum over west-central NV. The storms were
likely elevated in nature, rooted just above 700 mb given RAP
analysis point soundings, within a small region of weak
instability ranging from 250 to just over 500 J/kg (via 14Z
RAP/SPC mesoanalysis). Precipitable water values were very
anomalous across central CA with standardized anomalies of 2 to 3+
according to 12Z area soundings and short term GFS forecasts.

With RAP-derived LFC-EL layer winds averaging near 5 kt, cell
motions have been slow and MRMS-derived rainfall rates have been
1-2 in/hr over portions of Fresno and Madera counties. Scattered
thunderstorms are expected to continue over the next few hours but
due to a lack of stronger winds aloft, storm organization should
remain poor and new cell development will be aided by thunderstorm
outflows. Localized flash flooding will remain possible over the
next 2-4 hours. Trends will be monitored for updates as needed
with the onset of better surface heating and turbulent mixing
within the boundary layer potentially disrupting ongoing activity.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!8sfJDnoD6T2oMTfFWM8mVKZEd0QpDHKC1kOgY7cujgR-4eFyevQO7XgMIUZFqEULC3Vx=
CasgZXSdzkQ61BPG6-5h_Po$  for graphic product...

ATTN...WFO...HNX...STO...

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

LAT...LON   38222076 37642001 37131943 36481908 36121922=20
            35971958 36071985 36692046 37222088 37862113=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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