Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Jan 05 2023 23:17:43

AWUS01 KWNH 052317
FFGMPD
CAZ000-060300-

Mesoscale Precipitation Discussion 0023
NWS Weather Prediction Center College Park MD
616 PM EST Thu Jan 05 2023

Areas affected...Central California

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

Valid 052309Z - 060300Z

SUMMARY...A risk for widely scattered shallow thunderstorms
capable of localized hourly totals up to 1" over saturated grounds
will linger into the evening with a the possibility flash
flooding.=20

DISCUSSION...GOES-W WV suite depicts an elongated negative tilt
trof approaching the California coast from the eastern Pacific
with one vorticity sliding eastward; concurrently with a
speed/curvature max in the jetstreak across the central Sierra
Nevada Range, providing a broad area of divergence along/ahead of
the trof axis.  Surface Tds remain in the low 50s, steepening
lapse rates with cooling and modest mid to upper level drying is
supporting a wedge of enhanced SBCAPES of 500 J/kg along the coast
bleeding into portions of the Central Valley with 150-250 J/kg
analyzed as far north as Sutter/Yuba counties.  RAOB and RAP
soundings, suggest that saturation though remains in the low
profile (70-80%+ RH), so rainfall efficiency should be fairly high
even with low theta-E environment as supported by HRRR 15 minute
forecast totals of .3 to .5" could be expected with strongest
cores.=20=20=20

Given the cooling mid-level temperatures and the resulting
steepening lapse rates...the potential for a few convective cells
will linger into the early evening before the low levels begin to
stabilize.  The nature of the intense rainfall will be short in
duration (about 1 hr max) and may still result in possible
isolated to widely scattered flash flooding conditions given the
intense rates.  The greatest risk is if any of these cells would
form/track across recent burn scars; if so, debris flows would be
increasingly likely but the nature of the coverage does not allow
for that precision/ confidence that any cell may do this.=20

Bann

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4UaPM1JkcyV7xKO30ozjgFThMwmKuM0-tFazG2pgSHhqcAaUhJ2sJwGRS50BMrx1Flel=
Lm7ESuJoRHfji5WSYSIdtKo$  for graphic product...

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

ATTN...RFC...CNRFC...NWC...

LAT...LON   39022081 38192020 37861987 37181936 36741891=20
            36321851 35951845 35221835 34761878 34501950=20
            35681952 36541968 37652038 38682125=20

=3D =3D =3D
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