Graphic for MPD #0081

Mesoscale Precipitation Discussion 0081
NWS Weather Prediction Center College Park MD
505 PM EST Wed Mar 06 2024

Areas affected...Coastal Ranges of Central and Southern CA

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

Valid 062205Z - 070405Z

SUMMARY...A localized threat of runoff problems and flash flooding
will exist through this evening across portions of the coastal
ranges and interior foothills of central and southern CA from
areas of heavy showers.

DISCUSSION...The latest GOES-W satellite imagery shows a rather
vigorous mid-level shortwave trough and compact area of low
pressure offshore of the coastal ranges of central and southern CA
advancing gradually off to the east. This energy coupled with the
diurnal heating cycle has been fostering the development and
expansion of heavy shower activity over the last couple of hours
for areas south of the Bay Area, and especially for areas south of
Monterey down toward San Luis Obispo and Santa Barbara counties.

Steepening mid-level lapse rates coupled with DPVA/forcing aloft
and low-level convergence out ahead of the approaching low center
and associated front should maintain concerns heading through the
late afternoon and early evening hours for locally heavy showers
and even a few thunderstorms. MUCAPE values along the coast have
risen to as high as 500 J/kg, and this in conjunction with
somewhat favorable moisture convergence aligning itself down near
the Transverse Range ahead of the surface low should help yield
locally heavy rainfall rates that will also have some assistance
with orographic ascent over the terrain.

The 12Z/18Z HREF guidance shows rather good agreement in seeing
some banded convective showers advancing inland over the
Transverse Range, and perhaps reaching the Peninsular Range by
late this evening. Furthermore, the HREF guidance does show rather
high probabilities (50% to 70%) of seeing rainfall rates exceed a
0.50"/hour over the upslope areas of the higher terrain, and
already some of the more discrete convective showers farther north
in Monterey County have been producing 1 inch totals in less than
30 minutes.

Given the current radar and satellite trends, there should be a
further increase in coverage of convective showers over the next
few hours with heavy rainfall rates. Expect some localized
rainfall totals of 1.5 to 2.5 inches to be possible by late this
evening where any of the more organized/focused bands of
convection set up. This should favor at least some localized
runoff concerns with an isolated threat for flash flooding, and
the potential for spotty debris flow/mudslide activity.

Orrison

ATTN...WFO...HNX...LOX...MTR...SGX...STO...

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

LAT...LON   37402221 37292130 36692091 35682018 34881935
            34791879 34401806 33821743 33421716 32861690
            32591719 32731747 33361798 33801873 34161953
            34372042 34792081 35212092 35522130 36012172
            36402202 36732204 37052232
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Last Updated: 505 PM EST Wed Mar 06 2024