Key Messages:
*Parade of storm systems through next week
*Most impactful storm appears to be Monday into Tuesday
*Rainfall totals between today and Saturday: North Bay: 2"-6",
locally up to 9", rest of the Bay Area: 1-4", Central Coast:
0.25"-1.50", locally up to 5" in the Santa Cruz Mountains and
locally up to 3" along the Big Sur Coast
*Wind gusts up to 45 mph on Tuesday
*Life-threatening beach and ocean conditions linger into next week.
A widespread impactful system will move through the region Monday
afternoon through Tuesday afternoon. Rainfall totals up to 2.50" are
forecast for the higher terrain of the North Bay with a gradual
taper in rainfall amounts from north to south with higher rainfall
totals expected in higher terrain. The greatest impacts are expected
in the North Bay as portions of Marin, Napa, and Sonoma Counties
have been highlighted by the Weather Prediction Center (WPC) for a
marginal/at least 5% risk of rainfall exceeding flash flood guidance
between 4 AM Monday and 4 AM Tuesday. This means that isolatedflash
floods will be possible and that their nature will be localized and
primarily affecting places that can experience rapid runoff with
heavy rainfall. Fortunately, no mainstem river forecast points are
forecast to reach minor flood stage according to deterministic
forecasts; however, rivers and their creeks and streams will have no
problem responding quickly to rainfall. While it is too early to
issue any wind headlines, there is increasing probability of wind
gusts reaching or exceeding 45 mph during this system. Whether
southerly winds meet Wind Advisory criteria or not, soils
approaching saturation in addition to tree damage from last
weekend`s storms will allow for plentiful tree debris. Isolated
thunderstorms will also be possible with this system with the Storm
Prediction Center (SPC) highlighting all counties with the exception
of Monterey and San Benito for general or non-severe thunderstorms
between 4 AM Tuesday and 4 AM Wednesday. Remember
that lightning and flooding threats exist with all thunderstorms. An
ECMWF point sounding forecast for STS at 10 AM Tuesday shows that
the environment will be that of low CAPE and high shear, but that
the parcel will have to overcome a stablelapse rate in the
850-700 mb layer.
