Weather Alerts
Frost Advisory issued December 10 at 7:02PM PST until December 11 at 9:00AM PST by NWS San Francisco CA
* WHAT...Temperatures as low as 36 will result in frost formation.
* WHERE...The East Bay Hills and Valleys, Most of San Benito County
and the Cholame Hills in Southeast Monterey County, North Bay
Interior Valleys, Eastern Santa Clara Hills, and Southern Salinas
Valley/Arroyo Seco and Lake San Antonio.
* WHEN...From midnight tonight to 9 AM PST Wednesday.
* IMPACTS...Cold conditions will be hazardous to sensitive
populations such as unhoused individuals. Cold Conditions can lead
to hypothermia with prolonged exposure.
Hydrologic Outlook issued December 10 at 2:01PM PST by NWS San Francisco CA
ESFMTR
A SERIES OF STORMS WILL BRING PERIODS OF RAINFALL TO THE REGION
LEADING TO POTENTIALLY RAPID RISES ON AREA CREEKS AND STREAMS
* WHATA series of storms over the next week will bring periods
of light to moderate rainfall to the region. The first in the
series of storms is a shortwave trough that will move into the
North Bay Wednesday evening and slide south across the region
Wednesday night into Thursday. Confidence has increased
significantly with this system and it is expected to bring light
rain across the North Bay and the San Francisco Bay Area. The
higher elevations of the North Bay will likely see around a half
an inch of precipitation while North Bay valleys see around a
quarter of an inch. Bay Area locations south of the Golden Gate,
including the Santa Cruz Mountains, will see a tenth to a
quarter of an inch. Less than a tenth of an inch of rain is
forecast across the Central Coast.
A stronger, more significant rainfall event is anticipated to
impact the region Friday and Saturday. This second system is a
significantly stronger low pressure system accompanied by a
moderately strong cold front. The latest model guidance depicts
rainfall beginning Friday evening in the North Bay and
progressing southward across the Bay Area and Central Coast
overnight into Saturday. While we expect these totals to
change a bit, current solutions bring 3 to 5 inches of
precipitation to the North Bay coastal range and 1 to 2.5
inches to the North Bay Valleys, 0.5 to 1 inch in the Bay
Area, and Monterey Bay region, 1 to 2 inches across the Santa
Cruz and Santa Lucia mountain range, and a trace to 0.25
inch over the interior portions of Monterey and San Benito
counties. Showers will linger into Sunday.
Area streams and creeks will only see a slight to moderate
rise with the first storm, and while streams are expected to
stay below action/monitor stage with this storm it will prime
the soils for quicker and more noteworthy rises with
subsequent storms. The second stronger and wetter storm will
result in greater and more rapid rises on small creeks,
streams and rivers.
Main stem rivers are currently forecast to remain below flood
stage, however the 10% probability of exceedance (very low
chance) show GUEC1- Russian River at Guerneville (10%), SHEC1-
Napa near Saint Helena (9%), and APCC1- Napa near Napa (7%)
may rise slightly above minor flood stage on Saturday. A few
other rivers to keep an eye on that show higher probability of
reaching Action/Monitor or Minor flood stage according to the
latest CNRFC forecast are MWEC1 - Mark West Creek at Mirabel
Heights has a 70% probability of reaching Action/Monitor Stage
and a 45% probability of reaching Minor flood stage on
Saturday. CTIC1 - Laguna De Santa Rosa at Stony Pt Rd near
Cotati has a 64% probability of reaching Action/Monitor
Stage and a 41% probability of reaching Minor flood stage on
Saturday. GEYC1- Russian River at Geyserville has a 27%
probability of reaching Action/Monitor Stage and a 14%
probability of reaching Minor flood stage on Saturday.
* WHERESonoma and Napa Counties. Latest model guidance suggests
the North Bay will receive the greatest accumulation of
precipitation with the heaviest rainfall expected over the
North Bay coastal range and mountains.
* WHENFriday through Sunday. Light to Moderate rainfall expected
over the North Bay Friday and Saturday. The heaviest rainfall
accumulation is expected Friday and Saturday. Showers will
linger into Sunday.
* ADDITIONAL DETAILS...In addition to the moderate rainfall and
localized ponding of water in low-lying or poorly drained areas,
such as freeway offramps. Locally strong and gusty winds may
result in downed trees, and potential power outages.
Confidence is high that we will receive rainfall from this system
however, confidence is moderate with respect to the exact location
and timing of the most intense rainfall. Details regarding this
storm will likely change as the system nears. Therefore, stay
tuned to the latest forecast for the most up to date weather
information.