Special Weather Statement, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1125 PM PST Sat Jan 7 2017

...Potential for flooding from late Saturday evening through
Sunday evening...
...Strong winds forecast Saturday night and Sunday...

.SYNOPSIS...Rainfall will become widespread overnight and rainfall
intensity will increase. Periods of heavy rain are expected tonight
through Sunday. In addition, strong and gusty southerly winds will
continue through Sunday. Strongest winds will be from late
Saturday night through early Sunday afternoon. Rain will slowly
taper off from north to south from last Sunday afternoon through
Sunday night. Periods of rain will continue into Monday night
along with cooler temperatures. The next significant storm system
will spread rain over our region Tuesday and Tuesday Night with
the potential for more heavy rain.

&&

.DISCUSSION...As of 9:15 PM PST Sunday...Rainfall and winds
decreased in most areas this afternoon and early evening. Since
early evening, rainfall has become more widespread, initially
around the Monterey Bay Area and now northward into portions of
the San Francisco Bay Area. This is consistent with model data
which indicates rainfall spreading northward overnight and
becoming heavy at times. Rain rates will be heavy at times south
of the Golden Gate for the remainder of the evening, with the
heaviest rain then expected to shift into the North Bay after
midnight. The band of heaviest rain will then shift slowly back to
the south during the day Sunday, back into the Santa Cruz
Mountains by midday and into the Santa Lucias in the afternoon.
Given that precipitable water values up near 2 inches are
approaching our coast at the present time, rain rates overnight
and through the day Sunday will be in excess of a half inch per
hour at times and may be as high as an inch or more per hour in
the coastal ranges. Rain totals through late Sunday look to be
about 2 to 4 inches at lower elevations and from 4 to 8 inches in
the coastal ranges, except locally up to 10 inches or more in the
Santa Cruz and Santa Lucia Mountains. A flash flood watch is in
effect for much of our area through late Sunday and there is a
potential for flash flood warnings later tonight through Sunday
based on latest model guidance. In addition, some of the larger
rivers are forecast to reach or exceed bankfull on Sunday or
Sunday Night. The latest forecast numbers have just come in from
the River Forecast Center and these numbers show at least minor
flooding on Sunday afternoon on the Napa River near Saint Helena
and the Guadalupe River in Santa Clara County above Almaden
Expressway. A flood warning has just been issued for these two
forecast points.

Rainfall will taper off from north to south from late Sunday
afternoon through Sunday Night.

In addition to heavy rain and flooding potential, this current
storm will continue to generate locally strong and gusty winds.
Southerly winds will increase by midnight and then remain strong
through at least early Sunday afternoon. Gusts of 50 to 60 mph are
likely in the hills and locally near the coast, with 40 to 50 mph
wind gusts possible for other lower elevation locations. High wind
warnings and wind advisories blanket much of our forecast area and
remain in effect through mid-afternoon Sunday.

Periods of rain will continue Monday and Monday night, mainly
across the San Francisco Bay Area. The next organized system with
potentially heavy rain and strong winds is due in on Tuesday and
Tuesday Night. The models are now indicating a decreased
likelihood of strong storms for the remainder of next week.

&&

.AVIATION...As of 10:20 PM PST Saturday...Moderate to heavy rain
associated with the atmospheric river is over the MRY Bay Area and
will be shifting north into the SFO Bay Area after 08Z and the
North Bay after 10Z. This band will then shift back to the south
late Sunday morning back towards the MRY Bay Area by Sunday
afternoon. Winds over the waters are picking up into gale force
territory so there could be gusts to 40 kt after 12Z. Satellite
image shows lightning strikes offshore that may hold together as
it comes ashore. Therefore have added VCTS for SFO and OAK 13Z
through 19Z and it may need to be extended into the afternoon. Winds
will decrease from north to south during the afternoon.

Vicinity of KSFO....MVFR cigs. A period of moderate rain is
expected from 08Z-12Z then become light as the main rain band
shifts north of the area. Rain should pick up after 19Z as the
band shifts back to the south. Possible thunderstorms in the
vicinity after 13Z. Southeast winds 15-20 kt gusting to 30 kt
after 10Z increasing to 25-30 kt gusting to 40 kt after 13Z with
low level wind shear. Wind decreasing after 23Z with rain turning
to showers.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...MVFR cigs. Moderate rain will shift
north of the area in the next hour or two. Light rain will then
prevail through Sunday morning then intensify Sunday afternoon.
South to southeast winds 15-20 kt gusting to 25 kt increasing to
25-30 kt with gusts to 45 kt by morning in the Salinas Valley
with low level wind shear.

&&

.HYDROLOGY...Many creeks and rivers are expected to flood with
this weekend's storm. With much of the rainfall expected to
strongly influence the coastal ranges from Sonoma County down
through Monterey County, expect Coast Range drainages to be hit
hard and with the first pulse of strong rain late Saturday.
Smaller creeks will likely crest in the overnight hours of
Sat/Sun. Larger rivers such as the Russian, Napa, Guadalupe,
Carmel, and Pajaro will crest on Sunday or Monday. At this point,
forecast simulations of streamflow put the following forecast
locations above flood stage this weekend/early next week: Russian
River in Guerneville, Napa River near St. Helena, and San Lorenzo
River in Felton. It is likely that many tributaries to both the
Russian and Napa Rivers will flood as well. Other creeks and
rivers in the Santa Cruz Mountains and Santa Lucia Mountains will
likely flood...stay tuned for specific information in Flash Flood
Watches, Warnings and Advisories for detailed information on flood
prone locations.

It is also likely that burn scars such as the Loma and Soberanes
will experience debris flows where rainfall rates exceed 1" per
hour. We expect these rates to develop, possibly overnight
Saturday and into Sunday. Debris flows, mudslides, and general
road-cut slope instability is highly likely in Coast Range
mountain settings outside the burn scars, although exact timing,
magnitude, and location is impossible to predict. Take heed of
local Public Works, Emergency Management, and CHP notifications to
steer clear of these areas.

Widespread urban flooding is expected from excessive rainfall,
clogged storm drains, and backwatered drainage systems. Avoid
driving through flooded roadways, and adhere to all road hazard
notifications. Drive slowly to avoid hydroplaning.

&&

.MARINE...as of 10:00 PM PST Saturday...A 995 mb low off the
northern California coast will lift northeast on Sunday. Moderate
to strong southeasterly winds will prevail through Sunday then
decrease and switch to southwest Sunday night. Another system will
affect the area on Tuesday with wind and seas increasing again.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...Wind Advisory...Most low elevations in the San Francisco Bay Area and
              Monterey Bay Area
             High Wind Warning...Elevations above 1000 feet across the San Francisco
              Bay Area and the Santa Lucias
             Flash Flood Watch...Most of the San Francisco Bay Area and Monterey Bay Area
             SCA...Mry Bay until 3 AM
             SCA...Mry Bay until 3 AM
             SCA...Pt Arena to Pt Reyes 0-10 nm until 3 AM
             SCA...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM
             SCA...Pigeon Pt to Pt Pinos 0-10 nm until 3 AM
             SCA...Pt Arena to Pigeon Pt 10-60 nm until 3 AM
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM
             GLW...Mry Bay from 3 AM
             GLW...Pigeon Pt to Pt Pinos 0-10 nm from 3 AM
             GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm
             GLW...Pt Arena to Pt Reyes 0-10 nm from 3 AM
             GLW...Pt Reyes to Pigeon Pt 0-10 nm from 3 AM
             GLW...Pt Arena to Pigeon Pt 10-60 nm from 3 AM
             GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 3 AM
             SCA...SF Bay

&&

PUBLIC FORECAST: Dykema
AVIATION: W Pi
MARINE: W Pi

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HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
112 PM PST SAT JAN 7 2017

CAZ006-505>513-516>518-528>530-082115-
SAN FRANCISCO-
COASTAL NORTH BAY INCLUDING POINT REYES NATIONAL SEASHORE-
NORTH BAY INTERIOR VALLEYS-NORTH BAY MOUNTAINS-
SAN FRANCISCO BAY SHORELINE-SAN FRANCISCO PENINSULA COAST-
EAST BAY INTERIOR VALLEYS-EAST BAY HILLS AND THE DIABLO RANGE-
SANTA CRUZ MOUNTAINS-SANTA CLARA VALLEY INCLUDING SAN JOSE-
SOUTHERN SALINAS VALLEY/ARROYO SECO AND LAKE SAN ANTONIO-
SANTA LUCIA MOUNTAINS AND LOS PADRES NATIONAL FOREST-
MOUNTAINS OF SAN BENITO COUNTY AND INTERIOR MONTEREY COUNTY
INCLUDING PINNACLES NATIONAL MONUMENT-
NORTHERN SALINAS VALLEY/HOLLISTER VALLEY AND CARMEL VALLEY-
NORTHERN MONTEREY BAY-SOUTHERN MONTEREY BAY AND BIG SUR COAST-
112 PM PST SAT JAN 7 2017

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF WESTERN
CALIFORNIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT
AN ATMOSPHERIC RIVER EVENT IS SLATED TO AFFECT THE SAN FRANCISCO
BAY AREA AND THE CENTRAL COAST THIS WEEKEND. HEAVY RAINS ARE
EXPECTED TO BEGIN TONIGHT AND CONTINUE THROUGH SUNDAY.
HIGH WIND WARNINGS ARE IN EFFECT FOR THE HIGHER TERRAIN LOCATIONS
AND A WIND ADVISORY IS IN EFFECT FOR COASTAL LOCATIONS AS WELL AS
SOME INLAND VALLEYS. SEE SFONPWMTR WWUS76 KMTR FOR DETAILED
INFORMATION.

A FLASH FLOOD WATCH IS IN EFFECT FOR HIGHER TERRAIN AREAS AS WELL
AS SOME COASTAL AREAS. SEE SFOFFAMTR WGUS55 KMTR FOR DETAILED
INFORMATION.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY
HEAVY RAIN AND GUSTY WINDS TO CONTINUE SUNDAY. RAINFALL AMOUNTS
WILL BE GREATEST ACROSS THE COASTAL MOUNTAIN RANGES WHERE UPWARDS
OF 10 TO 12 INCHES ARE POSSIBLE THROUGH MONDAY MORNING. A FLASH
FLOOD WATCH IS IN EFFECT FOR HIGHER TERRAIN AREAS AS WELL AS SOME
COASTAL AREAS. SEE SFOFFAMTR WGUS55 KMTR FOR DETAILED
INFORMATION. THE FLASH FLOOD WATCH IS IN EFFECT THROUGH SUNDAY
AFTERNOON. SEE SFOFFAMTR WGUS55 KMTR FOR DETAILED INFORMATION.

RAIN IS EXPECTED TO TAPER OFF ON MONDAY BUT ANOTHER STORM IS
EXPECTED TO AFFECT THE AREA ON TUESDAY. A VERY ACTIVE WEATHER
PATTERN IS ANTICIPATED TO PERSIST THROUGH THE REST OF THE WEEK.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
846 PM PST SAT JAN 07 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0802 PM     FLASH FLOOD      5 WNW BIG SUR VILLAGE   36.30N 121.88W
01/07/2017                   MONTEREY           CA   LAW ENFORCEMENT

0819 PM     FLASH FLOOD      2 ESE MARINA            36.67N 121.77W
01/07/2017                   MONTEREY           CA   LAW ENFORCEMENT

            WATER COVERING RESERVATION ROAD.

0826 PM     NON-TSTM WND DMG 3 NW PRUNEDALE          36.83N 121.69W
01/07/2017                   MONTEREY           CA   LAW ENFORCEMENT

            OAK TREE DOWN ACROSS ENTIRE ROADWAY

0826 PM     NON-TSTM WND DMG 3 W MILL VALLEY         37.90N 122.60W
01/07/2017                   MARIN              CA   LAW ENFORCEMENT

            TREE BLOCKING ROADWAY APPROX 7 MI FROM HWY 1

&&

MMEHLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
920 PM PST SAT JAN 07 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0904 PM     FLOOD            5 SSE BERKELEY          37.80N 122.27W
01/07/2017                   ALAMEDA            CA   LAW ENFORCEMENT

            FLOODING 880N AND JACKSON ST

&&

MMEHLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1032 PM PST SAT JAN 07 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1006 PM     DEBRIS FLOW      4 NNE SANTA CRUZ        37.03N 122.01W
01/07/2017                   SANTA CRUZ         CA   LAW ENFORCEMENT

            MUD AND ROCKS IN ROADWAY

&&

MMEHLE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1147 PM PST SAT JAN 07 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1039 PM     NON-TSTM WND DMG 6 SSW BEN LOMOND RAWS   37.05N 122.21W
01/07/2017                   SANTA CRUZ         CA   UTILITY COMPANY

            TREES BLOCKING ROAD AND POWERLINES DOWN

&&

MMEHLE

Special Weather Statement
National Weather Service San Francisco CA
1249 AM PST SUN JAN 8 2017

CAZ517-528-530-080915-
Santa Lucia Mountains and Los Padres National Forest CA-
Northern Salinas Valley/Hollister Valley and Carmel Valley CA-
Southern Monterey Bay and Big Sur Coast CA-
1249 AM PST SUN JAN 8 2017

...SIGNIFICANT WEATHER ADVISORY FOR WEST CENTRAL MONTEREY COUNTY
UNTIL 115 AM PST...

At 1247 AM PST, Doppler radar was tracking a strong thunderstorm 12
miles southwest of Del Monte Forest, or 15 miles southwest of
Monterey, moving northeast at 40 mph.

Nickel size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Seaside, Monterey, Marina, Pacific Grove, Carmel-By-The-Sea, Del
Monte Forest, Del Rey Oaks, Sand City.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3658 12206 3671 12182 3653 12164 3642 12182
      3636 12201
TIME...MOT...LOC 0847Z 235DEG 41KT 3645 12210

MM