Flash Flood Warning 60, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
948 AM PST Mon Feb 20 2017

.SYNOPSIS...High impact event unfolding across the region this
Monday morning and will likely persist through the afternoon hours
as an atmospheric river takes aim at the central California coast.
Periods of heavy rainfall are expected, especially along the coastal
ranges, along with strong and gusty southerly winds through this
evening. These conditions will likely result in widespread flooding,
downed trees and power lines resulting in isolated to widespread
power outages. Flooding of area creeks, streams and low lying,
poorly drained areas can also be expected as well as rises on main-
stem rivers. The threat for rock/mud slides, shallow landslides and
debris flows in recent burn scar areas will also increase during the
next 12 to 24 hours. Rainfall and winds will taper off late tonight
into Tuesday. Cool and somewhat drier weather conditions are
expected during the second half of the work week.

&&

.DISCUSSION...as of 09:05 AM PST Monday...The much advertised and
talked about high impact event is now taking aim at the Central
Coast. Thus far, moderate to locally heavy rain has fallen since
last night. Highest rainfall amounts have occurred across the
North Bay, Santa Cruz Mountains and the Big Sur Coast. Amounts
range from 1 to 5 inches. Elsewhere, a general 0.25-1 inch have
occurred. Given the already full streams/creeks/river numerous
flooding reports have been coming in this morning.

Winds have been rather gusty overnight into this morning as well.
Highest gust thus far was 58 mph at Pacific Vista RAWS in Big
Sur. Other stations easily had gusts in excess of 30 mph.

For the rest of today/evening...not a lot has changed from the
overnight forecast. Models continue to show moderate to heavy
rainfall is still projected through this evening. Orographics will
heavily play into QPF over Santa Cruz Mts and East Bay Hills and
Big Sur Mts. For specifics see below. Winds are still expected to
increase this afternoon and the high wind warning still seems
warranted.

In short, if you are able to hunker down today and stay at home it
would be wise. If you do have to venture out today, use caution
and play it safe. Never cross any flooded roadways. Give the rain
that has already fallen and the expected additional rainfall
flooding is likely across the Bay Area through tonight. Follow
NWSBayArea social and on weather.gov for the latest watches and
warnings.

&&

.PREV DISCUSSION...as of 02:34 AM PST Monday...The latest
forecast models continue to indicate a band of heavy rainfall will
develop and become more narrow in focus somewhere between San
Francisco and the Big Sur coast. At this point, rainfall rates in
excess of 0.50"/hr and potentially as much as 1.00"/hr will be
possible, especially along the southwest facing slopes, which will
greatly increased the threat for flooding and flash flooding
where/when this boundary stalls. Current thinking is that the San
Mateo and Santa Cruz coast and points inland may be hardest hit
through the morning hours. However, given the rapidly developing
nature of this system, a jog north or south remains possible and
thus current trends will need to be closely monitored through the
morning. For additional information, feel free to read the latest
Mesoscale Precipitation Discussion from the WPC:
http://origin.wpc.ncep.noaa.gov/metwatch/metwatch_mpd_multi.php?md=00
60&yr=2017

Southerly winds out ahead of this system have also increased early
this morning with gusts in excess of 45 MPH over the Pacific and in
the highest peaks across the region. Expecting these winds to
further intensify through the afternoon and evening as surface low
pressure deepens offshore and races toward northern California/
southwest Oregon. Wind gusts of 60 MPH or greater will be possible
this afternoon and evening, mainly in elevations above 1000 feet and
along the coastal ranges. Downed trees and power lines will likely
result in isolated to widespread power outages through the day.
Thus, a High Wind Warning and Wind Advisory remain in effect through
late tonight.

A Flood Watch also remains in effect for the entire region through
tonight given the intense rainfall forecast over already saturated
soils. The combination of heavy rainfall and strong winds will also
result in an increased threat for rock/mud slides, shallow
landslides and debris flows in recent burn scar areas through this
afternoon. Through early Tuesday morning, storm total rainfall
amounts of 1.50-2.00" will be possible for inland San Benito and
Monterey County with amounts less than 1.00" possible in the rain
shadowed valley locations. Santa Clara Valley, also rain shadowed
can expect between 1.25-3.00" (higher amounts closer to the
foothills and lesser possible in downtown San Jose). Inland East
Bay, San Francisco Bay Shoreline, and North Bay Valley areas can
expect 2.25-3.50", locally higher if the heavy band of precipitation
makes a shift to the north. Big Sur and East Bay peaks and ranges,
4.00-7.00", Coastal North Bay 3.00-5.00", Coastal Santa Cruz and San
Mateo ridges, 5.00-10.00", again locally higher depending on
if/when/where the band of heaviest precipitation stalls.

The AR and frontal boundary will then shift southward this afternoon
as the aforementioned surface low off of the coast shifts inland
well to our north and the main mid/upper level low deepens off of
the Pacific Northwest coast.  In wake of the frontal passage, light
to occasionally moderate precipitation will persist along the
southwest facing slopes while diminishing over inland valley
locations. With the arrive of mid/upper level support and a colder
air mass aloft, isolated thunderstorms will also be possible from
late tonight into Tuesday morning. While organized, heavy rainfall
will tapper off on Tuesday during the day, lingering showers will
remain possible into Wednesday morning as the trough axis shifts
inland across the region.

Cooler and drier conditions are forecast from Wednesday into early
Friday as a weak ridge builds in behind the exiting trough. Late in
the week and into the upcoming weekend, forecast models continue to
differ yet show the potential for cool, unsettled weather
conditions. However, widespread, heavy rainfall is not currently
anticipated with this colder system given the lack of a deep
moisture tap. Stay tuned for the latest!

&&

.AVIATION...As of 9:40 AM PST Monday...For 18z tafs. Strong
southerly winds are expected to affect all taf sites today as a
slow moving cold front approaches the area. Up to 60 kt SW winds
at around 2000 feet are expected this afternoon and evening.
Therefore, low level wind shear remains in the tafs. MVFR cigs and
vis expected with IFR conditions during periods of heavy rain.
Rain will persist through late tomorrow morning.

Vicinity of KSFO...Oscillating between VFR and MVFR cig/vsby,
heavy rain and wind today through this evening. IFR possible at
times in downpours.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR cigs/vsbys, heavy rain and wind
today through this evening. IFR possible at times in downpours.

&&

.MARINE...as of 09:05 AM PST Monday...A slow moving cold front
currently sits across the waters bringing strong winds to the area
today and tomorrow. Gale force winds are expected today and
tonight with small craft winds by tomorrow morning. This system
will bring widespread rain and a chance for isolated thunderstorms
late tonight into tomorrow morning. Moderate swell over the waters
in addition to the strong winds will result in hazardous seas.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tday...High Wind Warning...Higher terrain Bay Area to Monterey
			 and San Benito counties.
             Flood Watch...Entire forecast area.
             Wind Advisory...Entire forecast area.
             GLW...Pt Reyes to Pigeon Pt 0-10 nm
             GLW...Pigeon Pt to Pt Pinos 0-10 nm
             GLW...Pt Pinos to Pt Piedras Blancas 0-10 nm
             SCA...Pt Arena to Pt Reyes 0-10 nm
             SCA...Pt Arena to Pigeon Pt 10-60 nm
             SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 12 PM
             GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 12 PM
             SCA...Rough Bar Advisory for SF Bar
             SCA...Mry Bay until 1 PM
             GLW...Mry Bay from 1 PM
             GLW...SF Bay

&&

PUBLIC FORECAST: MM/RGass
AVIATION: Anna
MARINE: Anna

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
839 AM PST MON FEB 20 2017

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

0818 AM     FLOOD            8 W TRACY               37.75N 121.57W
02/20/2017                   ALAMEDA            CA   LAW ENFORCEMENT

            EAST BOUND LANE OF MOUNTAIN HOUES ROAD AT GRANT LINE RD
            FLOODED

0822 AM     FLOOD            5 SW AT&T PARK          37.72N 122.45W
02/20/2017                   SAN FRANCISCO      CA   LAW ENFORCEMENT

            APPROX 2 FT OF WATER ACROSS GENEVA ON RAMP TO I280

&&

BBENJAMI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
845 AM PST MON FEB 20 2017

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

0836 AM     DEBRIS FLOW      6 NE MOSS LANDING       36.85N 121.71W
02/20/2017                   MONTEREY           CA   LAW ENFORCEMENT

            TRERE AND MUDSLIDE BLOCKING WHOLE ROAD...LIVE OAK RD AT
            MCGINNIS RD

0836 AM     FLOOD            4 NW ROHNERT PARK       38.39N 122.74W
02/20/2017                   SONOMA             CA   LAW ENFORCEMENT

            ENTIRE ROADWAY FLOODED TODD RD AT STONY POINT RD

&&

BBENJAMI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
854 AM PST MON FEB 20 2017

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

0836 AM     DEBRIS FLOW      5 SSW SALINAS           36.63N 121.68W
02/20/2017                   MONTEREY           CA   LAW ENFORCEMENT

            1 FT DEEP MUD OVER BOTH LANES RIVER RD AT HWY 68

&&

BBENJAMI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
903 AM PST MON FEB 20 2017

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

0855 AM     NON-TSTM WND DMG 11 SE PLASKETT CREEK CA 35.80N 121.35W
02/20/2017                   MONTEREY           CA   LAW ENFORCEMENT

            TREE AND WIRES DOWN OVER HWY 1 AT MM47

&&

BBENJAMI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
907 AM PST MON FEB 20 2017

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

0900 AM     DEBRIS FLOW      1 SSE SONOMA RACEWAY    38.15N 122.45W
02/20/2017                   SONOMA             CA   LAW ENFORCEMENT

            MUD SLIDE PARTIALLY BLOCKING SOUTH BOUND LANE SR121 AT
            SR37

&&

BBENJAMI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1026 AM PST MON FEB 20 2017

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

1008 AM     FLOOD            4 E MOSS LANDING        36.80N 121.72W
02/20/2017                   MONTEREY           CA   LAW ENFORCEMENT

            ELKHORN RD AT SPRINGPOINT RD...ROAD IS FLOODING.

1017 AM     DEBRIS FLOW      3 SSW LOS GATOS         37.18N 121.98W
02/20/2017                   SANTA CLARA        CA   LAW ENFORCEMENT

            MUD AND ROCKS BLOCKING LIMEKIN CYN RD AT SODA SPRINGS RD

&&

BBENJAMI