Flash Flood Warning 61, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
241 PM PST Mon Feb 20 2017

.SYNOPSIS...High impact event will 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 02:40 PM PST Monday...Much of the afternoon
forecast will be focused on the next 12 to 24 hours as a high
impact event persists over the Bay Area.

Over the last 24 hours rain and wind battered the Central Coast
with a wide range of impacts: downed trees, downed power lines,
flooding both small/large scale and debris/mud and rock slides.
Rainfall was greatest over the North Bay, East Bay Hills, Santa
Cruz Mountains and Santa Lucia Mts. Many remote stations in the
Santa Lucias had over 5 inches since yesterday. One interesting
factoid is SF Downtown surpassed their water year (Oct-Sep) this
morning at 10AM with 24.50 inches. Normal value for the year is
23.65 inches. Winds have been rather strong with numerous gusts
over 50 mph, most notably over the Santa Lucias.

Current situation synoptically puts a cold front moving into the
North Bay as we speak. The main focus of the heaviest rain is
confined to the front and just south of it. Farther upstream,
abundant lightning is being observed offshore near the upper
low/shortwave trough near 130W. Additionally there is an upper and
lower level jet heading toward the coast. Latest thinking is that
over the next few hours the front will continue to move southward
as the upper low/shortwave move toward the coast. As a result,
expect an increase in rain coverage/intensity. The biggest
increase will be mainly from the North Bay down to the Santa Cruz
Mountains. The additional rainfall tonight through tomorrow will
be a general 1-2" for mainly locations...lesser amounts in the
rain shadowed Santa Clara/Salinas Valley. Coastal Mts, North Bay
Mts, East Bay Hills and Santa Lucias 2-4" locally 6-7". Lots of
available moisture and orographics will lead to the higher
rainfall amounts in terrain favored spots. The other fly in the
ointment are thunderstorms. Latest model guidance, lightning
offshore and Storm Prediction Center indicate thunderstorms will
be possible later this afternoon/evening through Tuesday mainly
from Monterey northward. Any developed thunderstorm will cause
locally higher rainfall amounts. All that being, any additional
rainfall will only exacerbate already stressed
streams/creeks/rivers. Numerous hydro products are currently in
effect. Visit weather.gov/sanfrancisco for the latest information.

Winds will also ramp up with more widespread wind gusts/damage.
Highest gust as of late was Bottchers Gap with a gusts up to 70
mph. High wind warning remains in effect for coast and higher
terrain with wind advisory for inland valleys through 3 AM.

Simply put, we are not out of the woods yet. There maybe parts of
the Bay Area that are seeing sunshine and even a break in precip
this afternoon, but do not let your guard down. The second push
could get interesting, especially if convection really kicks in.

Expect overall conditions to improve late Tuesday into Wednesday
behind the departing AR and frontal boundary with a few lingering
showers.

High pressure builds in bringing cooler and drier conditions mid
week. In fact, enough clearing occurs overnight temps could drop
toward freezing with patchy frost for interior valleys. Medium
range models still indicate active late in the week and next
weekend. This next system looks to be much colder with lower snow
levels. 12z runs looks more impressive than the last run.

&&

.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...
     .Tngt...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 from 1 AM
             GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 1 AM
             SCA...Rough Bar Advisory for SF Bar
             SCA...Mry Bay from 10 PM
             GLW...Mry Bay until 10 PM
             SCA...SF Bay from 11 PM
             GLW...SF Bay until 11 PM

&&

PUBLIC FORECAST: MM
AVIATION: Anna
MARINE: Anna

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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

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1044 AM PST MON FEB 20 2017

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

1030 AM     DEBRIS FLOW      1 NE PRUNEDALE          36.82N 121.64W
02/20/2017                   MONTEREY           CA   LAW ENFORCEMENT

            MUD, DIRT AND TREES IN SLO LANE HWY101 AT CRAZY HORSE CYN
            RD

1037 AM     FLOOD            4 ESE WATSONVILLE       36.89N 121.70W
02/20/2017                   MONTEREY           CA   LAW ENFORCEMENT

            FLOODING OVER VEGA RD AT KARI LN. ROADWAY MAY CRACK

&&

BBENJAMI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1224 PM PST MON FEB 20 2017

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

1212 PM     FLOOD            9 N HOLLISTER           36.99N 121.38W
02/20/2017                   SANTA CLARA        CA   LAW ENFORCEMENT

            ROADWAY FLOODING SR 152 AT CASA DE FRUTA

1212 PM     FLOOD            5 NW GEYSERVILLE        38.76N 122.97W
02/20/2017                   SONOMA             CA   LAW ENFORCEMENT

            ABOUT 1 FT OF WATER IN ASTI RD AT ASTI STORE RD

&&

BBENJAMI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
102 PM PST MON FEB 20 2017

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

1237 PM     NON-TSTM WND DMG 2 N CARMEL RIVER BEACH  36.56N 121.93W
02/20/2017                   MONTEREY           CA   LAW ENFORCEMENT

            TREE BLOWN DOWN ACROSS ALL LANES OF CARMEL WAY AT 17 MILE
            DR

&&

BBENJAMI

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
159 PM PST MON FEB 20 2017

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

0121 PM     DEBRIS FLOW      3 WNW SAN JUAN BAUTISTA 36.86N 121.58W
02/20/2017                   SAN BENITO         CA   LAW ENFORCEMENT

            MUD AND ROCKS BLOCKING FAST LANE OF HWY 101 WEST
            CONNECTION TO HWY 156

0131 PM     FLOOD            5 SW CORRALITOS         36.93N 121.86W
02/20/2017                   SANTA CRUZ         CA   LAW ENFORCEMENT

            ROADWAY FLOODED ON SAN ANDREAS RD AT MAREA AVE.

&&

BBENJAMI