River Flood Warning 10, NWS San Francisco Bay Area, CA

Area Forecast Discussion
National Weather Service San Francisco Bay Area
1013 PM PST Mon Feb 25 2019

.SYNOPSIS...An atmospheric river will bring heavy rain to primarily
the North Bay through Tuesday morning. Heavy rain will then spread
from north to south through the rest of the Forecast Area from
Tuesday afternoon through Tuesday night. Widespread flooding is
possible across the North Bay from tonight through Wednesday.
Flooding is also possible across the remainder of the San
Francisco Bay Area and Santa Cruz County from late Tuesday through
Tuesday night. In addition, strong and gusty winds are forecast
to occur near the coast and in the hills, with strongest winds
expected late Tuesday and Tuesday night. Rain will change to
showers by Wednesday and winds will decrease. Generally dry
weather is expected Thursday and Friday with the next chance of
rain Friday night and Saturday.

&&

.DISCUSSION...As of 9:10 PM PST Monday...Steady moderate to heavy
rain has been falling across the North Bay for much of the day.
Most rain has thus far been confined to areas north of the Golden
Gate, although rain has dipped a bit farther south into San
Francisco and the northern portion of the East Bay at times. Rain
totals through 8 pm range from a tenth of an inch in San Francisco
to just over 5 inches at Venado in northwest Sonoma County.
Venado, as is often the case, is by far the wettest location. Most
locations in the North Bay have received between 0.75 and 2.00
inches so far.

Satellite and radar show that the frontal boundary remains nearly
stationary across the North Bay and satellite data shows the
narrow plume of very moist air (atmospheric river) flowing along
the boundary and across the North Bay. The 00Z NAM and latest HRRR
both keep moderate to heavy rain confined primarily to the North
Bay overnight and through Tuesday morning, although the NAM
forecasts some orographic precipitation in the Santa Cruz and
Santa Lucia Mountains. A forecast update was completed earlier
this evening to significantly reduce rain chances across inland
areas of the central and southern SF Bay Area, as well as points
south, tonight and Tuesday morning.

The Weather Prediction Center notes that there will be an
increase in the magnitude of the low level jet overnight as a
wave along the frontal boundary approaches the coast. This will
enhance the moisture transport into the North Bay terrain and
likely increase rain rates overnight. Stream gages on small creeks
and streams in the North Bay are already showing sharp rises and
additional heavy rain overnight may very well lead to flooding. A
flood watch remains in effect for the North Bay. Flood warnings
may be issued overnight in the North Bay if heavy rains persist as
expected, and especially if rain rates increase.

The models generally agree that the frontal boundary and moisture
plume will finally begin to shift southward on Tuesday afternoon
as a strong shortwave trough approaches from the west. The HRRR
begins shifting heavy rainfall south of the Golden Gate a bit
sooner - by late morning. In any case, expect the incoming
shortwave to initially enhance rainfall across the northern and
central portions of the SF Bay Area Tuesday afternoon and evening,
and then push the frontal boundary and heavy rain south through
the rest of our forecast area on Tuesday night. Thus, all parts of
our area will likely see heavy rain, but the North Bay will see
heavy rain for significantly longer than points south.

In the North Bay, additional rainfall through Tuesday night is
forecast to range from 2 to 5 inches in urban/coastal/valley
locations and from 5 to 10 inches in the hills and mountains.
North Bay flooding potential along smaller rivers and streams (as
well as urban and low lying areas) will continue through Tuesday
and Tuesday night. Concerning the North Bay mainstem rivers: the
Russian River at Guerneville is expected to reach flood stage
early Wednesday morning and not crest until Wednesday evening. In
addition, the Napa River at Napa is forecast to reach flood stage
by Tuesday evening. A Flood Warning will likely be issued for the
Napa River shortly, once the latest forecast from the River
Forecast Center is completed.

For the central and southern San Francisco Bay Area and Santa Cruz
County, rainfall totals through Tuesday night are forecast to
range from 1 to 2 inches in the Santa Clara Valley, with 2 to 4
inches elsewhere except 4 to 6 inches in the Santa Cruz Mountains.
Flooding potential in the Santa Cruz Mountains and elsewhere will
be highest late Tuesday and Tuesday night.

Finally, for Monterey and San Benito Counties rain totals through
early Wednesday are forecast to range from 0.5-1.5 inches except 2
to 5 inches in the Santa Lucias. Flooding concerns for the Carmel
River and rivers in the Santa Lucias are lower compared to points
north, but flooding is still possible, especially if the frontal
boundary moves through more slowly than anticipated.

Southerly winds are gusting as high as 45 mph along the coast this
evening and up to 55 mph in the hills. Winds will remain strong
and gusty overnight and will likely increase further later tonight
as the incoming wave along the frontal boundary approaches. Winds
may then subside a bit Tuesday morning before increasing again Tuesday
afternoon and evening as the strong shortwave and associate
surface low approach. Strongest winds are likely from late Tuesday
afternoon through the early morning hours of Wednesday. A Wind
Advisory is in effect for coastal areas and elevations above 1000
feet through 3 am Wednesday.

Rain will change to showers by Wednesday morning and scattered
showers will likely persist into Wednesday night as an unstable
airmass associate with the upper trough moves over our area. A few
showers may linger into Thursday morning, but for the most part
Thursday and Friday are expected to be dry. The next system is
expected to bring more widespread rainfall by late Friday night
into Saturday. Models indicate that the focus of heaviest
precipitation with that system will be across the southern half of
our area, although any heavy rain that does develop is currently
expected to be of relatively short duration.

&&

.AVIATION...As of 10:13 PM PST Monday...VFR-MVFR except IFR in
the North Bay where the heaviest rain due to warm air advection
and strong orographic enhancement is presently focusing. Low level
wind shear for all terminals extends through the period; strong
and gusty surface winds have been mixing and transferring down to
surface in the Bay Area which will likely continue through tonight.

Vicinity of KSFO...An airport weather warning for strong and gusty
south wind is valid through early Tuesday morning before a temporary
relatively quieter lull develops. VFR with occasionally MVFR ceiling
and light rain tonight and Tuesday. More wind redeveloping Tuesday
afternoon and evening along with MVFR borderline temporary IFR in
moderate to heavy rain.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR, gusty SE winds and occasional MVFR
tonight and Tuesday. Low level wind shear develops tonight and
lasts through Tuesday. Rain will stay mainly to our north until
later Tuesday afternoon and evening.

&&

.MARINE...as of 10:04 PM PST Monday...Rain, heavy at times,
remains focused along a nearly stationary front over the northern
coastal waters, the southern extent of the rain band reaching San
Francisco Bay. High end small craft advisory winds continue over
much of the waters with marginal gale force gusts. The front over
the northern waters is not quite as robust as earlier forecast by
models thus surface winds are generally a bit lower than forecast.
A warm front will likely consolidate Tuesday and push eastward
Tuesday evening with a cold front now set to arrive early Thursday
morning. It's a complex weather pattern with an ongoing hazardous
sea state, a mixed fresh southerly swell with light northwest
swell continues through Tuesday. A longer period northwest swell
arrives late this week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...Flash Flood Watch...CAZ006-508>513-529
             Wind Advisory...CAZ006-505-507-509-511-512-517-529-530
             Flood Watch...CAZ505>507
             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
             GLW...Pigeon Pt to Pt Piedras Blancas 10-60 nm
             GLW...Pt Arena to Pt Reyes 0-10 nm
             GLW...SF Bay
             SCA...Mry Bay
             SCA...Pt Arena to Pigeon Pt 10-60 nm

&&

PUBLIC FORECAST: Dykema
AVIATION/MARINE: Canepa

Visit us at www.weather.gov/sanfrancisco

Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
922 PM PST MON FEB 25 2019

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

0528 PM     NON-TSTM WND GST SAUSALITO               37.85N 122.49W
02/25/2019  M51 MPH          MARIN              CA   TRAINED SPOTTER

            51 MPH SUSTAINED 19-36 MPH FROM THE SSW.

&&

CW

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
935 PM PST MON FEB 25 2019

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

0850 PM     FLOOD            1 WNW ROHNERT PARK      38.35N 122.72W
02/25/2019                   SONOMA             CA   PUBLIC

            DETAIL INFORMATION 8:50 PM 6 [9] LOG 2688 NB
            101 AT WINDSOR RIVER #1 8:44 PM 5 [8] LOG
            2609 MILL STATION AT FERGUSON NB AND SB
            LANES FLOODED SIGNS ON SB 1039 CORDS FOR NB
            LANES 8:43 PM 4 [7] LOG 2517 EASTSIDE JWO
            WINDSOR RIVER 2-3 INCHES FLOODING 1039 CORDS
            8:30 PM 3 [6] LOG 2584 EB EASTSIDE 1/2 MILE
            JEO TRENTON HEALDSBURG 1039 CORD ENTIRE RD
            FLOODED 7:08 PM 2 [4] 17-FLD GG02362 4080
            OLD REDWOOD HWY X EDWARDS RANCH / 6 INCHES
            IN NB LN / 1039 CORDS 5:52 PM 1 [3] 17-FLD
            GG02226 GREEN VALLEY AT SULLIVAN / CORDS
            ENRT FOR FULL CLOSURE.

&&

CW

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
937 PM PST MON FEB 25 2019

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

0830 PM     FLOOD            2 NE FORESTVILLE        38.51N 122.86W
02/25/2019                   SONOMA             CA   DEPT OF HIGHWAYS

            DETAIL INFORMATION 9:31 PM 12 [18]
            [NOTIFICATION] [CHP]-[17] PER SONSO ETA UP
            TO AN HOUR 9:31 PM 11 [17] PER SONSO ETA UP
            TO AN HOUR 9:27 PM 10 [15] [NOTIFICATION]
            [CHP]-SON SO / NO ETA FRM CORDS - WILL ADV
            WHEN THEY GET 1 9:26 PM 9 [14] 1039 SONSO //
            WLL CB WITH ETA 9:25 PM 8 [13] REQ UPDATED
            ETA FOR CORDS 8:30 PM 7 [11] 1039 CORDS 8:28
            PM 6 [9] 17-32B / ENTIRE RD FLOODED 8:28 PM
            5 [8] 17-32B ENTIRE ROAD FLOODED 8:27 PM 4
            [7] B17-032B NB LN FLOODED RESPOND WITH
            SIGNS 8:21 PM 3 [6] 1039 SONS SO CORDS FOR
            SIGNS 8:20 PM 2 [4] 1039 SON SO FOR CORDS
            FOR SIGN 8:06 PM 1 [1] BOTH EB AND WB LNS
            FLOODED.

&&

CW

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
938 PM PST MON FEB 25 2019

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

0930 PM     NON-TSTM WND DMG 3 W COTATI              38.32N 122.76W
02/25/2019                   SONOMA             CA   DEPT OF HIGHWAYS

            TREE DOWN PARTIALLY 1125.

&&

CW

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1027 PM PST MON FEB 25 2019

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

1008 PM     DEBRIS FLOW      10 WNW MONTE RIO        38.53N 123.18W
02/25/2019                   SONOMA             CA   LAW ENFORCEMENT

            ROCK SLIDE IN ROADWAY BLOCKING ALMOST ENTIRE
            ROADWAY. FORT ROSS RD / NIESTRATH RD.

&&

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1049 PM PST MON FEB 25 2019

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

1032 PM     FLOOD            3 ESE TEMELEC           38.24N 122.45W
02/25/2019                   SONOMA             CA   LAW ENFORCEMENT

            SR 121 AT SCHELLVILLE FIRE CLOSED.

1031 PM     DEBRIS FLOW      2 SE GUERNEVILLE        38.49N 122.96W
02/25/2019                   SONOMA             CA   LAW ENFORCEMENT

            MUD SLIDE AND OTHER DEBRIS IN WESTBOUND
            LANE. ON WB 116 BETWEEN CANYON AND TRENTON.

1031 PM     DEBRIS FLOW      3 ENE ROHNERT PARK      38.37N 122.65W
02/25/2019                   SONOMA             CA   LAW ENFORCEMENT

            DEBRIS FLOW ON EASTBOUND CRANE CANYON HALF A
            MILE FROM JUNCTION WITH PETALUMA HILL RD.

&&