Hazardous Weather Continues Through Thursday

• Coastal Flood Advisory in effect from January 10, 08:00 AM PST until January 12, 12:00 PM PST
• Wind Advisory in effect from January 10, 12:00 PM PST until January 11, 12:00 AM PST
• Flash Flood Watch in effect from January 10, 04:00 AM PST until January 11, 04:00 AM PST
• Hazardous Weather Outlook

SYNOPSIS
The cold front is just starting to move into the north bay now (11:15AM).  We should see the area fully engulfed with intense rainfall within the next 2 to 3 hours.  Then, expect the intensity to continue for another 4 to 6 hours.  Rainfall amounts today are predicted to be 1.75” to 2.0” along the eastern and southern County borders, 2.0” to 3.0” along the coast and in the coastal hills and up to 4.0” at Mt. Tam.   After the intense rainfall passes, we should expect to see an additional 0.25” to 0.50” in the form of isolated showers throughout the County.  Then showers and light rain are predicted to continue into Wednesday and Thursday with a drier trend to the end of the week and into the weekend.

Note that some areas, such as the lower Novato Creek levees, are not draining very fast as the tide recedes.  Expect drainage areas at lower elevations throughout the County to behave similarly.  With this condition and with the predicted high rainfall intensities, flooding in low-lying areas (mostly near the bay) and areas near creeks and drainage channels is expected.

High tides today are showing about a half a food higher than predicted, so expect flooding in flood-pron areas and at low-lying areas in the vicinity of tidally influenced creeks and channels.

PRECIPITATION OUTLOOK

• Tue Jan 10: Rain – 1.7” to 2.0” along the eastern and southern borders, up to 3.0”” along the coast and coastal hills and 4.0” over Mt. Tam
• Wed Jan 11: Light Rain – 0.30”  in lower areas, 0.57” at higher elevations
• Thu Jan 12: Light Rain -- less than an 0.25” throughout the County
• Fri Jan 13: Dry
• Sat Jan 14: Dry
• Sun Jan 15: Dry

Total forecast precipitation amounts (beginning 4am Tuesday January 10th through 4amMonday January 16th): About 2.25” to 4.77”.

Hazardous Weather Outlook

National Weather Service San Francisco, CA

430 am PST Tuesday Jan 10 2017

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,

This hazardous weather outlook is for the San Francisco and Monterey bay region.

Day one, today and tonight, Rain and gusty southerly winds will go through our region today.  Flooding is possible. A high wind warning, wind advisory, flash flood watch, and coastal flood advisory are all in effect for our region. 

Days two through seven, Wednesday through Monday, showers are forecast for Wednesday into Thursday. Drier weather is likely Friday through Monday.

Flash Flood Watch

Flash flood watch issued for a portion of the San Francisco Bay Area and central coast.

Periods of moderate heavy rain are expected late tonight into Tuesday night. Heavy rain on already saturated soils will likely lead to flash flooding of area streams and rivers as well as local urban areas. 

Coastal north bay including Point Reyes National Seashore, North bay interior valleys, north bay mountains, San Francisco Peninsula Coast, Santa Cruz mountains, Santa Clara valley including San Jose, Santa Lucia mountains and Los padres national forest, Northern Monterey bay, southern Monterey bay and big sur coast, Including the cities of, Tamalpais, homestead, Sausalito, Santa Rosa, south Santa Rosa, Napa, San Rafael, Petaluma, Novato, Rohnert park, Anglin, Lagunitas, forest knolls, Woodacre, Pacifica, Scotts valley, Boulder Creek, Day valley, San Jose, Santa Cruz, Watsonville, live oak, Seaside, Monterey, Marin. 

Flash flood watch remains in effect from 4 am PST Tuesday through late Tuesday night.

The flash flood watch continues for a portion of western California, including the following areas, coastal north bay including Point Reyes national seashore, north bay interior valleys, north bay mountains, northern Monterey bay, San Francisco Peninsula coast, Santa Clara valley including San Jose, Santa Cruz mountains, Santa Lucia mountains and Los padres national forest and southern Monterey bay and big sur coast from 4 am PST Tuesday through late Tuesday night

Periods of heavy rain will impact the region from late tonight through Tuesday night. Rainfall amounts from 1 to 2 inches are possible at lower elevations with 3 to 6 inches across higher terrain of the north bay and along the coastal ranges.

 The primary impacts will be localized ponding of water on low lying roadways with poor drainage, rapid rises on streams and creeks with some likely exceeding bankfull, some river flooding, and potential rock and mud slides. Recent burn scars will also be susceptible to debris flows during periods of intense rainfall.

Precautionary/preparedness actions:

A flash flood watch means that conditions may develop that lead to flash flooding. Flash flooding is a very dangerous situation.  You should monitor later forecasts and be prepared to take action should flash flood warnings be issued.

Wind advisory

Urgent Weather Message

National weather service San Francisco, CA

922 pm PST mon Jan 9 2017

Another round of strong southerly winds expected.  A pacific storm system will move through the region on Tuesday and result in strong to gusty southerly winds during the afternoon and evening. Given already saturated soils, the threat for downed trees and power lines will exist.

San Francisco, coastal North Bay including Marin, Point Reyes National Seashore, North bay interior valleys, San Francisco bay shoreline, San Francisco Peninsula coast, northern Monterey bay, Southern Monterey bay and big sur coast, including the cities of, San Francisco, Tamalpais, homestead, Sausalito, Santa Rosa, south Santa Rosa, Napa, San Rafael, Petaluma, Novato, Rohnert park, Oakland, Fremont, Hayward, Daly city, Berkeley, Pacifica, Santa Cruz, Watsonville, Live oak, seaside, Monterey, Marin.

Wind advisory remains in effect from noon Tuesday to midnight PST Tuesday night.

Timing, Tuesday afternoon through Tuesday evening.

 Winds, southerly winds of 20 to 35 mph with local gusts over 45 mph in lower elevation locations.

 Impacts, potential for downed trees and power lines plus difficult driving conditions.

A wind advisory means that winds of 35 mph are expected. Winds this strong can make driving difficult, especially for high Profile vehicles. Use extra caution.

Coastal flood advisory

Coastal Hazard Message

National Weather Service San Francisco, CA

226 PM PST Mon Jan 9, 2017

King tides will impact the coastline and waterfronts Tuesday through Thursday,

Higher than normal tides, known as the king tides, will impact The Bay Area this week. A passing storm system will bring Additional rain runoff and onshore winds reinforcing coastal Flooding. Lastly, westerly swell will build and peak midweek.

Coastal North Bay including Point Reyes National Seashore, North Bay interior valleys, San Francisco bay shoreline, San Francisco Peninsula coast, Southern Monterey bay and big sur coast.

Coastal flood advisory remains in effect from 8 am Tuesday to 12:00 Noon PST Thursday.

• * Coastal flooding, high tides, onshore winds, rain runoff and building west swell will result in coastal flooding.
• * Timing: abnormally high tides are expected to occur during the mid to late morning hours of Tuesday, Wednesday and Thursday. Extreme low tides will occur during the late afternoon to early evening hours as well. 
• * Locations: low lying areas along the immediate coast and bay front including marshes and sloughs. These locations may include parking lots, coastal trails, sidewalks, underpasses and roadways.
• * Impacts, sea water on roadways, parking lots, trails and sidewalks. People visiting beaches may lose entry and exit to coves and narrow beaches.

Precautionary/preparedness actions:

A coastal flood statement indicates that excessive high tides will result in minor coastal flooding of low areas along the Shore. Do not leave your vehicle in low lying parking lots near the coast or bay front.  Do not travel through flooded roadways. If visiting the coast avoid narrow beaches and coves where your entry and or exit could be blocked by rising waters.