Upcoming Rain Event(s)

11:00 AM – UPDATE FROM NWS:

“FLASH FLOOD WATCH – Sobreanes and Chimney Burn Scar areas
This message is for any of the areas inside/alongside/or downslope of the Soberanes and Chimney Burn Scar Areas. The National Weather Service has issued a FLASH FLOOD WATCH for your area. The FLASH FLOOD WATCH is in effect from 12/15/2016 10:00 AM to 12/16/2016 4:00 AM PST. A WATCH is used when the risk of a hazardous weather or hydrologic event has increased significantly, but its occurrence, location, and/or timing is still uncertain. It is intended to provide enough lead time so that those who need to set their plans in motion can do so.”

Rain will return to our region starting on Tuesday and be mostly focused on the North Bay at first. By Thursday a second system with a cold front will produce widespread rainfall that could be heavy at times along with gusty winds.

UPDATED INFORMATION
· This is the first statement for the upcoming systems.
IMPACTS

*Impact (Rain from the first system):
· (Did not include as the bulk of the impact is north of SF)
*Impact (Rain from the second system):
· Widespread rain can be expected starting late Wednesday night and down to the remainder of our region on Thursday as a cold front goes through.
· Rain will likely be moderate to heavy at times as the front approaches. Any locations that have prolonged periods of moderate to heavy rain will have the potential for flooding.
· Debris flows are of concern especially around coastal ranges and recent burn scars.
· Rainfall amounts are forecast to range from 2 to 4 inches for coastal ranges with locally more than 6 inches possible. For urban spots generally 3/4″ to 1 3/4″ can be expected. .
o Please see attach graphic (part 2) for potential rainfall amounts. However, please do not focus on exact values.
o Please not that the bulk of the rain may fall during a short period leading to a heightened risk of flooding.
· Driving conditions will likely be poor with ponding on roadways along with low visibility.
· Locations with poor drainage and intersections and on/off ramps prone to flooding will likely have flooding.
*Impact (Wind from the second system):
· South to southeast winds will increase Wednesday evening into Thursday as a cold front approaches our region.
· The strongest winds will be on Thursday with many urban locations likely to see gusts of 25 to 35 mph.
· Higher elevation spots will likely see gusts of 35 to 45 mph with some areas gusting to over 55 mph.
o Please see attach graphic for general wind gusts Thursday afternoon. However, please be aware that peak gusts could be higher.
· Locally strong winds will make for difficult driving conditions.
· The winds could topple trees and power lines especially for locations that are susceptible to winds that funnel in from the south or higher elevation locations.

*Current Watches/Warnings/Advisories:
· Currently none in effect although watches and advisories are likely to be issued as the event gets closer.
· For all current watch/warning/advisories, http://1.usa.gov/1boSTTW
FORECAST CONFIDENCE
· Moderate to high for rainfall and wind.
LOCATIONS
· This is for the entire San Francisco and Monterey Bay Region..
Weather Summary
Wet weather returns as two systems will bring a return to rainy conditions to our region. The first system will mostly be focused north of San Francisco with moderate amounts of rain expected Tuesday into Wednesday. A bigger concern is with the second system mainly on Thursday that will bring widespread moderate to even heavy rainfall to our region as a cold front goes through. Gusty southerly winds can also be expected with the second system.