Red Flag Warning 4, NWS San Francisco Bay Area, CA

438 
WWUS86 KMTR 172150
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
250 PM PDT Tue Aug 17 2021

...Critical fire weather conditions from late Tuesday evening
into Wednesday afternoon over the interior North Bay Mountains
and portions of the East Bay Hills/Diablo Range due to gusty
offshore winds and low humidity...

.A period of gusty, offshore winds and low humidity are expected
late Tuesday evening into Wednesday afternoon and locally again
the following night, but not as strong. The areas of greatest 
concern are across the hills and mountains of Napa County where 
minimum relative humidity values will drop into teens along with 
wind gusts up to 45 to 55 mph. There is the potential these 
stronger winds and low humidity could also spread into the 
interior hills of Sonoma County and into the East Bay Hills/Diablo
Range of Alameda and Contra Costa counties. Meanwhile, the risk 
is significantly lower across Marin and Santa Clara counties.

CAZ507-511-180600-
/O.CON.KMTR.FW.W.0004.210818T0600Z-210818T2200Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
250 PM PDT Tue Aug 17 2021

...RED FLAG WARNING REMAINS IN EFFECT FROM 11 PM THIS EVENING TO
3 PM PDT WEDNESDAY FOR GUSTY OFFSHORE WINDS AND LOW HUMIDITY FOR 
THE INTERIOR NORTH BAY MOUNTAINS AND PORTIONS OF THE EAST BAY 
HILLS/DIABLO RANGE...

* AFFECTED AREA...Fire weather zones 507 and 511. Area of greatest
  concern will be across the interior North Bay Mountains of Napa
  County.

* TIMING...11 PM Tuesday through 3 PM Wednesday.

* WINDS...North to northeast winds 10 to 25 mph with gusts up to 
  45 mph, locally up to 55 mph in the highest peaks.

* RELATIVE HUMIDITY...As low as 10 to 15 percent expected
  Wednesday.

* IMPACTS...Any fire starts would likely see rapid spread due to 
  dry fuels, low humidity and gusty winds.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Red Flag Warning means that critical fire weather conditions
are either occurring now...or will shortly. A combination of
strong winds...low relative humidity...and warm temperatures can
contribute to extreme fire behavior.

&&

$$

506 
WWUS86 KMTR 180544
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
1044 PM PDT Tue Aug 17 2021

...Critical fire weather conditions expected through Wednesday 
afternoon over the interior North Bay Mountains and portions of 
the East Bay Hills/Diablo Range due to gusty offshore winds and 
low humidity...

.A period of gusty, offshore winds and low humidity are expected
through Wednesday afternoon and locally again Wednesday night into
Thursday morning, yet not as strong. The areas of greatest 
concern are across the hills and mountains of Napa County where 
minimum relative humidity values will drop into teens along with 
wind gusts up to 45 to 55 mph. There is the potential these 
stronger winds and low humidity could also spread into the 
interior hills of Sonoma County and into the East Bay Hills/Diablo
Range of Alameda and Contra Costa counties. Meanwhile, the risk 
is significantly lower across Marin and Santa Clara counties.

CAZ507-511-181200-
/O.CON.KMTR.FW.W.0004.210818T0600Z-210818T2200Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
1044 PM PDT Tue Aug 17 2021

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 3 PM PDT WEDNESDAY
FOR GUSTY OFFSHORE WINDS AND LOW HUMIDITY FOR THE INTERIOR NORTH
BAY MOUNTAINS AND PORTIONS OF THE EAST BAY HILLS/DIABLO RANGE...

* AFFECTED AREA...Fire weather zones 507 and 511. Area of greatest
  concern will be across the interior North Bay Mountains of Napa
  County.

* TIMING...Through 3 PM Wednesday.

* WINDS...North to northeast winds 10 to 25 mph with gusts up to 
  45 mph, locally up to 55 mph in the highest peaks.

* RELATIVE HUMIDITY...As low as 10 to 15 percent expected
  Wednesday.

* IMPACTS...Any fire starts would likely see rapid spread due to 
  dry fuels, low humidity and gusty winds.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Red Flag Warning means that critical fire weather conditions
are either occurring now...or will shortly. A combination of
strong winds...low relative humidity...and warm temperatures can
contribute to extreme fire behavior.

&&

$$

228 
WWUS86 KMTR 181038
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
338 AM PDT Wed Aug 18 2021

...Critical fire weather conditions expected through Wednesday 
afternoon over the interior North Bay Mountains and portions of 
the East Bay Hills/Diablo Range due to gusty offshore winds and 
low humidity...

.A period of gusty, offshore winds and low humidity are expected
through this afternoon and locally again tonight into Thursday 
morning, yet not as strong. The areas of greatest concern are 
across the hills and mountains of Napa County where minimum 
relative humidity values will drop into teens along with wind 
gusts up to 45 to 55 mph. There is the potential these stronger 
winds and low humidity could also spread into the interior hills 
of Sonoma County and into the East Bay Hills/Diablo Range of 
Alameda and Contra Costa counties. Meanwhile, the risk is 
significantly lower across Marin and Santa Clara counties.

CAZ507-511-182200-
/O.CON.KMTR.FW.W.0004.000000T0000Z-210818T2200Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
338 AM PDT Wed Aug 18 2021

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 3 PM PDT THIS
AFTERNOON FOR GUSTY OFFSHORE WINDS AND LOW HUMIDITY FOR THE
INTERIOR NORTH BAY MOUNTAINS AND PORTIONS OF THE EAST BAY
HILLS/DIABLO RANGE...

* AFFECTED AREA...Fire weather zones 507 and 511. Area of greatest
  concern will be across the interior North Bay Mountains of Napa
  County.

* TIMING...Through 3 PM Wednesday.

* WINDS...North to northeast winds 10 to 25 mph with gusts up to 
  45 mph, locally up to 55 mph in the highest peaks.

* RELATIVE HUMIDITY...As low as 8 to 12 percent expected 
  Wednesday.

* IMPACTS...Any fire starts would likely see rapid spread due to 
  dry fuels, low humidity and gusty winds.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Red Flag Warning means that critical fire weather conditions
are either occurring now...or will shortly. A combination of
strong winds...low relative humidity...and warm temperatures can
contribute to extreme fire behavior.

&&

$$

739 
WWUS86 KMTR 181852
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
1152 AM PDT Wed Aug 18 2021

CAZ507-511-182000-
/O.CAN.KMTR.FW.W.0004.000000T0000Z-210818T2200Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
1152 AM PDT Wed Aug 18 2021

...RED FLAG WARNING IS CANCELLED FOR GUSTY OFFSHORE WINDS AND LOW
HUMIDITY FOR THE INTERIOR NORTH BAY MOUNTAINS AND PORTIONS OF THE
EAST BAY HILLS/DIABLO RANGE...

The National Weather Service in San Francisco has cancelled the
Red Flag Warning.

Offshore winds remain breezy, but have generally subsided below 30
mph. Models are indicating that winds will remain below red flag 
criteria for the rest of the afternoon which provides confidence 
for the red flag warning to be cancelled early. Conditions will 
remain dry so caution is still advised.

Offshore winds are forecast to increase once again Wednesday
night into Thursday morning, but are not expected to be as strong
as the previous. Strongest winds will likely be over the North Bay
Mountains, specifically in Napa County, around midnight for a
short period. While dry and gusty conditions may briefly be
expected, no Red Flag Warning is expected at this time.

$$