Alert archive / California / Red Flag Warnings in 2017

Red Flag Warning 3, NWS San Francisco Bay Area, CA

August 30, 20175 counties in California

NWS San Francisco Bay Area, CA issued this red flag warning at Aug 30, 2017, 12:00 PM PDT for 5 counties in California. It took effect at Aug 31, 2017, 9:00 PM PDT. It was in force for 48 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Aug 30, 2017, 12:00 PM PDT (19:00 UTC)
In effect from
Aug 31, 2017, 9:00 PM PDT
Expired
Sep 2, 2017, 9:00 PM PDT
In force
48 hr
Issued by
NWS San Francisco Bay Area, CA

Counties Monterey County, CA, San Benito County, CA, San Mateo County, CA, Santa Clara County, CA, Santa Cruz County, CA

The radar

The San Francisco radar (KMUX), 33 km from the middle of the area, began a volume at 19:00 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Oakland, CA (KOAK), launched 12:00Z, 7.0 hours before the alert went out and 102 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Oakland, CA at 12:00Z on 2017-08-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Oakland, CA at 12:00Z on 2017-08-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -31 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1917 m above ground
0-6 km bulk shear
23 kt
0-1 km storm-relative helicity
-31 m²/s²
0-3 km storm-relative helicity
123 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

630 
WWUS86 KMTR 301900
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
1200 PM PDT Wed Aug 30 2017

...HOT AND DRY CONDITIONS WILL IMPACT THE REGION THURSDAY NIGHT
INTO THE WEEKEND ALONG WITH LOCALLY GUSTY WINDS IN THE HILLS...

.Strong high pressure currently over the Desert Southwest will
build over California resulting in a prolonged period of hot and
dry weather. Poor to very poor humidity recoveries will occur in 
the hills above 1000 feet overnight and daytime relative humidity 
values will drop as low as the single digits and teens. Overnight
temperatures will remain mild and in the 70s and 80s with daytime
temperatures exceeding 100 degrees. In addition, locally gusty 
north to northeast winds will develop in the hills at night and 
become northwesterly during the day. These weather factors will 
result in the potential for rapid fire spread in the warned area. 


CAZ507-511-512-517-518-310430-
/O.NEW.KMTR.FW.W.0003.170901T0400Z-170902T1500Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
Santa Cruz Mountains-
Santa Lucia Mountains and Los Padres National Forest-
Mountains Of San Benito County And Interior Monterey County
Including Pinnacles National Park-
1200 PM PDT Wed Aug 30 2017

...RED FLAG WARNING IN EFFECT FROM 9 PM THURSDAY TO 8 AM PDT
SATURDAY FOR HOT AND DRY CONDITIONS WITH POOR OVERNIGHT HUMIDITY
RECOVERIES FOR FIRE WEATHER ZONES 507, 511, 512, 517, AND 518...

The National Weather Service in San Francisco has issued a Red
Flag Warning, which is in effect from 9 PM Thursday to 8 AM PDT
Saturday. 

* AFFECTED AREA...Fire weather zones 507, 511, 512, 517, and 
  518. This includes elevations above 1000 feet in the North and 
  East Bay Hills, the Santa Cruz Mountains, the Diablo Range, 
  the Santa Lucia Range, and the interior mountains of Monterey 
  and San Benito Counties.

* WIND...North to Northeast winds 5 to 10 mph with gusts 20 mph
  during the night and North to Northwest winds 5 to 10 mph with
  gusts 20-25 mph during the day.

* HUMIDITY...Humidity recovery at night will generally be 20-30%
  and dropping to 10-20% during the day.

* IMPACTS...any fires that develop will likely spread rapidly. 
  Outdoor burning is not recommended.

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.

&&

$$

MM
7 follow-up statements
662 
WWUS86 KMTR 310426
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
926 PM PDT Wed Aug 30 2017

...HOT AND DRY CONDITIONS WILL IMPACT THE REGION THURSDAY NIGHT
INTO THE WEEKEND ALONG WITH LOCALLY GUSTY WINDS IN THE HILLS...

.Strong high pressure will build over California Thursday and
Friday, resulting in a prolonged period of hot and dry weather
through the Labor Day weekend. Poor to very poor humidity 
recoveries will occur in the hills above 1000 feet overnight and 
daytime relative humidity values will drop as low as the single 
digits and teens. Overnight temperatures will remain quite warm in
the 70s and 80s with daytime temperatures exceeding 100 degrees 
across most inland areas. In addition, locally gusty north to 
northeast winds will develop in the hills at night and become 
northwesterly during the day. These weather factors will result in
the potential for rapid fire spread in the warned area beginning 
late Thursday and continuing through at least Saturday morning. 

CAZ507-511-512-517-518-312300-
/O.CON.KMTR.FW.W.0003.170901T0400Z-170902T1500Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
Santa Cruz Mountains-
Santa Lucia Mountains and Los Padres National Forest-
Mountains Of San Benito County And Interior Monterey County
Including Pinnacles National Park-
926 PM PDT Wed Aug 30 2017

...RED FLAG WARNING REMAINS IN EFFECT FROM 9 PM THURSDAY TO 8 AM
PDT SATURDAY FOR HOT AND DRY CONDITIONS WITH POOR OVERNIGHT
HUMIDITY RECOVERIES FOR FIRE WEATHER ZONES 507, 511, 512, 517,
AND 518...

* AFFECTED AREA...Fire weather zones 507, 511, 512, 517, and 
  518. This includes elevations above 1000 feet in the North and 
  East Bay Hills, the Santa Cruz Mountains, the Diablo Range, 
  the Santa Lucia Range, and the interior mountains of Monterey 
  and San Benito Counties. 

* WIND...North to Northeast winds 5 to 10 mph with gusts 20 mph 
  during the night and North to Northwest winds 5 to 15 mph 
  with gusts 20 to 25 mph during the day.

* HUMIDITY...Daytime relative humidity values in the single digits
  and teens. Nighttime humidity recoveries very poor with humidity
  values remaining below 30 percent for locations in the hills. 

* IMPACTS...Any fires that develop will likely spread rapidly. 
  Outdoor burning is not recommended.

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.

&&

$$
886 
WWUS86 KMTR 311949
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
1249 PM PDT Thu Aug 31 2017

...HOT AND DRY CONDITIONS WILL IMPACT THE REGION THURSDAY NIGHT
INTO THE WEEKEND ALONG WITH LOCALLY GUSTY WINDS IN THE HILLS...

.Strong high pressure will build over California Thursday and
Friday, resulting in a prolonged period of hot and dry weather
through the Labor Day weekend. Poor to very poor humidity
recoveries will occur in the hills above 1000 feet overnight and
daytime relative humidity values will drop as low as the single
digits and teens. Overnight temperatures will remain quite warm
in the 70s and 80s with daytime temperatures exceeding
100 degrees across most inland areas. In addition, locally gusty
north to northeast winds will develop in the hills at night and
become northwesterly during the day. These weather factors will
result in the potential for rapid fire spread in the warned area
beginning late Thursday and continuing through at least Saturday
morning.

CAZ507-511-512-517-518-011500-
/O.CON.KMTR.FW.W.0003.170901T0400Z-170902T1500Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
Santa Cruz Mountains-
Santa Lucia Mountains and Los Padres National Forest-
Mountains Of San Benito County And Interior Monterey County
Including Pinnacles National Park-
1249 PM PDT Thu Aug 31 2017

...RED FLAG WARNING REMAINS IN EFFECT FROM 9 PM THIS EVENING TO
8 AM PDT SATURDAY FOR HOT AND DRY CONDITIONS WITH POOR OVERNIGHT
HUMIDITY RECOVERIES FOR FIRE WEATHER ZONES 507, 511, 512, 517,
AND 518...

* AFFECTED AREA...Fire weather zones 507, 511, 512, 517, and 
  518. This includes elevations above 1000 feet in the North and 
  East Bay Hills, the Santa Cruz Mountains, the Diablo Range, 
  the Santa Lucia Range, and the interior mountains of Monterey 
  and San Benito Counties. 

* WIND...North to Northeast winds 5 to 10 mph with gusts 20 mph 
  during the night and North to Northwest winds 5 to 15 mph 
  with gusts 20 to 25 mph during the day.

* HUMIDITY...Daytime relative humidity values in the single
  digits and teens. Nighttime humidity recoveries very poor 
  with humidity values remaining below 30 percent for locations 
  in the hills.

* IMPACTS...Any fires that develop will likely spread rapidly. 
  Outdoor burning is not recommended.

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.

&&

$$
866 
WWUS86 KMTR 011058
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
358 AM PDT Fri Sep 1 2017

...HOT AND DRY CONDITIONS WILL IMPACT THE REGION FRIDAY INTO THE 
WEEKEND ALONG WITH LOCALLY GUSTY WINDS IN THE HILLS...

.Strong high pressure will build over California through the Labor
Day weekend, resulting in a prolonged period of hot and dry 
weather. Poor to very poor humidity recoveries will occur in the 
hills above 1000 feet overnight and daytime relative humidity 
values will drop as low as the single digits and teens. Overnight 
temperatures will remain quite warm in the 70s and 80s with 
daytime temperatures exceeding 100 degrees across most inland 
areas. In addition, locally gusty north to northeast winds will 
develop in the hills at night and become northwesterly during the 
day. These weather factors will result in the potential for rapid 
fire spread in the warned area through at least Saturday morning.

CAZ507-511-512-517-518-012200-
/O.CON.KMTR.FW.W.0003.000000T0000Z-170902T1500Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
Santa Cruz Mountains-
Santa Lucia Mountains and Los Padres National Forest-
Mountains Of San Benito County And Interior Monterey County
Including Pinnacles National Park-
358 AM PDT Fri Sep 1 2017

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 8 AM PDT SATURDAY FOR
HOT AND DRY CONDITIONS WITH POOR OVERNIGHT HUMIDITY RECOVERIES
FOR FIRE WEATHER ZONES 507, 511, 512, 517, AND 518...

* AFFECTED AREA...Fire weather zones 507, 511, 512, 517, and 
  518. This includes elevations above 1000 feet in the North and 
  East Bay Hills, the Santa Cruz Mountains, the Diablo Range, 
  the Santa Lucia Range, and the interior mountains of Monterey 
  and San Benito Counties. 

* WIND...North to Northeast winds 5 to 10 mph with gusts 20 mph 
  during the night and North to Northwest winds 5 to 15 mph 
  with gusts 20 to 25 mph during the day.

* HUMIDITY...Daytime relative humidity values in the single 
  digits and teens. Nighttime humidity recoveries very poor 
  with humidity values remaining below 30 percent for locations 
  in the hills.

* IMPACTS...Any fires that develop will likely spread rapidly. 
  Outdoor burning is not recommended.

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.

&&

$$
169 
WWUS86 KMTR 012110
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
210 PM PDT Fri Sep 1 2017

...HOT AND DRY CONDITIONS WILL CONTINUE TO IMPACT THE REGION 
INTO THE WEEKEND...ALONG WITH LOCALLY GUSTY WINDS IN THE HILLS...

.Strong high pressure over California will continue to produce
very hot and dry weather across the entire district through
Saturday. Very poor humidity recoveries will occur in the hills 
above 1000 feet overnight, and daytime relative humidity values 
will drop as low as the single digits and teens. Overnight 
temperatures will remain quite warm in the 70s and 80s with 
daytime temperatures exceeding 100 degrees across most areas and
up to 110 to 115 in the hottest inland areas. In addition, 
moderate and locally gusty north to northeast winds are expected 
in the hills at night, becoming northwesterly during the day. 
These weather factors will result in the potential for rapid fire 
spread in the warned area through at least Saturday evening.

CAZ507-511-512-517-518-021300-
/O.EXT.KMTR.FW.W.0003.000000T0000Z-170903T0400Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
Santa Cruz Mountains-
Santa Lucia Mountains and Los Padres National Forest-
Mountains Of San Benito County And Interior Monterey County
Including Pinnacles National Park-
210 PM PDT Fri Sep 1 2017

...RED FLAG WARNING NOW IN EFFECT UNTIL 9 PM PDT SATURDAY FOR HOT
AND DRY CONDITIONS WITH POOR OVERNIGHT HUMIDITY RECOVERIES FOR
FIRE WEATHER ZONES 507, 511, 512, 517, AND 518...

* AFFECTED AREA...Fire weather zones 507, 511, 512, 517, and 
  518. This includes elevations above 1000 feet in the North and 
  East Bay Hills, the Santa Cruz Mountains, the Diablo Range, 
  the Santa Lucia Range, and the interior mountains of Monterey 
  and San Benito Counties. 

* WIND...North to Northeast winds 5 to 10 mph with gusts 20 mph 
  during the night and North to Northwest winds 5 to 15 mph 
  with gusts 20 to 25 mph during the day.

* HUMIDITY...Daytime relative humidity values in the single 
  digits and teens. Nighttime humidity recoveries very poor 
  with humidity values remaining below 30 percent for locations 
  in the hills.

* IMPACTS...Any fires that develop will likely spread rapidly. 
  Outdoor burning is not recommended.

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.

&&

$$
911 
WWUS86 KMTR 021137
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
437 AM PDT Sat Sep 2 2017

...HOT AND DRY CONDITIONS WILL CONTINUE TO IMPACT THE REGION INTO
THE WEEKEND...ALONG WITH LOCALLY GUSTY WINDS IN THE HILLS...

.Strong high pressure over California will continue to produce
very hot and dry weather across the entire district through
Saturday. After very poor humidity recoveries overnight, daytime 
relative humidity values will drop as low as the single digits and
teens. Daytime temperatures will also once again exceed 100 
degrees across most areas and up to 110 to 115 in the hottest 
inland areas. In addition, moderate and locally gusty northerly
winds are forecast through at least this evening. These weather 
factors will result in the potential for rapid fire spread in the 
warned area through at least Saturday evening.

CAZ507-511-512-517-518-022200-
/O.CON.KMTR.FW.W.0003.000000T0000Z-170903T0400Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
Santa Cruz Mountains-
Santa Lucia Mountains and Los Padres National Forest-
Mountains Of San Benito County And Interior Monterey County
Including Pinnacles National Park-
437 AM PDT Sat Sep 2 2017

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 9 PM PDT THIS EVENING
FOR HOT AND DRY CONDITIONS WITH POOR OVERNIGHT HUMIDITY
RECOVERIES FOR FIRE WEATHER ZONES 507, 511, 512, 517, AND 518...

* AFFECTED AREA...Fire weather zones 507, 511, 512, 517, and 
  518. This includes elevations above 1000 feet in the North and 
  East Bay Hills, the Santa Cruz Mountains, the Diablo Range, 
  the Santa Lucia Range, and the interior mountains of Monterey 
  and San Benito Counties. 

* WIND...North to Northeast winds 5 to 10 mph with gusts 20 mph 
  during the night and North to Northwest winds 5 to 15 mph 
  with gusts 20 to 25 mph during the day.

* HUMIDITY...Daytime relative humidity values in the single 
  digits and teens. Nighttime humidity recoveries very poor 
  with humidity values remaining below 30 percent for locations 
  in the hills.

* IMPACTS...Any fires that develop will likely spread rapidly. 
  Outdoor burning is not recommended.

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.

&&

$$
356 
WWUS86 KMTR 021918
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
1218 PM PDT Sat Sep 2 2017

...HOT AND DRY CONDITIONS WILL CONTINUE TO IMPACT THE REGION INTO
THE WEEKEND...ALONG WITH LOCALLY GUSTY WINDS IN THE HILLS...

.Strong high pressure over California will continue to produce
very hot and dry weather across the entire district through
Saturday. After very poor humidity recoveries overnight, daytime
relative humidity values will drop as low as the single digits
and teens. Daytime temperatures will also once again exceed
100 degrees across most areas and up to 110 to 115 in the hottest
inland areas. In addition, moderate and locally gusty offshore winds
are forecast into this evening. These weather factors will result
in the potential for rapid fire spread in the warned area through
at least Saturday evening.

CAZ507-511-512-517-518-030400-
/O.CON.KMTR.FW.W.0003.000000T0000Z-170903T0400Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
Santa Cruz Mountains-
Santa Lucia Mountains and Los Padres National Forest-
Mountains Of San Benito County And Interior Monterey County
Including Pinnacles National Park-
1218 PM PDT Sat Sep 2 2017

...RED FLAG WARNING REMAINS IN EFFECT UNTIL 9 PM PDT THIS EVENING
FOR HOT AND DRY CONDITIONS FOR FIRE WEATHER ZONES 507, 511, 512, 
517, AND 518...

* AFFECTED AREA...Fire weather zones 507, 511, 512, 517, and 
  518. This includes elevations above 1000 feet in the North and 
  East Bay Hills, the Santa Cruz Mountains, the Diablo Range, 
  the Santa Lucia Range, and the interior mountains of Monterey 
  and San Benito Counties.

* WIND...North to Northeast winds 5 to 10 mph with gusts 20 mph 
  during the night and North to Northwest winds 5 to 15 mph 
  with gusts 20 to 25 mph during the day.

* HUMIDITY...Daytime relative humidity values in the single 
  digits and teens. Nighttime humidity recoveries very poor 
  with humidity values remaining below 30 percent for locations 
  in the hills.

* IMPACTS...Any fires that develop will likely spread rapidly. 
  Outdoor burning is not recommended.

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.

&&

$$
655 
WWUS86 KMTR 030357
RFWMTR

URGENT - FIRE WEATHER MESSAGE
National Weather Service San Francisco CA
857 PM PDT Sat Sep 2 2017

CAZ507-511-512-517-518-030500-
/O.EXP.KMTR.FW.W.0003.000000T0000Z-170903T0400Z/
North Bay Mountains-East Bay Hills and the Diablo Range-
Santa Cruz Mountains-
Santa Lucia Mountains and Los Padres National Forest-
Mountains Of San Benito County And Interior Monterey County
Including Pinnacles National Park-
857 PM PDT Sat Sep 2 2017

...RED FLAG WARNING WILL EXPIRE AT 9 PM PDT THIS EVENING FOR HOT
AND DRY CONDITIONS FOR FIRE WEATHER ZONES 507, 511, 512, 517, AND
518...

Even though the Red Flag Warning will expire this evening, fire 
weather concerns will continue through at least Sunday evening. 
Temperatures will be trending downward starting on Sunday, but 
inland areas and the hills will remain hot and dry. Also, 
southerly winds will begin to increase across the far southern 
portion of the district late Sunday and then across most of the 
rest of the district on Sunday night. Moderate and gusty southerly
winds are expected in the hills and locally in the valleys on 
Sunday night. However, relative humidity values are forecast to 
increase significantly on Sunday night. 

Also, increasing moisture from the remnants of Tropical Storm
Lidia will result in a slight chance of showers and thunderstorms
beginning in the southern portion of the district by Sunday
afternoon. These chances will remain across the south through
Monday morning. Shower and thunderstorm chances will then advance
northward into at least the southern half of the San Francisco 
Bay Area by Monday afternoon and evening. When thunderstorm 
chances first develop late on Sunday, the sub-cloud layer will 
still be very dry and so conditions could be favorable for dry 
lightning across Monterey and San Benito Counties. But with time 
the lower levels should moisten and any thunderstorms that develop
from Sunday night onward will most likely be accompanied by 
wetting rains.

$$

The office that day

Everything else NWS San Francisco Bay Area, CA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 29, 9:02 PM PDTSmall Craft AdvisoryMTR36 hr
Aug 30, 1:27 PM PDTExcessive Heat WarningMTRAlameda, Contra Costa, Marin, Monterey, Napa, San Benito and 5 more4 days
Aug 30, 1:27 PM PDTHeat AdvisoryMTRAlameda, Contra Costa, Marin, Monterey, Napa, San Benito and 2 more32 hr
Aug 30, 1:27 PM PDTHeat AdvisoryMTRMarin, Monterey, City and County of San Francisco, San Mateo, Santa Cruz, Sonoma47 hr

Nearby

Red Flag Warnings in California, 2017Every red flag warning in 2017

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.