Alert archive / California / Red Flag Warnings in 2021
Red Flag Warning 5, NWS San Francisco Bay Area, CA
NWS San Francisco Bay Area, CA issued this red flag warning at Sep 9, 2021, 9:30 AM PDT for 5 counties in California. It took effect at Sep 9, 2021, 5:00 PM PDT. It was in force for 15 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
- Sep 9, 2021, 9:30 AM PDT (16:30 UTC)
- In effect from
- Sep 9, 2021, 5:00 PM PDT
- Expired
- Sep 10, 2021, 8:29 AM PDT
- In force
- 15 hr
- Issued by
- NWS San Francisco Bay Area, CA
Counties Alameda County, CA, Contra Costa County, CA, Marin County, CA, Napa County, CA, Sonoma County, CA
The radar
The Sacramento radar (KDAX), 73 km from the middle of the area, began a volume at 16:27 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, 4.5 hours before the alert went out and 47 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.
- Mixed-layer CAPE
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 2428 m above ground
- 0-6 km bulk shear
- 43 kt
- 0-1 km storm-relative helicity
- 15 m²/s²
- 0-3 km storm-relative helicity
- 69 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
447 WWUS86 KMTR 091630 RFWMTR URGENT - FIRE WEATHER MESSAGE National Weather Service San Francisco CA 930 AM PDT Thu Sep 9 2021 ...Dry lightning as well as gusty/erratic wind potential this afternoon through Friday morning... .Upper level moisture continues to increase over the region from south to north. The sub-tropical moisture will interact with an upper level disturbance moving in from the west. Thunderstorm chances increase late this afternoon into early Friday morning as the disturbance moves inland. Thunderstorms will be a mix of wet and dry, but given how dry the fuels are any lightning strikes will be problematic. The threat for thunderstorms diminishes early Friday as the moisture exits eastward. CAZ506-507-510-511-100600- /O.UPG.KMTR.FW.A.0004.210910T0000Z-210910T1800Z/ /O.NEW.KMTR.FW.W.0005.210910T0000Z-210910T1800Z/ North Bay Interior Valleys-North Bay Mountains- East Bay Interior Valleys-East Bay Hills and the Diablo Range- 930 AM PDT Thu Sep 9 2021 ...RED FLAG WARNING IN EFFECT FROM 5 PM THIS AFTERNOON TO 11 AM PDT FRIDAY FOR DRY LIGHTNING FOR FIRE WEATHER ZONES 506,507,510,511... The National Weather Service in San Francisco has issued a Red Flag Warning for Dry Lightning, which is in effect from 5 PM this afternoon to 11 AM PDT Friday. The Fire Weather Watch is no longer in effect. * AFFECTED AREA...Fire Weather Zone 506 North Bay Interior Valleys, Fire Weather Zone 507 North Bay Mountains, Fire Weather Zone 510 East Bay Interior Valleys and Fire Weather Zone 511 East Bay Hills and the Diablo Range. * TIMING...Thursday afternoon through Friday morning. * WINDS...Gusty and erratic winds are possible near any showers or thunderstorms. * LIGHTNING...Isolated to scattered thunderstorms may develop late this afternoon and continue overnight into Friday morning. Fast-moving storms may produce dry lightning. * IMPACTS...Given the dry fuels, any cloud to ground lightning strikes have the potential of starting new wildfires. Rapid spread may occur with any gusty and erratic 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. && $$
3 follow-up statements
887 WWUS86 KMTR 100427 RFWMTR URGENT - FIRE WEATHER MESSAGE National Weather Service San Francisco CA 927 PM PDT Thu Sep 9 2021 ...Dry lightning as well as gusty/erratic wind potential tonight through Friday morning... .Upper level moisture continues to increase over the region from south to north. The sub-tropical moisture will interact with an upper level disturbance moving in from the west. Thunderstorm chances increase tonight into early Friday morning as the disturbance moves inland. Thunderstorms will be a mix of wet and dry, but given how dry the fuels are any lightning strikes will be problematic. The threat for thunderstorms diminishes early Friday as the moisture exits eastward. CAZ506-507-510-511-101300- /O.CON.KMTR.FW.W.0005.000000T0000Z-210910T1800Z/ North Bay Interior Valleys-North Bay Mountains- East Bay Interior Valleys-East Bay Hills and the Diablo Range- 927 PM PDT Thu Sep 9 2021 ...RED FLAG WARNING REMAINS IN EFFECT UNTIL 11 AM PDT FRIDAY FOR DRY LIGHTNING FOR FIRE WEATHER ZONES 506,507,510,511... * AFFECTED AREA...Fire Weather Zone 506 North Bay Interior Valleys, Fire Weather Zone 507 North Bay Mountains, Fire Weather Zone 510 East Bay Interior Valleys and Fire Weather Zone 511 East Bay Hills and the Diablo Range. * TIMING...Tonight through Friday morning. * WINDS...West 10 to 15 mph with gusts up to 25 mph. * LIGHTNING...Isolated to scattered thunderstorms may develop overnight into Friday morning. Fast-moving storms may produce dry lightning. * IMPACTS...Given the dry fuels, any cloud to ground lightning strikes have the potential of starting new wildfires. Rapid spread may occur with any gusty and erratic winds. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Red Flag Warning means that critical fire weather conditions are either occurring now...or will shortly. A combination of strong winds...low relative humidity...and warm temperatures can contribute to extreme fire behavior. && $$
063 WWUS86 KMTR 101100 RFWMTR URGENT - FIRE WEATHER MESSAGE National Weather Service San Francisco CA 400 AM PDT Fri Sep 10 2021 ...Dry lightning as well as gusty/erratic wind potential through this morning... .A weather system will continue to push inland over the Bay Area this morning producing isolated to scattered high-based showers and thunderstorms. Dry lightning remains the greatest threat as convection overnight and into this morning has produced little to no rainfall, generally less than 0.10". The threat for thunderstorms will diminish through the morning as the weather system pushes inland. CAZ506-507-510-511-101800- /O.CON.KMTR.FW.W.0005.000000T0000Z-210910T1800Z/ North Bay Interior Valleys-North Bay Mountains- East Bay Interior Valleys-East Bay Hills and the Diablo Range- 400 AM PDT Fri Sep 10 2021 ...RED FLAG WARNING REMAINS IN EFFECT UNTIL 11 AM PDT THIS MORNING FOR DRY LIGHTNING FOR FIRE WEATHER ZONES 506,507,510,511... * AFFECTED AREA...North Bay Mountains and Valleys, East Bay Hills and Valleys, and the Diablo Range. * WINDS...Gusty and erratic winds are possible near any showers or thunderstorms. * THUNDERSTORMS...Isolated to scattered thunderstorms will be possible through this morning. Fast-moving storms may produce dry lightning. * IMPACTS...Given the dry fuels, any cloud to ground lightning strikes have the potential of starting new wildfires. Rapid spread may occur with any gusty and erratic 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. && $$
527 WWUS86 KMTR 101529 RFWMTR URGENT - FIRE WEATHER MESSAGE National Weather Service San Francisco CA 829 AM PDT Fri Sep 10 2021 CAZ506-507-510-511-101630- /O.CAN.KMTR.FW.W.0005.000000T0000Z-210910T1800Z/ North Bay Interior Valleys-North Bay Mountains- East Bay Interior Valleys-East Bay Hills and the Diablo Range- 829 AM PDT Fri Sep 10 2021 ...RED FLAG WARNING IS CANCELLED FROM THE DRY LIGHTNING THREAT... The National Weather Service in San Francisco has cancelled the Red Flag Warning. As the showers and storms move east and out of the region, the threat of dry lightning has diminished. $$
The office that day
Everything else NWS San Francisco Bay Area, CA issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 8, 8:47 PM PDT | Small Craft Advisory | MTR | 5 days |
Nearby
Red Flag Warnings in California, 2021Every red flag warning in 2021
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.