Alert archive / California / Frost Advisories in 2021
Frost Advisory 2, NWS San Francisco Bay Area, CA
NWS San Francisco Bay Area, CA issued this frost advisory at Mar 20, 2021, 12:51 PM PDT for 4 counties in California. It took effect at Mar 21, 2021, 3:00 AM PDT. It was in force for 6 hr.
The area
The counties it named.
The facts
- Issued
- Mar 20, 2021, 12:51 PM PDT (19:51 UTC)
- In effect from
- Mar 21, 2021, 3:00 AM PDT
- Expired
- Mar 21, 2021, 9:00 AM PDT
- In force
- 6 hr
- Issued by
- NWS San Francisco Bay Area, CA
Counties Marin County, CA, Monterey County, CA, Napa County, CA, Sonoma County, CA
The radar
The San Francisco radar (KMUX), 84 km from the middle of the area, began a volume at 19:54 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, 7.9 hours before the alert went out and 16 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
- 8 J/kg
- Mixed-layer CIN
- -43 J/kg
- Mixed-layer LCL
- 1025 m above ground
- 0-6 km bulk shear
- 37 kt
- 0-1 km storm-relative helicity
- -36 m²/s²
- 0-3 km storm-relative helicity
- 42 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
047 WWUS76 KMTR 201951 NPWMTR URGENT - WEATHER MESSAGE National Weather Service San Francisco Bay Area 1251 PM PDT Sat Mar 20 2021 Cooler air from northwest winds provide mild temperatures Saturday afternoon and will decrease Saturday night. Patchy cloud cover decreases Saturday evening, with clearing expected early Sunday morning. This clearing will aide in decreasing temperatures toward freezing, providing the opportunity for frost development and prompting the issuance of the advisory. CAZ506-516-210400- /O.NEW.KMTR.FR.Y.0002.210321T1000Z-210321T1600Z/ North Bay Interior Valleys- Southern Salinas Valley/Arroyo Seco and Lake San Antonio- Including the cities of Santa Rosa, South Santa Rosa, Napa, San Rafael, Petaluma, Novato, Rohnert Park, Greenfield, and King City 1251 PM PDT Sat Mar 20 2021 ...FROST ADVISORY IN EFFECT FROM 3 AM TO 9 AM PDT SUNDAY... * WHAT...Temperatures as low as 31 will result in frost formation. * WHERE...North Bay Interior Valleys and Southern Salinas Valley/Arroyo Seco and Lake San Antonio. * WHEN...From 3 AM to 9 AM PDT Sunday. * IMPACTS...Frost could kill sensitive outdoor vegetation if left uncovered. PRECAUTIONARY/PREPAREDNESS ACTIONS... Sensitive plants and crops may be at risk in these conditions. Take steps now to protect tender plants from the cold. Ensure all animals have a warm and dry shelter. && $$ For more information from the National Weather Service visit http://weather.gov/mtr
2 follow-up statements
894 WWUS76 KMTR 210352 NPWMTR URGENT - WEATHER MESSAGE National Weather Service San Francisco Bay Area 852 PM PDT Sat Mar 20 2021 CAZ506-516-211600- /O.CON.KMTR.FR.Y.0002.210321T1000Z-210321T1600Z/ North Bay Interior Valleys- Southern Salinas Valley/Arroyo Seco and Lake San Antonio- Including the cities of Santa Rosa, South Santa Rosa, Napa, San Rafael, Petaluma, Novato, Rohnert Park, Greenfield, and King City 852 PM PDT Sat Mar 20 2021 ...FROST ADVISORY REMAINS IN EFFECT FROM 3 AM TO 9 AM PDT SUNDAY... * WHAT...Overnight low temperatures from 30 to 35 will result in areas of late night and early morning frost. * WHERE...North Bay Interior Valleys and Southern Salinas Valley, Arroyo Seco and Lake San Antonio. * WHEN...From 3 AM to 9 AM PDT Sunday. * IMPACTS...Frost could kill sensitive outdoor vegetation if left uncovered. PRECAUTIONARY/PREPAREDNESS ACTIONS... Sensitive plants and crops may be at risk in these conditions. Take steps now to protect tender plants from the cold. Ensure all animals have a warm and dry shelter. && $$ For more information from the National Weather Service visit http://weather.gov/mtr
470 WWUS76 KMTR 211536 NPWMTR URGENT - WEATHER MESSAGE National Weather Service San Francisco Bay Area 836 AM PDT Sun Mar 21 2021 CAZ506-516-211645- /O.EXP.KMTR.FR.Y.0002.000000T0000Z-210321T1600Z/ North Bay Interior Valleys- Southern Salinas Valley/Arroyo Seco and Lake San Antonio- Including the cities of Santa Rosa, South Santa Rosa, Napa, San Rafael, Petaluma, Novato, Rohnert Park, Greenfield, and King City 836 AM PDT Sun Mar 21 2021 ...FROST ADVISORY WILL EXPIRE AT 9 AM PDT THIS MORNING... Temperatures are starting to steadily increase toward the afternoon highs expected in the 60s. Any accumulated frost should slowly melt if it hasn't done so already. Therefore the advisory will be allowed to expire at 9 AM. $$ For more information from the National Weather Service visit http://weather.gov/mtr
The office that day
Everything else NWS San Francisco Bay Area, CA issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 20, 2:37 AM PDT | Small Craft Advisory | MTR | 42 hr | |
| Mar 20, 2:04 PM PDT | Small Craft Advisory | MTR | 4 days |
Nearby
Frost Advisories in California, 2021Every frost advisory 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.