Alert archive / California / Areal Flood Advisories in 2021

Areal Flood Advisory 4, NWS San Francisco Bay Area, CA

January 27, 20216 counties in California

NWS San Francisco Bay Area, CA issued this areal flood advisory at Jan 27, 2021, 2:11 PM PST for 6 counties in California. It was in force for 5 hr.

The area

The counties it named.

The facts

Issued
Jan 27, 2021, 2:11 PM PST (22:11 UTC)
Expired
Jan 27, 2021, 7:15 PM PST
In force
5 hr
Issued by
NWS San Francisco Bay Area, CA
Area
Storm-based polygon

Counties Alameda County, CA, 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), 20 km from the middle of the area, began a volume at 22:09 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, 10.2 hours before the alert went out and 88 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 2021-01-27Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 25 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Oakland, CA at 12:00Z on 2021-01-27The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity -42 square meters per square second.1939587897117136Sfc1 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
25 J/kg
Mixed-layer CIN
-15 J/kg
Mixed-layer LCL
572 m above ground
0-6 km bulk shear
94 kt
0-1 km storm-relative helicity
-42 m²/s²
0-3 km storm-relative helicity
139 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this areal flood advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS San Francisco Bay Area, CA wrote its last area forecast discussion before this areal flood advisory went out at Jan 27, 1:34 PM PST, 37 minutes earlier.

Area forecast discussion, Jan 27, 1:34 PM PST, 37 minutes before
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In the hours before

Local storm report, Jan 27, 10:46 AM PST, 3 hours 25 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1046 AM PST WED JAN 27 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1040 AM     DEBRIS FLOW      27 SW GREENFIELD        36.05N 121.59W
01/27/2021                   MONTEREY           CA   PUBLIC

            MUDSLIDE ONTO HWY 1 AT MILE MARKER 27.

1037 AM     DEBRIS FLOW      7 SSE SALINAS           36.59N 121.61W
01/27/2021                   MONTEREY           CA   FIRE DEPT/RESCUE

            MUDSLIDE FROM THE RIVER FIRE BURN SCAR.

&&

The office that day

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

IssuedProductOfficeCountiesLasted
Jan 26, 9:39 PM PSTFlash Flood Warning Considerable damage threatMTRSonoma81 min
Jan 26, 10:22 PM PSTAreal Flood AdvisoryMTRMarin, Napa, Sonoma4 hr
Jan 26, 10:56 PM PSTFlash Flood Warning Considerable damage threatMTRSan Mateo, Santa Cruz4 hr
Jan 26, 11:18 PM PSTAreal Flood AdvisoryMTRAlameda, City and County of San Francisco, San Mateo, Santa Clara4 hr
Jan 26, 11:46 PM PSTSpecial Marine WarningMTR14 min
Jan 27, 1:31 AM PSTFlash Flood Warning Considerable damage threatMTRMonterey3 hr
Jan 27, 1:38 AM PSTFlash Flood Warning Considerable damage threatMTRMonterey14 hr
Jan 27, 1:45 AM PSTFlash Flood Warning Considerable damage threatMTRMonterey3 hr
Jan 27, 2:06 AM PSTSpecial Marine WarningMTR24 min
Jan 27, 2:18 AM PSTAreal Flood AdvisoryMTRMonterey, Santa Cruz117 min
Jan 27, 2:23 AM PSTGale WarningMTR3 hr
Jan 27, 2:23 AM PSTSmall Craft AdvisoryMTR55 hr
Jan 27, 5:27 AM PSTGale WarningMTR21 hr
Jan 27, 12:03 PM PSTFlash Flood Warning Considerable damage threatMTRMonterey3 hr
Jan 27, 12:05 PM PSTFlash Flood WarningMTRMonterey3 hr
Jan 27, 12:33 PM PSTFlash Flood WarningMTRSan Mateo, Santa Cruz6 hr
Jan 27, 12:53 PM PSTSpecial Marine WarningMTR52 min

Nearby

Areal Flood Advisories in California, 2021Every areal flood 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.