Alert archive / Alabama / Dense Fog Advisories in 2021

Dense Fog Advisory 7, NWS Birmingham, AL

July 28, 202111 counties in Alabama

NWS Birmingham, AL issued this dense fog advisory at Jul 28, 2021, 1:10 AM CDT for 11 counties in Alabama. It was in force for 7 hr.

The area

The counties it named.

The facts

Issued: Jul 28, 2021, 1:10 AM CDT (06:10 UTC)
Expired: Jul 28, 2021, 8:00 AM CDT
In force: 7 hr
Issued by: NWS Birmingham, AL

Counties Blount County, AL, Calhoun County, AL, Cherokee County, AL, Clay County, AL, Cleburne County, AL, Etowah County, AL, Jefferson County, AL, Randolph County, AL, Shelby County, AL, St. Clair County, AL, Talladega County, AL

The radar

The Birmingham radar (KBMX), 83 km from the middle of the area, began a volume at 06:12 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

Birmingham, AL (KBMX), launched 00:00Z, 6.2 hours before the alert went out and 83 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-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

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: 144 J/kg
Mixed-layer CIN: -238 J/kg
Mixed-layer LCL: 1293 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: -24 m²/s²
0-3 km storm-relative helicity: -16 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 dense fog advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Birmingham, AL wrote its last area forecast discussion before this dense fog advisory went out at Jul 28, 12:57 AM CDT, 13 minutes earlier.

Area forecast discussion, Jul 28, 12:57 AM CDT, 13 minutes before

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Hazardous weather outlook, Jul 27, 8:42 PM CDT, 4 hours 28 minutes before

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In the hours before

Special weather statement, Jul 27, 7:13 PM CDT, 5 hours 57 minutes before

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      <div class="status" id="status">Temporary Notice</div>
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The office that day

Everything else NWS Birmingham, AL issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 27, 7:13 PM CDT	Special Weather Statement	BMX	Marengo	47 min
Jul 28, 6:35 PM CDT	Special Weather Statement	BMX	Russell	25 min

Nearby

Dense Fog Advisories in Alabama, 2021 Every dense fog 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.