Alert archive / Virginia / Heat Advisories in 2021

Heat Advisory 5, NWS Baltimore/Washington

August 12, 202125 counties in Virginia; 15 counties in Maryland; 7 counties in West Virginia

NWS Baltimore/Washington issued this heat advisory at Aug 12, 2021, 2:15 AM EDT for 25 counties in Virginia; 15 counties in Maryland; 7 counties in West Virginia. It took effect at Aug 12, 2021, 12:00 PM EDT. It was in force for 8 hr.

The area

The counties it named.

The facts

Issued: Aug 12, 2021, 2:15 AM EDT (06:15 UTC)
In effect from: Aug 12, 2021, 12:00 PM EDT
Expired: Aug 12, 2021, 8:00 PM EDT
In force: 8 hr
Issued by: NWS Baltimore/Washington

All 47 counties

Allegany County, MD, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Carroll County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Saint Mary's County, MD, Washington County, MD, Arlington County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Page County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV

The radar

The Sterling radar (KLWX), 19 km from the middle of the area, began a volume at 06:16 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

Washington/Dulle, VA (KIAD), launched 00:00Z, 6.3 hours before the alert went out and 26 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: 163 J/kg
Mixed-layer CIN: -269 J/kg
Mixed-layer LCL: 1456 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: 11 m²/s²
0-3 km storm-relative helicity: 48 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 heat advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Baltimore/Washington wrote its last area forecast discussion before this heat advisory went out at Aug 11, 9:29 PM EDT, 4 hours 46 minutes earlier.

Area forecast discussion, Aug 11, 9:29 PM EDT, 4 hours 46 minutes before

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Hazardous weather outlook, Aug 11, 8:26 PM EDT, 5 hours 49 minutes before

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In the hours before

Local storm report, Aug 11, 8:48 PM EDT, 5 hours 27 minutes before

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Local storm report, Aug 11, 8:49 PM EDT, 5 hours 26 minutes before

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Local storm report, Aug 11, 8:50 PM EDT, 5 hours 25 minutes before

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Local storm report, Aug 11, 8:52 PM EDT, 5 hours 23 minutes before

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Local storm report, Aug 11, 8:53 PM EDT, 5 hours 22 minutes before

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Local storm report, Aug 11, 9:03 PM EDT, 5 hours 12 minutes before

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The office that day

Everything else NWS Baltimore/Washington issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 11, 10:49 PM EDT	Special Marine Warning	LWX		86 min
Aug 12, 6:04 PM EDT	Heat Advisory	LWX	Arlington, Clarke, Culpeper, Fairfax, Fauquier, Frederick and 20 more	25 hr

Nearby

Heat Advisories in Virginia, 2021 Heat Advisories in Maryland, 2021 Heat Advisories in West Virginia, 2021 Every heat 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.