Alert archive / Virginia / Flash Flood Watches in 2021

Flash Flood Watch 14, NWS Baltimore/Washington

August 30, 202133 counties in Virginia; 15 counties in Maryland; 8 counties in West Virginia

NWS Baltimore/Washington issued this flash flood watch at Aug 30, 2021, 4:54 AM EDT for 33 counties in Virginia; 15 counties in Maryland; 8 counties in West Virginia. It took effect at Sep 1, 2021, 2:00 AM EDT. It was in force for 17 hr.

The area

The counties it named.

The facts

Issued: Aug 30, 2021, 4:54 AM EDT (08:54 UTC)
In effect from: Sep 1, 2021, 2:00 AM EDT
Expired: Sep 1, 2021, 6:48 PM EDT
In force: 17 hr
Issued by: NWS Baltimore/Washington
Flood severity: None

All 56 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, Albemarle County, VA, Amherst County, VA, Arlington County, VA, Augusta 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 Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, Highland County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Rappahannock County, VA, Rockbridge 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, Pendleton County, WV

The radar

The Sterling radar (KLWX), 44 km from the middle of the area, began a volume at 08:54 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

Roanoke, VA (KRNK), launched 00:00Z, 8.9 hours before the alert went out and 223 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: 413 J/kg
Mixed-layer CIN: -46 J/kg
Mixed-layer LCL: 827 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: -15 m²/s²
0-3 km storm-relative helicity: 22 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 flash flood watch 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 flash flood watch went out at Aug 30, 4:02 AM EDT, 52 minutes earlier.

Area forecast discussion, Aug 30, 4:02 AM EDT, 52 minutes before

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Hazardous weather outlook, Aug 29, 10:42 PM EDT, 6 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 30, 11:48 AM EDT	Flash Flood Watch	LWX	Albemarle, Amherst, Arlington, Augusta, Culpeper, Fairfax and 19 more	6 hr
Aug 30, 2:39 PM EDT	Severe Thunderstorm Warning	LWX	Augusta, Rockingham, City of Harrisonburg	51 min
Aug 30, 2:54 PM EDT	Special Marine Warning	LWX		48 min
Aug 30, 3:59 PM EDT	Severe Thunderstorm Warning	LWX	Fauquier, Prince William, City of Manassas	33 min
Aug 30, 4:01 PM EDT	Special Marine Warning	LWX		119 min
Aug 30, 4:16 PM EDT	Severe Thunderstorm Warning	LWX	Augusta	15 min
Aug 30, 4:29 PM EDT	Severe Thunderstorm Warning	LWX	Fauquier, Prince William, Stafford, City of Manassas	17 min
Aug 30, 5:30 PM EDT	Special Marine Warning	LWX		2 hr
Aug 30, 6:09 PM EDT	Special Marine Warning	LWX		96 min
Aug 30, 7:00 PM EDT	Special Marine Warning	LWX		90 min
Aug 30, 7:53 PM EDT	Special Marine Warning	LWX		18 min
Aug 30, 6:04 PM EDT	Severe Thunderstorm Warning	LWX	Charles, Saint Mary's	25 min
Aug 30, 7:17 AM EDT	Dense Fog Advisory	LWX	Berkeley, Grant, Hampshire, Hardy, Jefferson, Mineral and 1 more	103 min

Nearby

Flash Flood Watches in Virginia, 2021 Flash Flood Watches in Maryland, 2021 Flash Flood Watches in West Virginia, 2021 Every flash flood watch 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.