Alert archive / Maryland / Flash Flood Watches in 2021

Flash Flood Watch 6, NWS Baltimore/Washington

July 16, 20215 counties in Virginia; 8 counties in Maryland

NWS Baltimore/Washington issued this flash flood watch at Jul 16, 2021, 10:20 PM EDT for 5 counties in Virginia; 8 counties in Maryland. It took effect at Jul 17, 2021, 2:00 PM EDT. It was in force for 8 hr.

The area

The counties it named.

The facts

Issued: Jul 16, 2021, 10:20 PM EDT (02:20 UTC)
In effect from: Jul 17, 2021, 2:00 PM EDT
Expired: Jul 17, 2021, 10:00 PM EDT
In force: 8 hr
Issued by: NWS Baltimore/Washington
Flood severity: None

Counties Anne Arundel County, MD, Baltimore County, MD, Cecil County, MD, City of Baltimore, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, Fairfax County, VA

The radar

The Sterling radar (KLWX), 58 km from the middle of the area, began a volume at 02:22 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, 2.3 hours before the alert went out and 51 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: 182 J/kg
Mixed-layer CIN: -41 J/kg
Mixed-layer LCL: 2058 m above ground
0-6 km bulk shear: 11 kt
0-1 km storm-relative helicity: 17 m²/s²
0-3 km storm-relative helicity: 36 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 Jul 16, 9:03 PM EDT, 1 hour 17 minutes earlier.

Area forecast discussion, Jul 16, 9:03 PM EDT, 1 hour 17 minutes before

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Hazardous weather outlook, Jul 16, 5:01 PM EDT, 5 hours 19 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
Jul 16, 10:54 PM EDT	Small Craft Advisory	LWX		41 hr
Jul 17, 12:45 PM EDT	Severe Thunderstorm Warning	LWX	Albemarle, Greene, Madison, Orange	45 min
Jul 17, 1:06 PM EDT	Severe Thunderstorm Warning	LWX	Albemarle, City of Charlottesville	18 min
Jul 17, 1:42 PM EDT	Severe Thunderstorm Warning	LWX	Albemarle, Culpeper, Greene, Madison, Orange	48 min
Jul 17, 2:07 PM EDT	Special Marine Warning	LWX		83 min
Jul 17, 2:10 PM EDT	Special Marine Warning	LWX		95 min
Jul 17, 2:19 PM EDT	Severe Thunderstorm Warning	LWX	Culpeper, Fauquier, Orange, Spotsylvania	41 min
Jul 17, 2:21 PM EDT	Severe Thunderstorm Warning	LWX	Clarke, Warren	39 min
Jul 17, 2:42 PM EDT	Severe Thunderstorm Warning	LWX	Culpeper, Fauquier, Prince William, City of Manassas	48 min
Jul 17, 2:58 PM EDT	Severe Thunderstorm Warning	LWX	Clarke, Loudoun	28 min
Jul 17, 3:06 PM EDT	Special Marine Warning	LWX		30 min
Jul 17, 3:09 PM EDT	Severe Thunderstorm Warning	LWX	Orange, Spotsylvania	23 min
Jul 17, 3:09 PM EDT	Severe Thunderstorm Warning	LWX	Fauquier, Loudoun, Prince William	39 min
Jul 17, 3:30 PM EDT	Severe Thunderstorm Warning	LWX	Fairfax, Loudoun	45 min
Jul 17, 3:43 PM EDT	Special Marine Warning	LWX		2 hr
Jul 17, 4:12 PM EDT	Severe Thunderstorm Warning	LWX	Fairfax	36 min
Jul 17, 5:42 PM EDT	Special Marine Warning	LWX		82 min
Jul 17, 5:47 PM EDT	Special Marine Warning	LWX		88 min
Jul 17, 5:50 PM EDT	Severe Thunderstorm Warning	LWX	Rockingham	40 min
Jul 17, 6:03 PM EDT	Severe Thunderstorm Warning	LWX	Clarke, Frederick, Shenandoah, Warren, City of Winchester	42 min
Jul 17, 6:31 PM EDT	Areal Flood Warning	LWX	Frederick, City of Winchester	57 min
Jul 17, 6:35 PM EDT	Severe Thunderstorm Warning	LWX	Loudoun	40 min
Jul 17, 6:54 PM EDT	Special Marine Warning	LWX		2 hr
Jul 17, 1:29 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll, Howard	46 min
Jul 17, 2:40 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Cecil, Harford, City of Baltimore	50 min
Jul 17, 2:59 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Harford, City of Baltimore	31 min
Jul 17, 3:24 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll, Frederick, Howard	24 min
Jul 17, 3:27 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Harford, City of Baltimore	63 min
Jul 17, 3:34 PM EDT	Flash Flood Warning Considerable damage threat	LWX	Baltimore, City of Baltimore	2 hr
Jul 17, 3:50 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll, Frederick, Howard, Montgomery	40 min
Jul 17, 3:59 PM EDT	Severe Thunderstorm Warning	LWX	Anne Arundel, Baltimore, Howard, City of Baltimore	46 min
Jul 17, 4:28 PM EDT	Severe Thunderstorm Warning	LWX	Anne Arundel, Baltimore, City of Baltimore	62 min
Jul 17, 4:45 PM EDT	Flash Flood Warning Considerable damage threat	LWX	Baltimore	101 min
Jul 17, 5:20 PM EDT	Severe Thunderstorm Warning	LWX	Allegany, Washington	40 min
Jul 17, 5:44 PM EDT	Severe Thunderstorm Warning	LWX	Carroll, Frederick, Washington	46 min
Jul 17, 6:01 PM EDT	Areal Flood Warning	LWX	Baltimore, City of Baltimore	6 hr
Jul 17, 6:26 PM EDT	Areal Flood Warning	LWX	Baltimore	5 hr
Jul 17, 6:45 PM EDT	Severe Thunderstorm Warning	LWX	Frederick, Washington	30 min
Jul 17, 7:11 PM EDT	Severe Thunderstorm Warning	LWX	Carroll, Frederick, Howard, Montgomery	49 min
Jul 17, 7:55 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll, Harford	27 min
Jul 17, 6:16 PM EDT	Severe Thunderstorm Warning	LWX	Berkeley, Jefferson	29 min

Nearby

Flash Flood Watches in Maryland, 2021 Flash Flood Watches in 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.