Alert archive / Maryland / Flash Flood Warnings in 2020

Flash Flood Warning 64, NWS Baltimore/Washington

September 10, 2020Prince George's County, Maryland

NWS Baltimore/Washington issued this flash flood warning at Sep 10, 2020, 2:34 PM EDT for Prince George's County, Maryland. It was in force for 2 hr. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Sep 10, 2020, 2:34 PM EDT (18:34 UTC)
Expired: Sep 10, 2020, 4:37 PM EDT
In force: 2 hr
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

County Prince George's County, MD

The radar

The Sterling radar (KLWX), 58 km from the middle of the area, began a volume at 18:37 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 6.6 hours before the alert went out and 161 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: 1088 J/kg
Mixed-layer CIN: -15 J/kg
Mixed-layer LCL: 575 m above ground
0-6 km bulk shear: 31 kt
0-1 km storm-relative helicity: 142 m²/s²
0-3 km storm-relative helicity: 167 m²/s²
Significant tornado parameter: 0.5
Supercell composite: 3.9

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this flash flood warning 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 warning went out at Sep 10, 2:28 PM EDT, 6 minutes earlier.

Area forecast discussion, Sep 10, 2:28 PM EDT, 6 minutes before

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Hazardous weather outlook, Sep 10, 1:37 PM EDT, 57 minutes before

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In the hours before

Local storm report, Sep 10, 2:15 PM EDT, 19 minutes before

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Local storm report, Sep 10, 2:19 PM EDT, 15 minutes before

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Local storm report, Sep 10, 2:23 PM EDT, 11 minutes before

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Local storm report, Sep 10, 2:26 PM EDT, 8 minutes before

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Local storm report, Sep 10, 2:32 PM EDT, 2 minutes before

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Local storm report, Sep 10, 2:33 PM EDT, 1 minute 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
Sep 10, 12:03 AM EDT	Areal Flood Warning	LWX	Fairfax	3 hr
Sep 10, 2:09 AM EDT	Areal Flood Warning	LWX	Fairfax	83 min
Sep 10, 4:05 AM EDT	Areal Flood Warning	LWX	Fauquier, Frederick, Warren	4 hr
Sep 10, 7:40 AM EDT	Special Marine Warning	LWX		37 min
Sep 10, 12:54 PM EDT	Areal Flood Warning	LWX	Clarke, Frederick	2 hr
Sep 10, 1:28 PM EDT	Flash Flood Warning	LWX	Arlington, Fairfax, City of Alexandria	3 hr
Sep 10, 4:14 PM EDT	Areal Flood Warning	LWX	Arlington, Fairfax, City of Alexandria	9 hr
Sep 10, 4:18 PM EDT	Special Marine Warning	LWX		54 min
Sep 10, 4:37 PM EDT	Special Marine Warning	LWX		22 min
Sep 10, 4:35 AM EDT	Flash Flood Warning Considerable damage threat	LWX	Saint Mary's	4 hr
Sep 10, 6:33 AM EDT	Flash Flood Warning Considerable damage threat	LWX	Charles	2 hr
Sep 10, 8:21 AM EDT	Areal Flood Warning	LWX	Charles, Saint Mary's	7 hr
Sep 10, 8:35 AM EDT	Areal Flood Warning	LWX	Saint Mary's	8 hr
Sep 10, 12:41 PM EDT	Flash Flood Warning	LWX	Montgomery	4 hr
Sep 10, 2:01 PM EDT	Areal Flood Warning	LWX	Charles	3 hr
Sep 10, 3:47 PM EDT	Flash Flood Warning Considerable damage threat	LWX	Charles, Saint Mary's	3 hr
Sep 10, 4:33 PM EDT	Areal Flood Warning	LWX	Calvert, Charles, Prince George's	5 hr
Sep 10, 4:37 PM EDT	Areal Flood Warning	LWX	Prince George's	4 hr
Sep 10, 6:37 PM EDT	Areal Flood Warning	LWX	Charles, Saint Mary's	4 hr

Nearby

Flash Flood Warnings in Maryland, 2020 Every flash flood warning in 2020

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.