Alert archive / Maryland / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 99, NWS Baltimore/Washington

June 10, 2020Loudoun County, Virginia; Frederick County, Montgomery County, Maryland

NWS Baltimore/Washington issued this severe thunderstorm warning at Jun 10, 2020, 7:23 PM EDT for Loudoun County, Virginia; Frederick County, Montgomery County, Maryland. It was in force for 37 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Jun 10, 2020, 7:23 PM EDT (23:23 UTC)
Expired: Jun 10, 2020, 8:00 PM EDT
In force: 37 min
Issued by: NWS Baltimore/Washington
Area: Storm-based polygon
Hail: 0.75 in
Wind: 60.0 mph

Counties Frederick County, MD, Montgomery County, MD, Loudoun County, VA

The radar

The Sterling radar (KLWX), 29 km from the middle of the area, began a volume at 23:24 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 12:00Z, 11.4 hours before the alert went out and 31 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: 330 J/kg
Mixed-layer CIN: -150 J/kg
Mixed-layer LCL: 790 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 70 m²/s²
0-3 km storm-relative helicity: 38 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 severe thunderstorm 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 severe thunderstorm warning went out at Jun 10, 5:52 PM EDT, 1 hour 31 minutes earlier.

Area forecast discussion, Jun 10, 5:52 PM EDT, 1 hour 31 minutes before

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Hazardous weather outlook, Jun 10, 5:07 PM EDT, 2 hours 16 minutes before

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In the hours before

Local storm report, Jun 10, 6:35 PM EDT, 48 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
Jun 10, 7:00 PM EDT	Special Marine Warning	LWX		78 min
Jun 10, 7:02 PM EDT	Severe Thunderstorm Warning	LWX	Fairfax, Loudoun, Prince William	43 min
Jun 10, 7:45 PM EDT	Severe Thunderstorm Warning	LWX	Fairfax	33 min
Jun 10, 3:12 PM EDT	Severe Thunderstorm Warning	LWX	Allegany, Washington	21 min
Jun 10, 4:12 PM EDT	Severe Thunderstorm Warning	LWX	Allegany	33 min
Jun 10, 3:37 PM EDT	Severe Thunderstorm Warning	LWX	Grant, Hampshire, Hardy, Mineral	18 min

Nearby

Severe Thunderstorm Warnings in Maryland, 2020 Severe Thunderstorm Warnings in Virginia, 2020 Every severe thunderstorm 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.