Alert archive / West Virginia / Severe Thunderstorm Warnings in 2018

Severe Thunderstorm Warning 258, NWS Baltimore/Washington

August 21, 2018Allegany County, Maryland; Grant County, Mineral County, West Virginia

NWS Baltimore/Washington issued this severe thunderstorm warning at Aug 21, 2018, 2:34 PM EDT for Allegany County, Maryland; Grant County, Mineral County, West Virginia. It was in force for 41 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
Aug 21, 2018, 2:34 PM EDT (18:34 UTC)
Expired
Aug 21, 2018, 3:15 PM EDT
In force
41 min
Issued by
NWS Baltimore/Washington
Area
Storm-based polygon
Hail
1.0 in
Wind
60.0 mph

Counties Allegany County, MD, Grant County, WV, Mineral County, WV

The radar

The Sterling radar (KLWX), 134 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 6.6 hours before the alert went out and 142 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-pSkew-T log-p diagram, Washington/Dulle, VA at 12:00Z on 2018-08-21Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 187 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 12:00Z on 2018-08-21The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 122 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
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
187 J/kg
Mixed-layer CIN
-22 J/kg
Mixed-layer LCL
597 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
122 m²/s²
0-3 km storm-relative helicity
183 m²/s²
Significant tornado parameter
0.1
Supercell composite
0.6

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 Aug 21, 10:12 AM EDT, 4 hours 22 minutes earlier.

Area forecast discussion, Aug 21, 10:12 AM EDT, 4 hours 22 minutes before
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Hazardous weather outlook, Aug 21, 10:27 AM EDT, 4 hours 7 minutes before
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In the hours before

Local storm report, Aug 21, 12:08 PM EDT, 2 hours 26 minutes before
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Local storm report, Aug 21, 1:55 PM EDT, 39 minutes before
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Local storm report, Aug 21, 2:17 PM EDT, 17 minutes before
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Local storm report, Aug 21, 2:19 PM EDT, 15 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
219 PM EDT TUE AUG 21 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0200 PM     FLOOD            2 SSW CENTREVILLE       38.82N  77.46W
08/21/2018                   FAIRFAX            VA   EMERGENCY MNGR

            COMPTON RD. CLOSED DUE TO HIGH WATER UNDER I-66

&&

EVENT NUMBER LWX1801717

CJL
Local storm report, Aug 21, 2:29 PM EDT, 5 minutes before
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Local storm report, Aug 21, 2:32 PM EDT, 2 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
232 PM EDT TUE AUG 21 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0225 PM     FLOOD            2 ESE GAINESVILLE       38.79N  77.59W
08/21/2018                   PRINCE WILLIAM     VA   EMERGENCY MNGR

            WELLINGTON RD. CLOSED DUE TO HIGH WATER AT INTERSECTION
            WITH CELLAR DOOR DR.

&&

EVENT NUMBER LWX1801719

CJL

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 20, 9:50 PM EDTSmall Craft AdvisoryLWX8 hr
Aug 21, 7:58 AM EDTSmall Craft AdvisoryLWX26 hr
Aug 21, 9:11 AM EDTAreal Flood WarningLWXCulpeper, Fauquier, Greene, Madison, Rappahannock12 hr
Aug 21, 9:38 AM EDTSpecial Marine WarningLWX97 min
Aug 21, 11:14 AM EDTSpecial Marine WarningLWX91 min
Aug 21, 1:16 PM EDTAreal Flood WarningLWXArlington, Fairfax, Prince William, City of Alexandria, City of Fairfax, City of Falls Church and 1 more21 hr
Aug 21, 1:25 PM EDTCoastal Flood AdvisoryLWXArlington, City of Alexandria, City of Falls Church21 hr
Aug 21, 1:40 PM EDTSmall Craft AdvisoryLWX52 hr
Aug 21, 2:28 PM EDTSpecial Marine WarningLWX48 min
Aug 21, 2:30 PM EDTSpecial Marine WarningLWX46 min
Aug 21, 3:38 PM EDTSpecial Marine WarningLWX71 min
Aug 21, 4:32 PM EDTSevere Thunderstorm WarningLWXFrederick43 min
Aug 21, 5:35 PM EDTSpecial Marine WarningLWX64 min
Aug 21, 5:50 PM EDTSpecial Marine WarningLWX85 min
Aug 21, 5:52 PM EDTSevere Thunderstorm WarningLWXFrederick38 min
Aug 21, 6:02 PM EDTAreal Flood WarningLWXFrederick9 hr
Aug 21, 6:09 PM EDTAreal Flood WarningLWXPrince William6 hr
Aug 21, 6:13 PM EDTSpecial Marine WarningLWX69 min
Aug 21, 6:16 PM EDTSpecial Marine WarningLWX89 min
Aug 21, 6:22 PM EDTSevere Thunderstorm WarningLWXClarke, Frederick38 min
Aug 21, 6:59 PM EDTSevere Thunderstorm WarningLWXLoudoun46 min
Aug 21, 7:06 PM EDTSpecial Marine WarningLWX84 min
Aug 21, 7:07 PM EDTSpecial Marine WarningLWX83 min
Aug 21, 7:58 PM EDTSevere Thunderstorm WarningLWXFrederick, Shenandoah, Warren47 min
Aug 21, 11:00 AM EDTCoastal Flood AdvisoryLWXSaint Mary's2 hr
Aug 21, 1:55 PM EDTAreal Flood WarningLWXPrince George's5 hr
Aug 21, 3:00 PM EDTSevere Thunderstorm WarningLWXAllegany45 min
Aug 21, 3:13 PM EDTSevere Thunderstorm WarningLWXAllegany47 min
Aug 21, 3:32 PM EDTTornado WarningLWXAllegany28 min
Aug 21, 3:43 PM EDTSevere Thunderstorm WarningLWXAllegany, Washington47 min
Aug 21, 3:48 PM EDTAreal Flood WarningLWXCharles, Saint Mary's3 hr
Aug 21, 3:49 PM EDTTornado WarningLWXSaint Mary's26 min
Aug 21, 3:59 PM EDTSevere Thunderstorm WarningLWXAllegany, Washington34 min
Aug 21, 5:12 PM EDTSevere Thunderstorm WarningLWXWashington48 min
Aug 21, 6:09 PM EDTSevere Thunderstorm WarningLWXFrederick, Washington51 min
Aug 21, 3:56 PM EDTSevere Thunderstorm WarningLWXHampshire, Mineral49 min

Nearby

Severe Thunderstorm Warnings in West Virginia, 2018Severe Thunderstorm Warnings in Maryland, 2018Every severe thunderstorm warning in 2018

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.