Alert archive / Virginia / Flash Flood Watches in 2018

Flash Flood Watch 2, NWS Baltimore/Washington

May 15, 201818 counties in Virginia; 11 counties in Maryland; 7 counties in West Virginia

NWS Baltimore/Washington issued this flash flood watch at May 15, 2018, 4:33 AM EDT for 18 counties in Virginia; 11 counties in Maryland; 7 counties in West Virginia. It took effect at May 15, 2018, 3:00 PM EDT. It was in force for 10 hr.

The area

The counties it named.

The facts

Issued: May 15, 2018, 4:33 AM EDT (08:33 UTC)
In effect from: May 15, 2018, 3:00 PM EDT
Expired: May 16, 2018, 1:00 AM EDT
In force: 10 hr
Issued by: NWS Baltimore/Washington
Flood severity: None

All 36 counties

Allegany County, MD, Anne Arundel County, MD, Baltimore County, MD, Carroll County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Washington County, MD, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, Loudoun County, VA, Madison County, VA, Page County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah 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

The radar

The Sterling radar (KLWX), 28 km from the middle of the area, began a volume at 08:35 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 00:00Z, 8.6 hours before the alert went out and 243 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: 2 J/kg
Mixed-layer CIN: -306 J/kg
Mixed-layer LCL: 1134 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 82 m²/s²
0-3 km storm-relative helicity: 104 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 May 15, 4:06 AM EDT, 27 minutes earlier.

Area forecast discussion, May 15, 4:06 AM EDT, 27 minutes before

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Hazardous weather outlook, May 14, 9:48 PM EDT, 6 hours 45 minutes before

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In the hours before

Local storm report, May 14, 11:26 PM EDT, 5 hours 7 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
May 14, 8:40 PM EDT	Special Marine Warning	LWX		61 min
May 15, 12:28 AM EDT	Severe Thunderstorm Warning	LWX	Clarke, Frederick	47 min
May 15, 5:46 PM EDT	Severe Thunderstorm Warning	LWX	Page, Rockingham	44 min
May 15, 5:54 PM EDT	Areal Flood Warning	LWX	Rockingham	4 hr
May 15, 6:11 PM EDT	Severe Thunderstorm Warning	LWX	Fauquier, Rappahannock, Warren	26 min
May 15, 6:24 PM EDT	Severe Thunderstorm Warning	LWX	Greene, Madison, Page	35 min
May 15, 6:34 PM EDT	Areal Flood Warning	LWX	Page, Rockingham	2 hr
May 15, 7:00 PM EDT	Special Marine Warning	LWX		2 hr
May 15, 7:18 PM EDT	Severe Thunderstorm Warning	LWX	Loudoun	42 min
May 15, 7:22 PM EDT	Areal Flood Warning	LWX	Greene, Madison, Page, Rockingham	96 min
May 15, 7:51 PM EDT	Special Marine Warning	LWX		114 min
May 15, 7:54 PM EDT	Severe Thunderstorm Warning	LWX	Loudoun	51 min
May 14, 10:36 PM EDT	Coastal Flood Advisory	LWX	Saint Mary's	6 hr
May 15, 6:07 PM EDT	Severe Thunderstorm Warning	LWX	Carroll, Frederick	38 min
May 15, 6:33 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll, Harford	42 min
May 15, 6:35 PM EDT	Severe Thunderstorm Warning	LWX	Carroll, Frederick	40 min
May 15, 6:55 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll, Frederick, Harford, Howard, Montgomery and 1 more	65 min
May 15, 7:16 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, Carroll, Frederick, Harford	44 min
May 15, 7:17 PM EDT	Areal Flood Warning	LWX	Baltimore, Carroll, Frederick, Harford	4 hr
May 15, 7:41 PM EDT	Flash Flood Warning	LWX	Frederick	3 hr
May 15, 7:56 PM EDT	Flash Flood Warning	LWX	Frederick	3 hr

Nearby

Flash Flood Watches in Virginia, 2018 Flash Flood Watches in Maryland, 2018 Flash Flood Watches in West Virginia, 2018 Every flash flood watch 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.