Alert archive / Virginia / Flash Flood Watches in 2011

Flash Flood Watch 9, NWS Baltimore/Washington

July 7, 201126 counties in Virginia; 9 counties in Maryland; Pendleton County, West Virginia

NWS Baltimore/Washington issued this flash flood watch at Jul 7, 2011, 3:14 PM EDT for 26 counties in Virginia; 9 counties in Maryland; Pendleton County, West Virginia. It took effect at Jul 8, 2011, 12:00 PM EDT. It was in force for 8 hr.

The area

The counties it named.

The facts

Issued: Jul 7, 2011, 3:14 PM EDT (19:14 UTC)
In effect from: Jul 8, 2011, 12:00 PM EDT
Expired: Jul 8, 2011, 7:55 PM EDT
In force: 8 hr
Issued by: NWS Baltimore/Washington
Flood severity: None

All 36 counties

Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Carroll County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Prince George's County, MD, Saint Mary's County, MD, Arlington County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Staunton, VA, City of Waynesboro, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Greene County, VA, Highland County, VA, King George County, VA, Madison County, VA, Nelson County, VA, Orange County, VA, Page County, VA, Rappahannock County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Pendleton County, WV

The radar

The Sterling radar (KLWX), 47 km from the middle of the area, began a volume at 19:15 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, 7.2 hours before the alert went out and 50 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: 482 J/kg
Mixed-layer CIN: -113 J/kg
Mixed-layer LCL: 1251 m above ground
0-6 km bulk shear: 15 kt
0-1 km storm-relative helicity: -6 m²/s²
0-3 km storm-relative helicity: 35 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 7, 10:26 AM EDT, 4 hours 48 minutes earlier.

Area forecast discussion, Jul 7, 10:26 AM EDT, 4 hours 48 minutes before

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Hazardous weather outlook, Jul 7, 1:30 PM EDT, 1 hour 44 minutes before

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In the hours before

Special weather statement, Jul 7, 2:56 PM EDT, 18 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
256 PM EDT THU JUL 7 2011

MDZ006-007-071930-
NORTHERN BALTIMORE MD-HARFORD MD-
256 PM EDT THU JUL 7 2011

...HEAVY RAIN TO AFFECT NORTHERN BALTIMORE AND HARFORD COUNTIES...

AT 256 PM EDT...DOPPLER RADAR INDICATED THUNDERSTORMS PRODUCING VERY
HEAVY RAIN ALONG A LINE EXTENDING FROM 7 MILES NORTHWEST OF MARYLAND
LINE TO 4 MILES NORTHEAST OF SCARBORO...MOVING EAST AT 10 MPH.

LOCATIONS IMPACTED INCLUDE DARLINGTON.

HEAVY RAIN WITH THESE STORMS WILL REDUCE VISIBILITIES TO BELOW ONE
MILE AND MAY CAUSE PONDING OF WATER ON ROADWAYS.

&&

LAT...LON 3970 7622 3965 7615 3962 7615 3960 7612
      3968 7667 3972 7669 3973 7623
TIME...MOT...LOC 1856Z 260DEG 10KT 3980 7673 3969 7624

KRAMAR

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 7, 5:39 PM EDT	Special Marine Warning	LWX		66 min
Jul 7, 6:01 PM EDT	Special Marine Warning	LWX		89 min
Jul 7, 7:39 PM EDT	Special Marine Warning	LWX		96 min
Jul 7, 2:56 PM EDT	Special Weather Statement	LWX	Harford	34 min
Jul 7, 4:31 PM EDT	Special Weather Statement	LWX	Allegany	29 min
Jul 7, 4:37 PM EDT	Severe Thunderstorm Warning	LWX	Allegany	38 min
Jul 7, 4:58 PM EDT	Flash Flood Warning	LWX	Allegany	91 min
Jul 7, 5:01 PM EDT	Special Weather Statement	LWX	Harford	29 min
Jul 7, 5:14 PM EDT	Special Weather Statement	LWX	Harford	31 min
Jul 7, 5:16 PM EDT	Special Weather Statement	LWX	Allegany	29 min
Jul 7, 5:36 PM EDT	Flash Flood Warning	LWX	Harford	113 min
Jul 7, 5:49 PM EDT	Special Weather Statement	LWX	City of Baltimore	26 min
Jul 7, 5:54 PM EDT	Special Weather Statement	LWX	City of Baltimore	36 min
Jul 7, 6:04 PM EDT	Severe Thunderstorm Warning	LWX	Baltimore, City of Baltimore	41 min
Jul 7, 6:16 PM EDT	Severe Thunderstorm Warning	LWX	Anne Arundel, Baltimore, City of Baltimore	44 min
Jul 7, 6:21 PM EDT	Flash Flood Warning	LWX	Baltimore, City of Baltimore	3 hr
Jul 7, 6:44 PM EDT	Special Weather Statement	LWX	City of Baltimore	31 min
Jul 7, 6:52 PM EDT	Special Weather Statement	LWX	Anne Arundel	23 min
Jul 7, 7:15 PM EDT	Special Weather Statement	LWX	Frederick	30 min
Jul 7, 7:38 PM EDT	Special Weather Statement	LWX	City of Baltimore	37 min
Jul 7, 7:24 PM EDT	Special Weather Statement	LWX	Grant	36 min
Jul 7, 7:44 PM EDT	Special Weather Statement	LWX	Grant	31 min
Jul 7, 7:49 PM EDT	Flash Flood Warning	LWX	Grant	3 hr

Nearby

Flash Flood Watches in Virginia, 2011 Flash Flood Watches in Maryland, 2011 Flash Flood Watches in West Virginia, 2011 Every flash flood watch in 2011

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.