Alert archive / Virginia / Flood Watches in 2012

Flood Watch 3, NWS Baltimore/Washington

October 27, 201221 counties in Virginia; 11 counties in Maryland; 7 counties in West Virginia

NWS Baltimore/Washington issued this flood watch at Oct 27, 2012, 4:39 AM EDT for 21 counties in Virginia; 11 counties in Maryland; 7 counties in West Virginia. It took effect at Oct 29, 2012, 2:00 AM EDT. It was in force for 16 hr.

The area

The counties it named.

The facts

Issued: Oct 27, 2012, 4:39 AM EDT (08:39 UTC)
In effect from: Oct 29, 2012, 2:00 AM EDT
Expired: Oct 29, 2012, 5:47 PM EDT
In force: 16 hr
Issued by: NWS Baltimore/Washington
Flood severity: None

All 39 counties

Allegany County, MD, 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, Washington County, MD, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Frederick County, VA, Greene County, VA, King George County, VA, Madison County, VA, Orange County, VA, Page County, VA, Rappahannock County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford 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), 22 km from the middle of the area, began a volume at 08:39 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 00:00Z, 8.7 hours before the alert went out and 29 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: 3 J/kg
Mixed-layer CIN: -12 J/kg
Mixed-layer LCL: 844 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 68 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 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 flood watch went out at Oct 27, 4:34 AM EDT, 5 minutes earlier.

Area forecast discussion, Oct 27, 4:34 AM EDT, 5 minutes before

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Hazardous weather outlook, Oct 27, 1:32 AM EDT, 3 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
Oct 27, 1:28 AM EDT	Gale Warning	LWX		16 hr
Oct 27, 5:01 PM EDT	Storm Warning	LWX		58 hr
Oct 27, 5:02 PM EDT	Coastal Flood Watch	LWX	Arlington, Fairfax, King George, Stafford, City of Alexandria, City of Fairfax and 1 more	24 hr
Oct 27, 5:02 PM EDT	Coastal Flood Advisory	LWX	Arlington, City of Alexandria, City of Falls Church	48 hr
Oct 27, 5:02 PM EDT	High Wind Watch	LWX	Arlington, Clarke, Culpeper, Fairfax, Fauquier, Frederick and 22 more	12 hr

Nearby

Flood Watches in Virginia, 2012 Flood Watches in Maryland, 2012 Flood Watches in West Virginia, 2012 Every flood watch in 2012

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.