Alert archive / Virginia / Flash Flood Watches in 2018

Flash Flood Watch 17, NWS Blacksburg, VA

September 27, 201824 counties in Virginia; Alleghany County, Ashe County, Watauga County, North Carolina; 4 counties in West Virginia

NWS Blacksburg, VA issued this flash flood watch at Sep 27, 2018, 3:11 AM EDT for 24 counties in Virginia; Alleghany County, Ashe County, Watauga County, North Carolina; 4 counties in West Virginia. It took effect at Sep 27, 2018, 5:00 AM EDT. It was in force for 19 hr.

The area

The counties it named.

The facts

Issued: Sep 27, 2018, 3:11 AM EDT (07:11 UTC)
In effect from: Sep 27, 2018, 5:00 AM EDT
Expired: Sep 28, 2018, 12:00 AM EDT
In force: 19 hr
Issued by: NWS Blacksburg, VA
Flood severity: None

All 31 counties

Alleghany County, NC, Ashe County, NC, Watauga County, NC, Alleghany County, VA, Amherst County, VA, Bath County, VA, Bland County, VA, Botetourt County, VA, Carroll County, VA, City of Buena Vista, VA, City of Covington, VA, City of Galax, VA, City of Lexington, VA, City of Radford, VA, City of Roanoke, VA, City of Salem, VA, Craig County, VA, Floyd County, VA, Giles County, VA, Grayson County, VA, Montgomery County, VA, Pulaski County, VA, Roanoke County, VA, Rockbridge County, VA, Smyth County, VA, Tazewell County, VA, Wythe County, VA, Greenbrier County, WV, Mercer County, WV, Monroe County, WV, Summers County, WV

The radar

The Roanoke radar (KFCX), 32 km from the middle of the area, began a volume at 07:11 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, 7.2 hours before the alert went out and 330 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: 32 J/kg
Mixed-layer CIN: -60 J/kg
Mixed-layer LCL: 1002 m above ground
0-6 km bulk shear: 29 kt
0-1 km storm-relative helicity: 6 m²/s²
0-3 km storm-relative helicity: 59 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.2

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 Blacksburg, VA wrote its last area forecast discussion before this flash flood watch went out at Sep 27, 12:55 AM EDT, 2 hours 16 minutes earlier.

Area forecast discussion, Sep 27, 12:55 AM EDT, 2 hours 16 minutes before

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Hazardous weather outlook, Sep 26, 7:58 PM EDT, 7 hours 13 minutes before

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The office that day

Everything else NWS Blacksburg, VA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 27, 6:45 PM EDT	Special Weather Statement	RNK	Smyth, Wythe	60 min
Sep 27, 6:50 PM EDT	Special Weather Statement	RNK	Carroll, City of Galax	55 min
Sep 27, 5:58 PM EDT	Special Weather Statement	RNK	Rockingham	47 min
Sep 27, 6:09 PM EDT	Special Weather Statement	RNK	Stokes	51 min
Sep 27, 7:05 PM EDT	Special Weather Statement	RNK	Yadkin	55 min
Sep 27, 6:06 PM EDT	Special Weather Statement	RNK	Mercer, Summers	39 min

Nearby

Flash Flood Watches in Virginia, 2018 Flash Flood Watches in West Virginia, 2018 Flash Flood Watches in North Carolina, 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.