Alert archive / Virginia / Tornado Watches in 2018

Tornado Watch 54

April 15, 201814 counties in Virginia

The Storm Prediction Center issued this tornado watch at Apr 15, 2018, 6:14 PM EDT for 14 counties in Virginia. It was in force for 7 hr.

The area

The outline as issued.

The facts

Issued
Apr 15, 2018, 6:14 PM EDT (22:14 UTC)
Expired
Apr 16, 2018, 1:40 AM EDT
In force
7 hr
Issued by
the Storm Prediction Center
Largest hail expected
1 in
Strongest gust expected
60 kt

Counties Amelia County, VA, Brunswick County, VA, Chesterfield County, VA, City of Richmond, VA, Cumberland County, VA, Dinwiddie County, VA, Fluvanna County, VA, Goochland County, VA, Henrico County, VA, Lunenburg County, VA, Mecklenburg County, VA, Nottoway County, VA, Powhatan County, VA, Prince Edward County, VA

The radar

The Norfolk radar (KAKQ), 97 km from the middle of the area, began a volume at 22:15 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
50%
One or more EF2 to EF5 tornadoes
10%
Ten or more severe wind reports
60%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
10%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
70%

Warnings issued inside it

11 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

IssuedProductOfficeCountiesLasted
Apr 15, 7:05 PM EDTSevere Thunderstorm WarningAKQPrince Edward40 min
Apr 15, 7:48 PM EDTSevere Thunderstorm WarningAKQCumberland, Fluvanna, Goochland42 min
Apr 15, 8:24 PM EDTSevere Thunderstorm WarningAKQAmelia, Cumberland, Lunenburg, Nottoway, Prince Edward36 min
Apr 15, 8:30 PM EDTSevere Thunderstorm WarningAKQCumberland, Fluvanna, Goochland30 min
Apr 15, 8:38 PM EDTSevere Thunderstorm WarningAKQLunenburg, Mecklenburg37 min
Apr 15, 8:59 PM EDTSevere Thunderstorm WarningAKQAmelia, Cumberland, Goochland, Louisa, Powhatan61 min
Apr 15, 9:46 PM EDTTornado WarningAKQLunenburg, Nottoway29 min
Apr 15, 10:14 PM EDTTornado WarningAKQAmelia, Chesterfield, Nottoway31 min
Apr 15, 10:39 PM EDTTornado WarningAKQAmelia, Chesterfield, Goochland, Powhatan21 min
Apr 15, 11:04 PM EDTTornado WarningAKQBrunswick, Lunenburg, Nottoway17 min
Apr 15, 11:22 PM EDTSevere Thunderstorm WarningAKQGoochland, Hanover, Louisa, Powhatan23 min

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Roanoke, VA (KRNK), launched 12:00Z, 10.2 hours before the alert went out and 136 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, Roanoke, VA at 12:00Z on 2018-04-15Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 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, Roanoke, VA at 12:00Z on 2018-04-15The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 143 square meters per square second.19395878Sfc1 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
881 m above ground
0-6 km bulk shear
44 kt
0-1 km storm-relative helicity
143 m²/s²
0-3 km storm-relative helicity
148 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

485 
WWUS20 KWNS 152211
SEL4  
SPC WW 152211
VAZ000-160400-

URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 54
NWS Storm Prediction Center Norman OK
615 PM EDT Sun Apr 15 2018

The NWS Storm Prediction Center has issued a

* Tornado Watch for portions of 
  South Central Virginia

* Effective this Sunday night from 615 PM until Midnight EDT.

* Primary threats include...
  A few tornadoes possible
  Scattered damaging wind gusts to 70 mph likely

SUMMARY...A line of intense thunderstorms over central North
Carolina will track north-northeastward into the watch area this
evening, posing a threat of locally damaging wind gusts and a few
tornadoes.

The tornado watch area is approximately along and 30 statute miles
east and west of a line from 90 miles north of South Hill VA to 15
miles south southwest of South Hill VA. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU4).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and severe thunderstorms in and close to the watch
area. Persons in these areas should be on the lookout for
threatening weather conditions and listen for later statements
and possible warnings.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 52...WW 53...

AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 1 inch. Extreme turbulence and surface wind
gusts to 60 knots. A few cumulonimbi with maximum tops to 450. Mean
storm motion vector 21040.

...Hart

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 15, 12:13 PM EDTTornado WatchSPCCarroll, Floyd, Grayson, City of Galax9 hr
Apr 15, 2:29 PM EDTMesoscale DiscussionSPCAmherst, Appomattox, Bedford, Botetourt, Buckingham, Campbell and 21 more91 min
Apr 15, 3:02 PM EDTTornado WatchSPCAmherst, Appomattox, Bedford, Botetourt, Buckingham, Campbell and 20 more8 hr
Apr 15, 5:45 PM EDTMesoscale DiscussionSPCAlleghany, Amherst, Appomattox, Bedford, Botetourt, Buckingham and 22 more90 min
Apr 15, 6:28 PM EDTMesoscale DiscussionSPCAmelia, Brunswick, Buckingham, Charlotte, Chesterfield, Cumberland and 17 more62 min

Nearby

Tornado Watches in Virginia, 2018Every tornado 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.