Alert archive / Virginia / Severe Thunderstorm Watches in 2018
Severe Thunderstorm Watch 98
The Storm Prediction Center issued this severe thunderstorm watch at May 15, 2018, 5:54 PM EDT for 9 counties in Maryland; 12 counties in Virginia. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- May 15, 2018, 5:54 PM EDT (21:54 UTC)
- Expired
- May 15, 2018, 10:00 PM EDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 2 in
- Strongest gust expected
- 60 kt
All 21 counties
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, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Manassas, VA, City of Manassas Park, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Loudoun County, VA, Prince William County, VA, Rappahannock County, VA
The radar
The Sterling radar (KLWX), 42 km from the middle of the area, began a volume at 21:56 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
- 5%
- One or more EF2 to EF5 tornadoes
- 2%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 30%
- One or more hailstones of 2 inches or more
- 30%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
13 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 15, 6:07 PM EDT | Severe Thunderstorm Warning | LWX | Carroll, Frederick | 38 min |
| May 15, 6:11 PM EDT | Severe Thunderstorm Warning | LWX | Fauquier, Rappahannock, Warren | 26 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, 7:18 PM EDT | Severe Thunderstorm Warning | LWX | Frederick, Washington | 42 min |
| May 15, 7:41 PM EDT | Flash Flood Warning | LWX | Frederick | 3 hr |
| May 15, 7:54 PM EDT | Severe Thunderstorm Warning | LWX | Frederick, Montgomery, Washington | 51 min |
| May 15, 7:56 PM EDT | Flash Flood Warning | LWX | Frederick | 3 hr |
| May 15, 8:20 PM EDT | Flash Flood Warning | LWX | Frederick, Washington | 3 hr |
| May 15, 8:34 PM EDT | Severe Thunderstorm Warning | LWX | Montgomery, Prince George's | 41 min |
| May 15, 8:40 PM EDT | Flash Flood Warning | LWX | Frederick | 3 hr |
Discussions around it
SPC mesoscale discussions over the same counties from four hours before the watch to its end.
The nearest sounding before it
Washington/Dulle, VA (KIAD), launched 12:00Z, 9.9 hours before the alert went out and 39 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.
- Mixed-layer CAPE
- 47 J/kg
- Mixed-layer CIN
- -484 J/kg
- Mixed-layer LCL
- 1259 m above ground
- 0-6 km bulk shear
- 21 kt
- 0-1 km storm-relative helicity
- 117 m²/s²
- 0-3 km storm-relative helicity
- 79 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 15, 1:46 PM EDT | Severe Thunderstorm Watch | SPC | Caroline, Cecil, Kent, Queen Anne's, Talbot | 9 hr |
| May 15, 3:33 PM EDT | Mesoscale Discussion | SPC | Cecil, Harford | 117 min |
| May 15, 5:43 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Caroline, Charles, Dorchester and 10 more | 92 min |
Nearby
Severe Thunderstorm Watches in Virginia, 2018Severe Thunderstorm Watches in Maryland, 2018Every severe thunderstorm 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.