Alert archive / Maryland / Severe Thunderstorm Watches in 2020
Severe Thunderstorm Watch 484
The Storm Prediction Center issued this severe thunderstorm watch at Sep 2, 2020, 6:43 PM EDT for 5 states. It was in force for 5 hr.
The area
The outline as issued.
The facts
- Issued
- Sep 2, 2020, 6:43 PM EDT (22:43 UTC)
- Expired
- Sep 2, 2020, 11:13 PM EDT
- In force
- 5 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1 in
- Strongest gust expected
- 60 kt
All 46 counties
Kent County, DE, New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Carroll County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Talbot County, MD, Cumberland County, NJ, Gloucester County, NJ, Salem County, NJ, Adams County, PA, Berks County, PA, Chester County, PA, Cumberland County, PA, Dauphin County, PA, Delaware County, PA, Lancaster County, PA, Lebanon County, PA, Montgomery County, PA, Philadelphia County, PA, York County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, Fairfax County, VA, Fauquier County, VA, King George County, VA, Loudoun County, VA, Prince William County, VA, Spotsylvania County, VA, Stafford County, VA
The radar
The Sterling radar (KLWX), 88 km from the middle of the area, began a volume at 22:43 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
- 20%
- One or more EF2 to EF5 tornadoes
- 5%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 5%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 50%
Warnings issued inside it
9 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 2, 6:54 PM EDT | Severe Thunderstorm Warning | LWX | Carroll, Frederick | 51 min |
| Sep 2, 7:06 PM EDT | Severe Thunderstorm Warning | LWX | Frederick, Howard, Montgomery | 39 min |
| Sep 2, 7:36 PM EDT | Severe Thunderstorm Warning | LWX | Baltimore, Carroll, Harford, Howard | 39 min |
| Sep 2, 7:38 PM EDT | Severe Thunderstorm Warning | LWX | Howard, Montgomery | 33 min |
| Sep 2, 8:02 PM EDT | Severe Thunderstorm Warning | LWX | Harford | 43 min |
| Sep 2, 8:07 PM EDT | Severe Thunderstorm Warning | PHI | Cecil | 53 min |
| Sep 2, 8:45 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel | 9 min |
| Sep 2, 8:47 PM EDT | Severe Thunderstorm Warning | PHI | Caroline, Cecil, Kent, Queen Anne's, Talbot | 58 min |
| Sep 2, 10:08 PM EDT | Severe Thunderstorm Warning | PHI | Caroline, Queen Anne's, Talbot | 67 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
Washington/Dulle, VA (KIAD), launched 12:00Z, 10.7 hours before the alert went out and 82 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
- 158 J/kg
- Mixed-layer CIN
- -27 J/kg
- Mixed-layer LCL
- 488 m above ground
- 0-6 km bulk shear
- 44 kt
- 0-1 km storm-relative helicity
- 126 m²/s²
- 0-3 km storm-relative helicity
- 173 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.4
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 2, 3:37 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 9 more | 53 min |
Nearby
Severe Thunderstorm Watches in Maryland, 2020Severe Thunderstorm Watches in Virginia, 2020Severe Thunderstorm Watches in Pennsylvania, 2020Every severe thunderstorm watch in 2020
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.