Alert archive / Maryland / Severe Thunderstorm Watches in 2021
Severe Thunderstorm Watch 69
The Storm Prediction Center issued this severe thunderstorm watch at Mar 28, 2021, 5:05 PM EDT for 4 states. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Mar 28, 2021, 5:05 PM EDT (21:05 UTC)
- Expired
- Mar 28, 2021, 9:00 PM EDT
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 0.5 in
- Strongest gust expected
- 60 kt
All 34 counties
Kent County, DE, New Castle County, DE, Sussex 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, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Talbot County, MD, Atlantic County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Mercer County, NJ, Monmouth County, NJ, Ocean County, NJ, Salem County, NJ, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA
The radar
The Dover AFB radar (KDOX), 65 km from the middle of the area, began a volume at 21:05 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 |
|---|---|---|---|---|
| Mar 28, 5:05 PM EDT | Severe Thunderstorm Warning | LWX | Baltimore, Carroll, Howard, Montgomery | 40 min |
| Mar 28, 5:37 PM EDT | Severe Thunderstorm Warning | LWX | Baltimore, Harford, City of Baltimore | 38 min |
| Mar 28, 5:43 PM EDT | Severe Thunderstorm Warning | LWX | Cecil, Harford | 47 min |
| Mar 28, 6:12 PM EDT | Severe Thunderstorm Warning | PHI | New Castle | 48 min |
| Mar 28, 6:43 PM EDT | Severe Thunderstorm Warning | PHI | Hunterdon, Mercer, Middlesex, Morris, Somerset, Warren | 47 min |
| Mar 28, 6:47 PM EDT | Severe Thunderstorm Warning | PHI | New Castle | 43 min |
| Mar 28, 7:05 PM EDT | Severe Thunderstorm Warning | LWX | Anne Arundel, Calvert, Charles, Prince George's, Saint Mary's | 55 min |
| Mar 28, 7:17 PM EDT | Severe Thunderstorm Warning | PHI | Mercer, Middlesex, Monmouth, Ocean, Somerset | 60 min |
| Mar 28, 7:20 PM EDT | Severe Thunderstorm Warning | PHI | Atlantic, Burlington, Camden, Gloucester, Monmouth, Ocean | 70 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
Wallops Is Stn, VA (KWAL), launched 12:00Z, 9.1 hours before the alert went out and 162 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
- 0 J/kg
- Mixed-layer CIN
- No buoyant parcel
- Mixed-layer LCL
- 644 m above ground
- 0-6 km bulk shear
- 64 kt
- 0-1 km storm-relative helicity
- 140 m²/s²
- 0-3 km storm-relative helicity
- 249 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- -0.0
The text
As transmitted.
399 WWUS20 KWNS 282101 SEL9 SPC WW 282101 DCZ000-DEZ000-MDZ000-NJZ000-PAZ000-VAZ000-CWZ000-290100- URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 69 NWS Storm Prediction Center Norman OK 505 PM EDT Sun Mar 28 2021 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of District Of Columbia Delaware Eastern Maryland Southern New Jersey Extreme southeastern Pennsylvania Northeastern Virginia Coastal Waters * Effective this Sunday afternoon and evening from 505 PM until 900 PM EDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible A tornado or two possible SUMMARY...A narrow band of shallow convection along a cold front will likely persist while moving eastward from Maryland and Virginia into New Jersey and Delaware the remainder of this afternoon into this evening. A few damaging gusts will be the main threat, though a brief tornado with embedded circulations cannot be ruled out. The severe thunderstorm watch area is approximately along and 70 statute miles east and west of a line from 10 miles north of Philadelphia PA to 50 miles south southwest of Dover DE. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU9). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for 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. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 68... AVIATION...A few severe thunderstorms with hail surface and aloft to 0.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 400. Mean storm motion vector 27040. ...Thompson
SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 28, 1:24 PM EDT | Mesoscale Discussion | SPC | Kent, Sussex | 2 hr |
| Mar 28, 7:05 PM EDT | Mesoscale Discussion | SPC | New Castle | 115 min |
Nearby
Severe Thunderstorm Watches in Maryland, 2021Severe Thunderstorm Watches in New Jersey, 2021Severe Thunderstorm Watches in Pennsylvania, 2021Every severe thunderstorm watch in 2021
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.