Alert archive / Massachusetts / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 83, NWS Boston/Norton, MA

July 17, 2021Middlesex County, Worcester County, Massachusetts

NWS Boston/Norton, MA issued this severe thunderstorm warning at Jul 17, 2021, 5:10 PM EDT for Middlesex County, Worcester County, Massachusetts. It was in force for 65 min. 5 reports came from inside the area while it was in force.

The area

The outline as issued, with what was reported inside it.

The facts

Issued: Jul 17, 2021, 5:10 PM EDT (21:10 UTC)
Expired: Jul 17, 2021, 6:15 PM EDT
In force: 65 min
Issued by: NWS Boston/Norton, MA
Area: Storm-based polygon
Hail: 1.25 in
Wind: 60.0 mph

Counties Middlesex County, MA, Worcester County, MA

The radar

The Boston radar (KBOX), 75 km from the middle of the area, began a volume at 21:09 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 was reported inside it

Time	Report	Where	Remark
Jul 17, 5:13 PM EDT	TSTM WND DMG	Clinton, MA	POWER LINES DOWN ON BEACON STREET AND ON RTE 110. ALSO POWER LINES DOWN ON CALIFORNIA COURT AT BECON STREET
Jul 17, 5:15 PM EDT	TSTM WND DMG	Clinton, MA	TREES AND WIRES DOWN ON A CAR ON PARKER STREET.
Jul 17, 5:15 PM EDT	HAIL 1	Clinton, MA
Jul 17, 5:15 PM EDT	HAIL 1	Clinton, MA
Jul 17, 5:22 PM EDT	HAIL 1.25	Berlin, MA

Local storm reports filed while the alert was in force, from inside its polygon or its counties.

The nearest sounding before it

Gray, ME (KGYX), launched 12:00Z, 9.2 hours before the alert went out and 178 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1373 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: 57 m²/s²
0-3 km storm-relative helicity: 66 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

696 
WUUS51 KBOX 172110
SVRBOX
MAC017-027-172215-
/O.NEW.KBOX.SV.W.0083.210717T2110Z-210717T2215Z/

BULLETIN - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Warning
National Weather Service Boston/Norton MA
510 PM EDT Sat Jul 17 2021

The National Weather Service in Boston/Norton has issued a

* Severe Thunderstorm Warning for...
  Northeastern Worcester County in central Massachusetts...
  North central Middlesex County in northeastern Massachusetts...

* Until 615 PM EDT.

* At 509 PM EDT, a severe thunderstorm was located over Clinton, or 7
  miles north of Shrewsbury, moving northeast at 25 mph.

  HAZARD...60 mph wind gusts and half dollar size hail.

  SOURCE...Radar indicated.

  IMPACT...Expect wind damage to trees and power lines. Minor hail 
           damage to vehicles is possible.

* Locations impacted include...
  Lowell, Leominster, Marlborough, Shrewsbury, Chelmsford, Dracut,
  Westford, Acton, Hudson, Holden, Northborough, Clinton, Pepperell,
  Tyngsborough, Groton, Lunenburg, Townsend, Littleton, Lancaster and
  Sterling.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4270 7129 4268 7125 4228 7166 4237 7187
      4271 7164
TIME...MOT...LOC 2109Z 211DEG 20KT 4240 7171 

HAIL...1.25IN
WIND...60MPH
 
$$

Chai

1 follow-up statement

695 
WWUS51 KBOX 172129
SVSBOX

Severe Weather Statement
National Weather Service Boston/Norton MA
529 PM EDT Sat Jul 17 2021

MAC017-027-172215-
/O.CON.KBOX.SV.W.0083.000000T0000Z-210717T2215Z/
Worcester MA-Middlesex MA-
529 PM EDT Sat Jul 17 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 615 PM EDT
FOR NORTHEASTERN WORCESTER AND NORTH CENTRAL MIDDLESEX COUNTIES...

At 528 PM EDT, a severe thunderstorm was located over Lancaster, or 7
miles east of Leominster, moving northeast at 25 mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated. At 522 PM, half dollar size hail reported 
         in Berlin, MA per Amateur Radio. 

IMPACT...Expect wind damage to trees and power lines. Minor hail 
         damage to vehicles is possible.

Locations impacted include...
Lowell, Leominster, Chelmsford, Dracut, Westford, Acton, Hudson,
Clinton, Pepperell, Tyngsborough, Groton, Lunenburg, Townsend,
Littleton, Lancaster, Sterling, Ayer, Shirley, Stow and Harvard.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Torrential rainfall is occurring with this storm, and may lead to
flash flooding. Do not drive your vehicle through flooded roadways.

&&

LAT...LON 4270 7129 4268 7125 4239 7155 4247 7180
      4271 7164
TIME...MOT...LOC 2128Z 211DEG 20KT 4249 7163 

HAIL...1.25IN
WIND...60MPH
 
$$

Chai

The office that day

Everything else NWS Boston/Norton, MA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 17, 2:37 PM EDT	Special Weather Statement	BOX	Franklin	38 min
Jul 17, 2:45 PM EDT	Special Weather Statement	BOX	Plymouth	45 min
Jul 17, 2:53 PM EDT	Special Weather Statement	BOX	Hampshire	52 min
Jul 17, 2:53 PM EDT	Severe Thunderstorm Warning	BOX	Bristol, Norfolk	52 min
Jul 17, 3:36 PM EDT	Areal Flood Warning	BOX	Bristol	114 min
Jul 17, 4:05 PM EDT	Severe Thunderstorm Warning	BOX	Worcester	34 min
Jul 17, 4:15 PM EDT	Severe Thunderstorm Warning	BOX	Hampden, Worcester	60 min
Jul 17, 4:34 PM EDT	Severe Thunderstorm Warning	BOX	Middlesex, Worcester	36 min
Jul 17, 4:38 PM EDT	Severe Thunderstorm Warning	BOX	Hampden, Hampshire	67 min
Jul 17, 4:48 PM EDT	Flash Flood Warning	BOX	Worcester	3 hr
Jul 17, 4:58 PM EDT	Flash Flood Warning	BOX	Hampden	2 hr
Jul 17, 5:34 PM EDT	Special Weather Statement	BOX	Hampshire	41 min
Jul 17, 5:35 PM EDT	Flash Flood Warning	BOX	Hampden, Hampshire	3 hr
Jul 17, 6:04 PM EDT	Flash Flood Warning	BOX	Hampden, Hampshire	3 hr
Jul 17, 6:05 PM EDT	Severe Thunderstorm Warning	BOX	Bristol	26 min
Jul 17, 7:49 PM EDT	Areal Flood Warning	BOX	Hampden, Worcester	116 min

Nearby

Severe Thunderstorm Warnings in Massachusetts, 2021 Every severe thunderstorm warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.