Alert archive / Massachusetts / Severe Thunderstorm Warnings in 2021

Severe Thunderstorm Warning 77, NWS Boston/Norton, MA

July 17, 2021Worcester County, Massachusetts

NWS Boston/Norton, MA issued this severe thunderstorm warning at Jul 17, 2021, 4:05 PM EDT for Worcester County, Massachusetts. It was in force for 34 min. 1 report 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, 4:05 PM EDT (20:05 UTC)
Expired: Jul 17, 2021, 4:39 PM EDT
In force: 34 min
Issued by: NWS Boston/Norton, MA
Area: Storm-based polygon
Hail: 1.0 in
Wind: 60.0 mph

County Worcester County, MA

The radar

The Boston radar (KBOX), 53 km from the middle of the area, began a volume at 20:09 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, 4:27 PM EDT	TSTM WND DMG	Auburn, MA	UTILLITY POLE AND WIRES DOWN ON ROCK AVE

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

The nearest sounding before it

Brookhaven, NY (KOKX), launched 12:00Z, 8.1 hours before the alert went out and 174 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: 1203 J/kg
Mixed-layer CIN: -55 J/kg
Mixed-layer LCL: 1054 m above ground
0-6 km bulk shear: 24 kt
0-1 km storm-relative helicity: 35 m²/s²
0-3 km storm-relative helicity: 46 m²/s²
Significant tornado parameter: 0.2
Supercell composite: 1.0

Open this sounding in Storm Lab

The text

As transmitted.

689 
WUUS51 KBOX 172005
SVRBOX
MAC027-172100-
/O.NEW.KBOX.SV.W.0077.210717T2005Z-210717T2100Z/

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

The National Weather Service in Boston/Norton has issued a

* Severe Thunderstorm Warning for...
  Southeastern Worcester County in central Massachusetts...

* Until 500 PM EDT.

* At 405 PM EDT, a severe thunderstorm was located over Oxford, or 12
  miles southwest of Worcester, moving east at 15 mph.

  HAZARD...60 mph wind gusts and quarter size hail.

  SOURCE...Radar indicated.

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

* Locations impacted include...
  Worcester, Westborough, Grafton, Webster, Auburn, Northbridge,
  Oxford, Uxbridge, Millbury, Charlton, Dudley, Leicester, Sutton,
  Douglas, Upton, Mendon and Millville.

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 4227 7160 4221 7160 4220 7159 4202 7157
      4203 7199 4218 7200
TIME...MOT...LOC 2005Z 259DEG 11KT 4210 7190 

HAIL...1.00IN
WIND...60MPH
 
$$

Chai

1 follow-up statement

223 
WWUS51 KBOX 172039
SVSBOX

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

MAC027-172049-
/O.CAN.KBOX.SV.W.0077.000000T0000Z-210717T2100Z/
Worcester MA-
439 PM EDT Sat Jul 17 2021

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN WORCESTER COUNTY
IS CANCELLED...
        
The storm which prompted the warning has moved out of the area.
Therefore, the warning has been cancelled.

LAT...LON 4227 7160 4221 7160 4220 7159 4202 7157
      4203 7199 4218 7200
TIME...MOT...LOC 2038Z 259DEG 11KT 4212 7176 

$$

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, 4:15 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, 5:10 PM EDT	Severe Thunderstorm Warning	BOX	Middlesex, Worcester	65 min
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.