Alert archive / Massachusetts / Flash Flood Warnings in 2021

Flash Flood Warning 17, NWS Boston/Norton, MA

July 29, 2021Essex County, Massachusetts

NWS Boston/Norton, MA issued this flash flood warning at Jul 29, 2021, 11:30 PM EDT for Essex County, Massachusetts. It was in force for 96 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Jul 29, 2021, 11:30 PM EDT (03:30 UTC)
Expired: Jul 30, 2021, 1:06 AM EDT
In force: 96 min
Issued by: NWS Boston/Norton, MA
Area: Storm-based polygon
Flood severity: None

County Essex County, MA

The radar

The Boston radar (KBOX), 93 km from the middle of the area, began a volume at 03:33 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.

The nearest sounding before it

Gray, ME (KGYX), launched 00:00Z, 3.5 hours before the alert went out and 136 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: 158 J/kg
Mixed-layer CIN: -1 J/kg
Mixed-layer LCL: 492 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: 63 m²/s²
0-3 km storm-relative helicity: 133 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

As transmitted.

717 
WGUS51 KBOX 300330
FFWBOX
MAC009-300730-
/O.NEW.KBOX.FF.W.0017.210730T0330Z-210730T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boston/Norton MA
1130 PM EDT Thu Jul 29 2021

The National Weather Service in Norton has issued a

* Flash Flood Warning for...
  Northwestern Essex County in northeastern Massachusetts...

* Until 330 AM EDT.

* At 1130 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 1 and 2 inches of rain 
  have fallen. Additional rainfall amounts of 1 to 2 inches are 
  possible in the warned area. Flash flooding is ongoing or expected 
  to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar.

  IMPACT...Flash flooding of small creeks and streams, urban
           areas, highways, streets and underpasses as well as
           other poor drainage and low-lying areas.

* Some locations that will experience flash flooding include...
  Lawrence, Haverhill, Methuen, Andover, North Andover, Newburyport, 
  Amesbury, Ipswich, Salisbury, Georgetown, Boxford, Newbury, 
  Groveland, Merrimac, Topsfield, Rowley and West Newbury.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood 
deaths occur in vehicles.

&&

LAT...LON 4263 7118 4274 7125 4274 7118 4281 7117
      4282 7113 4281 7107 4286 7103 4289 7091
      4286 7085 4287 7082 4282 7082 4281 7081
      4281 7082 4280 7081 4281 7068 4276 7066
      4264 7103

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 2 HOURS

$$

Chai

1 follow-up statement

056 
WGUS71 KBOX 300506
FFSBOX

Flash Flood Statement
National Weather Service Boston/Norton MA
106 AM EDT Fri Jul 30 2021

MAC009-300516-
/O.CAN.KBOX.FF.W.0017.000000T0000Z-210730T0730Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Essex MA-
106 AM EDT Fri Jul 30 2021

...FLASH FLOOD WARNING IS CANCELLED FOR NORTHWESTERN ESSEX COUNTY...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed remaining road closures.

LAT...LON 4263 7118 4274 7125 4274 7118 4281 7117
      4281 7107 4286 7103 4289 7091 4286 7085
      4287 7082 4282 7082 4281 7082 4280 7081
      4281 7068 4276 7066 4264 7103

$$

Chai

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 29, 9:12 PM EDT	Special Weather Statement	BOX	Franklin	48 min
Jul 29, 9:30 PM EDT	Special Weather Statement	BOX	Franklin, Hampden, Hampshire	45 min
Jul 29, 10:01 PM EDT	Special Weather Statement	BOX	Hampden, Hampshire	44 min
Jul 29, 10:22 PM EDT	Special Weather Statement	BOX	Hampden, Hampshire	38 min
Jul 29, 10:44 PM EDT	Special Weather Statement	BOX	Hampden	46 min
Jul 29, 11:15 PM EDT	Special Weather Statement	BOX	Essex	45 min
Jul 29, 11:19 PM EDT	Special Weather Statement	BOX	Middlesex	41 min
Jul 29, 11:49 PM EDT	Special Marine Warning	BOX		56 min
Jul 29, 11:52 PM EDT	Special Marine Warning	BOX		53 min
Jul 30, 12:22 AM EDT	Special Weather Statement	BOX	Dukes, Nantucket	38 min
Jul 30, 12:34 AM EDT	Special Weather Statement	BOX	Essex	41 min
Jul 30, 12:43 AM EDT	Special Marine Warning	BOX		62 min
Jul 30, 12:55 AM EDT	Special Marine Warning	BOX		65 min

Nearby

Flash Flood Warnings in Massachusetts, 2021 Every flash flood 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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.