Alert archive / Massachusetts / Flash Flood Warnings in 2020

Flash Flood Warning 13, NWS Boston/Norton, MA

August 23, 20204 counties in Massachusetts

NWS Boston/Norton, MA issued this flash flood warning at Aug 23, 2020, 5:47 PM EDT for 4 counties in Massachusetts. It was in force for 118 min. 6 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: Aug 23, 2020, 5:47 PM EDT (21:47 UTC)
Expired: Aug 23, 2020, 7:45 PM EDT
In force: 118 min
Issued by: NWS Boston/Norton, MA
Area: Storm-based polygon
Flood severity: None

Counties Middlesex County, MA, Norfolk County, MA, Suffolk County, MA, Worcester County, MA

The radar

The Boston radar (KBOX), 36 km from the middle of the area, began a volume at 21:48 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
Aug 23, 5:47 PM EDT	FLOOD	Worcester, MA	CATCH BASINS OVERFLOWED RESULTING IN FLOODING INTO RESIDENCE ON OUTLOOK DRIVE
Aug 23, 5:51 PM EDT	FLOOD	Worcester, MA	VEHICLE DROVE INTO FLOOD WATERS AND GOT STUCK ON DEWEY ST. STREET IMPASSABLE.
Aug 23, 5:59 PM EDT	FLOOD	Worcester, MA	CAR FILLED WITH WATER, PERSON TRAPPED DUE TO FLOODING ON WEBSTER ST
Aug 23, 5:59 PM EDT	FLOOD	Worcester, MA	GRAFTON ST CLOSED FROM DANA ST TO WARNER AVE DUE TO FLOODING.
Aug 23, 6:10 PM EDT	FLOOD	Westwood, MA	YALE ST AT UNIVERSITY AVE FLOODED AND IMPASSABLE
Aug 23, 6:30 PM EDT	FLOOD	Canton, MA	CAR STUCK IN FLOODING ON BOLIVAR ST

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

The nearest sounding before it

Chatham, MA (KCHH), launched 12:00Z, 9.8 hours before the alert went out and 126 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: 20 J/kg
Mixed-layer CIN: -159 J/kg
Mixed-layer LCL: 1231 m above ground
0-6 km bulk shear: 23 kt
0-1 km storm-relative helicity: 15 m²/s²
0-3 km storm-relative helicity: 33 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted.

400 
WGUS51 KBOX 232147
FFWBOX
MAC017-021-025-027-232345-
/O.NEW.KBOX.FF.W.0013.200823T2147Z-200823T2345Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boston/Norton MA
547 PM EDT Sun Aug 23 2020

The National Weather Service in Boston/Norton has issued a

* Flash Flood Warning for...
  Suffolk County in eastern Massachusetts...
  Central Norfolk County in eastern Massachusetts...
  Southeastern Worcester County in central Massachusetts...
  Southeastern Middlesex County in northeastern Massachusetts...

* Until 745 PM EDT.

* At 546 PM EDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Flash flooding is ongoing or
  expected to begin shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar indicated.

  IMPACT...Flooding of small creeks and streams, urban areas, 
           highways, streets and underpasses as well as other 
           drainage and low lying areas.

* Some locations that will experience flooding include...
  Boston, Worcester, Cambridge, Quincy, Newton, Somerville,
  Framingham, Waltham, Brookline, Marlborough, Braintree, Shrewsbury,
  Natick, Randolph, Watertown, Franklin, Needham, Norwood, Milford
  and Wellesley.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Excessive runoff from heavy rainfall will cause flooding of small
creeks and streams, urban areas, highways, streets and underpasses as
well as other drainage areas and low lying spots.

&&

LAT...LON 4239 7108 4231 7104 4230 7105 4230 7104
      4216 7097 4211 7140 4207 7190 4230 7194

FLASH FLOOD...RADAR INDICATED

$$

Chai

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 23, 1:50 PM EDT	Special Weather Statement	BOX	Franklin	25 min
Aug 23, 2:17 PM EDT	Special Weather Statement	BOX	Franklin	43 min
Aug 23, 2:21 PM EDT	Severe Thunderstorm Warning	BOX	Franklin, Worcester	54 min
Aug 23, 2:36 PM EDT	Special Weather Statement	BOX	Essex	39 min
Aug 23, 3:14 PM EDT	Severe Thunderstorm Warning	BOX	Franklin, Middlesex, Worcester	61 min
Aug 23, 3:47 PM EDT	Severe Thunderstorm Warning	BOX	Essex, Franklin, Middlesex, Worcester	58 min
Aug 23, 4:01 PM EDT	Areal Flood Warning	BOX	Essex	119 min
Aug 23, 4:05 PM EDT	Special Marine Warning	BOX		85 min
Aug 23, 4:12 PM EDT	Severe Thunderstorm Warning	BOX	Middlesex, Worcester	63 min
Aug 23, 4:34 PM EDT	Severe Thunderstorm Warning	BOX	Essex, Middlesex, Norfolk, Suffolk, Worcester	56 min
Aug 23, 4:39 PM EDT	Special Marine Warning	BOX		96 min
Aug 23, 4:44 PM EDT	Severe Thunderstorm Warning	BOX	Middlesex, Worcester	50 min
Aug 23, 4:55 PM EDT	Severe Thunderstorm Warning	BOX	Middlesex, Worcester	65 min
Aug 23, 5:04 PM EDT	Areal Flood Warning	BOX	Essex, Middlesex, Plymouth, Suffolk	116 min
Aug 23, 5:07 PM EDT	Special Marine Warning	BOX		83 min
Aug 23, 5:12 PM EDT	Severe Thunderstorm Warning	BOX	Essex, Middlesex, Norfolk, Plymouth, Suffolk	63 min
Aug 23, 5:17 PM EDT	Areal Flood Warning	BOX	Middlesex, Worcester	118 min
Aug 23, 5:28 PM EDT	Severe Thunderstorm Warning	BOX	Hampden, Hampshire, Worcester	62 min
Aug 23, 5:38 PM EDT	Severe Thunderstorm Warning	BOX	Bristol, Middlesex, Norfolk, Plymouth, Suffolk, Worcester	52 min
Aug 23, 6:03 PM EDT	Special Weather Statement	BOX	Worcester	42 min
Aug 23, 6:10 PM EDT	Severe Thunderstorm Warning	BOX	Bristol, Norfolk, Plymouth	49 min
Aug 23, 6:11 PM EDT	Special Marine Warning	BOX		51 min
Aug 23, 6:15 PM EDT	Severe Thunderstorm Warning	BOX	Franklin, Hampshire, Worcester	60 min
Aug 23, 6:20 PM EDT	Severe Thunderstorm Warning	BOX	Bristol, Norfolk, Plymouth, Worcester	40 min
Aug 23, 6:26 PM EDT	Flash Flood Warning	BOX	Bristol, Norfolk, Plymouth, Suffolk	2 hr
Aug 23, 6:32 PM EDT	Severe Thunderstorm Warning	BOX	Franklin, Hampden, Hampshire, Worcester	58 min
Aug 23, 6:39 PM EDT	Areal Flood Warning	BOX	Bristol, Norfolk, Worcester	2 hr
Aug 23, 6:50 PM EDT	Special Marine Warning	BOX		36 min
Aug 23, 6:55 PM EDT	Flash Flood Warning	BOX	Franklin, Hampden, Hampshire, Worcester	2 hr
Aug 23, 7:22 PM EDT	Severe Thunderstorm Warning	BOX	Hampden, Hampshire, Worcester	53 min
Aug 23, 7:43 PM EDT	Areal Flood Warning	BOX	Middlesex, Norfolk, Suffolk, Worcester	2 hr

Nearby

Flash Flood Warnings in Massachusetts, 2020 Every flash flood warning 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.