Alert archive / Massachusetts / Flash Flood Warnings in 2021
Flash Flood Warning 20, NWS Boston/Norton, MA
NWS Boston/Norton, MA issued this flash flood warning at Aug 19, 2021, 10:46 AM EDT for 5 counties in Massachusetts. It was in force for 3 hr. 2 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 19, 2021, 10:46 AM EDT (14:46 UTC)
- Expired
- Aug 19, 2021, 1:45 PM EDT
- In force
- 3 hr
- Issued by
- NWS Boston/Norton, MA
- Area
- Storm-based polygon
- Flood severity
- None
Counties Essex County, MA, Middlesex County, MA, Norfolk County, MA, Suffolk County, MA, Worcester County, MA
The radar
The Boston radar (KBOX), 32 km from the middle of the area, began a volume at 14:47 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 19, 12:56 PM EDT | FLOOD | Somerville, MA | MCGRATH HIGHWAY AT MIDDLESEX AVE FLOODED AND IMPASSABLE |
| Aug 19, 1:23 PM EDT | FLOOD | Lynn, MA | MULTIPLE ROAD CLOSED DUE TO FLOODING ACROSS TOWN |
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, 2.8 hours before the alert went out and 200 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
- 110 J/kg
- Mixed-layer CIN
- -40 J/kg
- Mixed-layer LCL
- 884 m above ground
- 0-6 km bulk shear
- 13 kt
- 0-1 km storm-relative helicity
- 36 m²/s²
- 0-3 km storm-relative helicity
- 68 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted.
026
WGUS51 KBOX 191446
FFWBOX
MAC009-017-021-025-027-191745-
/O.NEW.KBOX.FF.W.0020.210819T1446Z-210819T1745Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boston/Norton MA
1046 AM EDT Thu Aug 19 2021
The National Weather Service in Norton has issued a
* Flash Flood Warning for...
Southeastern Worcester County in central Massachusetts...
Norfolk County in eastern Massachusetts...
Suffolk County in eastern Massachusetts...
Southwestern Essex County in northeastern Massachusetts...
Southeastern Middlesex County in northeastern Massachusetts...
* Until 145 PM EDT.
* At 1046 AM EDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Torrential rainfall moving into
the warned area had produced several areas of urban flooding and
road closures in the Worcester area. Up to 1 inch of rain has
fallen. The expected rainfall rate is 1.5 inches in 1 hour. 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...
Boston, Cambridge, Quincy, Lynn, Newton, Somerville, Framingham,
Waltham, Malden, Brookline, Medford, Weymouth, Revere, Peabody,
Arlington, Everett, Salem, Marlborough, Woburn and Braintree.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
&&
LAT...LON 4230 7093 4219 7094 4206 7125 4203 7143
4201 7171 4249 7164 4250 7093
FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1.5 INCHES IN 1 HOUR
$$
AL3 follow-up statements
805
WGUS71 KBOX 191636
FFSBOX
Flash Flood Statement
National Weather Service Boston/Norton MA
1236 PM EDT Thu Aug 19 2021
MAC009-017-021-025-027-191745-
/O.CON.KBOX.FF.W.0020.000000T0000Z-210819T1745Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Essex MA-Middlesex MA-Norfolk MA-Suffolk MA-Worcester MA-
1236 PM EDT Thu Aug 19 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 145 PM EDT THIS
AFTERNOON FOR SOUTHEASTERN WORCESTER, NORFOLK, SUFFOLK, SOUTHWESTERN
ESSEX AND SOUTHEASTERN MIDDLESEX COUNTIES...
At 1236 PM EDT, Doppler radar indicated thunderstorms producing
heavy rain across the warned area. Between 0.5 and 2.5 inches of
rain have fallen. The expected rainfall rate is 1 inch in 1 hour.
There have been no confirmed reports of flooding as of yet, but
flash flooding is ongoing or expected to begin shortly as additional
torrential rain moves over the warned area.
HAZARD...Flash flooding caused by thunderstorms.
SOURCE...Radar.
IMPACT...Flash flooding of small creeks and streams, urban areas,
highways, streets and underpasses as well as other poor
drainage and low-lying areas.
Some locations that will experience flash flooding include...
Boston, Cambridge, Quincy, Lynn, Newton, Somerville, Framingham,
Waltham, Malden, Brookline, Medford, Weymouth, Revere, Peabody,
Arlington, Everett, Salem, Marlborough, Woburn and Braintree.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
&&
LAT...LON 4230 7093 4219 7094 4206 7125 4203 7143
4201 7171 4249 7164 4250 7093
FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1 INCH IN 1 HOUR
$$
AL109
WGUS71 KBOX 191716
FFSBOX
Flash Flood Statement
National Weather Service Boston/Norton MA
116 PM EDT Thu Aug 19 2021
MAC009-017-021-025-027-191745-
/O.CON.KBOX.FF.W.0020.000000T0000Z-210819T1745Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Essex MA-Middlesex MA-Norfolk MA-Suffolk MA-Worcester MA-
116 PM EDT Thu Aug 19 2021
...FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 145 PM EDT THIS
AFTERNOON FOR SOUTHEASTERN WORCESTER, NORFOLK, SUFFOLK, SOUTHWESTERN
ESSEX AND SOUTHEASTERN MIDDLESEX COUNTIES...
At 116 PM EDT, trained weather spotters reported heavy rain
producing thunderstorms producing heavy rain across the warned area
that has triggered flooding. McGrath Highway at Middlesex Ave in
Somerville is flooded and impassable, with a vehicle floating in
floodwaters. Basement flooding was also reported in some homes in
Arlington. A number of gages in Middlesex County are also
experiencing sharp rises due to the excessive rain. Between 0.5 and
2.5 inches of rain have fallen. The expected rainfall rate is 1 inch
in 1 hour. Flash flooding is already occurring, and additional rain
in the warned area may worsen or trigger new areas of flooding.
HAZARD...Flash flooding caused by thunderstorms.
SOURCE...Trained spotters reported.
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...
Boston, Cambridge, Quincy, Lynn, Newton, Somerville, Framingham,
Waltham, Malden, Brookline, Medford, Weymouth, Revere, Peabody,
Arlington, Everett, Salem, Marlborough, Woburn and Braintree.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
&&
LAT...LON 4230 7093 4219 7094 4206 7125 4203 7143
4201 7171 4249 7164 4250 7093
FLASH FLOOD...OBSERVED
EXPECTED RAINFALL...1 INCH IN 1 HOUR
$$
AL513
WGUS71 KBOX 191738
FFSBOX
Flash Flood Statement
National Weather Service Boston/Norton MA
138 PM EDT Thu Aug 19 2021
MAC009-017-021-025-027-191748-
/O.EXP.KBOX.FF.W.0020.000000T0000Z-210819T1745Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Essex MA-Middlesex MA-Norfolk MA-Suffolk MA-Worcester MA-
138 PM EDT Thu Aug 19 2021
...FLASH FLOOD WARNING WILL EXPIRE AT 145 PM EDT THIS AFTERNOON FOR
SOUTHEASTERN WORCESTER, NORFOLK, SUFFOLK, SOUTHWESTERN ESSEX AND
SOUTHEASTERN MIDDLESEX COUNTIES...
The heavy rain has ended. Flooding is no longer expected to pose a
threat. Please continue to heed remaining road closures.
LAT...LON 4230 7093 4219 7094 4206 7125 4203 7143
4201 7171 4249 7164 4250 7093
$$
ALThe office that day
Everything else NWS Boston/Norton, MA issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Aug 19, 8:14 AM EDT | Flash Flood Warning | BOX | Hampden, Worcester | 3 hr |
| Aug 19, 9:18 AM EDT | Flash Flood Warning | BOX | Hampden, Hampshire, Worcester | 3 hr |
| Aug 19, 10:14 AM EDT | Severe Thunderstorm Warning | BOX | Middlesex, Worcester | 44 min |
| Aug 19, 10:21 AM EDT | Tornado Warning | BOX | Middlesex, Worcester | 29 min |
| Aug 19, 11:36 AM EDT | Severe Thunderstorm Warning | BOX | Essex, Middlesex, Norfolk, Suffolk, Worcester | 54 min |
| Aug 19, 11:40 AM EDT | Flash Flood Warning | BOX | Essex, Middlesex | 3 hr |
| Aug 19, 12:32 PM EDT | Severe Thunderstorm Warning | BOX | Essex, Middlesex, Norfolk, Suffolk | 58 min |
| Aug 19, 12:33 PM EDT | Special Marine Warning | BOX | 57 min | |
| Aug 19, 12:49 PM EDT | Tornado Warning | BOX | Essex, Middlesex, Suffolk | 39 min |
| Aug 19, 1:18 PM EDT | Tornado Warning | BOX | Middlesex, Worcester | 27 min |
| Aug 19, 1:37 PM EDT | Special Weather Statement | BOX | Essex | 38 min |
| Aug 19, 1:38 PM EDT | Special Marine Warning | BOX | 67 min | |
| Aug 19, 1:46 PM EDT | Special Weather Statement | BOX | Barnstable | 59 min |
| Aug 19, 1:48 PM EDT | Special Marine Warning | BOX | 57 min | |
| Aug 19, 1:54 PM EDT | Special Weather Statement | BOX | Middlesex | 51 min |
| Aug 19, 2:23 PM EDT | Severe Thunderstorm Warning | BOX | Middlesex | 37 min |
Nearby
Flash Flood Warnings in Massachusetts, 2021Every 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.