Alert archive / Massachusetts / Flash Flood Warnings in 2021

Flash Flood Warning 15, NWS Boston/Norton, MA

July 18, 2021Hampden County, Hampshire County, Massachusetts

NWS Boston/Norton, MA issued this flash flood warning at Jul 18, 2021, 7:11 PM EDT for Hampden County, Hampshire County, Massachusetts. It was in force for 3 hr. 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 18, 2021, 7:11 PM EDT (23:11 UTC)
Expired: Jul 18, 2021, 10:05 PM EDT
In force: 3 hr
Issued by: NWS Boston/Norton, MA
Area: Storm-based polygon
Flood severity: None

Counties Hampden County, MA, Hampshire County, MA

The radar

The Albany radar (KENX), 102 km from the middle of the area, began a volume at 23:13 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

Albany, NY (KALY), launched 12:00Z, 11.2 hours before the alert went out and 89 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: 4 J/kg
Mixed-layer CIN: -107 J/kg
Mixed-layer LCL: 522 m above ground
0-6 km bulk shear: 18 kt
0-1 km storm-relative helicity: 85 m²/s²
0-3 km storm-relative helicity: 107 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

048 
WGUS51 KBOX 182311
FFWBOX
MAC013-015-190215-
/O.NEW.KBOX.FF.W.0015.210718T2311Z-210719T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Boston/Norton MA
711 PM EDT Sun Jul 18 2021

The National Weather Service in Norton has issued a

* Flash Flood Warning for...
  Western Hampden County in western Massachusetts...
  Western Hampshire County in western Massachusetts...

* Until 1015 PM EDT.

* At 711 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 0.5 and 1 inch of rain 
  has fallen. The expected rainfall rate is 1 to 2 inches in 3 
  hours. Flash flooding is 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...
  Westfield, Northampton, Southwick, Southampton, Hatfield, 
  Williamsburg, Huntington, Conway, Russell, Ashfield, Westhampton, 
  Granville, Whately, Chester, Blandford, Chesterfield, Worthington, 
  Goshen, Cummington and Montgomery.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly terrain there are hundreds of low water crossings which are 
potentially dangerous in heavy rain. Do not attempt to cross flooded 
roads. Find an alternate route.

&&

LAT...LON 4231 7300 4233 7306 4238 7307 4238 7301
      4256 7298 4254 7288 4248 7287 4245 7270
      4241 7270 4241 7267 4237 7267 4236 7274
      4227 7274 4226 7281 4220 7278 4212 7285
      4204 7283 4204 7305 4215 7307 4214 7303

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1-2 INCHES IN 3 HOURS

$$

GF

1 follow-up statement

047 
WGUS71 KBOX 190205
FFSBOX

Flash Flood Statement
National Weather Service Boston/Norton MA
1005 PM EDT Sun Jul 18 2021

MAC013-015-190215-
/O.CAN.KBOX.FF.W.0015.000000T0000Z-210719T0215Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Hampden MA-Hampshire MA-
1005 PM EDT Sun Jul 18 2021

...FLASH FLOOD WARNING IS CANCELLED FOR WESTERN HAMPDEN AND WESTERN 
HAMPSHIRE COUNTIES...

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

A Flash Flood Watch remains in effect until 1100 PM EDT for portions 
of northern Connecticut and Massachusetts.

LAT...LON 4231 7300 4233 7306 4238 7307 4238 7301
      4256 7298 4254 7288 4248 7287 4245 7270
      4241 7270 4241 7267 4237 7267 4236 7274
      4227 7274 4226 7281 4220 7278 4212 7285
      4204 7283 4204 7305 4215 7307 4214 7303

$$

BW

The office that day

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

Issued	Product	Office	Counties	Lasted
Jul 17, 9:54 PM EDT	Special Weather Statement	BOX	Hampden, Hampshire	51 min
Jul 17, 10:38 PM EDT	Special Weather Statement	BOX	Franklin, Hampshire	52 min
Jul 17, 11:37 PM EDT	Special Weather Statement	BOX	Worcester	38 min
Jul 18, 2:48 AM EDT	Areal Flood Warning	BOX	Hampden, Hampshire, Worcester	105 min
Jul 18, 2:59 AM EDT	Special Weather Statement	BOX	Worcester	61 min
Jul 18, 3:54 AM EDT	Special Weather Statement	BOX	Worcester	51 min
Jul 18, 6:17 AM EDT	Areal Flood Warning	BOX	Franklin	3 hr
Jul 18, 6:22 AM EDT	Areal Flood Warning	BOX	Hampden, Hampshire, Worcester	5 hr
Jul 18, 12:19 PM EDT	Areal Flood Warning	BOX	Hampden, Hampshire, Worcester	21 hr
Jul 18, 1:40 PM EDT	Areal Flood Warning	BOX	Worcester	6 hr
Jul 18, 5:49 PM EDT	Special Weather Statement	BOX	Hampden	56 min
Jul 18, 6:36 PM EDT	Special Weather Statement	BOX	Hampshire	54 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.