Alert archive / New Hampshire / Flash Flood Warnings in 2021

Flash Flood Warning 13, NWS Gray, ME

July 29, 2021Cheshire County, Hillsborough County, New Hampshire

NWS Gray, ME issued this flash flood warning at Jul 29, 2021, 10:32 PM EDT for Cheshire County, Hillsborough County, New Hampshire. 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: Jul 29, 2021, 10:32 PM EDT (02:32 UTC)
Expired: Jul 30, 2021, 1:30 AM EDT
In force: 3 hr
Issued by: NWS Gray, ME
Area: Storm-based polygon
Flood severity: None

Counties Cheshire County, NH, Hillsborough County, NH

The radar

The Boston radar (KBOX), 125 km from the middle of the area, began a volume at 02:32 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 29, 10:55 PM EDT	FLASH FLOOD	2 Ssw Peterborough, NH	OLD JAFFREY ROAD WASHED OUT.
Jul 29, 10:55 PM EDT	FLASH FLOOD	2 Ssw Peterborough, NH	OLD TOWN FARM ROAD WASHED OUT.

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

The nearest sounding before it

Albany, NY (KALY), launched 00:00Z, 2.5 hours before the alert went out and 134 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: 172 J/kg
Mixed-layer CIN: -50 J/kg
Mixed-layer LCL: 842 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 494 m²/s²
0-3 km storm-relative helicity: 635 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 8.8

Open this sounding in Storm Lab

The text

As transmitted.

794 
WGUS51 KGYX 300232
FFWGYX
NHC005-011-300530-
/O.NEW.KGYX.FF.W.0013.210730T0232Z-210730T0530Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Gray ME
1032 PM EDT Thu Jul 29 2021

The National Weather Service in Gray has issued a

* Flash Flood Warning for...
  Southern Cheshire County in southern New Hampshire...
  Southwestern Hillsborough County in southern New Hampshire...

* Until 130 AM EDT.

* At 1032 PM EDT, Doppler radar and automated rain gauges indicated 
  heavy rain falling 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 heavy rain.

  SOURCE...Radar and automated gauges.

  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...
  Jaffrey, Swanzey, Peterborough, Rindge, Winchester, Fitzwilliam, 
  Greenfield, Lyndeborough, Dublin, and Francestown.

This includes the following Rec locations...
	North Pack Monadnock.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Flooding is occurring or is imminent. It is important to know where 
you are relative to streams, rivers, or creeks which can become 
killers in heavy rains. Campers and hikers should avoid streams or 
creeks.

&&

LAT...LON 4284 7243 4285 7229 4285 7219 4285 7205
      4298 7180 4271 7171 4271 7191 4272 7221
      4272 7222 4272 7223 4272 7226 4272 7227
      4272 7228 4272 7229 4272 7230 4272 7231

FLASH FLOOD...RADAR AND GAUGE INDICATED

$$

MLE

The office that day

Everything else NWS Gray, ME issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 29, 8:35 PM EDT	Flash Flood Warning	GYX	Cheshire, Hillsborough, Merrimack, Sullivan	6 hr
Jul 29, 8:58 PM EDT	Areal Flood Advisory	GYX	Belknap, Carroll, Grafton, Hillsborough, Merrimack, Rockingham and 2 more	4 hr
Jul 29, 9:14 PM EDT	Special Weather Statement	GYX	Hillsborough	46 min
Jul 29, 9:33 PM EDT	Flash Flood Warning	GYX	Belknap, Carroll, Grafton, Merrimack, Rockingham, Strafford and 1 more	5 hr
Jul 29, 9:57 PM EDT	Special Weather Statement	GYX	Rockingham, Strafford	48 min
Jul 29, 10:36 PM EDT	Areal Flood Advisory	GYX	Hillsborough, Merrimack, Rockingham	3 hr
Jul 29, 10:58 PM EDT	Flash Flood Warning	GYX	Hillsborough, Rockingham	3 hr
Jul 30, 1:34 AM EDT	River Flood Warning	GYX	Merrimack	41 hr
Jul 30, 6:10 AM EDT	River Flood Warning	GYX	Merrimack	24 hr
Jul 30, 4:05 PM EDT	River Flood Warning	GYX	Merrimack	7 hr

Nearby

Flash Flood Warnings in New Hampshire, 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; local storm reports from the same archive; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.