Alert archive / New Hampshire / Flash Flood Warnings in 2021

Flash Flood Warning 12, NWS Gray, ME

July 29, 20217 counties in New Hampshire

NWS Gray, ME issued this flash flood warning at Jul 29, 2021, 9:33 PM EDT for 7 counties in New Hampshire. It was in force for 5 hr. 11 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, 9:33 PM EDT (01:33 UTC)
Expired: Jul 30, 2021, 2:30 AM EDT
In force: 5 hr
Issued by: NWS Gray, ME
Area: Storm-based polygon
Flood severity: None

Counties Belknap County, NH, Carroll County, NH, Grafton County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH, Sullivan County, NH

The radar

The Portland,ME radar (KGYX), 107 km from the middle of the area, began a volume at 01:35 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, 9:35 PM EDT	FLASH FLOOD	1 Nw Brookfield, NH	REPORT FROM MPING: RIVER/CREEK OVERFLOWING; CROPLAND/YARD/BASEMENT FLOODING.
Jul 29, 10:30 PM EDT	FLASH FLOOD	1 Ssw Newport, NH	THE TOWN OF NEWPORT SUSTAINED SIGNIFICATE FLOODING ALONG NH RT 103 IN THE AREA OF 48 JOHN STARK HIGHWAY. BUSINESSES IN THE PLAZA AREA SUSTAINED FLOODING RANGING FROM 1 TO 2FT THROUGHOUT THE PLAZA FROM THE SUGAR RIVER. *DELAYED REPORT*.
Jul 29, 10:50 PM EDT	FLASH FLOOD	3 S Gilmanton, NH	NUMEROUS ROADS WASHED OUT AND FLOODED IN LOUDON. WASHOUTS WERE REPORTED ON BUMFAGON RD., STORRS DRIVE, HOLLOW ROUTE RD, AND GILMANTON RD WHERE SIGNIFICANT DAMAGE OCCURRED. ROADS CLOSED DUE TO FLOODING INCLUDED CURRIER ROAD, NH ROUTE 106, OLD SHAKER ROAD AND FL
Jul 29, 11:00 PM EDT	FLASH FLOOD	2 Nw Gilford, NH	MAJOR ROAD WASHOUT AND UNDERMINING ALONG LAKE SHORE RD. IN GILFORD. *DELAYED REPORT*.
Jul 29, 11:00 PM EDT	FLASH FLOOD	3 Ne Canterbury, NH	HACKLEBORO RD. AND MERRILL RD. WASHED OUT IN CANTERBURY. *DELAYED REPORT*.
Jul 29, 11:00 PM EDT	FLASH FLOOD	5 N Barnstead, NH	WASHOUT REPORTED ON WHITE OAK DRIVE IN BARNSTEAD. *DELAYED REPORT*.
Jul 29, 11:30 PM EDT	FLASH FLOOD	2 Nnw Milton, NH	MULTIPLE WASHOUTS AND ROADS UNDER WATER ON MASON RD, TENERIFFE RD, AND MORGAN DR, IN MILTON, NH.
Jul 29, 11:30 PM EDT	FLASH FLOOD	4 Wsw Salisbury, NH	BUCKHORN AND MILL RD. IN SALISBURY HAD WASHOUTS. *DELAYED REPORT*.
Jul 29, 11:55 PM EDT	HEAVY RAIN 3.46	1 N Milton, NH
Jul 30, 1:22 AM EDT	FLASH FLOOD	2 Sw Alton, NH	RT-140 AT HALLS HILL RD, ROAD WASH OUT.
Jul 30, 1:30 AM EDT	FLASH FLOOD	1 Nw Goshen, NH	CAMPGROUND HAD 25 PEOPLE EVACUATED DUE TO RISING WATER ON THE SUGAR RIVER IN NEWPORT. *DELAYED REPORT*.

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 00:00Z, 1.6 hours before the alert went out and 107 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.

209 
WGUS51 KGYX 300133
FFWGYX
NHC001-003-009-013-015-017-019-300630-
/O.NEW.KGYX.FF.W.0012.210730T0133Z-210730T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Gray has issued a

* Flash Flood Warning for...
  Belknap County in central New Hampshire...
  Central Merrimack County in central New Hampshire...
  Northwestern Strafford County in central New Hampshire...
  Central Sullivan County in central New Hampshire...
  Southern Carroll County in northern New Hampshire...
  Southeastern Grafton County in northern New Hampshire...
  Northwestern Rockingham County in southern New Hampshire...

* Until 230 AM EDT.

* At 933 PM EDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Between 2 and 3 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...
  Concord, Rochester, Laconia, Claremont, Franklin, Meredith, 
  Moultonborough, Plymouth, Northwood, and New London.

This includes the following Rec locations...
	Lake WinnipesaukeeMount Kearsage.

This includes the following highways...
	Interstate 93 between mile markers 41 and 74.
	Interstate 89 between mile markers 26 and 50.

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 4329 7230 4358 7218 4365 7214 4375 7100
      4357 7098 4352 7096 4348 7097 4344 7097
      4341 7100 4332 7097 4327 7093 4326 7122
      4323 7172 4335 7174

FLASH FLOOD...RADAR INDICATED

$$

MLE

1 follow-up statement

731 
WGUS71 KGYX 300623
FFSGYX

Flash Flood Statement
National Weather Service Gray ME
223 AM EDT Fri Jul 30 2021

NHC001-003-009-013-015-017-019-300633-
/O.EXP.KGYX.FF.W.0012.000000T0000Z-210730T0630Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Belknap NH-Carroll NH-Grafton NH-Merrimack NH-Rockingham NH-
Strafford NH-Sullivan NH-
223 AM EDT Fri Jul 30 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 230 AM EDT EARLY THIS MORNING 
FOR BELKNAP, CENTRAL MERRIMACK, NORTHWESTERN STRAFFORD, CENTRAL 
SULLIVAN, SOUTHERN CARROLL, SOUTHEASTERN GRAFTON, AND NORTHWESTERN 
ROCKINGHAM COUNTIES...

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

LAT...LON 4329 7230 4358 7218 4365 7214 4375 7100
      4357 7098 4352 7096 4348 7097 4344 7097
      4341 7100 4332 7097 4327 7093 4326 7122
      4323 7172 4335 7174

$$

MBC

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, 9:57 PM EDT	Special Weather Statement	GYX	Rockingham, Strafford	48 min
Jul 29, 10:32 PM EDT	Flash Flood Warning	GYX	Cheshire, Hillsborough	3 hr
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.