Alert archive / New Hampshire / Flash Flood Warnings in 2021

Flash Flood Warning 11, NWS Gray, ME

July 29, 20214 counties in New Hampshire

NWS Gray, ME issued this flash flood warning at Jul 29, 2021, 8:35 PM EDT for 4 counties in New Hampshire. It was in force for 6 hr. 10 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, 8:35 PM EDT (00:35 UTC)
Expired
Jul 30, 2021, 2:45 AM EDT
In force
6 hr
Issued by
NWS Gray, ME
Area
Storm-based polygon
Flood severity
None

Counties Cheshire County, NH, Hillsborough County, NH, Merrimack County, NH, Sullivan County, NH

The radar

The Albany radar (KENX), 147 km from the middle of the area, began a volume at 00:36 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

TimeReportWhereRemark
Jul 29, 9:28 PM EDTFLASH FLOOD2 Nw Spofford, NHREPORT FROM MPING: RIVER/CREEK OVERFLOWING; CROPLAND/YARD/BASEMENT FLOODING.
Jul 29, 9:35 PM EDTFLASH FLOOD2 Wnw Acworth, NHBOTH SIDES OF ROAD WASHED OUT WITH WATER OVER THE ROADWAY AT LUTHER HILL ROAD AND CHARLESTOWN ROAD.
Jul 29, 9:51 PM EDTFLASH FLOOD5 Nw Hillsborough, NHDANFORTH CORNERS ROAD FLOODED AND IMPASSABLE. ROAD IS CLOSED.
Jul 29, 10:56 PM EDTFLASH FLOOD1 Sse Goshen, NHRT 10 CLOSED FROM RT 31 TO GRANDVIEW RD. WATER OVER ROADWAY.
Jul 29, 11:30 PM EDTFLASH FLOOD2 S Newbury, NHMOUNTAIN RD AND CHENEY RD IN NEWBURY HAD SIGNIFICANT ROAD FLOODING AND WASHOUTS. ***DELAYED REPORT***.
Jul 29, 11:42 PM EDTFLASH FLOODSurry, NHRT 12A AT GILSUM RD CLOSED DUE TO FLOODING.
Jul 29, 11:44 PM EDTFLASH FLOOD3 N Walpole, NHRT 123 BRIDGE OVER COLD RIVER CLOSED DUE TO HIGH WATER.
Jul 30, 12:00 AM EDTHEAVY RAIN 5.073 Wnw Washington, NH
Jul 30, 12:24 AM EDTFLASH FLOOD1 Nw Antrim, NHCLINTON ROAD, NH 31, WASHED OUT IN ANTRIM FROM THE GREAT BROOK.
Jul 30, 12:40 AM EDTFLASH FLOOD1 Ene Alstead, NH123A CLOSED NEAR KELLEY ROAD DUE TO A WASHOUT.

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, 0.6 hours before the alert went out and 125 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-pSkew-T log-p diagram, Albany, NY at 00:00Z on 2021-07-30Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 172 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Albany, NY at 00:00Z on 2021-07-30The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 494 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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.

264 
WGUS51 KGYX 300035
FFWGYX
NHC005-011-013-019-300645-
/O.NEW.KGYX.FF.W.0011.210730T0035Z-210730T0645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

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

The National Weather Service in Gray has issued a

* Flash Flood Warning for...
  Southwestern Merrimack County in central New Hampshire...
  Southern Sullivan County in central New Hampshire...
  Cheshire County in southern New Hampshire...
  Northwestern Hillsborough County in southern New Hampshire...

* Until 245 AM EDT Friday.

* At 835 PM EDT, National Weather Service Doppler Radar and rain 
  gauge reports indicated heavy rain falling across the warned area. 
  Between 2 and 3 inches of rain have already fallen across portions 
  of the warning area since 3 pm. Additional rainfall amounts of 1 
  to 3 inches are possible in the warned area through midnight. 
  Flash flooding is ongoing or expected to begin shortly.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Gauges 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 may experience flash flooding include...
  Keene, Jaffrey, Henniker, Swanzey, Peterborough, Hopkinton, New 
  Boston, Charlestown, Winchester, Antrim, Alstead, Lempster.

This includes the following Rec locations...
	Mount Monadnock, Mount Sunapee.

This includes the following highways...
	Interstate 89 between mile markers 12 and 25.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be especially cautious at night when it is harder to recognize the 
dangers of flooding.

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 4318 7244 4319 7245 4320 7244 4325 7244
      4328 7241 4335 7175 4304 7168 4285 7206
      4284 7255 4285 7256 4288 7255 4292 7252
      4295 7253 4297 7247 4301 7244 4305 7247
      4308 7244 4310 7244 4312 7243 4315 7246

FLASH FLOOD...GAUGE INDICATED
EXPECTED RAINFALL...1-2.5 INCHES IN 1 HOUR

$$

MLE
1 follow-up statement
986 
WGUS71 KGYX 300636
FFSGYX

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

NHC005-011-013-019-300646-
/O.EXP.KGYX.FF.W.0011.000000T0000Z-210730T0645Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cheshire NH-Hillsborough NH-Merrimack NH-Sullivan NH-
236 AM EDT Fri Jul 30 2021

...FLASH FLOOD WARNING WILL EXPIRE AT 245 AM EDT EARLY THIS MORNING 
FOR SOUTHWESTERN MERRIMACK, SOUTHERN SULLIVAN, CHESHIRE, AND 
NORTHWESTERN HILLSBOROUGH COUNTIES...

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

LAT...LON 4318 7244 4319 7245 4320 7244 4325 7244
      4328 7241 4335 7175 4304 7168 4285 7206
      4284 7255 4285 7256 4288 7255 4292 7252
      4295 7253 4297 7247 4301 7244 4305 7247
      4308 7244 4310 7244 4312 7243 4315 7246

$$

MBC

The office that day

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

IssuedProductOfficeCountiesLasted
Jul 29, 8:58 PM EDTAreal Flood AdvisoryGYXBelknap, Carroll, Grafton, Hillsborough, Merrimack, Rockingham and 2 more4 hr
Jul 29, 9:14 PM EDTSpecial Weather StatementGYXHillsborough46 min
Jul 29, 9:33 PM EDTFlash Flood WarningGYXBelknap, Carroll, Grafton, Merrimack, Rockingham, Strafford and 1 more5 hr
Jul 29, 9:57 PM EDTSpecial Weather StatementGYXRockingham, Strafford48 min
Jul 29, 10:32 PM EDTFlash Flood WarningGYXCheshire, Hillsborough3 hr
Jul 29, 10:36 PM EDTAreal Flood AdvisoryGYXHillsborough, Merrimack, Rockingham3 hr
Jul 29, 10:58 PM EDTFlash Flood WarningGYXHillsborough, Rockingham3 hr
Jul 30, 1:34 AM EDTRiver Flood WarningGYXMerrimack41 hr
Jul 30, 6:10 AM EDTRiver Flood WarningGYXMerrimack24 hr
Jul 30, 4:05 PM EDTRiver Flood WarningGYXMerrimack7 hr

Nearby

Flash Flood Warnings in New Hampshire, 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.