Alert archive / New Hampshire / Flash Flood Warnings in 2021

Flash Flood Warning 16, NWS Gray, ME

August 19, 2021Rockingham County, New Hampshire

NWS Gray, ME issued this flash flood warning at Aug 19, 2021, 3:46 PM EDT for Rockingham County, New Hampshire. It was in force for 119 min. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Aug 19, 2021, 3:46 PM EDT (19:46 UTC)
Expired: Aug 19, 2021, 5:45 PM EDT
In force: 119 min
Issued by: NWS Gray, ME
Area: Storm-based polygon
Flood severity: None

County Rockingham County, NH

The radar

The Boston radar (KBOX), 97 km from the middle of the area, began a volume at 19:49 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

Gray, ME (KGYX), launched 12:00Z, 7.8 hours before the alert went out and 136 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: 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

Open this sounding in Storm Lab

The text

As transmitted.

218 
WGUS51 KGYX 191946
FFWGYX
NHC015-192145-
/O.NEW.KGYX.FF.W.0016.210819T1946Z-210819T2145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Gray ME
346 PM EDT Thu Aug 19 2021

The National Weather Service in Gray has issued a

* Flash Flood Warning for...
  South Central Rockingham County in southern New Hampshire...

* Until 545 PM EDT.

* At 346 PM EDT, Doppler radar indicated heavy rain across the 
  warned area. Between 1 and 3 inches of rain have fallen. The 
  expected rainfall rate is 1.5 to 2 inches in 1 hour. Flash 
  flooding is ongoing or expected to begin shortly. The heavy 
  rainfall will end by 530 PM.

  HAZARD...Flash flooding caused by heavy rain.

  SOURCE...Radar and rain gages.

  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...
  Exeter, Salem, Brentwood, Seabrook, Stratham, Hampstead, Atkinson, 
  Kingston, Danville, and East Kingston.

This includes the following highways...
	Interstate 93 between mile markers 1 and 2.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Be aware of your surroundings and do not drive on flooded roads.

&&

LAT...LON 4274 7124 4282 7124 4286 7119 4301 7092
      4288 7089 4289 7093 4287 7097 4286 7103
      4285 7104 4281 7107 4282 7113 4282 7115
      4279 7119 4274 7118 4275 7123

FLASH FLOOD...RADAR INDICATED
EXPECTED RAINFALL...1.5-2 INCHES IN 1 HOUR

$$

mle

The office that day

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

Issued	Product	Office	Counties	Lasted
Aug 19, 2:41 PM EDT	Special Weather Statement	GYX	Rockingham	34 min

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; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.