Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 6, NWS Reno, NV

July 31, 2021Alpine County, Mono County, California

NWS Reno, NV issued this flash flood warning at Jul 31, 2021, 2:34 PM PDT for Alpine County, Mono County, California. It was in force for 116 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: Jul 31, 2021, 2:34 PM PDT (21:34 UTC)
Expired: Jul 31, 2021, 4:30 PM PDT
In force: 116 min
Issued by: NWS Reno, NV
Area: Storm-based polygon
Damage threat: Considerable
Flood severity: None

Counties Alpine County, CA, Mono County, CA

The radar

The Reno radar (KRGX), 135 km from the middle of the area, began a volume at 21:34 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

Reno, NV (KREV), launched 12:00Z, 9.6 hours before the alert went out and 164 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: 1 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 2114 m above ground
0-6 km bulk shear: 4 kt
0-1 km storm-relative helicity: -11 m²/s²
0-3 km storm-relative helicity: 20 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

162 
WGUS55 KREV 312134
FFWREV
CAC003-051-312330-
/O.NEW.KREV.FF.W.0006.210731T2134Z-210731T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Reno NV
234 PM PDT Sat Jul 31 2021

The National Weather Service in Reno has issued a

* Flash Flood Warning for...
  Alpine County in northern California...
  Northern Mono County in northern California...

* Until 430 PM PDT.

* At 234 PM PDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the Slink Burn Scar. Between 0.5 and 1.0 inch of 
  rain have fallen. Flash flooding is ongoing or expected to begin 
  shortly.

Excessive rainfall over the burn scar will result in debris flow 
moving through the Slink Burn Scar. The debris flow can consist of 
rock, mud, vegetation and other loose materials.

  HAZARD...Life threatening flash flooding. Thunderstorms
           producing flash flooding.

  SOURCE...Radar.

  IMPACT...Life threatening flash flooding of creeks and streams,
           urban areas, highways, streets and underpasses.

* Some locations that will experience flash flooding include...
  mainly rural areas of Alpine and Northern Mono Counties

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Move away from recently burned areas. Life-threatening flooding of 
creeks, roads, and normally dry stream beds is likely. The heavy 
rains will likely trigger rockslides, mudslides and debris flows in 
steep terrain, especially in and around these areas.

&&

LAT...LON 3859 11957 3859 11956 3859 11955 3853 11950
      3847 11949 3846 11954 3850 11960 3855 11964
      3857 11962

FLASH FLOOD...RADAR INDICATED
FLASH FLOOD DAMAGE THREAT...CONSIDERABLE

$$

TF

1 follow-up statement

123 
WGUS75 KREV 312336
FFSREV

Flash Flood Statement
National Weather Service Reno NV
436 PM PDT Sat Jul 31 2021

CAC003-051-312346-
/O.EXP.KREV.FF.W.0006.000000T0000Z-210731T2330Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Alpine CA-Mono CA-
436 PM PDT Sat Jul 31 2021

...FLASH FLOOD WARNING HAS EXPIRED FOR ALPINE AND NORTHERN MONO 
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 PDT Saturday for 
portions of east central California and western Nevada.

LAT...LON 3859 11957 3859 11956 3859 11955 3853 11950
      3847 11949 3846 11954 3850 11960 3855 11964
      3857 11962

$$

CJ

The office that day

Everything else NWS Reno, NV issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 30, 5:10 PM PDT	Flash Flood Warning	REV	Alpine	110 min
Jul 30, 5:34 PM PDT	Special Weather Statement	REV	Alpine, Mono	86 min
Jul 30, 5:42 PM PDT	Areal Flood Advisory	REV	Alpine, Mono	3 hr
Jul 30, 6:27 PM PDT	Areal Flood Advisory	REV	Alpine, Mono	6 hr
Jul 31, 1:22 PM PDT	Special Weather Statement	REV	Lassen	38 min
Jul 31, 2:04 PM PDT	Special Weather Statement	REV	Lassen	41 min
Jul 31, 3:14 PM PDT	Special Weather Statement	REV	Alpine	31 min
Jul 31, 3:41 PM PDT	Areal Flood Advisory	REV	Mono	3 hr

Nearby

Flash Flood Warnings in California, 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.