Alert archive / California / Flash Flood Warnings in 2017

Flash Flood Warning 9, NWS Reno, NV

August 7, 2017Nevada County, Sierra County, California

NWS Reno, NV issued this flash flood warning at Aug 7, 2017, 4:46 PM PDT for Nevada County, Sierra County, California. 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 7, 2017, 4:46 PM PDT (23:46 UTC)
Expired
Aug 7, 2017, 6:45 PM PDT
In force
119 min
Issued by
NWS Reno, NV
Area
Storm-based polygon
Flood severity
None

Counties Nevada County, CA, Sierra County, CA

The radar

The Reno radar (KRGX), 58 km from the middle of the area, began a volume at 23:46 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, 11.8 hours before the alert went out and 156 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, Reno, NV at 12:00Z on 2017-08-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Reno, NV at 12:00Z on 2017-08-07The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 9 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
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1622 m above ground
0-6 km bulk shear
28 kt
0-1 km storm-relative helicity
9 m²/s²
0-3 km storm-relative helicity
51 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

623 
WGUS55 KREV 072346
FFWREV
CAC057-091-080145-
/O.NEW.KREV.FF.W.0009.170807T2346Z-170808T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Reno NV
446 PM PDT MON AUG 7 2017

The National Weather Service in Reno has issued a

* Flash Flood Warning for...
  Sierra County in northern California...
  Nevada County in northern California...

* Until 645 PM PDT

* At 444 PM PDT, Doppler radar indicated thunderstorms producing 
  heavy rain moving into the Farad Fire burn scar. Flash flooding 
  and debris flows affecting Interstate 80 are expected to begin 
  shortly.

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

Rainfall amounts of up to 1 inch in less than one hour are possible 
in the warned area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3947 12000 3945 12000 3944 12001 3943 12003
      3946 12004

$$
2 follow-up statements
628 
WGUS75 KREV 080032
FFSREV

Flash Flood Statement
National Weather Service Reno NV
532 PM PDT MON AUG 7 2017

CAC057-091-080145-
/O.CON.KREV.FF.W.0009.000000T0000Z-170808T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sierra CA-Nevada CA-
532 PM PDT MON AUG 7 2017

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 645 PM PDT FOR
SIERRA AND NEVADA COUNTIES...

At 530 PM PDT, most of the heavy rain on the Farad Fire burn scar 
has ended, but light to moderate rain will continue for another 45 
minutes.  Due to the steep nature of the terrain in the vicinity of 
the burn scar, flash flooding and debris flows may be possible with 
as little as 0.50 inches of rain. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3947 12000 3945 12000 3944 12001 3943 12003
      3946 12004

$$
526 
WGUS75 KREV 080139
FFSREV

Flash Flood Statement
National Weather Service Reno NV
639 PM PDT MON AUG 7 2017

CAC057-091-080149-
/O.EXP.KREV.FF.W.0009.000000T0000Z-170808T0145Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sierra CA-Nevada CA-
639 PM PDT MON AUG 7 2017

...THE FLASH FLOOD WARNING FOR SIERRA AND NEVADA COUNTIES WILL EXPIRE
AT 645 PM PDT...

The rain on the Farad Fire burn scar has ended. Flooding is no 
longer expected to pose a threat. 

LAT...LON 3947 12000 3945 12000 3944 12001 3943 12003
      3946 12004

$$

The office that day

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

IssuedProductOfficeCountiesLasted
Aug 6, 5:31 PM PDTSpecial Weather StatementREVSierra44 min
Aug 6, 5:56 PM PDTSpecial Weather StatementREVPlumas64 min
Aug 7, 1:41 PM PDTSpecial Weather StatementREVLassen49 min
Aug 7, 4:27 PM PDTSpecial Weather StatementREVLassen78 min

Nearby

Flash Flood Warnings in California, 2017Every flash flood warning in 2017

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.