Alert archive / California / Flash Flood Warnings in 2021

Flash Flood Warning 12, NWS Hanford, CA

July 30, 2021Mariposa County, Tuolumne County, California

NWS Hanford, CA issued this flash flood warning at Jul 30, 2021, 4:02 PM PDT for Mariposa County, Tuolumne 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 30, 2021, 4:02 PM PDT (23:02 UTC)
Expired: Jul 30, 2021, 5:58 PM PDT
In force: 116 min
Issued by: NWS Hanford, CA
Area: Storm-based polygon
Flood severity: None

Counties Mariposa County, CA, Tuolumne County, CA

The radar

The San Joaquin Valley radar (KHNX), 163 km from the middle of the area, began a volume at 23:05 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

Oakland, CA (KOAK), launched 12:00Z, 11.0 hours before the alert went out and 220 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 1819 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 28 m²/s²
0-3 km storm-relative helicity: 67 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

443 
WGUS56 KHNX 302302
FFWHNX
CAC043-109-310200-
/O.NEW.KHNX.FF.W.0012.210730T2302Z-210731T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service San Joaquin Valley CA
402 PM PDT Fri Jul 30 2021

The National Weather Service in Hanford CA has issued a

* Flash Flood Warning for...
  North central Mariposa County in central California...
  Southeastern Tuolumne County in northern California...

* Until 700 PM PDT.

* At 401 PM PDT, Doppler radar indicated thunderstorms producing
  heavy rain across the warned area. Up to two inches of rain have
  already fallen. Flash flooding is ongoing or expected to begin
  shortly.

  HAZARD...Flash flooding caused by thunderstorms.

  SOURCE...Radar indicated.

  IMPACT...Flooding of small creeks and streams, urban areas, 
           highways, streets and underpasses as well as other 
           drainage and low lying areas.

* Some locations that will experience flooding include...
  Tamarack Flat Campground and Gin Flat. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

In hilly terrain there are hundreds of low water crossings which are
potentially dangerous in heavy rain. Do not attempt to cross flooded
roads. Find an alternate route.

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 3783 11963 3773 11966 3771 11971 3775 11979
      3784 11976

FLASH FLOOD...RADAR INDICATED

$$

Andersen

1 follow-up statement

888 
WGUS76 KHNX 310058
FFSHNX

Flash Flood Statement
National Weather Service San Joaquin Valley CA
558 PM PDT Fri Jul 30 2021

CAC043-109-310108-
/O.CAN.KHNX.FF.W.0012.000000T0000Z-210731T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Mariposa CA-Tuolumne CA-
558 PM PDT Fri Jul 30 2021

...THE FLASH FLOOD WARNING FOR NORTH CENTRAL MARIPOSA AND
SOUTHEASTERN TUOLUMNE COUNTIES IS CANCELLED...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Runoff may continue for the next hour. Please continue to 
heed any remaining road closures.

LAT...LON 3783 11963 3773 11966 3771 11971 3775 11979
      3784 11976

$$

Andersen

The office that day

Everything else NWS Hanford, CA issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 29, 5:20 PM PDT	Flash Flood Warning Considerable damage threat	HNX	Madera	3 hr
Jul 30, 2:52 PM PDT	Flash Flood Warning	HNX	Fresno, Madera	38 min
Jul 30, 3:30 PM PDT	Flash Flood Warning	HNX	Fresno, Madera, Mariposa	60 min
Jul 30, 4:08 PM PDT	Special Weather Statement	HNX	Mariposa	22 min
Jul 30, 4:20 PM PDT	Special Weather Statement	HNX	Tuolumne	40 min
Jul 30, 4:30 PM PDT	Special Weather Statement	HNX	Mariposa	45 min
Jul 30, 4:33 PM PDT	Flash Flood Warning	HNX	Mariposa	57 min

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.