MARIPOSA – The National Weather Service in Hanford has issued a Flash Flood Warning for central Mariposa County until 8:15 p.m. There is a broader alert issued for Central California (see below).
At 2:16 p.m. today, Doppler radar indicated heavy rain across central Mariposa County. Flash flooding and debris flows are expected to begin shortly.
Some locations that will experience flooding include El Portal, Jerseydale and Crane Flat.
The possibility of flooding and debris flows should be taken very seriously in the Ferguson Fire burn area. Debris flows can consist of mud, rocks, boulders, vegetation, structures and loose materials in their path as they descend down the slope.
Especially vulnerable locations include the bridge across the Merced River and Highway 140 between Briceburg and El Portal, Highway 41 near Chinquapin in Yosemite National Park, Indian Flat, and Hites Cove Road and Trail.
The National Weather Service says “this is a life-threatening situation for those in the Ferguson Fire burn area. Heavy rain will cause extreme flash flooding of creeks and streams. Severe debris flows can also be anticipated across roads. Roadways and bridges may be washed away in places. Stay off the road in the burned areas. If you encounter flood waters, climb to safety and move away from recently burned areas.”
National Weather Service HANFORD CA
1015 AM PDT Thu May 9 2019
…RISING WATER LEVELS ANTICIPATED ON RIVERS AND STREAMS THROUGH THE WEEKEND…
Due to an upper-level low pressure system developing over Central California, there is a potential for slow moving thunderstorms with heavy rain possible over the mountain areas during later today through the weekend. As the system moves off the Central California coast by late Friday, the potential for thunderstorms and heavy rain could spread further south over the Sierra Nevada and into the Kern County mountain areas.
The combination of locally heavy rainfall and rapid snowmelt over the higher elevations of the Sierra Nevada and into the Kern County mountains has the potential to cause accelerated runoff and generate diurnal water rises on area streams and rivers on mainly this afternoon and evening and again on Friday. Additional precipitation is possible into the weekend over the mountain areas as the low pressure system remains offshore near the Southern California coast.
Many rivers in the foothills and higher elevations of the Sierra, as well as in the mountain areas in Kern County, could rise to near bank full late this week and into the weekend. However, confidence in this particular weather pattern is low.
In Yosemite National Park, the California-Nevada River Forecast Center forecasts the Merced River at Pohono Bridge to crest between a half foot to a foot below its respective Flood stage late tonight into early Friday morning and late Friday night into early Saturday morning.
Hikers, recreational boaters and campers should remain alert for rising waters on area streams and rivers during the next few days and be prepared to move to a place of safety if the threat of flooding becomes imminent. Keep in mind that rivers pose dangerous, life threatening hazards at this time of year due to their swift currents and very cold water temperatures. Fifteen minutes or less exposure to the icy cold waters of a river can lead to hypothermia.
Strong undercurrents can carry even an experienced swimmer into dangerous parts of the river. Don’t become the next drowning victim or the victim of a water rescue!
Stay tuned to NOAA Weather Radio or your favorite media source for further hydrologic updates. You can also follow them on Facebook and Twitter and on the NWS website at www.weather.gov/hnx.