The National Weather Service has issued a Flash Flood Warning for a potential Dam break in south central Tuolumne County on Moccasin Creek until 2:15 PM Friday
At 2:17 PM, dam operators reported the imminent failure of Moccasin Dam on Moccasin Creek.
At 2:51 PM, radar indicated a line of strong thunderstorms located in the Mother Lode from 10 miles northeast of Cooks Station to Arnold to Carson Hill to Tuttletown. Movement was east at 25 mph.
Winds in excess of 40 mph and dime size hail are possible with these storms.
Locations impacted include Sonora, Calaveras Big Trees State Park, Vallecito, Black Springs, Shriner Lake Campground, Jupiter, Springfield, Dorrington, Avery, Forest Meadows, Mountain Ranch, Rail Road Flat, Groveland-Big Oak, Tuolumne City, Murphys, Mi-Wuk Village and Twain Harte.
Very heavy rainfall is also occurring with this line of storms and may cause localized flooding.
Do not drive your vehicle through flooded roadways.
Brief funnel clouds are also possible with this line of storms.
The National Weather Service has issued a Flash Flood Warning southwestern Tuolumne County until 4:45 PM.
Heavy rain is likely during the next few hours in this region with the likelihood of flash flooding, mud flows and debris flows.
Additional rainfall of up to two inches is possible in the warned area this afternoon. Debris flows can consist of rock, mud, vegetation and other loose materials.
Move away from recently burned areas. Life-threatening flooding of creeks, roads and normally dry areas is likely. The heavy rains will likely trigger rockslides, mudslides and debris flows in steep terrain, especially in and around these areas.
The National Weather Service also issued an Urban and Small Stream Flood Advisory for southwestern Tuolumne County and all of Calaveras County until 5:15 PM.
Numerous flooded roadways and local streams have been reported, including mudslides and downed trees on roadways. Overflowing poor drainage areas continue to result in minor flooding in the Advisory area.
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. Please report flooding to your local law enforcement agency when you can do so safely.
The “Atmospheric River” continues to bring substantial rain to the foothills and mountains below 8,000 feet.
Because of that, a Flash Flood Watch remains in effect for the entire Mother Lode until 11 PM this evening.
And a Flash Flood Watch has also been issued by the National Weather Service for the Sierra Nevada through 8 PM tonight.
Heavy rainfall, in addition to snow melt, is creating excess runoff and bringing the threat of localized flash flooding, mud slides, rock slides and debris flows.
The severely burned areas are of particular concern. These areas are no longer able to absorb any rainfall, leading to enhanced runoff.
Rainfall rates could exceed one half inch per hour at times during the storm.
This could quickly become a dangerous situation. Hunters, residents and persons traveling in and around the burn areas should remain alert and take action should heavy rain develop.
Some roads may become impassable or become washed out.
Turn around, don’t drown when encountering flooded roads. Most flood deaths occur in vehicles. Excessive runoff from heavy rainfall will cause flooding of small creeks and streams, urban areas, highways, streets and underpasses as well as other drainage areas and low lying spots.
The National Weather Service has also issued a Winter Storm Warning for the Sierra Nevada above 6,500 feet until 11 PM tonight.
Additional snow accumulations will range from several inches to twenty-five inches above the 6,500 feet elevation.
Plan on difficult travel conditions. Damage to trees and power lines is possible. Significant reductions in visibility is likely.
The series of wet storms will continue to sweep through California into the weekend.
A colder system with lower snow levels and even heavier snow will drop over the region from Friday afternoon into the weekend.
A Winter Storm Watch has been issued for the Sierra Nevada above 3,000 feet from Friday afternoon through late Saturday night.
An additional fourteen to twenty-eight inches of snow is expected from Friday through Saturday.
A Flash Flood Warning means that flooding is imminent or occurring. If you are in the warned area move to higher ground immediately. Residents living along streams and creeks should take immediate precautions to protect life and property.
A Flood Advisory means river or stream flows are elevated, or ponding of water in urban or other areas is occurring or is imminent.
A Flash Flood Watch means that conditions may develop that lead to flash flooding. Flash flooding is a VERY DANGEROUS SITUATION. You should be prepared to take action should Flash Flood Warnings be issued.
A Winter Storm Warning for snow means severe winter weather conditions will make travel very hazardous or impossible. If you must travel, keep an extra flashlight, food and water in your vehicle in case of an emergency.
A Winter Storm Watch means there is potential for significant snow, sleet or ice accumulations that may impact travel.