Heavy Rain, Mariposa
- When
- May 21, 2:00 PM PST to May 22, 1:00 AM PST
- Where
- Mariposa County, Yosemite Vlg
- Reported by
- OFFICIAL NWS OBS.
- Coordinates
- 37.582, -119.905 (the zone’s center; the record gives no point)
Flood and Heavy Rain in California, May 21 to 22, 2006
Heavy rain through high elevations onto saturated soils from the Spring snowmelt in the Southern Sierra Nevada led to a dramatic spike in the Merced River height in Yosemite Valley late on the 21st through the morning of the 22nd. 86".
Where it happened
Every event with a place to put it; 2 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
- Tornadoes
- Tropical storms and surge
- Floods
- Wind
- Hail
- Winter weather
- Heat and drought
- Cold
- Fire, smoke and dust
- Marine and coastal
- Other
The toll
- Deaths
- 0
- Injuries
- 0
- Property damage
- None recorded
- Crop damage
- None recorded
- Events
- 2
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
What happened
The episode as NWS HNX wrote it up.
Heavy rain through high elevations onto saturated soils from the Spring snowmelt in the Southern Sierra Nevada led to a dramatic spike in the Merced River height in Yosemite Valley late on the 21st through the morning of the 22nd. In the S.Sierra Nevada Cedar Grove reported 1.29" of rain, Wishon Dam 1.33", Huntington Lake 1.44", Nature Point 1.96", Chilkoot 1.56" Telegraph Hill 2.84", Black Springs 2.38" and Huysink 1.80", and Yosemite Valley 0.86". Just north of Yosemite in Tuolumne County, Mt. Elizabeth reported 3.35" of rain from the event. The Merced River climbed quickly from a low diurnal point of 8.7 feet as measured at Pohono Bridge at 1400 PST on the 21st to a peak of 10.7 feet at 0030 PST on the 22nd. The normal diurnal river fluctuation is only about 1 foot. While the river did surpass the flood stage of 10.0 feet, minimal damage was done in the Yosemite Valley area in this post-1997 flood-of-record event. The heavy rainfall ending on the 22nd and subsequent flooding on the Merced River ended the Spring 2006 snowmelt threat.
What forecasters said that day
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Hanford, CA wrote its last area forecast discussion before the first event at May 21, 1:00 PM PST, 1 hour earlier.
Area forecast discussion, May 21, 1:00 PM PST, 1 hour before
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA 200 PM PDT SUN MAY 21 2006 .SHORT TERM...THE UPPER CUT-OFF LOW, CURRENTLY SPINNING NEAR 32N/127W, IS SHOWING SIGNS OF OPENING UP AND FILLING IN AS ANOTHER SHARP TROUGH DROPS OUT OF THE GULF OF AK. THIS IS RESULTING IN AN INCREASING EASTERLY COMPONENT TO THE LOWS MOVEMENT. MEANWHILE, A JET STREAK HAS CARVED AROUND THE BASE OF THE TROUGH AND ENHANCED PRECIP ON THE EAST SIDE OF THE LOW EVIDENT BY THE COOLER CLOUD TOPS ON IR SAT IMAGES AND LARGE SHIELD OF RAINFALL ALONG THE CENTRAL CA COAST DEPICTED BY THE REGIONAL RADAR MOSAIC. THIS AREA OF LIGHT TO MODERATE RAIN HAS BEEN AFFECTING WESTERN FRESNO AND MERCED COUNTIES MOST OF THE DAY. ANOTHER BAND OF PRECIPITATION ORIENTED N-S IS SPANNING FROM TAFT UP THROUGH WESTERN TULARE COUNTY AND INTO EASTERN FRESNO COUNTY. OTHERWISE, CONDITIONS ARE DRY FOR THE MOST PART, ALTHOUGH THIS IS EXPECTED TO CHANGE OVER THE NEXT 12 HOURS WHEN A BAROCLINIC ZONE CURRENTLY SITUATED ALONG THE COAST WILL CROSS THE CWA AND BRING THE BEST THREAT FOR RAIN. LOOK FOR SOME PRETTY IMPRESSIVE PRECIPITATION TOTALS FOR LATE MAY, ESPECIALLY ACROSS THE SOUTHERN CWA WHERE DYNAMICS AND MOISTURE WILL BE FOCUSED. DESERT AND SJ VALLEY LOCATIONS COULD SEE 0.25-0.50, FOOTHILLS 0.50 TO 1, AND MOUNTAINS 1 TO 2 BEFORE ALL IS SAID AND DONE LATE MONDAY. THERE IS A FAIRLY SIGNIFICANT DISCREPANCY BETWEEN THE NAM AND GFS REGARDING THE SPEED OF THE EXITING DISTURBANCE. THE GFS IS QUICKER TO FILL IT IN AND MOVE IT OUT WHILE THE NAM FEATURES A SLOWER MORE CUT-OFF SOLUTION. THE CURRENT FORECAST IS A BLEND OF THE TWO...AND FEATURES SHOWERS AND T-STORMS LINGERING INTO MONDAY EVENING, ESPECIALLY ALONG THE EAST SIDE OF THE SJV, FOOTHILLS, AND SIERRA IN A POST-FRONTAL UPSLOPE FLOW REGIME. THINGS BEGIN TO QUIET DOWN MONDAY NIGHT INTO TUESDAY AS A RIDGE BEGINS TO BUILD OVER CENTRAL CA. BY WEDNESDAY, TEMPERATURES WILL RETURN TO NORMAL UNDER MOSTLY SUNNY SKIES. .LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...MEDIUM RANGE MODELS REMAIN IN FAIRLY GOOD AGREEMENT DURING THIS TIME FRAME. CENTRAL CA WILL BE UNDER A DRY SOUTHWEST FLOW PATTERN ON THURSDAY WITH AN UPPER RIDGE OVER THE DESERT SOUTHWEST AND SHORTWAVE ENERGY STREAMING INTO THE PAC NW. THE RESULT WILL BE DRY WEATHER WITH TEMPERATURES NEAR SEASONAL NORMALS. PROGS CONTINUE TO INDICATE A LARGE UPPER LOW DROPPING OUT OF THE GULF OF AK TO JUST OFF THE PAC NW COAST ON FRIDAY THEN PUSH THE LOW INLAND OVER THE WEEKEND. ALL OF THE OPERATIONAL MODELS HAVE BEEN TRENDING FURTHER NORTH WITH THIS SYSTEM...AND KEEP ANY SIGNIFICANT MOISTURE ASSOCIATED WITH IT WELL TO THE NORTH OF OUR AREA. HOWEVER...SYNOPTIC COOLING IS EXPECTED ACROSS OUR AREA NEXT WEEKEND AS HEIGHTS AND DIURNAL THICKNESSES LOWER...RESULTING IN THE RETURN OF BELOW SEASONAL TEMPERATURES. && .AVIATION...MAINLY MVFR CEILINGS AND VISIBILITIES IN SHOWERS OVER THE SOUTHERN SIERRA NEVADA AND TEHACHAPI MOUNTAINS WITH AREAS OF IFR IN MOUNTAIN OBSCURATIONS. ELSEWHERE...MAINLY VFR CONDITIONS WITH AREAS OF MVFR CEILINGS AND VISIBILITIES IN MODERATE SHOWERS AND ISOLATED THUNDERSTORMS THROUGH 00Z TUESDAY. FOR SPECIFIC DETAILS...PLEASE REFER TO TAFS FOR KMCE...KFAT AND KBFL. && .HNX WATCHES/WARNINGS/ADVISORIES... FLOOD WATCH THROUGH MONDAY EVENING FOR CAZ093-CAZ094-CAZ096-CAZ097. FLOOD WARNING FOR THE UPPER MERCED RIVER AT POHONO BRIDGE. && MYERS/DS
Hazardous weather outlook, May 21, 4:56 AM PST, 9 hours 4 minutes before
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA 556 AM PDT SUN MAY 21 2006 CAZ093-094-096-097-221300- MARIPOSA MADERA AND FRESNO COUNTY FOOTHILLS-TULARE COUNTY FOOTHILLS- SIERRA NEVADA FROM YOSEMITE TO KINGS CANYON-TULARE COUNTY MOUNTAINS- 556 AM PDT SUN MAY 21 2006 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE SOUTHERN SIERRA NEVADA FROM YOSEMITE TO KINGS CANYON AND THE SIERRA FOOTHILLS. .DAY ONE...TODAY A FLOOD WARNING IS IN EFFECT UNTIL 10 AM MONDAY MORNING FOR THE MERCED RIVER AT POHONO BRIDGE IN YOSEMITE NATIONAL PARK. PLEASE REFER TO THE LATEST FLOOD WARNING /SFOFLWUSJ...WGUS46/ FOR MORE INFORMATION. A FLOOD WATCH REMAINS IN EFFECT FOR THE FOOTHILLS AND SIERRA FROM YOSEMITE TO THE KERN COUNTY LINE. THE POTENTIAL OF SIGNIFICANT RAIN RUNOFF INTO STREAMS ALREADY FLOWING HIGH AND FAST FROM SNOW MELT HAS MADE NECESSARY A FLASH FLOOD WATCH FOR TODAY THROUGH MONDAY EVENING. IN ADDITION, SCATTERED THUNDERSTORMS ARE A POSSIBILITY FROM TODAY THROUGH MONDAY. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE FLOOD WARNING WILL REMAIN IN EFFECT THROUGH MONDAY MORNING. HOWEVER...THE WARNING MAY BE EXTENDED DUE TO CONTINUED HIGH RIVER FLOWS. A FLOOD WATCH WILL REMAIN IN EFFECT FOR THE FOOTHILLS AND SIERRA FROM YOSEMITE TO THE KERN COUNTY LINE. THE POTENTIAL OF SIGNIFICANT RAIN RUNOFF INTO STREAMS ALREADY FLOWING HIGH AND FAST FROM SNOW MELT HAS MADE NECESSARY A FLASH FLOOD WATCH. IN ADDITION, SCATTERED THUNDERSTORMS ARE A POSSIBILITY. SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS TO THE SAN JOAQUIN VALLEY NATIONAL WEATHER SERVICE OFFICE. CAZ089>092-095-098-099-221300- WEST CENTRAL SAN JOAQUIN VALLEY-EAST CENTRAL SAN JOAQUIN VALLEY- SOUTHWESTERN SAN JOAQUIN VALLEY-SOUTHEASTERN SAN JOAQUIN VALLEY- KERN COUNTY MOUNTAINS-INDIAN WELLS VALLEY- SOUTHEASTERN KERN COUNTY DESERT- 556 AM PDT SUN MAY 21 2006 THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE CENTRAL AND SOUTHERN SAN JOAQUIN VALLEY...AND THE KERN COUNTY MOUNTAINS AND DESERT. .DAY ONE...SCATTERED THUNDERSTORMS ARE POSSIBLE TODAY. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY SCATTERED THUNDERSTORMS ARE POSSIBLE MONDAY. SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS TO THE SAN JOAQUIN VALLEY NATIONAL WEATHER SERVICE OFFICE. DUDLEY
The radar
The national radar mosaic for the moment the first event began.
Event by event
1 heavy rain, 1 flood. Local standard time, as filed.
Flood, Mariposa
- When
- May 21, 8:00 PM PST to May 22, 7:00 AM PST
- Where
- Mariposa County, 1 mi ESE of Yosemite Vlg
- Reported by
- OFFICIAL NWS OBS.
- Coordinates
- 37.582, -119.905 (the zone’s center; the record gives no point)
What these are
- Heavy Rain
- Rainfall totals unusual for the place and season that did not produce a flood.
- Flood
- Flooding that develops more slowly than a flash flood: rivers leaving their banks, or water standing over land for an extended time.
After NWS Directive 10-1605, the rules offices file Storm Data by.
The same day elsewhere
- Strong Wind in Arizona, May 21, 2006
- Tornado in New Hampshire, May 21, 2006
- Hail and Damaging Winds in Massachusetts, May 21, 2006
- Hail and Damaging Winds in Massachusetts, May 21, 2006
- Hail and Damaging Winds in Texas, May 21, 2006
- Hail and Damaging Winds in Kansas, May 21, 2006
- Strong Wind in West Virginia, May 21, 2006
- Hail and Damaging Winds in Connecticut, May 21, 2006
- Hail and Damaging Winds in Connecticut, May 21, 2006
- Strong Wind in Maryland, May 21, 2006
- Damaging Winds in Texas, May 21, 2006
- Hail and Damaging Winds in South Carolina, May 21, 2006
More
Every storm in California in 2006Every state in 2006This day in weather historyWarnings in California, May 2006
Sources
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 5509836, 5509835.