Flash Flooding and Heavy Snow in California, May 7 to 8, 2015

Name: Flash Flooding and Heavy Snow in California, May 7 to 8, 2015
Start: 2015-05-07T05:00
End: 2015-05-08T10:30
Location: California

May 7 to 8, 2015 · NWS SGX · 4 events in 3 counties and zones

Where it happened

Every event with a place to put it; 1 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

Open the live radar over this ground

The toll

Deaths: 0
Injuries: 0
Property damage: $4,000
Crop damage: None recorded
Events: 4

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 SGX wrote it up.

A very large and cold upper-level low deepened along the West Coast before moving inland directly over southern California. This late-season system brought significant rain and snow showers over and west of the mountains on the 7th and 8th. Most of these areas saw between one-quarter of an inch and one inch of precipitation over these two days. The snow level dropped to around 3500 feet with light snow falling, but not sticking at that elevation. Above 4000 feet, snow amounts ranged from 1 to 6 inches, requiring chain control on Sunrise Highway in San Diego County. Flooding due to heavy rainfall was reported at the Spring Valley Quarry Road dip and Escondido Creek on Country Club Drive, where the roads were closed. At the beginning of the event, strong westerly winds produced gusts to 60 mph at Edom Hill and 65 mph at Whitewater RAWS, both in the Banning Pass/mountain desert slope region of Riverside County.

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 San Diego, CA wrote its last area forecast discussion before the first event at May 7, 1:50 AM PST, 3 hours 10 minutes earlier.

Area forecast discussion, May 7, 1:50 AM PST, 3 hours 10 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
250 AM PDT THU MAY 7 2015

.SYNOPSIS...
A DEEP LOW PRESSURE SYSTEM WILL BRING CLOUDY AND COLDER
WEATHER THURSDAY AND FRIDAY...ALONG WITH SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS. GUSTY WEST WINDS WILL CONTINUE IN THE
MOUNTAINS AND DESERTS. CONTINUED COOL SATURDAY...THEN DRY AND WARMER
SUNDAY AND MONDAY WITH WEAK HIGH PRESSURE ALOFT. COOLER...UNSETTELED
WEATHER COULD RETURN FOR THE SECOND HALF OF NEXT WEEK.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

THIS MORNING...A LOW PRESSURE SYSTEM IS MOVING STEADILY SOUTHWARD
ACROSS NORTHERN CALIFORNIA...AND SHOULD ARRIVE IN SOCAL BY THIS
EVENING. AHEAD OF THE LOW...STRONG WEST WINDS WILL CONTINUE OVER THE
MTNS AND ADJACENT DESERT AREAS. WIND GUSTS OF 45 MPH ARE EXPECTED AT
TIMES AND GUSTS TO 55 MPH ARE POSSIBLE IN THE MORE WIND-PRONE
LOCATIONS.

AS THE LOW APPROACHES AND HEIGHTS FALL...THE MARINE LAYER WILL
CONTINUE TO DEEPEN AND COULD BRING ISOLATED SPRINKLES OR LIGHT
SHOWERS OVER AND WEST OF THE MTNS DURING THE DAY TODAY. AS THE LOW
MOVES INTO SOCAL THIS EVENING THROUGH FRI MORNING...A COMBINATION OF
COLD AIR INSTABILITY...DYNAMIC FORCING AND MODEST MOISTURE WILL
BRING THE BEST CHANCES FOR MORE WIDESPREAD SHOWERS ALONG WITH THE
POTENTIAL FOR TSTMS. ANY TSTMS THAT DEVELOP COULD PRODUCE
BRIEF...LOCALLY HEAVY DOWNPOURS AND SMALL HAIL.

DUE TO THE SHOWERY NATURE OF THE PRECIPITATION...AMOUNTS WILL BE
HIGHLY VARIABLE. THE GREATEST PRECIP TOTALS WILL LIKELY BE OVER THE
FOOTHILLS AND THE WEST FACING MTNS SLOPES WHERE ENHANCED OROGRAPHICS
WILL PRODUCE 1-2 INCHES IN SOME AREAS. TOTALS WEST OF THE MTNS WILL
GENERALLY RANGE FROM 0.10 INCH TO 0.33 INCH...WITH 0.5 TO 0.75 INCH
POSSIBLE DURING HEAVIER SHOWERS. THE LOWER DESERTS CAN EXPECT ONLY A
TRACE TO 0.10 INCH.

AS THE COLDEST AIR MOVES IN TONIGHT...SNOW LEVELS COULD LOWER TO
AROUND 5000 FEET IN THE SAN BERNARDINO MTNS AND ON MT SAN JACINTO.
SEVERAL INCHES OF SNOW COULD ACCUMULATE IN AREAS ABOVE 6000 FT.

EXPECT DAYTIME TEMPERATURES 5-10 DEGREES BELOW SEASONAL AVERAGES IN
MOST AREAS THROUGH SAT.

SHOWERS COULD LINGER INTO SAT MORNING...BEFORE TAPERING OFF AS THE
LOW MOVES EAST.

DRY AND WARMER FOR SUN AND MON AS A WEAK...TRANSITORY RIDGE OF HIGH
PRESSURE MOVES IN FROM THE WEST.

COOLER AGAIN WITH INCREASING CLOUDS FOR TUE THROUGH THU AS ANOTHER
LOW PRESSURE SYSTEM MOVES IN FROM THE NW.

&&

.AVIATION...

070935Z...OVC-BKN STRATUS...WITH BASES GENERALLY 3000-4000 FT MSL
AND TOPS 5000-7000 FT MSL...WILL CONTINUE TO COVER THE
COAST...VALLEY...AND MOST OF THE COASTAL MTN SLOPES...PASSES AND
RIDGE-TOPS THROUGH FRIDAY MORNING. BASES OCCASIONALLY WILL FALL TO
1500-2000 FT MSL...PARTICULARLY WHERE SHOWERS OCCUR. VIS 3-5 SM
POSSIBLE UNDERNEATH SHOWERS...WITH LOCAL VIS AOB 1 SM WHERE CLOUDS
INTERSECT TERRAIN. EMBEDDED ISOL LIGHT SHOWERS POSSIBLE THROUGH
08/0300 UTC...WITH SHOWERS INCREASING IN COVERAGE AFTER 08/0300
UTC...AND THE POSSIBILITY OF THUNDERSTORMS AS WELL. CB TOPS TO 30000-
35000 FT MSL. THUNDERSTORMS MAY PRODUCE SMALL
HAIL...DOWNDRAFTS...AND LOCAL VIS AOB 1 SM. MTN OBSCURATION OF
COASTAL SLOPES WILL CONTINUE. DESERTS WILL HAVE MOSTLY UNRESTRICTED
VIS AND SKC THROUGH FRIDAY MORNING...EXCEPT THE HIGH DESERTS MAY GET
SOME SHOWERS FRIDAY MORNING...AND SOME LOCALLY LOWER VIS IN BLDU
WILL BE POSSIBLE IN THE LOWER DESERTS.

WEST WINDS OF 20-30 KTS WITH GUSTS 35-45 KT OVER THE MTN
RIDGES...THROUGH AND BELOW PASSES/CANYONS...ALONG THE DESERT
SLOPES...AND LOCALLY INTO THE ADJACENT DESERTS WILL CREATE AREAS OF
STG UDDFS/LLWS OVER AND EAST OF THE MTNS THROUGH FRIDAY MORNING. 30
KT WNW WIND GUSTS ARE LIKELY FOR KPSP AND KTRM FOR MOST OF TODAY.

&&

.MARINE...

235 AM...THERE IS A CHANCE OF THUNDERSTORMS WITH ISOLATED CLOUD-TO-
WATER LIGHTNING STRIKES OVER THE COASTAL WATERS THURSDAY NIGHT INTO
EARLY FRIDAY AS A TROUGH OF LOW PRESSURE BRINGS AN UNSTABLE
ATMOSPHERE TO THE AREA. SEE THE MARINE WEATHER STATEMENT FOR MORE
DETAILS. NO HAZARDOUS MARINE WEATHER IS EXPECTED SATURDAY THROUGH
MONDAY.

&&

.SKYWARN...
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...

CA...WIND ADVISORY UNTIL 3 AM PDT FRIDAY FOR THE APPLE AND LUCERNE
     VALLEYS-SAN DIEGO COUNTY DESERTS-SAN GORGONIO PASS NEAR BANNING.

PZ...NONE.

&&

PUBLIC...PG
AVIATION/MARINE/BEACHES...HARRISON

The radar

The Santa Ana Mts radar (KSOX), 48 km away, was scanning. The volume nearest the first event began at 13:02 UTC.

Open the radar archive at this moment

Event by event

2 flash flood, 1 funnel cloud, 1 heavy snow. Local standard time, as filed.

Funnel Cloud, San Bernardino

When: May 7, 5:00 AM PST to 5:30 AM PST
Where: San Bernardino County, 0.69 mi NE of San Bernardino
Reported by: Public
Coordinates: 34.137, -117.291

Funnel cloud reported near San Bernardino by a local resident.

Flash Flood, San Diego

When: May 7, 6:30 AM PST to 7:30 AM PST
Where: San Diego County, 2.73 mi N of Del Dios to 2.38 mi NNW of Del Dios
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 33.109, -117.125

CHP reported Country Club Drive closed due to water flowing over road at dip.

Heavy Snow, San Bernardino County Mountains

When: May 8, 1:00 AM PST to 9:00 AM PST
Where: San Bernardino County Mountains forecast zone
Property damage: $4,000
Reported by: County Official
Coordinates: 34.841, -116.178 (the zone’s center; the record gives no point)

CalTrans and San Bernardino County Public Works reported power lines down due to 2-6 inches of heavy, wet snow.

Flash Flood, San Diego

When: May 8, 9:30 AM PST to 10:30 AM PST
Where: San Diego County, 1.23 mi SSE of La Presa to 1.62 mi SSE of La Presa
Cause: Heavy Rain
Reported by: Law Enforcement
Coordinates: 32.704, -117.011

CHP reported Quarry Road closed due to flooding in the low water crossing. The road had to be closed twice.

What these are

Funnel Cloud: A rotating column of cloud extending from a thunderstorm that did not reach the ground.
Flash Flood: Flooding that begins within six hours of the rain that causes it, or of a dam or levee failure or ice jam release, often with deadly speed.
Heavy Snow: Snowfall reaching the local warning threshold without the other hazards of a winter storm.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in California in 2015 Every state in 2015 This day in weather history Warnings in California, May 2015

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: 582565, 582566, 582569, 582573.