Name: Winter Storm in California, May 17 to 18, 2010
Start: 2010-05-17T11:00
End: 2010-05-18T00:44
Location: California

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

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.

Temperatures once again cooled off by the 17th as another low pressure system moved over the area, bringing rain to many locations in the San Joaquin Valley. Both Fresno and Bakersfield recorded at least a tenth of an inch of rainfall with that system. Fresno cooled 24 degrees from its high of 89 on May 16th to a high of only 65 the next day. Bakersfield also dropped 24 degrees, from a high of 93 on the 16th to a high of 69 on the 17th. Despite the relatively high rainfall amounts for May, snowfall in the Southern Sierra Nevada for the 16th and 17th was not heavy, although around 5 inches of the white stuff was reported around Sequoia National Park.

Another brief warming trend occurred on the 18th and 19th due to a weak short-wave ridge of high pressure, but temperatures only remained near normal with highs in the lower to mid 80s in the San Joaquin Valley. The warmest area was in the Kern County deserts where temperatures reached into the lower 90s during that period.

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 17, 8:32 AM PST, 2 hours 28 minutes earlier.

Area forecast discussion, May 17, 8:32 AM PST, 2 hours 28 minutes before

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
932 AM PDT MON MAY 17 2010

.SYNOPSIS...
A PACIFIC STORM WILL SPREAD PERIODS OF RAIN AND HIGHER ELEVATION
SNOW INLAND TODAY. THE LOW PRESSURE AREA WILL MOVE OFF TO THE EAST
TONIGHT...WITH RAIN AND SNOW DIMINISHING THIS EVENING...AND MOSTLY
ENDING BEFORE DAYBREAK TUESDAY. HIGH PRESSURE AND A WARMING TREND
WILL RETURN TUESDAY AND WEDNESDAY.

&&

.DISCUSSION...
PRECIPITATION HAS ARRIVED A FEW HOURS EARLIER THAN EXPECTED. HAVE
LOWERED TEMPS AND INCREASED POPS FOR THIS MORNING. WE HAVE ALSO
UPGRADED THE ADVISORY FOR THE SIERRA TO A WARNING.

LOW PRESSURE CENTER WILL REMAIN OFF THE COAST AND ASSOCIATED COLD
FRONT WILL MOVE THROUGH THE FORECAST AREA LATE TONIGHT AND INTO
TUESDAY MORNING. PRECIPITATION WILL CONTINUE TODAY AND INTO THIS
EVENING. SOME TROPICAL MOISTURE HAS BEEN ENTRAINED INTO THE SYSTEM
AND WILL KEEP SNOW LEVELS HIGH. IT MAY ALSO GIVE US MORE QPF IN
THE VALLEY AS WELL. TEMPERATURES ARE 15 TO 25 DEGREES COOLER TODAY
IN CLOUDS AND RAIN IN THE VALLEY.

NO CHANGES IN THE EXTENDED AS THE FORECAST APPEARS TO ON TRACK AT
THIS TIME.

&&

.PREV DISCUSSION... /ISSUED 352 AM PDT MON MAY 17 2010/

DISCUSSION...THE UPPER LEVEL LOW PRESSURE AREA THAT HAS BEEN
MOVING TOWARD CENTRAL CA FROM THE WESTERN PAC THE PAST SEVERAL
DAYS IS NOW INSIDE 130W. STRONGEST DYNAMICS ARE AIMED MORE TOWARD
NORCAL AS CAN BE SEEN IN THE ENHANCED CLOUD COVER. HOWEVER A LARGE
AREA OF WARM TOP CLOUDS IS SEEN WEST OF PT CONCEPTION...AND THESE
WILL MOVE INTO CENTRAL CA LATER THIS MORNING AND AFTERNOON AS THE
NEGATIVE TILT UPPER TROF MOVES INLAND. ALL MODELS NOW BRING A
SWATH OF PRECIP ACROSS ALL OF CENTRAL CA AND EVEN INTO THE HIGH
DESERT WITH THIS SYS. MADE UPWARD ADJUSTMENTS TO POPS...ESPECIALLY
KERN COUNTY WHERE A SIGNIFICANT BATCH OF MID AND LOW LEVEL
MOISTURE IS FCST LATER THIS AFTERNOON AND EARLY EVE.

THE FREEZING LEVEL THIS MORNING IS NEAR 10K AND DONT SEE AN
APPRECIABLE DROP UNTIL ONSET OF PRECIP. THUS SNOW LEVELS WILL
START OUT HIGH AND GRADUALLY LOWER THROUGHOUT THE DAY TO 6500 FT
NORTH TO 7500 FT SOUTH BY THIS EVE. MOISTURE CONTENT IS HIGH
HOWEVER OROGRAPHIC LIFT OVER THE SIERRA IS VERY WEAK...AT LEAST
UNTIL THE OVERNITE HOURS. PRECIP TOTALS WILL NOT BE A HIGH AS
WOULD NORMALLY OCCUR WITH PW/S OF 1 INCH NEAR THE CENTRAL COAST.
BECAUSE OF THE HIGH SNOW LEVELS AND LACK OF STRONG UPSLOPE FORCING
OVER THE SIERRA...CONVERTED TO WINTER STORM WATCH TO AN ADVISORY
WITH THE HIGHEST SNOWFALL TOTALS NEAR AND ALONG THE CREST.

FLAT HIGH PRESSURE ALOFT WILL MOVE IN FOR TUES AND WED. THIS WILL
BRING A WARMING TREND THRU WED. HOWEVER...MODELS FCST A NUMBER OF
SHORTWAVE TROFS TO TRAVERSE THE PAC NW THE NEXT SEVERAL DAYS.
THESE SYSTEMS WILL KEEP THE RIDGE FROM BUILDING MORE...AND
OCCASIONALLY INDUCE MARINE AIR TO MOVE INLAND INTO CENTRAL CA.

THESE SHORTWAVE TROFS WILL EVENTUALLY CARVE OUT A TROF OVER THE
WESTERN STATES BY THE WEEKEND. SO ANY WARM UP BY WED WILL BE SHORT
LIVED. IT NOW LOOKS LIKE TEMPS ALL THE WAY INTO NEXT WEEKEND WILL
BE A FEW DEG BELOW SEASONAL NORMS. TEMPS MAY BE CLOSE TO NORMAL BY
WED...THEN COOL TO ABOUT 10 DEGS BELOW NORM BY THE END OF THE
WEEK. NO PRECIP IS SEEN UNTIL POSSIBLY SAT WHEN COLD ADVECTION
INTO THE GREAT BASIN AND THE SIERRA COULD PRODUCE A FEW SHOWERS.

&&

.AVIATION...
MVFR CONDITIONS WITH AREAS OF IFR WILL DEVELOP OVER THE SOUTHERN
SIERRA NEVADA IN PRECIPITATION AND MOUNTAIN OBSCURATIONS BETWEEN 18Z
TODAY AND 00Z TUESDAY CONTINUING THROUGH 12Z TUESDAY. OTHERWISE VFR
CONDITIONS WILL PREVAIL OVER THE CENTRAL CA INTERIOR THROUGH 12Z
TUESDAY.

&&

.AIR QUALITY ISSUES...
NONE.

&&

.HNX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 5 AM PDT TUESDAY ABOVE 8000 FEET FOR
THE CAZ096-097.

&&

PUBLIC...JDB
AVN/FW...DURFEE
SYNOPSIS...WP

WEATHER.GOV/HANFORD

Hazardous weather outlook, May 17, 7:45 AM PST, 3 hours 15 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
845 AM PDT MON MAY 17 2010

CAZ096-097-181545-
SIERRA NEVADA FROM YOSEMITE TO KINGS CANYON-
TULARE COUNTY MOUNTAINS-
845 AM PDT MON MAY 17 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE HIGHER ELEVATIONS OF
THE SOUTHERN SIERRA NEVADA.

.DAY ONE...TODAY AND TONIGHT

WINTER WEATHER WARNING ABOVE 8000 FEET THIS AFTERNOON AND
TONIGHT. PLEASE SEE SFOWSWHNX.../WMO HEADER WWUS46 KHNX/ FOR
DETAILS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

WINTER STORM WARNING REMAINS IN EFFECT UNTIL 5 AM PDT TUESDAY.
OTHERWISE, NO HAZARDOUS WEATHER IS EXPECTED. PLEASE SEE
SFOWSWHNX.../WMO HEADER WWUS46 KHNX/ FOR DETAILS.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION WILL NOT BE NEEDED.

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT OR
UNUSUAL CONDITIONS TO THE NATIONAL WEATHER SERVICE.

WP

WEATHER.GOV/HANFORD

Event by event

1 winter storm. Local standard time, as filed.

Winter Storm, Tulare Cty Mtns

When: May 17, 11:00 AM PST to May 18, 12:44 AM PST
Where: Tulare Cty Mtns forecast zone
Reported by: Park/Forest Service

What these are

Winter Storm: A storm that brought snow, sleet or freezing rain at warning levels, usually over several hours or days.

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

The same day elsewhere

More

Every storm in California in 2010 Every state in 2010 This day in weather history Warnings in California, May 2010

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: 237855.