An upper level low pressure system on the coast coupled with an unstable atmosphere brought isolated thunderstorms over the mountains of interior northern California. Hail was reported locally in western Plumas County each day.
Every event with a place to put it. Tap one for its entry below.
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.
The episode as NWS STO wrote it up.
An upper level low pressure system on the coast coupled with an unstable atmosphere brought isolated thunderstorms over the mountains of interior northern California. Hail was reported locally in western Plumas County each 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 Sacramento, CA wrote its last area forecast discussion before the first event at Jul 28, 2:30 PM PST, 50 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SACRAMENTO CA 330 PM PDT TUE JUL 28 2009 .DISCUSSION... TEMPERATURES RUNNING A FULL 13 DEGREES COOLER AT SACRAMENTO THIS AFTERNOON THAN YESTERDAY. WINDS AT TRAVIS AFB CONTINUE TO BLOW OVER 25 KTS. THE MARINE LAYER SHOULD RE-ESTABLISH ITSELF OVERNIGHT AS THE UPPER RIDGE OVER OUR REGION HAS WEAKENED. A DECENT 3.8 MB ONSHORE GRADIENT KSFO-KSAC SHOULD HELP BRING SOME STRATUS CLOUDS INTO THE DELTA TONIGHT AND KEEP TEMPERATURES PLEASANTLY COOL IN SACRAMENTO. THE COOLING HAS WORKED INTO STOCKTON AND MODESTO...BUT THE FOLKS IN REDDING WILL HAVE TO WAIT ONE MORE DAY TO SEE THEIR COOLING TREND KICK IN. ISOLATED THUNDERSTORMS DEVELOPED NEAR THE SIERRA CREST LATE THIS AFTERNOON. ANOTHER CELL DEVELOPED NORTH OF CHESTER WHILE IT APPEARS SOME BUILDUPS ARE ALSO OCCURRING OVER THE COASTAL MOUNTAINS...BUT NO LIGHTNING HAS BEEN OBSERVED THERE. MOST OF THE ACTIVITY NEAR THE SIERRA WILL SOON SHIFT EAST OF THE CREST BUT WILL CONTINUE TO MONITOR. THE BUILDUPS ARE DUE TO THE DESTABILIZING OF THE ATMOSPHERE AS A WEAK UPPER LOW DEVELOPS ALONG THE CALIFORNIA COAST WHILE THE UPPER RIDGE WEAKENS. MODEST DIVERGENCE ALOFT CONTINUES TONIGHT NEAR THE CREST AS THE REMNANTS FROM AN EASTERLY WAVE LINGER NEAR THE CREST PER THE 18Z MODELS. THIS MAY KEEP SOME CLOUDS GOING IN THE SIERRA. WE DO NOT HAVE ANY SHOWERS IN OVERNIGHT BUT A STRAY ONE MAY SHIFT WEST OF THE CREST OVER TUOLUMNE / ALPINE COUNTIES IN WEAK EASTERLY 700-500MB FLOW. THE RIDGE BREAKS DOWN MORE TOMORROW. WE WILL HAVE ISOLATED THUNDERSTORMS IN ALL OF OUR MOUNTAIN AREAS. WEAK NORTHEAST 700-500MB FLOW SOUTH OF I-80 MAY LET SOME CLOUDS AND SHOWERS DRIFT INTO THE FOOTHILLS AS WELL. WITH MORE SYNOPTIC COOLING AND MORE MOISTURE IN PLACE (MODEL PRECIPITABLE WATER FORECASTS IN THE 0.75 INCH RANGE)...TOMORROW WILL BE OUR BETTER CHANCE OF CONVECTION AS THE THERMAL TROF EXPANDS OVER CALIFORNIA ABOVE 925 MB. TEMPERATURES SHOULD COOL A FEW MORE DEGREES. WE EXPECT HIGHS IN THE LOWER 90S IN SACRAMENTO AND PERHAPS 100-102 AT REDDING/RED BLUFF. BY THURSDAY A STRONGER SOUTHWEST FLOW ALOFT DEVELOPS WHICH DRIES AND STABILIZES THE ATMOSPHERE. A NICE BREEZE SHOULD BLOW THROUGH THE DELTA...KEEPING TEMPERATURES FROM GETTING TOO HOT IN SACRAMENTO. THE LATEST GFS IS MORE PROGRESSIVE AGAIN WITH A STRONGER UPPER LOW APPROACHING CALIFORNIA FROM THE PACIFIC. THE ECMWF IS SLOWER AND THE UKMET IS FARTHER SOUTH AND WEAKER. THE CURRENT FORECAST IS BASED ON THE SLOWER PROGRESSION OF THE LOW...WITH A SHORT WAVE RIDGE OVER THE REGION FRIDAY. THIS TRANSLATES TO SEASONALLY WARM TEMPERATURES AND DRY WEATHER. WE DID LINGER JUST A SLIGHT CHANCE OF A THUNDERSTORM NEAR THE CREST IN CASE THE LOW COMES IN EVEN SLOWER. SG .EXTENDED DISCUSSION (SATURDAY THROUGH TUESDAY)... THE BIG QUESTION IN THE EXTENDED FORECAST REMAINS...WHAT PATH WILL THE CUT-OFF LOW FOLLOW AS IT AFFECTS THE WEST COAST. MODELS START DIVERGING THE STORM TRACK SATURDAY. BOTH THE GFS AND ECMWF SHOW A 569 LOW EARLY SATURDAY AT 12Z. THE ECMWF HAS THE LOW CENTERED NEAR 38N 130W BUT THE GFS HAS THE CENTER OF THE LOW EAST OF 130W AND PROGRESSIVELY MOVES INTO THE WEST COAST BY EARLY SUNDAY MORNING. THE GFS THEN TRACKS THE LOW NORTHEAST AFFECTING CENTRAL AND NORTHERN CALIFORNIA UNTIL IT MOVES INTO OREGON LATE TUESDAY/EARLY WEDNESDAY. THE ECMWF SOLUTION HAS THE LOW BRUSHING THE NORCAL COASTLINE ON SUNDAY THEN RETROGRADING BACK OVER THE OCEAN AND MOVING NORTHWARD AS HIGH PRESSURE RIDGING RE-DEVELOPS ACROSS CALIFORNIA. WITH EITHER SOLUTION...TEMPERATURES WILL BE COOLER AND BELOW NORMAL OVER THE WEEKEND AS THE LOW APPROACHES...DEEPENS THE MARINE LAYER AND ENHANCES THE DELTA BREEZE. ON MONDAY TEMPERATURES WILL REMAIN BELOW NORMAL INTO MIDWEEK IF THE GFS PANS OUT OR GRADUALLY WARM IF THE ECMWF IS CORRECT. HAVE GONE WITH THE MIDDLE GROUND FOR TEMPS IN THE FORECAST. OTHER VARIABLES THAT MAY NEED TO BE ADJUSTED IN THE EXTENDED ARE THE POSSIBILITY OF GUSTY RIDGETOP WINDS AND THUNDERSTORMS/SHOWERS ACROSS HIGHER TERRAIN. HAVE LEFT FORECAST DRY UNTIL MODEL AGREEMENT IMPROVES AS MOST INSTABILITY LOOKS TO BE NORTH AND EAST OF OUR REGION. JBB && .AVIATION...VFR CONDS FOR ALL TAF SITES IN THE VALLEY IN THE NEXT 24 HRS. ONSHORE WINDS STARTING TO PICK UP THIS AFTERNOON AND WILL CONTINUE THAT TREND INTO TONIGHT. ONSHORE GRADIENT FROM SFO-SAC IS NOW AT 3.6 MB...OVER 1 MB STRONGER THAN YESTERDAY. WIND SPEEDS RANGING 8-15 MPH FOR THE TAF SITES...STRONGEST WINDS NEAR THE DELTA AND AROUND SAC METRO AREA. BUILDING CUMULUS CLOUDS ACROSS HIGHER TERRAIN INCLUDING THE COASTAL AND NORTHERN MTNS BUT MAINLY OVER THE SIERRA WHERE THUNDERSTORMS ARE NOW AFFECTING THE CREST NEAR LAKE TAHOE AND SOUTHWARD. THUNDERSTORMS MAY SPREAD NORTHWARD ALONG THE CREST...RADAR DETECTS A CELL NEAR THE PLUMAS/SHASTA COUNTY LINE THAT LOOKS PROMISING. JBB && .STO WATCHES/WARNINGS/ADVISORIES...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE SACRAMENTO CA 700 AM PDT TUE JUL 28 2009 CAZ013>019-063-064-066>069-291400- SHASTA LAKE AREA/NORTHERN SHASTA COUNTY- BURNEY BASIN/EASTERN SHASTA COUNTY-NORTHERN SACRAMENTO VALLEY- CENTRAL SACRAMENTO VALLEY-SOUTHERN SACRAMENTO VALLEY- CARQUINEZ STRAIT AND DELTA-NORTHERN SAN JOAQUIN VALLEY- MOUNTAINS SOUTHWESTERN SHASTA TO NORTHERN LAKE COUNTIES- CLEAR LAKE/SOUTHERN LAKE COUNTY-MOTHERLODE- EAST FOOTHILLS/NORTH SACRAMENTO VALLEY- WESTERN PLUMAS COUNTY/LASSEN PARK-WEST SLOPE NORTHERN SIERRA NEVADA- 700 AM PDT TUE JUL 28 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR INTERIOR NORTHERN CALIFORNIA. .DAY ONE...TODAY NEAR RECORD HIGH TEMPERATURES ARE EXPECTED THIS AFTERNOON IN SOME AREAS WITH HIGH TEMPERATURES 106 TO 112 IN THE NORTHERN SACRAMENTO VALLEY AND 80S IN THE MOUNTAINS. THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS NEAR THE SIERRA CREST THIS AFTERNOON AND EVENING. OTHERWISE NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY UPPER LEVEL LOW GRADUALLY APPROACHING THE WEST COAST WILL BRING COOLER TEMPERATURES THROUGH THE PERIOD. THUNDERSTORMS ARE POSSIBLE IN THE MOUNTAINS...MAINLY ON WEDNESDAY. OTHERWISE...NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. THE LATEST WEATHER INFORMATION IS AVAILABLE ON THE INTERNET AT (LOWER CASE): HTTP://WWW.WRH.NOAA.GOV/STO
The Beale AFB radar (KBBX), 96 km away, was scanning. The volume nearest the first event began at 23:21 UTC.
2 hail. Local standard time, as filed.
A Co-operative observer estimated hail from dime to penny sized.
Lassen Volcanic National Park rangers reported quarter sized hail.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2009Every state in 2009This day in weather historyWarnings in California, July 2009
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: 186734, 186733.