A strong cold frontal passage and trough moved through the area during the day on March 21. A large area of instability existed across the San Joaquin Valley behind the cold front.
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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 HNX wrote it up.
A strong cold frontal passage and trough moved through the area during the day on March 21. A large area of instability existed across the San Joaquin Valley behind the cold front. Due to the instability, severe thunderstorms developed during the afternoon and evening hours. Rainfall amounts were generally around a tenth to a quarter inch except locally heavier in stronger thunderstorms. Light snowfall was measured above 6500 feet.
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 Mar 21, 3:28 AM PST, 9 hours 47 minutes earlier.
Area Forecast Discussion National Weather Service San Joaquin Valley - Hanford CA 428 AM PDT Tue Mar 21 2017 .SYNOPSIS... A strong cold front will bring precipitation today as it moves through the region. Cooler than normal temperatures and unsettled conditions will then prevail through the middle of the week in a cooler and unstable airmass. Another storm will move through the area on Friday and Saturday bringing additional precipitation. && .DISCUSSION... Radar imagery shows scattered light precipitation at this time, mainly north of Kern County, with more approaching from the coast. Moderate rainfall late last night resulted in about one third of an inch around Los Banos and one quarter of an inch in Merced. Large upper trough off the coast will continue to provide a moist southwest flow. Blended TPW shows a 1.5" core off the coast with 1.0" pushing inland. This was supported by the 00Z KOAK & KVBG soundings of 1" & 0.91" respectively. Precipitation is expected to increase through the morning, especially over the Sierra Nevada. Due to the warm southwest flow aloft, snow levels are and will remain above 8000 feet today. Rainfall amounts in the Sierra may reach 1 to 2 inches in some areas by this evening, with 12 to 18 inches of snow possible over the high Sierra. Increased instability will bring the potential for thunderstorms this afternoon. The NAM12 shows MU CAPES up to 1400 J/KG with LI's nearing -6 DEG C. The best chances for T-storms will be north of Kern County, with frequent lightning, small hail and locally heavy rainfall all possible. Rainfall amounts in the SJ Valley are generally expected to be from a tenth to one quarter of an inch, but locally could exceed one half an inch in heavier showers or T-storms. A few light, mainly upslope showers will continue Tuesday night then increasing scattered showers on Wednesday as the upper trough begins to shift inland. An unstable air mass will again provide a slight chance for afternoon T-storms. Snow levels will lower to around 6000-7000 feet on Wednesday, then as low as 5000' Wednesday night into Thursday morning. QPf is lighter as the colder air moves in, with 3 to 6 inches of snow forecast above 6000 feet. Short wave ridging builds in on Thursday though a few light upslope showers will remain possible. The next east Pacific trough is still expected to bring more precipitation Friday through Saturday. But confidence is only medium as latest runs seemed to have backed off a bit on precip for central CA as it digs farther south. Short wave ridging looks to provide another brief break Saturday night into Sunday before another trough moves in Sunday night and Monday. But this one appears to favor northern California and Nevada. && .AVIATION... In the San Joaquin Valley...Showers. Isolated thunderstorms with local MVFR conditions through 03Z Wednesday. In the Sierra Nevada and foothills...areas of MVFR and local IFR in showers and isolated thunderstorms. In the Kern county mountains and desert...VFR conditions with scatttered showers. Isolated thunderstorms through 03Z Wednesday. && .AIR QUALITY ISSUES... None. && .CERTAINTY... The level of certainty for days 1 and 2 is high. The level of certainty for days 3 through 7 is medium. Certainty levels include low...medium...and high. Please visit www.weather.gov/hnx/certainty.php for additional information an/or to provide feedback. && .HNX Watches/Warnings/Advisories... NONE. && public...DCH avn/fw...Bean synopsis...DCH weather.gov/hanford
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HANFORD CA
848 AM PDT TUE MAR 21 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0747 AM HEAVY RAIN 5 W FISH CAMP 37.47N 119.74W
03/21/2017 M0.60 INCH MARIPOSA CA TRAINED SPOTTER
SPOTTER REPORT OF 24 HOUR RAINFALL TOTAL OF
0.60 INCHES NEAR PONDEROSA BASIN IN MARIPOSA
COUNTY.
&&
JAPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE HANFORD CA
850 AM PDT TUE MAR 21 2017
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0815 AM HEAVY RAIN 3 ESE CLOVIS 36.81N 119.65W
03/21/2017 M0.05 INCH FRESNO CA TRAINED SPOTTER
SPOTTER REPORT OF 24 HOUR RAINFALL TOTAL OF
0.04 INCHES NEAR CLOVIS IN FRESNO COUNTY.
&&
JASpecial Weather Statement National Weather Service San Joaquin Valley CA 1256 PM PDT TUE MAR 21 2017 CAZ089-090-212045- East-Central San Joaquin Valley CA-West- Central San Joaquin Valley CA- 1256 PM PDT TUE MAR 21 2017 ...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN MERCED COUNTY UNTIL 145 PM PDT... At 1255 PM PDT, Doppler radar was tracking a strong thunderstorm near Livingston, or 8 miles southwest of Atwater, moving east northeast at 30 mph. Dime size hail and winds in excess of 30 mph will be possible with this storm. Locations impacted include... Merced, Atwater, Livingston, Delhi, Hilmar-Irwin, Winton, Ballico and San Luis National Wildlife Refuge. PRECAUTIONARY/PREPAREDNESS ACTIONS... Frequent cloud to ground lightning is occurring with this storm. Lightning can strike 10 miles away from a thunderstorm. Seek a safe shelter inside a building or vehicle. && LAT...LON 3745 12086 3757 12055 3731 12032 3716 12086 TIME...MOT...LOC 1955Z 242DEG 25KT 3729 12073 Andersen
The San Francisco radar (KMUX), 121 km away, was scanning. The volume nearest the first event began at 21:16 UTC.
1 funnel cloud, 1 hail, 1 thunderstorm wind. Local standard time, as filed.
Several reports of a funnel cloud coming out of Merced County between 100 PM and 200 PM. News stations showed video of a clip verifying the presence of a funnel. The funnel reached approximately 3/4 of the way to the ground and the duration was around 5 minutes.
Public report of one inch hail.
Reports of trees uprooted and snapped midway up the trunk at the Tulare Golf Course. One forecaster did a quick survey of the area and estimated 40 trees down or damaged. Otherwise, little damage to the course or structures.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2017Every state in 2017This day in weather historyWarnings in California, March 2017
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: 677751, 677754, 677763.