A surge of upper level moisture combined with enough lift and instability during the afternoon of July 21 for widespread thunderstorm development to take place over the higher elevations of the southern Sierra Nevada. Brief heavy rainfall was observed with several of the thunderstorms and one storm produced flash flooding near Cedar Grove in Kings Canyon National Park.
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The episode as NWS HNX wrote it up.
A surge of upper level moisture combined with enough lift and instability during the afternoon of July 21 for widespread thunderstorm development to take place over the higher elevations of the southern Sierra Nevada. Brief heavy rainfall was observed with several of the thunderstorms and one storm produced flash flooding near Cedar Grove in Kings Canyon National Park.
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 Jul 21, 12:10 PM PST, 2 hours 55 minutes earlier.
Area Forecast Discussion National Weather Service San Joaquin Valley - Hanford CA 110 PM PDT Sat Jul 21 2018 .SYNOPSIS... Weak high pressure will keep in the warmth but also the humidity for the rest of this weekend across central California. There remains the slight chance for afternoon and evening thunderstorms over the high Sierra Nevada Mountains. Otherwise, it will remain dry with slightly above normal temperatures into Monday. Even a bigger heat wave is in store by the middle of next week. && .DISCUSSION... Moonsoon moisture will be first to mention in the short term forecast. It will be of the mid and upper level variety this evening and overnight. Thinking is there will enough for a partly to mostly cloudy sky over central CA. This will spread northwest from a thunderstorm complex currently over Las Vegas area. This cloud cover will also keep the hot temperatures from falling much this eve. In fact, parts of the San Joaquin Valley are likely to hold in the 80s most of the night. Current thinking is some clearing over the forecast area Sunday morning. Actually, Sunday looks to be the least hot day of the week with highs in the upper 90s to lower 100s across the valley and adjacent lower foothills. Surface wind should remain light. Current mesoscale models showing widely scattered thunderstorms continuing over the Sierra Nevada crest each afternoon and evening. It's hard to pinpoint where convection will be the strongest over the mountains, but the instability will certainly be in place from near Yosemite National Park to parts of the Kern County Mountains. Mid/upper level heights continue to build early next week, which means even hotter conditions for the entire region. Excessive Heat Watch will remain in place for the lower elevations beginning Tuesday afternoon. Temperatures across the Kern County Desert and San Joaquin Valley will easily exceed 100F almost all of next week. It will also remain dry with lower humidities, which will challenge ongoing wildfires in the Sierra. Will monitor both the strong heat and wildfires as we move into the last full week of July. && .AVIATION... Areas of MVFR visibility in smoke will continue in the vicinity of the Ferguson Fire in Mariposa County for at least the next 24 hours. A slight chance of thunderstorms will be possible near the Sierra crest until about 04z today and Sunday. Gusty outflow wind can be expected near any storms. Otherwise, VFR conditions will prevail over the central California interior during the next 24 hours. && .AIR QUALITY ISSUES... Please see SFOAQAHNX for an Air Quality Alert. On Saturday July 21 2018... Unhealthy for sensitive groups in Fresno... Kern and Tulare Counties. Further information is available at Valleyair.org && .CERTAINTY... The level of certainty for days 1 and 2 is medium. 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... Excessive Heat Watch from Tuesday afternoon through Thursday evening CAZ089>095-098-099. && public...Lynott avn/fw...Lynott synopsis...Lynott weather.gov/hanford
Special Weather Statement National Weather Service San Joaquin Valley CA 336 PM PDT SAT JUL 21 2018 CAZ099-212300- Southeastern Kern County Desert CA- 336 PM PDT SAT JUL 21 2018 ...SIGNIFICANT WEATHER ADVISORY FOR EASTERN KERN COUNTY UNTIL 400 PM PDT... At 335 PM PDT, Doppler radar was tracking a strong thunderstorm 9 miles east of Edwards AFB, or 25 miles north of Lake Los Angeles. This storm was moving north at 10 mph. Wind gusts up to 50 mph will be possible with this storm. Locations impacted include... North Edwards. 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 3505 11770 3489 11768 3489 11788 3505 11789 TIME...MOT...LOC 2235Z 086DEG 2KT 3496 11778 Dudley
Special Weather Statement
National Weather Service San Joaquin Valley CA
338 PM PDT SAT JUL 21 2018
CAZ096-097-212330-
Tulare County Mountains CA-
Sierra Nevada from Yosemite to Kings Canyon CA-
338 PM PDT SAT JUL 21 2018
...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL TULARE AND EASTERN
FRESNO COUNTIES UNTIL 430 PM PDT...
At 337 PM PDT, Doppler radar was tracking a strong thunderstorm 15
miles west of Onion Valley Campground, or 23 miles west of
Independence, moving northwest at 10 mph.
Dime size hail and winds in excess of 30 mph will be possible with
this storm.
Locations impacted include...
Mitchell Meadow, Charlotte Lake, Bishop Pass, State Lakes, Upper
Tyndall Creek and Cedar Grove.
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.
This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.
&&
LAT...LON 3647 11857 3698 11886 3712 11854 3710 11852
3678 11837 3675 11837 3670 11834 3669 11835
3669 11836 3667 11833 3665 11834 3660 11829
TIME...MOT...LOC 2237Z 157DEG 9KT 3681 11862
AndersenThe San Joaquin Valley radar (KHNX), 101 km away, was scanning. The volume nearest the first event began at 23:03 UTC.
1 flash flood. Local standard time, as filed.
California Highway Patrol reported water and debris across Kings Canyon Road in several places between Lewis and Hotel Creeks in Cedar Grove.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2018Every state in 2018This day in weather historyWarnings in California, July 2018
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: 759284.