Another low pressure system moved slowly from the central California coast to western Nevada on the 24th and 25th. This system produced two periods of showers and thunderstorms where rainfall totals were maximized across much of eastern California from Alpine County northward to Lassen County and western Nevada from Douglas County northward to the Oregon border.
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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 REV wrote it up.
Another low pressure system moved slowly from the central California coast to western Nevada on the 24th and 25th. This system produced two periods of showers and thunderstorms where rainfall totals were maximized across much of eastern California from Alpine County northward to Lassen County and western Nevada from Douglas County northward to the Oregon border. The first period occurred during the late afternoon and evening hours of the 24th, and the second occurred during the morning of the 25th.
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 Reno, NV wrote its last area forecast discussion before the first event at May 24, 2:44 AM PST, 3 hours 16 minutes earlier.
Area Forecast Discussion National Weather Service Reno NV 344 AM PDT Thu May 24 2018 .SYNOPSIS... Wet pattern will continue through Saturday with strong thunderstorms producing hail, heavy rain and frequent lightning today. Cooler conditions with more widespread bands of rain showers are likely Friday into Saturday, along with high elevation snow. An overall drying trend is expected Sunday into early next week with temperatures warming to above average. && .SHORT TERM... A potent low pressure system approaching the central CA coast today is projected to move slowly inland across CA/NV Friday through Saturday. This low will increase the potential for more organized and strong thunderstorm development this afternoon and evening, followed by more widespread bands of rain showers (and high elevation snow) with embedded thunderstorms Friday into Saturday. Additional details follow: * Today...While a mid level cap will initially inhibit thunderstorm formation until early afternoon, strong forcing ahead of the approaching low will combine with increasing instability to overcome this cap with CAPE values generally between 500-1000 J/kg, but some model soundings showed CAPE exceeding 1000 J/kg which is quite high for our region. Veering winds from east to south are projected upward through the cloud layer, which should help sustain thunderstorm strength with some rotating cells possible. Cells are most likely to initially form near the Sierra and northward into western Lassen County, then spread into the remainder of eastern CA and far western NV, with much of the model guidance favoring an organized cluster of storms affecting the Reno-Carson vicinity and parts of the Tahoe basin around the afternoon/early evening commute (4-7 pm). This storm cluster is then projected to move northward across eastern Lassen/Plumas and northern/central Washoe County during the evening. Heavy rainfall rates/localized flooding, hail, strong outflow gusts, and a large number of lightning strikes will all be in play with these storms. * Later tonight through Friday...As the evening thunderstorm cluster exits to the north, additional showers and thunderstorms will develop as deformation zone sets up ahead of the main low as it moves into central CA. Areas most likely to initially see this overnight activity include Alpine/northern Mono County, and adjacent sections of Douglas and Lyon counties, spreading northward to the Reno-Carson Tahoe region, and eventually to northeast CA and much of northwest/west central NV during the day Friday. Cooling 700 mb temperatures will lead to snow levels dropping to near 8500-9000 feet in the Sierra and Carson Range, while temperatures in some lower elevations may only reach the lower 60s due to widespread thick cloud cover and shower bands. As recently as last week, the upper portions of the Mt. Rose Highway received slushy snow accumulations even during the afternoon under a persistent precip band. This site along with the higher Sierra passes (Ebbetts, Sonora, Tioga) could receive a couple inches of snowfall, so anyone planning travel especially over the crest in Mono/Alpine counties should keep an eye on road conditions, and may even face the possibility of taking the long way around the Sierra to reach destinations along CA Highways 4, 108, or 120. * Friday night through Saturday night...As the low makes its closest approach to the Sierra, snow levels could drop to near 7500-8000 feet by early Saturday morning, although the latest guidance trends shift the best precip chances into northwest and west central NV. Overall precip rates by this time should be on the decline, with a decreasing chance for thunderstorms (most likely limited to Saturday afternoon-evening). As the low fills and moves into eastern NV, wrap around shower bands will finally wind down across the Basin and Range Saturday night. By the time all is said and done with this low, widespread rainfall totals of 0.50" or greater are likely across nearly all of eastern CA-western NV, with higher totals of 1" or more for areas in the path of today's thunderstorms, followed by the shower bands Friday through Saturday. MJD .LONG TERM...Sunday through Wednesday There were not many changes made to the inherited long term forecast this cycle as numerical guidance is in generally good agreement between the various models and from run to run. The upper low that moves in early this weekend should be drifting to the east by Sunday...but its proximity...along with the presence of residual moisture and daytime heating...is likely to drive at least isolated showers and thunderstorms over the eastern part of the forecast area and in favored upslope locations for northeast flow in the Sierra. That would be mainly the eastern portions of Pershing and Churchill counties and into Mono County. The low drifts farther east Monday. We have left some low end POPs in for the mountains of Mono County due to the presence of residual moisture and expected daytime heating. By then...the highs should be at or above seasonal norms. The model guidance is trying to develop a short wave ridge over the forecast area for Tuesday. But the models continue to struggle with this feature. The GFS is a bit more amplified while the ECMWF is flatter with the ridge. Both are trying to produce afternoon and evening convection due to differential heating near the Sierra. This is not out of the question so slight chances for showers and thunderstorms were left in the forecast...but the location and timing is a bit uncertain. By Wednesday both deterministic models are trying to push a trough of low pressure into the west coast. The GFS is more amplified and produces slightly stronger southwest flow aloft. This is critical for where any showers and storms would form. Right now we have slight chances across the northern forecast area...including parts of Lassen County...the Surprise Valley and northern Washoe County...and in the Mono/Alpine County area. The ECMWF is not as amplified and does not produce as much southwest flow aloft. This would tend to favor development in the Tahoe Basin as well...but we have left that out for now. && .AVIATION... Fog at KTRK should lift after sunrise...but until about 16 UTC look for IFR conditions. Another round of showers and thunderstorms should develop this afternoon and extend into the evening. The setup today is different from previous days. Today we are expecting more organized and potentially stronger storms due to increased upper level support. That means storms today could produce gusty outflow winds in excess of 35-40 kts along with hail up to around an inch in diameter. Of course...turbulence is likely near any thunderstorms and brief moderate to heavy rain will likely reduce cigs and vsbys to MVFR or less at times. The showers extend into the overnight hours...then the main upper low moves just south of the region Friday into Friday night. This will result in more widespread rain for both Friday and Saturday with embedded thunderstorms. While the storms will not be as strong as today...the widespread nature of the rain is likely to produce more areas with MVFR cigs/vsbys and more wide-ranging mountain obscurations. As the upper low moves away...conditions will begin to improve Sunday and Monday...but there will still be the potential for storms along the Sierra in Mono County and across central Nevada. && .REV Watches/Warnings/Advisories... NV...None. CA...None. && For more information from the National Weather Service visit... http://weather.gov/reno
Special Weather Statement National Weather Service RENO NV 456 AM PDT Thu May 24 2018 CAZ070>073-NVZ001>005-250000- Surprise Valley California-Lassen-Eastern Plumas- Eastern Sierra Counties-Greater Lake Tahoe Area-Mono County- Mineral and Southern Lyon Counties-Greater Reno-Carson City- Minden Area-Western Nevada Basin and Range including Pyramid Lake- Northern Washoe County- Including the cities of Cedarville, Eagleville, Fort Bidwell, Portola, Susanville, Westwood, Sierraville, Loyalton, South Lake Tahoe, Tahoe City, Truckee, Markleeville, Bridgeport, Coleville, Lee Vining, Mammoth Lakes, Hawthorne, Yerington, Smith Valley, Mina, Schurz, Stateline, Glenbrook, Incline Village, Sparks, Verdi, Gardnerville, Virginia City, Fernley, Fallon, Lovelock, Silver Springs, Nixon, Imlay, Empire, and Gerlach 456 AM PDT Thu May 24 2018 ...THUNDERSTORMS WITH HEAVY RAIN, HAIL AND STRONG WIND GUSTS THIS AFTERNOON AND EVENING... Low pressure approaching the California coast will bring favorable conditions for more widespread and stronger thunderstorms this afternoon and evening over the eastern Sierra and portions of western Nevada. Thunderstorms are most likely to form near the Sierra in Mono and Alpine counties early this afternoon, then move across the Reno, Carson City and Lake Tahoe vicinity during the afternoon commute hours between 4 and 7 PM. The strongest storms are then expected to move northward across Lassen County, the Surprise Valley and far northwest Nevada this evening, including Susanville and Cedarville. The stronger storms will be capable of producing hail up to 1 inch in diameter, wind gusts in excess of 45 mph, and significant lightning activity. Very heavy rainfall will produce ponding on roads and reduced visibility. Localized flash flooding is also possible, with the potential for debris flows, especially in areas where heavy rain falls on recent burn scars. For the commute this afternoon, allow extra time for travel and keep extra distance between vehicles. If you're planning outdoor activities, watch the sky for developing thunderstorms, and head indoors if you hear thunder. http://weather.gov/reno
The national radar mosaic for the moment the first event began.
9 heavy rain, 2 debris flow. Local standard time, as filed.
CoCoRaHS station CA-ED-20, 1 mile northwest of Meyers reported 1.24 inches of rainfall in a 24 hour period from 24 May 0600PST to 25 May 0600PST.
Mesonet station SPCC1, 2 miles southeast of Grover Hot Springs (elevation 6062 feet) reported 1.60 inches of rainfall in a 24-hour period from 24 May 0800PST to 25 May 0800PST.
Mesonet station MWKC1, 1 mile east of Blairsden (elevation 5149 feet) reported 1.25 inches of rainfall in a 24-hour period from 24 May 0834PST to 25 May 0834PST.
COOP observer measured 0.97 inches of rainfall in a 24-hour period from 24 May 0914PST to 25 May 0914PST.
COOP observer in Tahoe City measured 1.72 inches of rainfall in a 24-hour period from 24 May 0918PST to 25 May 0918PST.
Mesonet station D9436, 1 mile southwest of Sierraville (elevation 5100 feet) reported 1.52 inches of rainfall in a 24-hour period from 24 May 0920PST to 25 May 0920PST.
The Truckee Airport AWOS (elevation 5899 feet) measured 1.05 inches of heavy rain in a 24-hour period from 24 May 0926PST to 25 May 0926PST.
Trained weather spotter 1 mile north-northwest of Homewood reported 1.92 inches of rainfall in a 24-hour period from 24 May 0931PST to 25 May 0931PST.
ASOS Station TVL, South Lake Tahoe Airport (elevation 6257 feet) reported 0.97 inches of rainfall in a 24-hour period from 24 May 1000PST to 25 May 1000PST.
California Highway Patrol reported multiple debris flows near and south of the intersection of California Highway 4 and California Highway 89 that occurred after heavy rainfall. These debris flows occurred within the area of the Washington Fire burn scar. No damage estimates were available.
Placer County Sheriff reported that two debris flows occurred on Alpine Meadows Road near the Five Lakes Creek Trailhead. No injuries were reported and no one was caught in the flow. No damage estimates were available.
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, May 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: 763341, 763344, 763342, 763338, 763345, 763343, 763340, 763346, 763339, 763349, 763347.