A weak flux of moisture reached far southern San Bernardino County, fueling isolated thunderstorms. One storm produced flash flooding.
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The episode as NWS VEF wrote it up.
A weak flux of moisture reached far southern San Bernardino County, fueling isolated thunderstorms. One storm produced flash flooding.
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 Las Vegas, NV wrote its last area forecast discussion before the first event at Sep 24, 11:18 AM PST, 5 hours 42 minutes earlier.
Area Forecast Discussion National Weather Service Las Vegas NV 1218 PM PDT Sat Sep 24 2022 .SYNOPSIS...A few isolated showers or thunderstorms possible this afternoon across parts of San Bernardino and southern Mohave, but otherwise dry and above average temperatures expected through the weekend and into next week. A last gasp of monsoonal moisture is looking likely for mid week next week, bringing at least isolated thunderstorm chances back to the forecast for at least the eastern half of the CWA. && .SHORT TERM...Today through Monday. Overall, quiet conditions expected through Monday as building heights result in warming temperatures across the region. Despite the above normal temperatures expected, probabilistic Max T values in the NBM at KLAS are now below 20% through the peak heating period so no expectation of records being broken with this period of heat. Further, heat risk values are minor to moderate across the CWA and only really moderate where lows struggle to fall below 80 degrees, like Death Valley and the CRV. So little impact is expected from this warmer period. Outside of heat, 12Z HREF and later runs of the HRRR continues to produce isolated convection south of I-15 in San Bern and south of I-40 in Mohave where higher PWAT values exist today. While all probabilities today are pretty low, there exists an outside shot for some heavy rainfall over some typically very flashy areas of Morongo Basin, namely east of Twentynine Palms south of the SR62 corridor. NBM PoPs were quite low in these areas, so bumped them up with a heavy influence from the 12Z CAMs and now at least slight chance T exists in the grids for the Mojave Preserve and Morongo. From a QPF standpoint, confidence is low, but should the right conditions come together near JTNP, a slow moving heavy raining thunderstorm could produce some flash flood impacts as the 3hr HREF chances of >1" are greater than 10% for that area through 03Z. .LONG TERM...Tuesday through the end of the week. Temperatures should begin to subside heating into the mid-week period due to our ridge axis pushing eastward. This is in response to a series of disturbances in the Pacific pushing eastward towards the California coast. As the ridge shifts, the upper level pattern shifts back into a late season monsoonal situation, allowing moisture to increase up the CRV and into southern Nevada and northwest Arizona. In fact, there's even some signal for a weak inverted trough Tuesday evening pushing into western Arizona Wednesday per the 12Z ECWMF. Of note, the EC is quite a bit more robust with QPF generation than the GEFS/GEM, due to the fact that it's much more aggressive in PWAT recovery. But regardless, meteograms for several sites show a clear return of above average PWAT values and gradual decline thereafter. NBM currently shows PoPs returning to Mohave as early as Tuesday and farther west into southern Nevada and southeast California by Wednesday. PoPs peak Wednesday and Thursday before receding back to eastern Mohave Friday and into the weekend. During this last gasp of monsoon, rain rates shouldn't be 'quite' as heavy as they were back in July/August, but still heavy enough to cause some isolated flash flooding impacts, especially in known flashy washes and burn scars. && .AVIATION...For Harry Reid...Minimal impacts expected today and tomorrow for Harry Reid. Typical diurnal wind patterns are expected with sustained winds generally at or below 8 kts. A few cumulus clouds aoa 10kft possible this afternoon. For the rest of southern Nevada, northwest Arizona and southeast California...Generally favorable flying conditions for all regional terminals today. Isolated convection is possible over the Morongo Basin and Mojave Preserve area but not expecting this to impact the KDAG or KEED terminals. KEED/KIFP could see some minor northerly wind gusts up to 20 kts at times, but no significant impacts. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && DISCUSSION/AVIATION...TB3 For more forecast information...see us on our webpage: https://weather.gov/lasvegas or follow us on Facebook and Twitter
The Santa Ana Mts radar (KSOX), 128 km away, was scanning. The volume nearest the first event began at 00:59 UTC.
1 flash flood. Local standard time, as filed.
Park Blvd was closed just outside the west entrance to Joshua Tree National Park.
After NWS Directive 10-1605, the rules offices file Storm Data by.
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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: 1058567.