An upper level low off the SoCal coast en-trained moisture from northern Mexico, resulting showers and isolated thunderstorms over the mountains and deserts on the 29th.
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The episode as NWS SGX wrote it up.
An upper level low off the SoCal coast en-trained moisture from northern Mexico, resulting showers and isolated thunderstorms over the mountains and deserts on the 29th.
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 San Diego, CA wrote its last area forecast discussion before the first event at Sep 29, 12:50 PM PST, 2 hours 10 minutes earlier.
Area Forecast Discussion National Weather Service San Diego CA 150 PM PDT THU SEP 29 2016 .SYNOPSIS... Warm weather will continue over the next couple of days ahead of a longwave trough off the Pacific Northwest. This trough is poised to move through California this weekend into early next week, bringing a noticeable cool-down to Southern California after the recent heat. Onshore flow will strengthen with a return of the marine layer. Gusty winds will develop over the mountains and deserts each afternoon and evening beginning Saturday, strongest on Sunday and Monday. The trough will move east by the middle part of next week with warmer conditions returning. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Visible satellite imagery shows scattered mid/upper level clouds over the mountains this afternoon. Some light showers are showing up south of the border at this time, drifting slowly north, along with a few showers developing over the southern San Diego County mountains. The chance for showers remains for the SoCal mountains through this evening. It will continue to be rather warm through Friday along with increasing humidity near the coast, before noticeable changes to the cooler side occur with an incoming longwave trough this weekend. The large, longwave trough will amplify along the West Coast on Friday, ushering in drier southwest flow aloft. Some marine stratus may return to the immediate coastal areas as early as Friday morning as onshore flow strengthens. The trough then digs and slowly progresses inland Saturday through Monday, which will help to deepen the marine layer for more widespread night and morning low clouds and considerable cooling. The most significant cooling occurs Sun night through Monday. The result will be the coolest day in some time with Monday's high temps some 5 to 15 degrees F below normal for this time of year. The only locales in the 80s Monday will be the lower deserts, with highs elsewhere only in the 60s and 70s, and 50s in the mountains. Gusty onshore winds will develop in the mountains and deserts as well, with the strongest winds on Sunday and Monday as the main trough axis moves through. The latest run of the GFS brings the vort max further south into SoCal, and if this holds true, it could be very windy indeed. The 12Z ECMWF has backed off on precip indications with this trough for Monday, and the GFS keeps things mostly dry as well. Given the high uncertainty and current trends, will keep the forecast dry for now and monitor future model runs. That being said, the marine layer will be quite deep by then, so some drizzle west of the mountains is not out of the question. Temperatures will begin to rebound for the latter half of next week as weak high pressure aloft and possible offshore flow develops behind the departing trough. && .AVIATION... 292045Z...Coastal and Valley areas...Mostly clear through 06Z except for scattered low clouds over the coastal waters. After 06Z...SCT- BKN004-008 spreading 5-10 miles inland through 16Z Friday. Areas of vis 2-4 miles in fog, with vis below 2 miles on the coastal mesas including KCRQ. Low confidence of lengthy impact at coastal airports. Clearing skies after 16Z. Mountains and Deserts...Cumulus clouds over the mountains through 03Z with bases between 8000-12000 feet and isolated SHRA/-TSRA. Becoming clear after 03Z. && .MARINE... No hazardous marine weather is expected through Friday. Northwest winds will increase over the weekend, strongest from Sunday afternoon through Monday when winds over the Outer Waters will increase to 20-30 kt. A Small Craft Advisory may be needed Sunday and Monday for the combination of strong winds and high seas. && .BEACHES... Prevailing southerly swells through Sunday will bring 3-5 foot surf, with occasional sets to 6 feet in Orange County. High rip current risk. Strong gusty west winds may impact the beaches Sunday evening through Monday afternoon as a deep Pacific trough moves inland. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX Watches/Warnings/Advisories... CA...None. PZ...None. && PUBLIC...TS AVIATION/MARINE...Moede
The national radar mosaic for the moment the first event began.
1 flood. Local standard time, as filed.
A spotter reported minor urban flooding from a nearly stationary thunderstorm in Pine Valley.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in California in 2016Every state in 2016This day in weather historyWarnings in California, September 2016
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: 661637.