Swell Matrix

Area Forecast Discussion

National Weather Service San Diego CA

910 pm PDT Sat Jun 24 2017

Synopsis

Hot weather will continue in the Inland Empire, Mountains and deserts Sunday with high pressure aloft. The marine layer will keep coastal and western valley areas cooler. Cooler next Tuesday through Friday as a pair of low pressure systems move past to the north and break down the ridge.

Discussion

For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,

There was just enough moisture and instability associated with a passing shortwave for isolated thunderstorms to form over the San Bernardino mountains this afternoon. Most of the lightning was cloud- to-cloud, but there were a few cloud-to-ground strikes. Measurable rain was reported at Baldwin Lake (0.04") near Big Bear, and at Pinon Hills (0.12") north of Wrightwood. The thunderstorm threat looks to be a one-and-done with drier, more stable air moving in tonight and Sunday, although there will probably be some smaller cumulus buildups over the mountains tomorrow afternoon.

Heat is still in the headlines today. Palm Springs set a record high of 122. Elsewhere, record high maxes AND record high minimums were set at Big Bear (87/60) and Idyllwild (94/66). Continued hot Sunday in the I.E., the mountains and the deserts, even with 850 mb and 2- meter temps decreasing slightly. That minor cooling will be offset by a drier airmass for more efficient heating. In fact, high temperatures in the Inland Empire will be higher tomorrow than they were today, with triple digit highs in most areas.

Tuesday-Friday: The stalwart ridge over the Southwest finally gets flattened by a series of Pacific shortwaves passing through the intermountain west. Falling heights and increasing onshore flow will finally bring an end to the oppressive heat in the deserts. Max temps will be 10 to 15 degrees lower, and closer to where they should be for late June (the average high at PSP is 105).

Next weekend the GFS projects some height/thickness recovery over the SW, while the ECMWF forecasts continued troughing with lower heights and cooler weather. Either way, the max temps won't be anywhere near where they were over the last week.

Aviation

240400z, Coast/Valleys, Stratus re-developing and moving inland about 10 sm through 15Z Sunday morning, with bases around 200-700 ft msl, tops around 1200-1700 ft msl, areas of vis 2-4 sm, and patchy dense fog possible with vis as low as 1/2 sm along higher coastal terrain/inland mesas. CIGS gradually dissipating Sunday morning 15- 18Z to the coast. Confidence in cig heights/vis is moderate.

Mountains/Deserts, FEW-SCT AOA 15000 ft msl and P6SM vis continuing through Sunday afternoon.

Marine

Northwest wind gusts over the outer waters may reach 20-25 kt during the afternoons and evenings Sunday through Tuesday, potentially resulting in conditions hazardous to small craft.

Beaches

High tides will reach 7+ ft again this evening. Tides this high may result in minor tidal overflow at low lying beaches. The Beach Hazards Statement continues through 11 PM this evening. High tide will fall below 7 feet Sunday, lowering the tidal overflow threat.

Watches, Warnings, Advisories

Ca, Excessive Heat Warning until 9 PM PDT Monday for Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning.

Heat Advisory from 10 AM to 9 PM PDT Sunday for Riverside County Mountains-San Bernardino County Mountains-San Bernardino and Riverside County Valleys-The Inland Empire-San Diego County Mountains-Santa Ana Mountains and Foothills.

Excessive Heat Warning until 9 PM PDT Sunday for Apple and Lucerne Valleys.

PZ, NONE.

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