San Diego (SGX) — the National Weather Service forecast in plain English · Plaincast

Synopsis

Cooler wit periods of precipitation today through late next week. Light to moderate showers will continue this morning with chances of isolated thunderstorms over the coastal waters locally into the beaches. More widespread light to moderate showers tonight into Saturday. In addition to periods of rain, winds are expected to increase over the mountains, deserts, and coastal waters. Sunday will be dry with our next chance of precipitation and gusty winds Monday through Wednesday.

Discussion

FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE. SAN DIEGO. WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES.

. UPDATED AVIATION, MARINE, AND BEACHES DISCUSSIONS.

Isolated moderate showers have developed this morning ahead of the upper level low. So far the only detected lightning strikes have been closer to the center of the low, west-southwest of San Diego. Showers will become more widespread in the early morning as the upper low moves overhead, along with a 10-15% chance of thunderstorms over the coastal waters and coastal areas. Rainfall rates may briefly exceed 0.50"/hr in heavier showers, but this will be highly localized as storm cores are quite small. Lighter, more widely scattered showers persist into the afternoon with residual moisture and weakly cyclonic flow in place. Through this afternoon, rainfall totals will range from about 0.25-0.50" for the coasts and valleys with local amounts to 0.75", and a few hundredths to around 0.30" in the mountains. A few light showers could spread into the high desert with accumulations generally 0.10" or less. Snow levels will be near 8,000-8,500 ft today with only trace amounts on the higher peaks.

The next short-wave trough will move through tonight into Saturday morning, though models have trended a bit further north with the track of this wave and weaker forcing across Southern California. Still, there is a well-defined front that is forecast to sweep through, generating more widespread but lighter showers with peak rainfall rates closer to 0.25"/hr and only around a 5% chance of thunderstorms. Showers will end for most areas by late Saturday morning, but scattered showers could persist into Saturday afternoon for San Diego County, ending by Saturday evening. Rainfall totals for this second system range from around 0.10-0.30" for the coast to the mountains with locally higher amounts on the west facing coastal mountain slopes, less than 0.05" in the high desert, and no accumulations in the low desert. The snow level remains around 8,500 ft during the bulk of the precipitation, falling to around 7,000 ft behind the front as precipitation tapers off. Any accumulation at the resort levels will be less than an inch.

In addition to the precipitation, gusty southwest to west winds develop across the coastal waters, mountains, and deserts this afternoon and continuing into late Saturday morning, weakening behind the front Saturday afternoon. Wind gusts in the mountains and deserts will be between 30-40 mph with isolated higher gusts in the passes. Winds may briefly gust to around 20-30 mph near the immediate coast in the vicinity of the cold front Saturday morning.

A brief break in the weather is expected on Sunday under weak upper level ridging. High temperatures today and Saturday will be around 5-10 degrees below normal, warming by about 3-6 degrees on Sunday. Ensembles remain in good agreement with the timing of the next trough, sweeping through California Monday into Tuesday. Differences remain in the depth of the trough, resulting in more spread in precipitation amounts and snow levels. Around 52% of the members have a less amplified trough (less precipitation and snow levels closer to 7,000 ft), while the remaining 48% have a deeper trough (more precipitation and snow levels as low as 5,500 ft). Chances of at least 0.25" with this system range from 40-70% from the coast to the mountains, around 30% in the high desert, and 10% in the low desert. Chances of at least 0.50" range from 25-60% for the coast to the mountains, 10-20% in the high desert, and less than 10% in the low desert. Another break it the weather is expect on Wednesday, but another system follows quickly for Thursday into Friday. Ensemble solutions really begin to diverge on the track of this low - 58% have a more western/wetter track similar to the deterministic the American global model, while while the other 42% have a drier/inland track similar to the deterministic EC. For now precipitation chances are between 40-60% on Thursday, lowering to 15-20% by Friday afternoon.