Area Forecast Discussion

SYNOPSIS

Temperatures remain below normal until Wednesday with a present marine layer. Warmer weather returns for the end of next week as high pressure builds.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES...

Not much change to the forecast over the past 24 hours. In the short term, upper level riding will allow for temperatures to warm closer to normal today, with highs in the mid 70s along the coast, 80s for inland spots and High Desert, and around 100 for the lower deserts. Afternoon humidity will fall to around 10% for areas east of the mountains today, with these drier conditions prevailing into Sunday even as temperatures cool a degree or two for Sunday afternoon.

Mid-level water vapor satellite shows a deepening low off the coast of CA which is expected to move inland late this weekend, kicking the aforementioned ridge eastward. With that, a cooling trend sets in beginning Sunday, with more significant cooling Monday as the low settles over Central CA. Southwest flow and lower heights will encourage a deeper marine layer Monday and Tuesday mornings, with low (10-15% chance) of some localized marine layer drizzle either of those mornings. Clouds will make it further inland, with slow clearing at the coastline in the afternoons. Highs on Monday may not break above the 70s for many locations, with only double digits in the lower deserts. These highs will generally be 5-13 degrees below where they normally are for the latter half of September.

The cooler weather won't prevail beyond Tuesday as the low becomes absorbed into the upper level pattern and swings northward thanks to a massive low sitting off the Canadian coastline. With the departure, subsidence will start to build over the SoCal waters late next week. Models still disagree on the extent of high pressure and where it might set up, as well as the propagation of the Canadian low. Due to this, there remains a large spread on forecasted high temperatures for the latter half of next week and into the weekend, although general consensus is that temperatures will warm at least to near or slightly above normal. The forecast may change in the coming days as models become better aligned with the overall pattern, but quieter weather seems to prevail for now.

AVIATION

191800Z...Coast/Valleys...Low clouds have scattered out this morning, with VFR prevailing into the late afternoon. CIGs slightly lower (~1500-2200ft MSL) may return as early as 03z Sunday, but could be initially somewhat patchy between 03-06z. Clouds spread into Orange County and through 15-20 miles inland by 12z. There is a ~30-40% chance for CIGs to reach KONT between 12-16z. CIGs scatter back out 16-18z Sunday.

Mountains/Deserts...Mostly clear and VFR conditions through the weekend.

MARINE

No hazardous marine conditions are expected through Thursday.

SGX WATCHES / WARNINGS / ADVISORIES

CA...None. PZ...None.