textproduct: San Diego

SYNOPSIS

Mostly clear skies with near average temperatures will occur across the region this weekend. Monsoonal moisture continues to lower, so slight chances of weak showers and thunderstorms may occur over the mountains this weekend as well. Drier weather is expected across all areas next week. A noticeable cooling trend is expected by the middle of the week with highs from 5 to 15 degrees below average with breezier conditions across the deserts and adjacent mountains. The marine layer will also be deeper next week, contributing to clouds and fog west of the mountains each night and morning.

DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE

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

Today through Monday:

The upper level ridge centered over the Desert Southwest strengthens some today, allowing high temperatures today to be a touch warmer compared to Saturday. Enough monsoonal moisture remains in place that a few storms could develop over the mountains again this afternoon (~20% chance), primarily across the San Diego/Riverside County mountains. High resolution guidance is indicating that the strongest storms this afternoon could produce rainfall rates near 0.3-0.4" per hour. A few storms could drift eastward from the mountains into the adjacent deserts. After today, mid/upper level flow turns northwesterly ahead of an incoming trough, pushing monsoonal moisture back east, bringing an end to the shower/storm chances. High temperatures Monday afternoon look to be a few degrees cooler than Sunday as heights fall with the ridge weakening and beginning to give way to the incoming trough.

Tuesday through the end of the Week:

Ensemble guidance is quite consistent with a slow-moving longwave trough moving into northern California and Oregon Monday into Tuesday and is largely stationary through Thursday/Friday with shortwaves rounding the parent trough. This pattern will bring cooler, cloudier, and windier conditions for mid-late week. High temperatures are expected to be 10-15 degrees below normal for Tuesday through Friday with areas near 20 degrees below normal for early September on Wed/Thurs. While the marine layer today/tomorrow (Sun/Mon) will be fairly patchy and shallow, it will deepen considerably by Wednesday, likely extending well inland each morning. While unseasonably cool, the most notable impact from this pattern will be the windy conditions, especially for the mountains/mountain passes and high deserts. Westerly wind gusts near 25-35 mph expected for most of the deserts/desert slopes while vulnerable passes like San Gorgonio Pass could see gusts closer to 45-55 mph. Moving into the late-week, ensemble guidance suggests the tough will finally weaken and lift north. Moderating afternoon wind gusts and bringing temperatures closer to normal.

AVIATION

070930Z...Coast...Patchy low clouds based 600-1000 ft MSL should expand in coverage along the coastline through 13Z. Some spots may see clouds push 5-10 miles inland. Vis restrictions 2-5 SM are possible for coastal highlands. Clouds eroding east to west to beaches 15-17Z. Patchy low clouds will develop again late Sunday, pushing into coastal land areas after 07Z Monday with slightly lower bases than tonight. Vis restrictions 2-5 SM possible again for coastal highlands.

Valleys/Mountains/Deserts...Low chances for isolated SHRA and possibly a thunderstorm 20Z Sun to 01Z Mon for mountains of San Diego and southern Riverside counties. CB bases around 10K ft and any TSRA tops to 35K ft.

MARINE

No hazardous marine conditions are expected through Wednesday.

SGX WATCHES/WARNINGS/ADVISORIES

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