Showers are expected today, most likely across San Diego County. Gusty west to northwest winds will develop this evening into Thursday, strongest for the desert mountain slopes into the deserts. Santa Ana winds will quickly develop late Thursday. An offshore pattern will continue into next week, with strong northeast winds mainly for foothills and parts of the valleys. It will be warmer, but with cool nights, this weekend and beyond.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
A blob of rain to the southwest over the ocean has been approaching San Diego County for hours and as of 2 AM finally reached the coast. Eventually, light to locally moderate showers will fall today across the county, with showers less likely into Orange and Riverside Counties. The low pressure system sending us this rain will move east through northern Baja California today and out tonight, so chances of showers will end this evening. In the wake of this system, a new shortwave trough driven by the polar jet stream swiftly passes through SoCal tonight into Thursday. This inside slider will be a wind producer and not a precip producer. Onshore westerly winds will be strong in the mountains and deserts, especially the desert slopes of the mountains. Gusts should reach 55-65 mph in those windiest spots. On Thursday, the flow turns abruptly offshore behind the slider. These offshore winds will be strongest in foothills and locally into parts of the valleys where gusts could reach 40-50 mph Thursday night. And so begins a prolonged offshore flow pattern that will last into next week and maybe beyond. The inside slider will bring cold air and high surface pressure to the interior West, generating a pretty steep offshore pressure gradient. Ensembles vary on the strength of the northeast flow aloft and at the surface, but both will contribute to northeast winds in those favored areas each day for some time. With cold air in the interior, the warmup will be muted until an upper ridge of high pressure builds Friday into next week. That will help warm our air mass, and the Santa Ana effect will assist the warming west of the mountains. Some areas will get into the 70s by Saturday. Temps will rise a couple degrees each day through at least Tuesday, when highs could start to reach into the 80s. Skies will be mostly clear with occasional high clouds. While these warm, dry and windy conditions will boost the fire potential, a relatively high vegetation moisture well above critical levels will mitigate that threat. With dry air in place, temps will drop efficiently Friday and Saturday mornings for chilly starts to those days.
071000z, Coasts/Valleys, A swath of rainfall, largely over the ocean, has been ongoing over the last several hours, with only a few brief instances of -RA observed at KSAN. While confidence is still fairly low on the timing and the degree of impacts this precipitation may have on KSAN and KCRQ, confidence is increasing that showers should be limited to San Diego County. Any showers that do pass over KSAN or KCRQ this morning should be fairly light, but could be moderate at times. Should more moderate rain occur, brief CIGs near 1500ft MSL and VIS to 2-5SM in RA are possible. precipitation should be largely cleared out of the area by 18-20z late this morning. Outside of any shower activity, VFR conditions should continue through the period with only a few clouds near 7500- 15,000ft at times.
Mountains/Deserts, Aside from patchy lower clouds near 4500ft MSL and FEW-SCT mid level clouds near 15,000ft, VFR conditions expected through the period. However, increasing cloud cover along the coastal slopes of the San Diego County and Riverside County Mountains is possible this afternoon with the chance for weak, orographic showers.
West winds increasing across the mountains and deserts after 00z Thursday. Wind gusts across the deserts 25-40 kts and 40-55 kts across the desert slopes and passes will create MOD/STG UDDFS through much of Thursday.
Gusty northwest winds pick up tonight in the outer waters, with gusts 25-30 knots expected on Thursday, peaking in the afternoon. Additionally, locally steep 8 to 11 foot seas with an 8-9 second period will occur in the outer waters starting tonight, peaking on Thursday afternoon, and waning Thursday night. A Small Craft Advisory remains in effect from 4 PM this afternoon until 10 PM Thursday evening for these potential hazards and contains more details. Outside of this period, no hazardous marine conditions expected through this weekend.
Ca, High Wind Watch from this evening through Thursday evening for San Bernardino County Mountains.
High Wind Watch from this evening through Thursday afternoon for Riverside County Mountains-San Diego County Mountains-San Gorgonio Pass near Banning.
Wind Advisory from 8 PM this evening to 1 PM PST Thursday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts.
PZ, Small Craft Advisory from 4 PM this afternoon to 10 PM PST Thursday for Waters from San Mateo Point to the Mexican Border Extending 10 to 60 nm out including San Clemente Island.
