Weak Santa Ana winds will continue across the mountains and foothills today, followed by weak onshore flow on Saturday. Fog, potentially dense, could return to the coastal areas Sunday and Monday mornings. Gradual warming through the middle of next week and little change through the end of the week with high temperatures as much as 10-15 degrees above normal and periods of weak to locally moderate Santa Ana winds.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
.Morning Update,
Offshore flow continues at this hour with widespread wind gusts 15-25 MPH across the region, locally near 40 MPH in mountain passes. Classic offshore flow winter pattern was observed this morning with lows in the 30s across wind sheltered valleys, with elevated breezier areas seeing lows only in the lower 50s. Strengthening high pressure aloft will contribute to a warming trend by Sunday into next week with highs well above average. No changes currently to the forecast.
.Previous Discussion (429 AM Friday),
Weak Santa Ana winds will continue through the morning, then gradients and winds weaken through the afternoon. An upper level east- west ridge axis associated with the high over the East Pacific begins to nudge into So Cal today bringing warming across the region. Highs will generally be in the upper 60s to low 70s across the coastal areas, valleys, and low deserts, low 60s in the high deserts, and 50s in the mountains - around 2 to 4 degrees above normal.
Pressure gradients become neutral to the east and very weakly offshore to the north on Saturday, allowing a return of a more prominent sea breeze in the afternoon. This won't do anything in terms of moderating temperatures with the upper ridge continuing to nudge in from the west, but it could lead to the redevelopment of fog, first over the coastal waters during the afternoon Saturday, then spreading into the coastal areas Saturday night. Weak offshore flow develops again by Sunday morning as surface high pressure develops over the eastern Great Basin and Rockies, which could help push the fog back out to sea relatively early in the morning. Winds weaken again Sunday afternoon with another night of potential fog at the coast before offshore flow returns again Monday morning. Otherwise warmer on Sunday with highs around 5-10 degrees above normal.
The remainder of next week will be decidedly warm and dry with periods of weak to locally moderate Santa Ana winds. While there is high certainty in the overall upper level pattern with the ridge slowly shifting east, becoming directly overhead around Thu/Fri, ensembles have a bit of spread in the amplitude of the ridge. This will affect the track of any short waves to our north and the subsequent surface high pressure and Santa Ana wind strength behind them, as well as temperatures. Current forecast has temperatures peaking at around 10-15 degrees above normal Tuesday through Friday, reaching the low 80s in the valleys and low deserts. The CW3E West-WRF ensemble shows Santa Ana winds peaking Monday and Tuesday when there is around a 65% chance of a weak-to-moderate event, lowering to around a 40% chance on Wednesday. This translates to gusts around 30-45 mph in the wind prone passes, canyons, and foothills, locally around 50 mph in the favored spots. Ensembles are starting to hint at the East Pac ridge breaking down and precipitation returning around the middle of the month, but we'll have to see how well that holds up.
051615z. Mostly clear skies and VFR conditions are expected through early Sat.
No hazardous marine conditions are expected through Wednesday.
Ca, Beach Hazards Statement until 10 AM PST this morning for Orange County Coastal Areas-San Diego County Coastal Areas.
PZ, None.
