Low pressure systems will impact the region through Monday. These are going to be accompanied by cooler, wetter. amd windier weather. A chance for light showers will occur tonight into Saturday morning. These weather systems will also bring the chance of light to moderate rainfall and high elevation snow. The heaviest rainfall and mountain snowfall is expected on Sunday, where there is a slight chance of thunderstorms west of the mountains. This low pressure system may linger over the area into Monday, bringing additional light showers. Drier and slightly warmer weather is expected by the middle and end of next week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Precipitation,
Light and intermittent rain showers across the coastal basin this morning on the heels of a weak front that moved through, with drier conditions for the remainder of the day as a large upper level low moves into Northern California. Heights continue to fall both today and tomorrow with 850mb temps dropping to around 5C by Sunday, ushering in surface high temps in the mid-60s for most locations, and 30s-40s for the mountains. Ample mid and low level moisture will translate to light to moderate rain showers early Sunday morning as a cold front pushes through, with rain rates around 0.2-0.4"/hr, locally higher for the mountains. The front looks to arrive around sunrise on Sunday for Orange and San Bernardino counties, moving southward throughout the day with the heaviest rain expected late morning into early afternoon. While the threat is low, there remains a chance for thunderstorms associated with the frontal passage on Sunday, primarily late Sunday morning into early afternoon. Should storms develop, brief but heavy rainfall with rain rates exceeding 0.50"/hr will be possible. Snow levels will be falling throughout the weekend, from around 6500 ft today closer to 5000-5500 ft Sunday afternoon. Elevations above 6000 ft may see light accumulating snow on Sunday. The coldest point of the system will be occurring as the rain tappers off, so snow accumulations will likely be 1" or less for populous areas. Rain chances decrease on the backside of the front by early Monday, although a shortwave embedded in the deeper low will quickly move through Monday afternoon before the system departs. With this shortwave, additional rain/snow in San Diego County and up along the spine of the mountains to the San Bernardino Mountains will be possible Monday afternoon and evening, but the lower levels will be quickly drying out and little in the way of precipitation is expected.
Ultimately, rain totals will be low with this event, likely at or below 0.50" for the coastal basin and inland areas, less than 0.25" for the immediate coast, and around 0.50-1.00" for the mountains. Higher elevations will perform better where upslope flow may assist in thunderstorm development on Sunday, allowing for spots of higher rain amounts.
Winds,
Increasing winds today and tonight with the tightening gradient as the low approaches, providing sustained surface winds 35+ mph and gusts as high as 55 mph through mountain passes and on the desert slopes of the mountains. Closer to mountain peaks, even stronger winds may make for dangerous conditions for low-flying aircraft and an increase in turbulence. While models project the strongest winds with this system to begin after 1 PM today and last through midnight/2 AM Sunday, the push of this cold front may maintain stronger wind gusts into Sunday afternoon, with no significant drop off between 2 AM and sunrise. Along with the gusty winds, blowing dust through the High Desert and Coachella Valley will be a threat today through Monday, before winds settle a bit on Tuesday.
Beyond Monday,
Increasing heights and drier air will settle in by Tuesday, with northwest flow and lighter winds. Weak upper level ridging attempts to build in and temperatures should rebound closer to near normal for mid April by Wednesday. A late week pattern change could potentially bring additional rainfall, although there are equal chances for an inside slider to bring about strong offshore winds. Currently, the forecast remains dry into next weekend with high temperatures increasing each day, but should this system be able to swing further south than currently projected, another rainy weekend may be in store. For now, plan on dry and warm with highs returning to the 80s for many inland areas, and gustier offshore winds.
111800z, Coasts/Valleys, Precipitation from this morning has cleared out, with FEW-SCT cumulus (based around 2000-3000ft MSL) draped across the coastal basin for this morning into the afternoon. VFR prevails through this evening with the next disturbance bringing the return of largely BKN clouds around 3500ft MSL, set to fill back in across the coastal basin starting after 02z Sunday. Very scattered -SHRA become possible around 12z, though a more defined band of precipitation will move from NW to SE from 14-22z Sunday morning. This band of rainfall will bring MVFR CIGs near 2000ft MSL, with VIS 4-6SM in -RA/BR. Pockets of heavier rainfall could bring CIGs below 1000ft with VIS closer to 2-4SM.
.Mountains/Deserts, West to southwest winds pick up after 19Z today, with gusts 35-50 kt through passes, along deserts slopes and locally into the deserts. Local areas BLDU (vis 3-5SM) expected. Moderate up/downdrafts in lee of mtns. Winds decrease by about 10-15 kts after 06z, but remains elevated into the overnight hours, picking back up by 18-21z Sunday.
There is a slight (~10%) chance of thunderstorms Sunday afternoon. Additionally there will be periods of increased northwest winds with gusts 15 to 20 kt and choppy seas through the day Sunday.
Ca, None. PZ, None.
