Two areas of low pressure will near the region into early next week, bringing increased winds for inland areas. This will also bring cooler weather with the chance of light to moderate rainfall. The heaviest rainfall and mountain snowfall is expected on Sunday, where there is a slight chance of thunderstorms west of the mountains. The weather 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,
Satellite imagery shows a coastal eddy over the California Bight, where low clouds are beginning to mix out near the coast and over the waters. An area of low pressure is also seen about 400 west of San Francisco, which is help stream in higher clouds from the southwest. Today will be the final day of above normal temperatures for this week as this weather system nears our region. Increased onshore flow will occur across the area with elevated winds across the mountains and deserts with winds gusting near 25-45 MPH. The low will move closer to the region Friday, ushering in cooler weather. Highs west of the mountains into the high desert will either be in the 60s or 70s, with Palm Springs seeing only a 25% chance of hitting 90 degrees. West winds will be pretty similar to Thursday's winds across mountains and deserts.
The low pressure system near the Bay Area and another currently in the Gulf of Alaska will move into the region over the next few days. The first system looks to be weaker and stay further to the north. The low pressure system near the Bay Area will move near our region by Friday night into Saturday. Models continue to show a downward trend in precipitation during this time with mostly dry conditions with isolated light showers along and west of the mountains early Friday evening into Saturday morning. Accumulations will mostly be a few hundredths for the coast / valleys to near one quarter inch across the mountain coastal slopes.
The area of low pressure situated in the Gulf of Alaska looks to be more potent. This will bring a greater chance for more widespread showers across the region. Prefrontal showers will begin as early as Saturday evening west of the mountains with showers becoming more widespread overnight into Sunday morning or afternoon. This system will be colder, so the chance for thunderstorms has increased for areas west of the mountains on Sunday. Most areas west of the mountains on Sunday will see near 0.25-0.50" of rainfall (NBM chance for greater than one half inch over this area is 20-40%). Snow levels will start to fall below 7,000 feet by Saturday night, going down near 5,500 feet by Sunday night. Areas like Wrightwood and Big Bear Lake have near a 25-40% chance to see snowfall over 1 inch. Model guidance continues to be in fair agreement on the potent area of low pressure becoming a more open wave trough, where another weak shortwave may move over the area into Monday. If this occurs, additional light precipitation would occur, including light mountain snow. Sunday and Monday will be the coolest days of the next week. High temperatures will be around 5 to 15 degrees below normal. Mountain communities will have highs in the 40s and lows in the 20s and 30s with mainly highs in the 60s west of the mountains into the high desert. Comfortable temperatures for the Coachella Valley will occur this weekend with highs in the 80s on Saturday to 70s on Sunday.
Tuesday into the latter part of next week looks dry as weak troughing occurs. This will keep temperatures in check with highs closer to normal with lighter winds.
091630z, Coasts/Valleys, Areas of low clouds based 900-1400 ft MSL are currently lingering over coastal areas up to 5 miles inland. Remaining low clouds will scatter out by 18z. Low clouds return initially to coastal San Diego County 00-03z Fri with slightly higher bases. Bases slowly continue to rise overnight as clouds expand northward and inland, reaching into the Inland Empire by 09- 12z. Clouds scatter toward the coast again 15-18z.
.Mountains/Deserts, West to southwest winds become elevated again starting 21z Thu-00z Fri with gusts 35-45 kts through passes, along deserts slopes and into the High Desert. Gusts 25-40 kts through the lower deserts. Areas BLDU (vis 3-5SM) expected. Moderate up/downdrafts in lee of mtns. Winds briefly weaken late Friday morning before strengthening again late Friday afternoon.
No hazardous marine conditions are expected through Monday, except for Sunday, when there is a slight chance of thunderstorms along with stronger northwest winds and choppy seas that could generate hazardous conditions.
Ca, None. PZ, None.
