Ation/marine discussion,
A low pressure system to the northwest has brought widespread clouds, lower temperatures and stronger onshore flow. Most of the clouds are high clouds and there is a weak marine layer inversion. Temperatures this afternoon were generally lower than yesterday, as much as 10 degrees lower in the mountains and high deserts. The strengthening onshore flow is producing southwest to west winds gusting 25-35 mph in the mtn passes and adjacent desert slopes.
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 will likely 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 estimates 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 will likely 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.
Two low pressure systems will impact the region into early next week, bringing stronger 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,
, Updated aviation/marine discussion,
A low pressure system to the northwest has brought widespread clouds, lower temperatures and stronger onshore flow. Most of the clouds are high clouds and there is a weak marine layer inversion. Temperatures this afternoon were generally lower than yesterday, as much as 10 degrees lower in the mountains and high deserts. The strengthening onshore flow is producing southwest to west winds gusting 25-35 mph in the mtn passes and adjacent desert slopes.
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 will likely 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 estimates 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 will likely 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.
100330z, Coasts/Valleys, Low clouds will become more widespread along the coast through 08Z with bases 1000-2000 ft MSL. Low clouds are expected to reach into the Inland Empire 09-12z, with a 40-60% chance of bases under 1000 ft. Clouds scatter toward the coast again 15-18z. BKN-OVC low to mid-level clouds expected Fri evening, with VCSH for Orange County starting around 03Z Sat.
.Mountains/Deserts, West to southwest winds with gusts 35-45 kt through passes, along deserts slopes and locally into the deserts overnight. Areas BLDU (vis 3-5SM) expected. Moderate up/downdrafts in lee of mtns. Winds briefly weaken late Fri morning before strengthening to similar speeds after 20Z Fri.
There is a slight chance of thunderstorms Sunday afternoon. Additionally there will be periods of increased northwest winds with gusts 15 to 20 kt and choppy seas that could generate hazardous conditions through the day Sunday.
Ca, None. PZ, None.
