05/256 AM.
Cloudy and cool conditions will continue through this afternoon. Warming and drying to follow Wednesday through the next weekend, with high temperatures approaching 90 degrees in some areas by Friday and even a few degrees higher over the weekend.
(tdy-Thu), 05/907 AM.
***UPDATE***
The low pressure system is continuing to slide to the southeast. Partly cloudy to cloudy skies are present across the region with higher ceilings than the typical marine layer low clouds. This afternoon and evening, the back half of the low will drive gusty west to northwesterly winds across coastal areas with the strongest winds (near advisory level) across the Santa Barbara County south coast and the Ventura County Coast. ***From Previous Discussion***
The large center of the upper low is currently over the entire forecast area with an unremarkable 559 central hgt. It will move quickly to the east during the day reaching the CA/AZ state line by late afternoon. NE return flow from the upper low will keep clouds and even a slight chc of a shower up against the north facing slopes. A deep moist layer west of the mtns will cook up into a strata-cu deck and skies will be partly to mostly cloudy through most of the day. The cool airmass will remain in place for one more day today and there will not be much change in temps from ydy's cool readings. Cst/vly highs again will only be in the 60s or 4 to 8 degrees blo normal.
A big change in the weather begins on Wednesday. A ridge will nose into the northern potion of the state and dry NE flow will set up over Srn CA. Hgts will quickly rise to 577 dam. The onshore flow to the east will weaken to only about 1 mb in the morning while the flow from north will be about a mb offshore at the same time. There may be some morning low clouds in the LGB-LAX area depending on how strong the eddy gets. Skies, otherwise, will be sunny. The rapidly rising hgts and copious sunshine will combine to bring 10 to 15 degrees of warming to the mtns and far interior and 5 to 10 degrees of warming to the vlys. The csts will not warm that much as the onshore flow will increase to about 7mb by afternoon and the seabreeze will temper the warm up. Still most coastal areas will see 2 to 4 degrees of warming.
That onshore flow will likely bring overnight to morning low clouds and fog to the Central Coast and the LA coast on Thursday. Aside from these low clouds skies will continue to be mostly sunny. The ridge will push further into the state and hgts will rise to 582 dam. Afternoon onshore flow will continue to thwart the coastal warming and only 1 to 3 degrees of warming is expected for most of the this area. The areas away from the cst will see another 5 to 10 degree warm up. Most max temps will end up above normal with 70s across the csts and 80s in the vlys.
(Fri-Mon), 05/256 AM.
The 4 day xtnd fcst is going to be a warm one, although just how warm remains a bit of question. The ridge with 582 hgts will remain over the state through Saturday. On Sunday and Monday the main upper high will move atop of Srn CA and hgts will around 585 dam. The big question mark is the sfc flow in the E/W direction. Good confidence that the N/S grad will vary from weak offshore flow in the morning to weak onshore in the afternoon. Looking at the EC ensembles for the E/W flow (The GFS ensembles have proven to have a drastic onshore bias and were not considered) there is an annoying near 50/50 split between the number with onshore flow and the number with offshore flow. The current forecast follows the average of them all which results in a fairly weak onshore push. This does not seem too unreasonable given that it is May. If the E/W grad turns out more onshore then the cst/vlys temp fcst will be too warm. Conversely if the flow is more offshore than fcst then there will be even more warming. That all said look for 1 to 2 locally up to 4 degrees of warming each day Friday through Monday with mid 70s to mid 80s across the csts and mid 80s to lower 90s across the vlys. These max temps would be 5 to 10 degrees over normal. The lower elevations of the mtns and the far interior will end up in the mid 90s or about 15 degrees over normal.
05/1705z.
At 15Z at KLAX, there was a deep moist layer up to 8000 ft.
High confidence in VFR TAFs for desert airfields (KPMD & KWJF).
Moderate confidence in remaining TAFs. Patchy MVFR CIGs possible across the LA Basin (06/10Z-18Z) that may affect airfields KSMO, KLAX, & KLGB. 20% chance low clouds do not develop at KPRB. 30% chance CIGs do not develop at KSBP.
For all sites with forecasted CIGs, arrival and clearing times should be accurate within +/- 2 hours.
KLAX, Moderate confidence in TAF. 30% chance MVFR CIGs enter airfield 06/10Z-18Z. Otherwise, VFR conditions are expected. Good confidence that any east wind component will remain less than 5 kts.
KBUR, Moderate confidence in TAF. 30% chance of IFR-MVFR CIGs to develop 10Z-15Z Wed. Otherwise, VFR conditions with no wind issues are expected.
05/738 AM.
Small Craft Advisory (SCA) winds will be common across the Santa Barbara Channel and near the Channel islands this afternoon and evening. These winds will likely reach the nearshore waters especially along the Ventura coastline. Low-end SCA level NW winds are also likely across along the Central coast.
From Wednesday through Saturday, SCA level NW winds are expected to strengthen each day and will peak Friday afternoon and evening. These winds are likely to reach 20 to 30 kts across the outer waters. There is about a 15% chance of GALE Force winds during this timeframe. SCA level winds are also likely at times across the nearshore waters along the Central coast and into at least western portions of the SB channel.
Short period seas will build during this timeframe especially across the outer waters - reaching 10 feet by Friday peaking at 11 to 13 feet Friday night through Saturday night.
Ca, NONE. PZ, Small Craft Advisory in effect until 9 PM PDT this evening for zones 645-650. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 9 PM PDT this evening for zone 655. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Wednesday for zones 670-673-676. (See LAXMWWLOX).
