07/150 AM.
Temperatures will cool some again on Tuesday with increasing onshore flow and areas of low clouds and fog near the coast. Warmer temperatures will return briefly Wednesday before a sustained cooling trend takes us into the weekend, along with a chance of rain.
(tdy-Thu), 07/939 AM.
***UPDATE***
No significant changes in the near term. Focus of today will be on the Friday/Saturday storm and potential secondary storm Sunday into Monday.
***From Previous Discussion***
Onshore trends again today will result in 1-3 degrees of additional cooling in most areas, though highs will still be 4-8 degrees above normal due to high pressure over California. Low clouds and fog are well entrenched along the Central Coast this morning but having a much harder time south of Pt Conception, likely due to the northerly pressure gradients that are creating some gusty winds from southwest Santa Barbara County through the I5 corridor. Those winds will continue through at least Thursday, though hi res models are showing winds mostly below advisory levels. Will leave that for a later decision. In the meantime, a wind advisory continues across southwest Santa Barbara County through this morning for continued sundowner winds there.
A brief warm up is expected Wednesday in response to an increase in northerly flow that will create some downslope warming across the coast and valleys. High temperatures should rise 3-6 degrees in most areas, pushing valleys into the mid to high 80s and coastal areas in the mid 70s to lower 80s.
A cooling trend will return Thursday as high pressure aloft weakens in response to an approaching upper low that is expected to bring rain to the area Friday and over the weekend.
(Fri-Mon), 07/305 AM.
Rain is expected to return to the area by Friday, with showers continuing through early next week as a second and even colder upper low moves into the area Sunday into Monday morning. Both systems have convective elements but the second upper low may prove to be the most active system due to a colder and more unstable airmass. Ensembles are still showing a big spread in possible outcomes with regard to rain amounts, though the mean has stayed consistent between a half and one inch. The large ensemble spread is likely due to the convective aspect of this system, and there is a reasonable chance that areas that experience convective rain bursts could see as much as 2-3 inches through Monday. Small hail and gusty winds are a strong possibility as well. Snow levels will be around 7000 feet for the first system through Saturday, then lowering to around 5000 feet late Sunday into Monday with that colder system coming through. Snow on the Grapevine is unlikely with either of these systems but if it happened it would most likely be Monday morning. At higher elevations at least a few inches of snow are possible. Will have a better idea on that as the storm gets closer.
Lastly, it won't be raining everywhere all weekend. There will be lengthy periods of no rain with sunshine, then quick escalation to brief heavy rain and possible thunderstorms. Given the convective aspect, periods of very heavy rain are possible that could create significant flooding issues in isolated areas.
07/1706z.
At 1553Z at KLAX, the marine layer was 1700 ft deep. The top of the inversion was at 3600 ft with a temperature of 17 C.
High confidence in VFR TAFs, except for KSMO, KLAX, & KLGB.
Chance for IFR CIGs KSMO (30%), KLAX (70%), & KLGB (80%).
KLAX, Moderate confidence in TAF. Arrival and clearing times of IFR CIGs 006-009 should be accurate within +/- 2 hours from current forecast. There is a 30% chance CIGs do not arrive. No significant east wind component expected.
KBUR, High confidence in VFR TAF.
07/815 AM.
Current Small Craft Advisories (SCA) look on track. SCA winds will continue across all Outer Waters through Wednesday. Local Gale force gusts (35 kts) are likely this evening through the overnight hours south of Point Conception - there is a 30% chance that a GALE Warning will be issued for this timeframe (PZZ676). Another chance for outer water gales comes Wednesday evening for the same general area.
The Inner Waters will reach SCA levels at times mainly during the afternoon and evening hours - lower chances along the Central Coast later in the week. There is a 30% chance of GALE force winds Wednesday night across the Santa Barbara Channel and near the Channel Islands.
Winds will diminish later in the week with moderate chances for SCA winds lingering south of Point Conception on Thursday and possibly into Friday.
A storm system is expected to impact the coastal waters starting Thursday night lasting into the weekend bringing rainfall and the potential for thunderstorms. Confidence is low on exact timing and details for now.
Ca, NONE. PZ, Small Craft Advisory in effect until 3 AM PDT Wednesday for zones 650-670-673-676. (See LAXMWWLOX).
