17/306 AM.
A few degrees of cooling are expected today with temperatures returning to normal over the weekend. Morning low clouds and fog will return to many coastal areas today and each day through early next week. A warming trend is expected by the middle of next week as upper level high pressure builds into the area.
(tdy-Sun), 17/300 AM.
Not much change in the upper level pattern over srn CA today thru Sun with the region under the SW periphery of a large western U.S. upper level high centered mainly between WY and CO. H5 heights over the forecast area will be generally in the 589-591 dam range thru the period. The upper level flow will start out mostly southerly thru Sat then turn more SE into Sun. Some monsoonal moisture will push back into SW CA this weekend with an increase mid level clouds at times, and by Sun some afternoon cu buildups cannot be ruled out in the mtns along with a non-zero chance (10%) of a shower or thunderstorm especially in the VTU/L.A. County mtns. Even so, it looks like the bulk of the monsoonal moisture will remain east of L.A. County thru Sun.
Pressure gradients will be onshore and increase over the next couple of days. This will promote cooler temps from the recent very hot weather, along with an increase in coastal night and morning low clouds and fog. Overall, it looks like temps will be near normal to several degrees below normal across the region today thru Sun. Afternoon highs should range from the 70s to low 80s for the coast, mid 80s to mid 90s for the vlys and lower mtns, and 90s to around 100 for the deserts.
(Mon-Thu), 17/303 AM.
The large western U.S upper level high center is forecast to drift S from Colorado on Mon to the area around New Mexico and the northern Texas panhandle by Thu. Southwestern CA will continue to be on the western periphery of this large upper level high, with H5 heights slowly increasing to 592-594 dam during the extended period.
The flow aloft will mostly be from the SE with monsoonal moisture expected to continue to push into the area. Precipitable water values are forecast to be in the 1.25 to 1.40 inch range for the most part which is about 150 to 160 percent of normal for this time of year. Although the deepest moisture and instability is forecast to remain east of L.A. County during the extended period, it does look like the best chance of afternoon convection will come Wednesday and Thursday over the mountains. For now, there is only a minimal chance of showers late Thu in the fcst for the eastern L.A. County mtns. Otherwise, there is a non-zero chance (10%) for a thunderstorm to develop in the mtns especially Wed and Thu. As we draw closer to early next week, we should have a better idea of the chance and extent of afternoon convection for the middle of next week.
Otherwise, it look like varying amounts of night and morning coastal low clouds and fog will prevail during the extended period, with a warming trend thru the middle of next week. By Wed, afternoon highs are forecast to top out around 100 degrees for the warmest vlys and lower mtns, with 80s edging closer to the coast. With potentially weaker onshore pressure gradients for Wed and Thu, high temps could actually wind up being a few degrees warmer than is currently forecast.
17/1736z.
At 1700Z at KLAX, the marine layer was 2000 ft deep. The top of the inversion was at 4500 ft with a max temperature of 23 C.
High confidence in VFR TAFs for KPMD and KWJF.
Low confidence KPRB, KBUR, and KVNY. There is a 30% chance for IFR conds at KPRB after 10Z. There is a chance VFR conds prevail at KBUR (40%) and KVNY (50%). If cigs do arrive, lower confidence in timing of cig which could be up to 4 hours earlier than forecast, and min cig height may be off by +/- 300 feet.
Moderate confidence in remaining TAFs. Cigs expected at each site, except for a 25% chance no low clouds at KSBP tonight. Flight cat changes may be off by 3 hours, with lowest confidence in time for KSBP and KSBA. Min cig heights may be off by +/- 200 feet.
KLAX, Moderate confidence in TAF. Arrival of cigs may be as early as early as 01Z or as late as 06Z. 10% chance for brief OVC008-009 cigs before 10Z. 30% chance of an east wind component reaching 6 kt overnight into Sat morning.
KBUR, Low confidence in TAF after 06Z. 40% chance VFR conds prevail. If cigs do arrive, lower confidence in timing of cig which could be up to 4 hours earlier than forecast, and min cig height may be off by +/- 300 feet.
17/929 AM.
For the outer waters, marginal Small Craft Advisory (SCA) level winds are likely to persist for the most part through late tonight, then winds and seas will largely be below SCA levels across these waters Saturday through Tuesday night. Some localized areas may see winds reach SCA levels at times during the period.
For the inner waters N of Point Sal, marginal SCA level winds will occur this afternoon and evening, then winds and seas are likely to remain below SCA levels through the remainder of the forecast period.
For the southern inner waters, conditions will largely remain below SCA levels through the forecast period, except over the western SBA Channel there is a 20% chance of SCA wind gusts Sunday evening and a 40% chance of SCA wind gusts Tuesday evening.
17/928 AM.
Over the eastern Pacific, Tropical storm Elida is still forecast to strengthen to hurricane status today or tomorrow. It is expected to move to the north and west well off the Baja coast. Another tropical disturbance is expected to strengthen next week and generally follow the path of Elida to the northwest. These tropical systems will produce generally 10-15 second period southerly swells, which will propagate northward and begin affecting south-facing beaches as early as Sunday evening. While there is quite a bit of uncertainty in timing and exact magnitude of these swells, it is likely that hazardous conditions will prevail at the beaches for much of next week.
Additionally, a long period southern hemisphere south swell is forecast to arrive sometime late next week, likely contributing to continued and potentially more hazardous beach conditions into the following weekend.
Ca, NONE. PZ, Small Craft Advisory in effect from 3 PM this afternoon to 10 PM PDT this evening for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Saturday for zones 670-673-676. (See LAXMWWLOX).
