14/145 PM.
Night through morning marine layer clouds will continue for the coast and valleys tonight then should shrink in coverage each day into next week. Much cooler than normal temperatures this weekend will gradually return to near normal early next week, then increase further to above normal by the middle of the week as upper level high pressure builds into the region.
(tdy-Mon), 14/137 PM.
Low clouds from a deep marine inversion this morning largely cleared back to or off the coast of VTU/L.A. Counties by early this afternoon, but have lingered along the S SBA County coast and the Central Coast. The stratus should persist in those areas for a while this afternoon, otherwise mostly sunny skies should prevail elsewhere. Good onshore flow can be expected this afternoon with breezy to gusty SW to W winds. Temps will be about 4-10 deg cooler-than-normal across the region this afternoon, with highs from the 70s along the coast to the 80s inland, except around 90 in the Antelope Vly.
A broad upper level trof along and just off the coast with H5 heights around 581-583 dam this morning will drift westward over the next couple of days as upper level ridging starts to build back toward the forecast area. By Sun afternoon, H5 heights are forecast to rebound back to 591-593 dam, then increase further to 594-595 dam by Mon afternoon. The upper level flow will largely remain out of the SW thru the period.
The marine inversion is forecast to lower each night thru the short term from about 2500-3000 feet tonight to 1000 ft or less by Sun night. Low clouds will also have a lesser inland extent each night and morning, with an increase in fog especially along the coast and by Mon morning it would not be out of the question for patchy dense fog to develop in some areas. Aside from the low clouds and fog, skies will be mostly clear through the period altho some afternoon cu buildups in the mtns will still be possible. Breezy to gusty SW to W afternoon winds can be expected each day. Temps are forecast to be several degrees below seasonal norms on Sat then warm several degrees by Mon to near normal to slightly below normal.
(Tue-Fri), 14/142 PM.
The EC and GFS deterministic and mean ensembles are in generally good agreement thru the extended period. Upper level ridging will build into SE CA by Tue then expand a bit further in srn CA on Wed. The upper high will then build back toward the Four Corners area on Thu and linger in this general area into Fri as an upper level trof approaches the central CA coast.
For SW CA, marine layer low clouds and fog will likely affect portions of the coast each night and morning with minimal inland penetration due to a shallow inversion. Otherwise, mostly clear skies should continue. There is also a hint that some monsoonal moisture may try to start moving back into L.A. County on Fri with the potential for afternoon convection in the mtns and deserts, but there is still too much uncertainty at this time to include any mention of this in the fcst.
A northerly surface pressure gradient is forecast to develop early next week, likely bringing gusty northerly winds across southern Santa Barbara County and through the Interstate 5 Corridor. Advisory level Sundowner winds could develop during this time, but there is some uncertainty in the timing and the actual strength of the winds.
Temps will warm up to above normal levels for many areas during the extended period, likely peaking Wed and Thu when highs could reach triple digits in the hottest vly and desert areas.
15/0005z.
At 2309Z at KLAX, the marine layer was at 1800 feet deep. The top of the inversion was near 3100 feet with a temperature of 20 C.
High confidence in VFR TAFs for desert airfields (KPMD & KWJF).
Moderate confidence in remaining TAFs. Arrival of IFR or MVFR CIGs and subsequent VFR transitions may be off +/- 3 hours. No significant wind issues expected for these airfields.
KLAX, Moderate confidence in TAF. Arrival and clearing of MVFR CIGs should be +/- 3 hrs of current forecast. CIGs will likely hover near 2,000 ft threshold. There is a 30% chance of brief (10% chc of intermittent) IFR CIGs around 008 thru 15/15Z. No significant east wind component expected.
KBUR, Moderate confidence in TAF. Arrival of MVFR CIGs may be off +/- 3 hours of current forecast. No wind issues expected.
14/153 PM.
There is high confidence that conditions will remain below Small Craft Advisory (SCA) criteria across the coastal waters through Saturday morning. There is a 30-50 percent chance of SCA winds develop from near Point Conception south to San Nicolas Island and in the vicinity of the Channel Islands and along the Central Coast in the vicinity of Point Piedras Blancas. The highest chances will be for the waters from near Point Conception south to San Nicolas Island and in the vicinity of the Channel Islands during the afternoon and evening hours.
The chances for SCA winds will increase Sunday afternoon. There is a high likelihood of widespread SCA conditions developing across the waters southwest through northwest of the Channel Islands and along the Central Coast by Monday. There is a 30-50 percent chance of GALES between Monday and Wednesday. Seas may approach 10 ft across portions of the Outer Waters Tuesday and Wednesday.
Ca, NONE. PZ, NONE.
