15/919 AM.
Moderate offshore flow will remain in place today through early Thursday with periods of gusty winds and very low humidities. Onshore flow will develop by Thursday afternoon, bringing cooler temperatures and higher humidities that will continue through the weekend. Cold overnight temperatures are expected tonight in wind protected areas.
(tdy-Fri), 15/931 AM.
***UPDATE***
Day 9 now of offshore flow and still getting some gusts into the 50s across some of the valleys of western LA and eastern Ventura Counties as well as the Santa Monica and San Gabriel Mountains. May see a 5-10 mph wind increase through the morning hours as is typical with offshore conditions, but weakening again in the afternoon and evening. Overall, we're definitely on the back end of this long stretch of Santa Ana winds but winds expected to continue into Thursday morning before onshore flow finally returns by afternoon.
As noted below, with less cold advection today we're looking at temperatures warming up well into the 70s for coast and valleys. Van Nuys is already 10 degrees warmer than it was yesterday and most other areas are trending at least 5 degrees warmer.
***From Previous Discussion***
The really good news is that today will be the last really windy day. Looked for a marked decrease in the winds this afternoon with the advisory level gusts ending by 300pm.
Red Flag conditions continue until 600pm (due to the very low humidities) and the extra critical fire conditions will continue until 300 pm when the winds subside.
Less cold air advection and higher hgts will bring 4 to 8 degrees of warming to the area today and max temps will end up 3 to 6 degrees above normal.
Current temperatures in the wind sheltered inland locations are well below freezing and another round of freezing temps is forecast again tonight.
Thursday will be a very nice day. There will still be enough offshore flow to bring 15 to 25 mph winds to the typical Santa Ana locations in the morning but thats it. Max temps will cool a few degrees (due to the weaker offshore flow) but will still be a few degrees above normal. Max temps across the csts vlys will be in the mid to upper 60s.
Friday will finally see the offshore flow reverse to onshore. At the upper levels the upper low that has been harmlessly spinning to the SW of KLAX will move to the east and pass just to the south of San Diego. There is a chance of some marine layer clouds, but that will likely have to wait until Saturday. The combination of the onshore flow and hgts falling to 564 dam will result is a dramatic 4 to 8 degrees cool down (except for the Antelope Vly which will not see much change). Max temps Friday will only be in the lower to mid 60s across the csts/vlys.
(Sat-Tue), 15/312 AM.
The weekend will feature a coastal and lower vly marine layer which will provide a very welcome boost to humidities. The afternoon onshore push to the east will be near 4 mb. Max temps will not change much each day and will mostly be in the lower to mid 60s across the csts/vlys.
Mdls and ensembles are showing significant differences on Mon and Tue as they struggle to resolve the interaction of cold energetic flow out of Canada and a weak upper low moving in from the East pac. The effects of the mdl disagreement will not be felt too much on Monday but there is less confidence on the exact forecast Tue and Wed which could feature a mdt-stg Santa Ana (about a 40 percent chc at this point with less confidence on which day)
15/1744z.
At 17Z at KLAX, there was no marine layer. There was a surfaced based inversion with a top at 800 ft and a temperature of 16 C.
Overall, high confidence in 18Z TAF Package. Wind shift timing may be off by +/- 2 hours and wind speeds could be off by up to 10 kt. Areas of LLWS and turbulence with mdt to locally strong UDDF is possible thru this afternoon (esp near foothills and mtns). Winds could be erratic at times. Otherwise, expect VFR conds to dominate the fcst pd.
KLAX, High confidence in VFR conds. There is a 20% chance of an east wind component reaching 8 kt between 06Z and 16Z.
KBUR, High confidence in VFR conds. Low confidence in winds at airfield. Wind speed may be off by 5-10 kt thru 06z. LLWS is possible to likely thru early afternoon, with moderate to locally strong turbulence and UDDF near the airport.
15/812 AM.
In the Outer Waters, Small Craft Advisory (SCA) level E-NE winds will persist in the southern zone (PZZ676) thru noon or so, with the strongest winds in eastern and northern portions. Local GALE force gusts are possible (30% chance) this morning in zone PZZ676 around the Channel Islands. There is a 20-30% chance that SCA winds will occur and late tonight into Thu morning. Otherwise and elsewhere, winds will likely be below SCA levels thru Sun night. There is a 20-30% chance of SCA level NW winds Fri night into Sat mainly in the two southern zones (PZZ673/676).
In the Inner Waters N of Pt Sal, SCA conds are not likely thru Sun night.
In the Santa Barbara Channel, from Ventura to Santa Cruz Island southward, winds are expected to increase to Gale force early this morning and continue thru noon. There is a 30-40% chance winds will not reach Gale force, and remain at SCA levels. In this area, there is a 40% chance of SCA level winds late tonight/Thu morning. Otherwise, SCA conds are not expected thru Sun night. Elsewhere, there is a 20% chance of SCA level E-NE winds thru noon, then SCA conds are not expected thru Sun night.
In the Southern Inner Waters, GALE force winds are expected early this morning continuing thru noon. There is a 20% chance winds will not reach Gale force, and will remain at SCA levels. In this area, there is a 30% chance of SCA level winds late tonight/Thu morning. Elsewhere, SCA level winds are likely (60% chance) thru the San Pedro Channel, south to off the coast of Orange County and out to Catalina Island (including Avalon and Two Harbors this morning). There is a 10-20% chance of brief Gale force wind gusts in this area this morning. Otherwise, SCA conds are not expected thru Sun night. Elsewhere, there is a 20% chance of SCA level E-NE winds thru noon, then SCA conds are not expected thru Sun night.
Ca, Wind Advisory remains in effect until 3 PM PST this afternoon for zones 88-354-355-358-362-369>380. (See LAXNPWLOX). Red Flag Warning in effect until 6 PM PST this evening for zones 288-345-352>358-362-369>374-376-377-380. (See LAXRFWLOX). Red Flag Warning in effect until 3 PM PST Thursday for zones 375-378-379. (See LAXRFWLOX). PZ, Gale Warning in effect until 3 PM PST this afternoon for zone 650. (See LAXMWWLOX). Gale Warning in effect until noon PST today for zone 655. (See LAXMWWLOX). Small Craft Advisory in effect until noon PST today for zone 676. (See LAXMWWLOX).
