29/946 AM.
Temperatures will remain above normal through Monday, especially inland of the beaches, warmest today. Dense fog may will affect coastal areas as late as Monday. Much cooler conditions Tuesday through Thursday with gusty onshore winds and chances of light rain. Weak to moderate offshore winds with warming drying to follow Friday and Saturday.
(tdy-Tue), 29/945 AM.
***UPDATE***
Patchy dense fog has mostly cleared out, except for a few areas along the Central Coast. Today is again on track to be warm across inland of the beaches and marine layer stratus will likely return to the coasts this evening.
***From Previous Discussion***
High pressure aloft will continue to dominate to region, leading to June-like conditions. High temperatures in the 80s to lower 90s will be common inland of the beaches on Sunday, which is 10 to 20 degrees above normal for this time of the year, then drop 5 to 10 degrees on Monday. We had a few records fall on Saturday (Paso Robles, Palmdale, and Lancaster) and records may fall again on Sunday (highest chances in those same 3 sites), but temperatures will not be extreme enough to need any Heat Advisories.
Low clouds and fog will continue to moderate coastal areas, with June Gloom conditions going nowhere through Monday. The typical parameters we use to predict trends in the marine layer (like onshore pressure gradients and 500 millibar heights) all point to some deepening going forward and thus less dense fog. Cloud heights however are already very low which usually points to dense fog by the morning hours. All this adds up to low confidence on how low the visibilities will go and how the low clouds and fog will behave.
High pressure aloft finally breaks down Tuesday as a deep and cold low starts pushing into the Pacific Northwest. This will drop temperatures further with highs in the low to mid 70s common, which is more typical for the end of March. High clouds will start to blanket the sky as a weak cold front associated with the low approaches the area.
(Wed-Sat), 28/939 PM.
The low over the Pacific Northwest will push into Montana by late Thursday. More of the latest projections show the low dipping a little further to the south along the way, which if that happens will keep that cold front marching down the west coast alive for a little longer. While rain is still not certain for southwest California, the chances perked up a few percentage points from yesterday. As it stands, there is a 30 to 50 percent chance for some rain in the Tuesday Night through Thursday time period, but still very unsure which 6 hour period in that range will see rain if we get it. That is why the daily PoPs are generally in the 10 to 30 percent range. If it does rain, very confident that amounts will be light with minimal impacts.
The winds will be the most significant piece to this system for our area. Gusty west to northwest winds are certain Wednesday and Thursday over much of the area, especially near the coast and over the mountains and deserts. As the parent low moves further to the east, cold air and surface high pressure will settle in over Idaho by Friday. This will drive the typical post-storm system wind reversal going from onshore to offshore. Weak to moderate offshore winds are looking more and more likely Friday and Saturday. High pressure aloft builds in at the same time, which will all add up to warming and drying once again heading into the following week.
29/1736z.
At 1653Z over KLAX, the marine layer was 400 ft deep. The top of the inversion was at 2300 feet with a temperature of 23 C.
High confidence in VFR TAFs for KPRB, KPMD, KWJF, KBUR, and KVNY.
Moderate confidence in remaining TAFs. Expecting mainly V/LIFR conditions tonight into tomorrow morning for coastal sites. Timing of CIG/VSBY restrictions may be off +/- 2 hours.
KLAX, Moderate confidence in TAF. Arrival and clearing times of CIGs may be off +/- 2 hours. Generally expecting 003-006 with vsbys 2-5SM. No significant east wind component expected.
KBUR, High confidence in VFR TAF.
29/732 AM.
High confidence in winds and seas staying under Small Craft Advisory (SCA) levels through at least Monday, except for a 30-50% chance of low-end SCA winds beyond 20 NM from the Central Coast.
Moderate risk of dense fog with visibility under one nautical mile will continue through Monday evening (focused evening to morning hours)
There is a growing risk for widespread strong SCA or low-end Gale Force winds over most coastal waters (including nearshore and the Santa Barbara Channel) late Thursday through Friday.
Ca, Dense Fog Advisory now in effect until 11 AM PDT this morning for zones 341-346-347. (See LAXNPWLOX). PZ, NONE.
