18/410 PM.
Dangerously hot temperatures will continue all week. Coastal areas likely peaked Tuesday, while valley and interior areas peak through Friday. Dense coastal fog may develop as early as Thursday. Temperatures lower significantly over the weekend and into next week, but remain well above normal.
(tdy-Sat), 18/204 PM.
A 2-3mb onshore gradient trend today resulted in a 4-8 degree temperature drop from yesterday within about 5 miles of the coast. The LA/Ventura valleys and the Central Coast were little changed and the mountains and deserts were warmer. This is a common scenario when there is strong high pressure aloft but offshore gradients are weakening. Similar to what happens at the tail end of a Santa Ana event when cold air advection is shifting to the east. Forecast models are indicating little change in the diurnal pressure gradients the next few days and also little change with temperatures aloft. Unless there is movement in those parameters expect temperatures to remain very close to today's levels. Record highs today were oddly several degrees lower than the surrounding days in many locations so while records were easier to achieve today, especially closer to the coast, going forward records will be more difficult. May see some very shallow and dense fog at the beaches as early as Friday morning but more likely Saturday.
In any case, records or not, the weather message for southern California remains the same through at least Friday: Very hot with temperatures 20-30 degrees above normal. Heat advisories and extreme heat warnings remain in effect through Friday and some inland hazards may have to be extended. Temperatures Saturday are expected to fall a good 5-10 degrees as the ridge shifts into AZ/NM which in turn will create an increase in onshore flow and possible fog near the coast. Highs still 15-20 degrees above normal.
Record highs for Downtown LA this week are as follows:
Thursday: 97 in 1997 Friday: 93 in 1997 Saturday: 93 in 1931
(Sun-Wed), 18/218 PM.
After the 5-10 degree drop Saturday along with some possible coastal fog Sunday morning, temperatures begin a very slow climb back up through the middle of next week. Not expecting temperatures to be as hot as this week, but still 15-20 degrees above normal with a less than 5% chance of reaching 100 in the valleys.
As for rain chances, the GFS and EC deterministic runs are dry through the 28th, looking at their respective ensembles and ensemble AI projections, rain chances were pushed back to the 29th or 30th of March at the earliest. Even then, projections are still very light in accumulations, and not even close to significant at this time.
18/2315z.
At 23Z at KLAX, there was no marine layer. The surface-based inversion top was at 1500 ft with a maximum temperature of 29 C.
There is a chance of LIFR FG at KLGB (60%), KLAX (40%), KSMO (30%) KOXR (20%), KCMA (10%), KSBA (20%), KSMX (10%) 10-17Z Thursday. Otherwise, high confidence in VFR conditions through Thursday. Chances for LIFR FG increases Thursday night into Friday.
KLAX, There is a 40% chance of LIFR FG 10-17Z Thursday, otherwise high confidence in VFR conditions and any east winds staying under 6 knots. LIFR fog chances increase for Friday morning.
KBUR, High confidence in VFR conditions through at least Thursday.
18/152 PM.
Conditions are likely to remain below Small Craft Advisory (SCA) levels through at least Thursday. Thursday evening and Friday evening there is a moderate (30-40 percent) chance of SCA level winds across the far northwestern coastal waters. Over the weekend, SCA winds are likely across the outer waters (with a 20 percent change of GAlE FORCE winds), and seas are likely to build to around 10 feet.
Dense fog will be possible tonight into Thursday morning, and again Thursday night into Friday morning.
Ca, Heat Advisory remains in effect until 8 PM PDT Friday for zones 38-87-340-341-343-344-346>350-354-355-362-366-367-549-550. (See LAXNPWLOX). Heat Advisory in effect until 8 PM PDT Friday for zones 38-87-343-344. (See LAXNPWLOX). Extreme Heat Warning in effect until 8 PM PDT Friday for zones 88-342-345-351>353-356>358-368>376-378>380-548. (See LAXNPWLOX). PZ, NONE.
