27/747 PM.
Mostly clear skies are expected through Tuesday with a warming trend. A 3 day Santa Ana wind event will start Sunday. It will peak on Monday with strong and gusty winds likely. The winds will not be as strong Sunday and Tuesday. Clouds will increase and a slight chance of rain will develop Wednesday. The new year will likely start off with quite a bit of rain.
(tdy-Mon), 27/817 PM.
***UPDATE***
Quite a nice day for recovery form the massive holiday storm. Skies were sunny all day. The cool airmass only allowed temps to rise into the lower to mid 60s which is 3 to 6 degrees below normal.
Attention no switches to the three day Santa Ana event which kicks off tomorrow. 00z mdls show a breezy but sub advisory level event. Copious sunshine and the offshore flow will bring 3 to 6 degrees of warming to most of the area.
All medium range mdls are beginning to diverge some for the end of week rain system. This is typical for a system coming in from the south as the mdls consistently struggle with that set up.
Current forecast is in good shape and no updates are planned.
***From Previous Discussion***
Overall, 12Z models have the same general synoptic idea, but differ in the details. At upper levels, trough will remain draped over far Southern CA through Sunday, before cutting off into a low offshore Monday/Tuesday. Near the surface, offshore flow will be on the increase through Monday/Tuesday.
Forecast-wise for the short term, main issue will be increasing offshore winds. Models indicate offshore LAX-DAG gradient increasing to -3.5 to -5.0 mb on Sunday then into the -5.0 to -8.0 range on Monday and Tuesday. As for upper level support, high resolution models indicate 950 mb winds increasing to the 40-50 knot range on Monday then decreasing slightly on Tuesday. Looking at the HREF, there is a 30-50% chance of advisory-level winds in the Santa Ana wind-prone areas of Ventura/LA counties late tonight/Sunday then a 70-100% chance on Monday evening through Tuesday afternoon. As for potential warning-level winds, there looks to be a 50-70% chance on Monday across parts of the LA Mountains as well as the Santa Susana Mountains in Ventura county, then a 30-50% chance on Tuesday. So, with the forecast, have issued a HIGH WIND WATCH from late Sunday evening through Monday afternoon for the Western San Gabriels, I-5 Corridor, western Santa Monicas and the Santa Susana mountains. As for advisories, currently think any advisory-level winds will be localized tonight/Sunday, so will not issue any at this time (although Swing/Mid shift may need to if 00Z models look a bit more impressive).
One thing to note with the expected winds, the recent significant rains and saturated soil will make trees more susceptible to blowing down in stronger winds. So, residents across Ventura and LA counties need to be aware of possible downed trees, resulting in power outages.
Otherwise, forecast will be rather benign. With northeasterly flow and lingering moisture, some clouds/fog will likely continue across interior sections of San Luis Obispo. Santa Barbara and Ventura counties the next couple of days. Otherwise, skies should remain mostly clear. As for temperatures, the offshore flow will allow for a warming trend, especially west of the mountains. By Tuesday, most coastal and coastal valley areas will be in the mid 60s to mid 70s.
(Tue-Fri), 27/206 PM.
For the extended, both the GFS and ECMWF, as well as their various ensembles, indicate another round of wet weather on New Years Eve and New Years Day. The models differ somewhat in the details (timing, amounts, etc.), but all indicate a wet holiday time period. Current forecast leans towards the more bullish ECWMF with light rain on New Years Eve (with most areas under 0.10 inches) and moderate rain on New Years Day (with most areas in the 0.25 to 0.75 inch range). So, totals for the two day period, totals will generally range between 0.50 to 1.25 inches (with the highest totals across the foothills and somewhat lower totals across interior sections). Do not anticipate any significant hydrologic issues, but the Rose Parade looks to be wet. As for snow levels, currently they are forecast to remain above 8000 feet through Thursday.
For Friday and Saturday, models indicate the wet weather will continue with additional totals between 0.25 to 1.00 inches. Snow levels will drop during this time period, down into the 6000 to 7500 foot range. So, will likely be some additional snowfall for the resorts.
As for temperatures, will expect most areas to exhibit a cooling trend through the period.
28/0016z.
At 0010Z at KLAX, there was no marine layer nor an inversion.
High confidence in most TAFs, with moderate confidence in KPRB and KLGB. There may be periods of brief IFR-MVFR vis overnight at any TAF location due to wet runways. VV002 cigs and 1/4-1/2 SM vis is likely after around 10Z-13Z Sun at KPRB and KLGB, and there is a 10-15% chance of similar conditions for all other coast and valley sites tonight.
KLAX, Moderate to high confidence in TAF. There is a 10% chance of vis as low as 1/2SM after 10Z Sun. High confidence in any east wind component at or less than 6 kt.
KBUR, Moderate to high confidence in TAF. There is a 10% chance of vis as low as 1/2SM after 10Z Sun.
27/815 PM.
Small Craft Advisory (SCA) northwest to north winds will affect the outer waters tonight. Seas will remain large and steep, gradually diminishing through this weekend and remaining below SCA levels through the week.
Offshore winds are expected to ramp up on Sunday across the coastal waters, then strengthen Sunday night through Monday, and potentially persist into Tuesday morning (and possibly again Tuesday night into Wednesday).Strong SCA level NE winds, with Gale Force gusts on Monday, will be focused from Ventura to Santa Monica with the strongest winds from Oxnard to Point Dume. These winds may extend all the way to the outer waters north of San Nicolas Island, with the highest chances on Monday morning.
Ca, High Wind Watch in effect from Sunday evening through Monday afternoon for zones 369-375-378-379. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 AM PST Sunday for zones 670-673-676. (See LAXMWWLOX).
