04/949 PM.
Mostly clear skies, dry conditions, a general warming trend with periods of offshore winds are likely through the week. The warmest and windiest conditions are likely on Friday and Sunday.
(tdy-Sun), 05/1242 PM.
Overall, latest models in good synoptic agreement through the short term period. At upper levels, ridge will build over the area tonight/Friday and remain in place through the weekend. At the surface, offshore flow will be increasing through the period.
Forecast-wise for the short term, main issues continue to be the offshore winds and temperatures. With respect to winds, models indicate LAX-DAG gradient bottoming out in the -3.0 to -4.0 mb range Friday through Sunday. Looking at the RRFS and other high resolution models, there will be decent upper level support (925/850 mb) winds in the 30-40 knot range by Saturday and Sunday. So, there will be the possibility of some low-end advisory level Santa Ana winds through the period. Based on ensembles, there is a 20-30% chance of advisory-level Santa Ana winds on Friday then about a 50-70% chance on Saturday and Sunday. So, future shifts may be issuing Wind Advisories for the Santa Ana wind corridor across eastern Ventura and western LA counties.
Second concern through the short term period will be temperatures. The combination of the upper level ridge and offshore surface flow will allow for a nice warmup across all areas through the weekend. By Saturday and Sunday, most areas will be about 5-10 degrees above normal. Fortunately, overnight low temperatures do not look to be too warm. So, there will be widespread moderate heat risk for the coastal plain and coastal valleys. The chances for the need of any heat products looks minimal (in the 20-30% range). Given the gusty offshore winds, warming temperatures and dry conditions, there will be elevated to locally critical fire weather conditions across the area by Friday and Saturday. Recent rainfall has helped mitigate the fire threat a bit, but live fuel moistures are still in the 65-80% range which means the area is not "out of the woods" with respect to the fire threat. There is a 30% chance of "targeted" Red Flag Warnings on Friday and Saturday.
(Mon-Thu), 05/1242 PM.
For the extended, rather benign weather should continue. Synoptically, the ridge will remain over the area through Wednesday (although a little bit weaker) then will be shifted eastward on Thursday as a trough approaches the West Coast. At the surface, this will be reflected with decreasing offshore flow through Tuesday then weak diurnal flow Wednesday and Thursday.
Forecast-wise, Monday through Wednesday will be rather unremarkable. With the weakening offshore flow and weakening upper ridge, there will be a slight cooling trend through this period although temperatures will generally remain 3-6 degrees above normal. Skies should remain mostly clear as lingering offshore flow will prevent any stratus development.
On Thursday, things will begin to change. With the approaching upper level trough, there will be a return of onshore flow and cooler temperatures for all areas. Based on current guidance, there will be a chance of some light rain developing during the day on Thursday.
Further out Friday through next weekend, deterministic and ensembles indicate some wet and unsettled weather, but differ dramatically in the details (timing, amounts, etc.). Ensembles from both the GFS and ECMWF indicate decent chances of widespread 1+ inch totals. Hopefully, models will come into some sort of focus as we draw nearer to next weekend.
05/1608z.
At 1545Z at KLAX, there was a surface-based inversion. The top of the inversion was 2000 feet with a temperature of 19 degrees Celsius.
For 18Z TAF package, high confidence in CAVU conditions for all sites.
KLAX, High confidence in 18Z TAF as CAVU conditions are expected through the period. No significant easterly wind component is expected.
KBUR, High confidence in 18Z TAF as CAVU conditions are expected through the period.
05/1242 PM.
For the Outer Waters, moderate to high confidence in current forecast. Through Saturday, high confidence in a combination of Small Craft Advisory (SCA) level winds and seas prevailing across all of the Outer Waters. For Sunday through Tuesday, there is a 50-70% chance of the combination of SCA level winds and seas continuing.
For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. Today through Saturday, high confidence in winds and seas remaining below SCA levels. For Sunday and Monday, there is a 50% chance of SCA level seas, but high confidence in winds remaining below SCA levels. For Tuesday, high confidence in winds and seas remaining below SCA levels.
For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Through tonight, high confidence in winds and seas remaining below SCA levels except for a 30% chance of SCA level winds across the western half of the Santa Barbara Channel this evening. For Friday, there is a 40% chance of SCA level northeast winds from Point Mugu to Santa Monica. On Saturday, there is a 60-70% chance of SCA level northeast winds from Point Mugu to Santa Monica. For Sunday through Tuesday, high confidence in winds and seas remaining below SCA levels.
05/1157 AM.
High tides will build each morning and peak Sunday and Monday at 7.2 to 7.6 feet (MLLW). Meanwhile, a west to northwest swell will slowly build into the area, peaking on the Central Coast Friday and Monday, and peaking everywhere else around Monday. This combination of high tides and high surf will bring hazardous swimming conditions, dangerous conditions on rock jetties, and a risk for moderate coastal flooding. If you are in the coastal area, listen to advice from your local officials.
With the daily high tides changing only a little Friday through Tuesday, the risk for coastal flooding will peak when the surf peaks (Friday and Monday for the Central Coast, and Monday for the rest of the coastal areas). This coastal flooding event will differ in several ways from the past episodes this year. First, while tides will be high, they will not be nearly as high as the record breaking tides from last week. This means that the impacts to harbor areas and Naples Island will generally be minor compared to last week. Shallow flooding should be expected, especially for low-lying walkways, but of a lesser degree less in severity and coverage. Second, for the beach-side coastal areas, the swell is from the west to northwest and not from the south, which characterized the coastal flooding episodes of September and early October. This means that areas hit hard in those events, like Long Beach and Malibu, are less at risk with this upcoming event. For west-facing shores however, the risk is much higher than events in the recent past. Areas like Oceano and Cayucos on the Central Coast, and Ventura on the southern coasts, have elevated risks of moderate coastal flooding. Moderate coastal flooding impacts include things like flooded sandy beach areas, moderate beach erosion, as well as shallow flooding of beach parking lots and bike paths. Isolated damage is unlikely but cannot be ruled out especially considering the extent of beach erosion we have already seen - which limits the natural protective buffer between the ocean and coastal infrastructure.
For the Central Coast, a High Surf Advisory and Coastal Flood Advisory will be in effect for Friday through Monday, since there will be an earlier peak to the surf. For all other coasts, A Beach Hazards Statement will be in effect for Friday through Tuesday, with a key note that some areas (especially Ventura County) may need to be upgraded around Monday when the surf peaks.
Ca, Beach Hazards Statement in effect from late tonight through Tuesday morning for zones 87-349-350-354-362-366. (See LAXCFWLOX). Coastal Flood Advisory in effect from 1 AM Friday to 10 PM PST Monday for zones 340-346. (See LAXCFWLOX). High Surf Advisory in effect from 1 AM Friday to 10 PM PST Monday for zones 340-346. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 3 PM PST Saturday for zones 670-673-676. (See LAXMWWLOX).
