05/316 AM.
A weakening atmospheric river system will move south from northern California into Central California through tonight, falling apart and weakening as it shifts into the Central Coast. A cooler weather pattern will linger with more clouds than Sun across the coast and valleys today. Then, a warming trend will develop through as high pressure builds aloft over the region. A wet weather pattern will likely develop for the latter half of next week.
(Wed-Sat), 05/148 PM.
Overall, 12Z models in good synoptic agreement through the short term period. At upper levels, broad trough sweeps across the area today then a ridge builds Thursday through Saturday. Near the surface, weak to moderate onshore flow will prevail through Thursday then weak to moderate north to northeast flow develops Friday through Saturday.
Forecast-wise, two main issues are rain chances and wind. With respect to rain, overall thinking has not changed. The tail end of a weak front will sweep across the area through tonight, bringing the threat of rain. At this time, best chances for any appreciable accumulation look to be across San Luis Obispo county and to a lesser extent Santa Barbara county. In these areas, rainfall totals under 0.25 inches are expected with maybe up to 1.00 across northwest SLO county. For Ventura/LA counties, the chances for measurable precipitation are much lower and only some isolated light showers or drizzle will be possible (with best chances over the foothills). Given the expected light amounts and intensities, no hydrologic issues are expected.
As for wind, the passing remnants of the front will generate some gusty southwesterly winds across interior sections today and tonight. However, any advisory-level winds look to remain localized. For Thursday through Saturday, attention will turn to offshore winds. High resolution models indicate an increase in both north and northeast offshore gradients. As the gradients increase, ensembles do indicate some decent chances of advisory- level winds across the area. The areas most "at risk" for advisory-level winds will be the Santa Ynez Range, the I-5 Corridor, the Santa Lucia Range as well as the Santa Ana wind- prone areas of Ventura/LA counties. Best northerly winds are expected Thursday night/Friday and the best northeast winds Friday night/Saturday.
As for clouds and temperatures, no surprises are anticipated. Clouds associated with frontal remnants will gradually thin out through tonight. Afterwards for Thursday through Saturday, skies should remain clear for most areas although some clouds may be possible across the LAX coast and interior sections of SLO/SBA counties each night. As for temperatures, will expect a warming trend, especially on Friday and Saturday with offshore surface flow and ridge building overhead. Do not anticipate any significant heat issues, but will be will 5-10 degrees above normal for most areas by Saturday.
(Sun-Wed), 05/148 PM.
For the extended, 12Z models continue to exhibit decent synoptic agreement. For Sunday and Monday, upper level ridge will peak in strength over the area as well as surface offshore flow. So for Sunday and Monday, will anticipate relatively benign weather. Skies will generally be mostly clear on Sunday, but could see an increase in high clouds on Monday. As for stratus/fog, coverage looks to be very limited Saturday night, but could be more extensive Sunday night (depending on the surface gradients). As for temperatures, Sunday will likely be the warmest day with some slight cooling on Monday. Offshore winds will be observed across the area, but should generally remain below advisory-levels.
On Tuesday, models are still holding firm to the beginning of a pattern change, bringing a chance of significant rainfall to the area Tuesday night through Saturday. In terms of details, models do differ in timing and amounts. The ECMWF and its ensembles bring the rain sooner than the GFS family and bring more rainfall. Essentially, there is high confidence in rain for the entire area sometime during the Tuesday through Saturday time frame, but amounts and exact timing remain very much in question. At this time, there is about a 40% chance of a moderate rainfall event with 1-2 inches for coastal/valley areas and 2-4 inches in the foothills and mountains. Stay tuned to the latest forecast details over the coming days for this developing weather situation.
06/0253z.
At 01726Z at KLAX, the marine layer was 1700 feet deep. The top of the inversion was at 4600 feet with a temperature of 15 C.
High confidence in TAFs for KWJF and KPMD.
Moderate confidence in remaining TAFs. For all coastal sites, moderate confidence in IFR to MVFR conds occuring tonight, but lower confidence in arrival timing. Light drizzle is possible at times for any sites with cigs. There is a 30% chance for LIFR conds at KPRB, KSBP, and KSMX when cigs are present, and a 30% chance for OVC010-0025 cigs from 12Z-18Z Thu for KBUR and KVNY.
KLAX, Moderate confidence in TAF. Cigs are expected to be >025 through around 13Z before lowering to 015-025. Timing may be off +/- 3 hours. No significant east wind component expected.
KBUR, Moderate confidence TAF. There is a 30% chance for OVC010-0025 cigs from 12Z-18Z Thu, and a 10% chance of cigs as low as BKN006.
05/134 PM.
High confidence in a combination of Small Craft Advisory (SCA) level winds and seas expanding tonight and tomorrow across the entirety of the outer waters and Central Coast nearshore waters. The west-northwest swell will bring peak seas up to 16 feet by Thursday mid-day. Wave heights will begin to decrease some Friday, but will remain large into at least Saturday morning. Conditions are expected to become relatively calm by Sunday.
Localized Gale Force winds will be possible across the outer waters from Point Conception south to San Nicolas Island and westward Thursday afternoon through Friday evening.
Seas across the inner waters south of Point Conception will rapidly increase tonight, peaking at 10 feet across the Santa Barbara Channel Thursday mid-day, and 6 feet across the waters adjacent to Los Angeles and Orange counties. NW winds of 20-30 knots will be common across the entire Santa Barbara Channel Thursday mid-day through evening. Localized Gale Force gusts up to 35 knots may occur across the far western portion of the Channel during the same timeframe. High confidence in conditions improving Friday and becoming relatively calm by Saturday.
On Thursday and Friday, large tidal swings between morning high tide and afternoon low tides (7-8 ft changes) will cause strong currents nearshore. The large west-northwest swell combined with the high tides will create breaking waves at Morro Bay Harbor and possibly Ventura Harbor.
05/1250 PM.
Coastal Flood Advisories, High Surf Advisories, and a Beach Hazards Statement have been issued across ALL coastal areas due to the high astronomical tides and a large west-northwest swell.
Peak surf heights are more likely to line up with the Thursday high tide along the Central Coast, although surf heights will be abnormally large throughout the region during morning high tide Thursday and Friday.
Refer to the CFWLOX and SRFLOX for additional details.
Ca, High Surf Advisory in effect until 9 PM PST Saturday for zones 340-346. (See LAXCFWLOX). Coastal Flood Advisory in effect from 4 AM Thursday to 2 PM PST Friday for zones 340-346-354-362-366. (See LAXCFWLOX). Beach Hazards Statement in effect from 4 AM PST Thursday through Friday afternoon for zones 349-350. (See LAXCFWLOX). High Surf Advisory in effect until 3 AM PST Saturday for zone 354. (See LAXCFWLOX). High Surf Advisory in effect from 7 AM Thursday to 2 PM PST Friday for zones 362-366. (See LAXCFWLOX). PZ, Small Craft Advisory in effect until 3 AM PST Saturday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 9 PM PST Saturday for zones 670-673-676. (See LAXMWWLOX).
