31/1204 AM.
Santa Ana winds will continue today under mostly cloudy skies. A storm system will move into the area from the south this morning and bring rain to most of the area through New Years afternoon. There will be a lull in the rain Thursday night through Friday with renewed rain activity Saturday. Wet weather is possible into early next week.
(tdy-Sat), 31/140 PM.
Overall, 12Z models in good synoptic agreement through the short term period. At upper levels, low currently offshore will move northeastward into Central California on Thursday, a weak ridge will prevail over the area on Friday then another storm will begin to impact the area on Saturday.
THIS AFTERNOON THROUGH THURSDAY EVENING: All models are still "on board" with a significant storm impacting the area. Rain will gradually increase in intensity through this evening with the heaviest rain moving across the area tonight and Thursday morning with rain diminishing Thursday afternoon and evening.
Rainfall totals through Thursday evening are expected to range from 1-2 inches across coastal and valley areas with 2-5 inches across the foothills and mountains. Rainfall rates will peak tonight through Thursday morning with 0.25-0.50 inch/hour rates common with local rates up to 1.00 inch/hour.
As the storm rolls through tonight/Thursday, there will be some increased instability. This will continue to bring a 15-30% chance of thunderstorms to the area. At this time, the STORM PREDICTION CENTER indicates a marginal risk of severe thunderstorms on Thursday.
As for snow levels, they will remain quite high through the duration of the storm, above the 8000-8500 foot range. So, no significant winter weather issues are expected.
For winds, there will be some gusty southeasterly winds across the area. The strongest and most widespread winds looks to develop across San Luis Obispo and Santa Barbara counties, but there will also be some strong winds across the I-5 Corridor and northern Ventura county mountains. So, WIND ADVISORIES are in effect for these area (check out LAXNPWLOX for those details).
Given the expected rainfall totals and rates, along with the fact the ground is still saturated from the Christmas storm, flooding will be an issue as most of the expected rain will run off. So, a FLOOD WATCH remains in effect from southern Santa Barbara county to LA county. Widespread urban flooding, mud and debris flow near burn scars, and rockslides and mudslides across canyon roads will be threats.
FRIDAY: For Friday, all models build a weak ridge over the area. So, precipitation chances diminish noticeably. Will keep a slight chance to chance of showers in the forecast. However, amounts, if any, will be light.
SATURDAY: 12Z models are in good agreement as another storm is forecast to sweep across the area through the day. Through Saturday evening, rainfall totals are expected to range between 0.25 and 1.00 inches with amounts up to around 2.00 inches across south-facing slopes. Snow levels looks to remain rather high, above the 8000 foot range, and no significant winter weather issues are expected.
(Sun-Wed), 31/140 PM.
For the extended period, 12Z models indicate an extended period of wet weather for area. Models differ in the details (exact timing, amounts, etc.), but all indicate wet and unsettled weather for the area.
Through the extended period, a series of impulses will bring additional moderate to heavy rainfall to the area. At this time, the most significant impulses look to be Sunday and Sunday night then Tuesday and Tuesday night.
Based on current QPF forecasts, the Sunday through Wednesday time frame looks to be very wet. Coastal/valley areas, during this period, could receive 1.50 to 3.00 inches while foothill and mountain areas could get 3 to 6 inches of additional rainfall. One thing to note during the extended period, snow levels will likely be lower (in the 6500-7000 foot range). So, there may be some winter weather issues at the higher elevations.
31/1807z.
At 1656Z, there was no marine layer depth at KLAX. There was a surface-based inversion up to 1200 feet with a temperature near 22 degrees Celsius.
Low to moderate confidence in TAFs. High confidence in rain through the period, but lower confidence in cigs/vsbys with rain. IFR to VFR conds most likely, with LIFR conds during heaviest rain (06Z-16Z most likely). There is a 15-30% chance for TSTM for coastal and valley sites, highest chances 06Z-18Z and south of Point Conception. Any TSTM can produce gusty erratic wind shifts, frequent lightning, and heavy downpours.
Wind gusts may be off +/- 10 kts and timing of wind group changes may be off +/- 3 hours.
Moderate to occasionally strong turbulence and LLWS is possible through the period, especially after 20Z over terrain.
KLAX, Low to moderate confidence in TAF. High confidence in rain through the period, with heaviest rain likely from around 04Z-16Z. Cigs and vsbys may vary between IFR and MVFR during rain, with a 20% chance for LIFR conds during heaviest rain. There is also a 20-30% chance for TSTM between 01/06Z and 02/00Z, highest 01/06Z - 01/18Z. Any TSTM can produce gusty erratic wind shifts, frequent lightning, and heavy downpours. Moderate confidence in winds, although there is a 30% chance for gusts to 25 knots from the ESE between 07Z and 17Z. High confidence in east winds through a majority of the period. Wind shift back to the WSW may be off +/- 3 hour, especially on the back end.
KBUR, Low to moderate confidence in TAF. High confidence in rain through the period, with heaviest rain likely from around 04Z-16Z. Cigs and vsbys may vary between IFR and MVFR during rain, with a 25% chance for LIFR conds during heaviest rain. There is also a 15-25% chance for TSTM between 01/06Z and 02/00Z, highest 01/06Z - 01/18Z. Any TSTM can produce gusty erratic wind shifts, frequent lightning, and heavy downpours. ESE wind gusts may be off +/- 10 kts and timing of wind group changes may be off +/- 3 hours.
31/149 PM.
Small Craft Advisory (SCA) winds will continue to expand across the waters as a storm system to the southwest of the region lifts northward across the coastal waters. SCA conditions will continue into tomorrow morning for virtually all areas. A Gale Warning is in effect for the Santa Barbara Channel and for the Outer Waters from the western Channel Islands north into the northern Outer Waters. The Warning is in effect through tonight.
There will likely be a lull in the winds on Thursday afternoon and evening, but there is a high chance of a return of SCA level southerly winds Friday into at least this weekend, highest north and west of Point Conception as a cold front moves through the area. There is a 40-60 percent chance of GALES north and west of Point Conception during this time. Periods of SCA level southerly winds will continue into early next week. Rough, choppy, short period seas will be common into early next week as well.
Rain will likely be heaviest tonight through Thursday (New Year's Day). There is a chance of thunderstorms (mainly south of Point Conception) during this period, but confidence is low in timing. Waterspouts, gusty and erratic winds, frequent lightning, and brief heavy rain are all possible with any thunderstorm. Rain will return this weekend and continue into next week.
31/104 PM.
Abnormally large high tides between 6.7 and 7.5 feet MLLW will occur during the morning hours, roughly between 5 am and 11 am Thursday through Sunday. The tides could combine with southerly winds a times to bring minor tidal overflows at area beaches. While the major threat would be from pooling from water over normally dry parking lots and walkways, elevated surf and strong rip currents cannot be ruled out. A Beach Hazards Statement has been issued from late tonight through Sunday afternoon, but there is a moderate chance that a Coastal Flood Advisory and/or a High Surf Advisory could be needed over the weekend as another storm will likely generate moderate to strong winds and larger swell. While there exists some uncertainty in timing of the highest surf, this would be the best chance for impacts such as shallow flooding of parking lots and roadways, some inundation of harbor walkways, and more significant beach erosion.
Ca, Beach Hazards Statement in effect from midnight PST tonight through Sunday afternoon for zones 87-340-346-349-350-354-362-366. (See LAXCFWLOX). Flood Watch remains in effect from 10 PM PST this evening through Thursday evening for zones 88-349>358-362-366>382-548. (See LAXFFALOX). Wind Advisory remains in effect until 3 PM PST Thursday for zones 340>342-345>353. (See LAXNPWLOX). Wind Advisory in effect from 7 PM this evening to 7 AM PST Thursday for zones 377-378. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 PM PST Thursday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 2 PM PST this afternoon for zones 650-673. (See LAXMWWLOX). Gale Warning in effect until 3 AM PST Thursday for zones 650-673. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PST Thursday for zones 655-676. (See LAXMWWLOX). Small Craft Advisory in effect until 6 PM PST this evening for zone 670. (See LAXMWWLOX). Gale Warning in effect from 6 PM this evening to 3 AM PST Thursday for zone 670. (See LAXMWWLOX).
