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-Fri), 31/256 AM.
An upper low southwest about 400 miles southwest of Point will remain nearly stationary through this afternoon. Early this evening it will swing to the northeast fairly rapidly, reaching a point just west of the Central Coast by dawn Thursday. It will then continue on a NE trajectory into NV during the day. It will advect a large area of deeper moisture and PVA starting today and peaking Thursday morning. Light rain will likely begin mid to late morning across the entire area. The late rain will continue through late afternoon. The rain will increase in intensity over night and will peak from midnight to noon, with areas of moderate rain expected to begin Wednesday afternoon. The heaviest rain will fall south of Pt Conception and esp across the south facing slopes and foothills. During the period of max PVA (Midnight to noon) there will be a slight chc of a TSTM as well.
Rainfall today will be fairly light with rates mostly under a quarter inch per hour. By late afternoon, most areas will have picked up about a half inch of rain with up to an inch across south facing slopes. As the storm intensifies similar amounts will likely fall in half of the time this evening, but with much lesser amounts across the Central Coast. During the peak of the storm most cst/vly locations south of Pt Conception will see an inch to an inch and half with double those amounts across the south facing slopes. The highest amounts in the valleys will occur near the foothills which, unfortunately, includes Pasadena. Rainfall rates are expected to range from 0.25 to 0.50 in/hr. Locally higher rates of around 0.50-1.00 in/hr are possible during the peak of the storm and under any TSTM that may form. Snow will not be an issue with this system as the warm southerly flow will keep the snow level above 8500 ft.
Since the ground is so saturated from the super soaking Christmas storm, almost all rainfall will become runoff. This will allow flooding to occur with less rain amounts and rates than is typical. A flood watch is in effect from 1000 PM Wednesday through 1000 PM Thursday to highlight this risk (see LAXFFALOX for details). As well as any flooding there will also be an enhanced risk of rockslides and mudslides across canyon roadways, urban flooding and small debris flows in and around the recent burn scars.
While SLO And most of SBA counties will miss the bulk of the rainfall they will see the strongest winds as the area will be closest to the low's center. Wind advisories are in effect for the two counties from this afternoon through New Years afternoon for gusts 35 to 45 mph. There will also be a 2 to 4 hour burst of strong south winds south of Pt Conception Thursday morning as the front moves across the area.
Weak ridging will build into Srn CA starting New Years afternoon. There will be a noticeable decrease in rainfall starting in the west and moving to the east (LA county will likely have a rainy afternoon). By evening and into Friday there will likely only be some scattered showers as the area waits for storm number 2.
The warm start to the day today will allow max temps to rise into the mid to upper 60s (although these high may occur fairly early in the day only to fall as the rain arrives). Max temps over the csts/vlys both Thu and Fri will be in the lower to mid 60s.
(Sat-Tue), 31/1221 AM.
There is good synoptic level mdl agreement for the xtnd period, but much disagreement in the timing and strength of rainy periods.
The upper level pattern will be rather static through the period with moist SW flow over the state. There is good agreement that a decent impulse will move over the area on Saturday bringing widespread rain to all areas. Snow levels will remain above 7500 ft. Early rainfall estimates call for .50"-.75" across the csts/vlys and .75"-1.25" inches over the mtns. Rainfall rates should be under a half inch per hour.
Sunday and Monday will not have widespread continuous rain. But it will be mostly cloudy with periods of rain. These rain events could add up over the two day period and bring up to an additional inch of rain to any one area. Snow levels will fall to about 6500 ft and there could be
Current long range mdls show another impulse moving across the state on Tuesday bringing another round of mdt locally hvy rain to the area along with strong southerly winds.
Max temps will not change much through the period with typical rainy day temps in the lower to mid 60s.
31/1102z.
Around 0830Z, there was no marine layer depth at KLAX. There was a surface-based inversion up to 750 feet with a temperature near 22 degrees Celsius.
Low to moderate confidence in the current forecast with confidence waning through the day into tonight. Frequent changes in ceilings and visibilities could occur as rain moves over area. There is a moderate chance of MVFR conditions after 16Z, increasing to a high chance after 00Z Thursday. There is a slight chance of thunderstorms tonight. Moderate to occasionally strong turbulence and low-level wind shear is possible after 20Z for terminals north of KNTD, highest between 02Z and 08Z Thursday.
KLAX, There is a 40 percent chance of MVFR conditions developing in rain as soon as 16Z, increasing to a 70 percent chance after 20Z. MVFR conditions are imminent after 10Z Thursday with a moderate chance of IFR conditions in heavy rainfall. There is a 20 percent chance of thunderstorms after 10Z Thursday. An easterly wind component is likely through the day. East winds between 7 and 12 knots are likely after 21Z with a 40 percent chance east winds being greater 10 knots between 23Z and 02Z Thursday, and again after 08Z Thursday.
KBUR, There is a 40 percent chance of MVFR conditions developing in rain as soon as 16Z, increasing to a 70 percent chance after 20Z. MVFR conditions are imminent after 10Z Thursday with a moderate chance of IFR conditions in heavy rainfall. There is a 20 percent chance of thunderstorms after 10Z Thursday. There is a 20 percent chance of moderate turbulence and low-level wind shear after 06Z Thursday.
31/302 AM.
Marginal Small Craft Advisory (SCA) winds this morning will increase and expand through this afternoon as a storm system to the southwest of the region lift northward across the coastal waters. There is a 80-100 percent chance of SCA conditions by this afternoon across the Santa Barbara Channel and the waters southwest through northwest of the Channel Islands, including the nearshore waters along the Central Coast. There is a 50-70 percent of SCA level winds developing this afternoon and tonight across the inner waters from Point Mugu to San Mateo Point. There is a 50-70 percent of south to southeast GALES from an area from the western portion of the Santa Barbara Channel, Point Conception to about to 40 NM offshore of Point Sal. The highest chance of GALES will be from an area near Point Conception to 40 NM offshore to San Miguel Island.
There could a lull in the winds on Thursday afternoon and evening, but there is a 60-80 percent chance of a return of SCA level southerly wind Friday into Saturday, highest north and west of Point Conception as a cold front moves through the area. There is a 40-50 percent chance of GALES north and west of Point Conception during this time.
Rain will likely be heaviest tonight (New Year's Eve) 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.
31/302 AM.
Abnormally large high tides around 7 feet will occur during the morning hours, roughly between 6am and 10 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 for some beaches along the Central Coast and the Ventura County coast. 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 late tonight through Sunday afternoon for zones 87-349-350-354-362-366. (See LAXCFWLOX). Flood Watch in effect from this evening through Thursday evening for zones 88-349>358-362-366>382-548. (See LAXFFALOX). Wind Advisory in effect from 4 PM this afternoon to 3 PM PST Thursday for zones 340>342-345>353. (See LAXNPWLOX). PZ, Small Craft Advisory in effect from 3 PM this afternoon to 3 PM PST Thursday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 10 AM PST Thursday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect from noon today to 9 AM PST Thursday for zone 655. (See LAXMWWLOX). Small Craft Advisory in effect from noon today to 8 PM PST this evening for zone 670. (See LAXMWWLOX). Gale Watch in effect from this evening through late tonight for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect from 8 AM this morning to 1 PM PST this afternoon for zone 673. (See LAXMWWLOX). Gale Warning in effect from 1 PM this afternoon to 3 AM PST Thursday for zone 673. (See LAXMWWLOX). Small Craft Advisory in effect from 7 AM this morning to 7 AM PST Thursday for zone 676. (See LAXMWWLOX).
