31/715 PM.
Periods of moderate to heavy rain are expected Thursday morning into early afternoon then tapering off in the evening. Friday will mainly be dry before another system brings rain back to the area Saturday off and on into early next week.
(tdy-Sat), 01/343 AM.
An upper low spinning just to the west of Pt Conception will swing a front and bands of rainfall through the area today with peak rainfall occuring through noon. Rain was a little slow to develop last evening but now covers the area with pockets of moderate to heavy rain. This is a very juicy storm with a good moisture tap from the warmer wetter south. PWATs are around 1.30" with this system which is very much above normal. The one question is for TSTM development, the current forecast calls for a 20 to 30 percent chc of a TSTM which seems reasonable given the amount of PVA wrapped around the low and CAPE values near 700j/kg. The problem is that the storm has been pretty much lightning free for the past 6 hours. Will keep the TSTM chcs as is, but would not be surprised if there is not much development.
What is not up for debate is the rain. This system will give the area south of Pt Conception a good soaking from now until noon with the Central Coast clearing out a few hours earlier. During this stretch rainfall amounts will likely be 1.00 to 1.50 inches cst/vlys and 1.50 to 2.50 local 3.00 inches across the coastal slopes and foothills (Pasadena is so close to the foothills that it will be near the 1.5 inch mark. 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. Snow levels should be over 8500 ft and winter weather is not a factor with this system.
This system is wrapped up tight and has produced a strong wind field. Since SLO and SBA counties are closest to the low those areas will have the strongest southeasterly winds. There will also be strong winds across the I-5 Corridor and northern Ventura county mountains. WIND ADVISORIES are in effect for these areas (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.
There will be a very noticeable fall off in rain in the afternoon as the main dynamics and the upper low move to the northeast into Central CA and NV. There still could be some lingering showers but for the most part the event will be over.
Max temps today will be in the lower to mid 60s across the csts and vlys which is 3 to 6 degrees blo normal.
A weak ridge will move into the state on Friday and it will be dry day with partly to mostly cloudy skies. Max temps will not change much from today's blo normal readings.
Another system will push the ridge off to the east and bring another round of rain to the area. The latest mdls are slowing the system down. The latest forecast call for rain to start across the Central Coast just after dawn and reach LA county around noon. There is only a 20 percent chc that rain will reach LA county in the morning. The period of maximum rain will likely be from noon to midnight. This system has its origins to the north and is colder and comes with less moisture. As a result rain totals will be less than today's moisture rich system. Most areas will see half inch to an inch and half of rainfall. LA county may only recieve a quarter to a half inch. Snow levels will remain rather high. Max temps will continue to run in the lower to mid 60s for the csts and vlys.
It might be difficult to tell when this storm ends and the next begins, see the xtnd fcst for details.
(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.
01/1142z.
At 0817Z at KLAX, there was no marine layer nor an inversion. There was a 7000+ ft deep moist layer.
Low confidence in TAFs through 21Z. Cigs and vis will vary frequently as numerous rain showers move over the area. There is a 10-15 percent chc of a tstms from 13Z-19Z. Better confidence after 21Z with only a 20 percent chc of brief MVFR conds with rain.
KLAX, Low confidence in TAF through 21Z. Cig and Vis will vary frequently as the rain moves over the terminal. There is a 10-15 percent chc of a TSTM 15Z-19Z. Better confidence after 21Z with only a 20 percent chc of brief 4SM -SHRA BKN015 conds through 00Z. High confidence in at least a 10kt east wind component through 18Z. Wind shift back to the WSW may occur anytime 18Z-21Z.
KBUR, Low confidence in TAF through 21Z. Cig and Vis will vary frequently as the rain moves over the terminal. There is a 10-15 percent chc of a TSTM 15Z-19Z. Better confidence after 21Z with only a 20 percent chc of brief 4SM -SHRA BKN012 conds through 00Z.
01/1254 AM.
Moderate to strong SE winds will continue to affect the waters this morning as a cold front moves over the waters. Small Craft Advisory (SCA) or stronger conditions will affect all areas.
There will likely be a lull in the winds this afternoon and evening, but there is a 70-80% chance of additional 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 Friday night into Saturday. Periods of SCA level southerly winds will continue into early next week. Rough and hazardous short period seas will be common into early next week.
Rain will likely be heaviest this morning. There is a chance of thunderstorms (best chances 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.
31/809 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 at 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, building surf and strong rip currents could increase the risk of minor coastal flooding.
A Beach Hazards Statement has been issued from late tonight through Sunday afternoon, but there is a 30-50% 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 is 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 through Sunday afternoon for zones 87-340-346-349-350-354-362-366. (See LAXCFWLOX). Flood Watch remains in effect through this evening for zones 88-349>358-362-366>382-548. (See LAXFFALOX). Wind Advisory remains in effect until 3 PM PST this afternoon for zones 340>342-345>353. (See LAXNPWLOX). Wind Advisory remains in effect until 7 AM PST this morning for zones 377-378. (See LAXNPWLOX). PZ, Small Craft Advisory in effect until 3 PM PST this afternoon for zones 645-650-655-670-673. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PST this morning for zone 676. (See LAXMWWLOX).
