11/1137 PM.
Moderate rain and a chance of thunderstorms will sweep through the area through this morning. Scattered shower activity is then possible this afternoon into Monday morning. Dry and warmer weather is expected the rest of next week.
(tdy-Tue), 12/257 AM.
The cold front is progressing a little slower than earlier thinking, likely because the low level jet aligned a little more parallel to the front and slowed its forward progress. It has created local heavy downpours over SLO county and radar indicated some rotating storms in the waters off of the Central Coast. Rainfall amounts so far are consistent with the forecast of a half inch to an inch of rain. Locally heavier amounts could occur under an area affected for a slow moving heavy shower or TSTM. There have been no TSTM so far, but there is enough instability and lift with this system to include a 20 percent chc of some developing. The best chc for TSTMs will be later this morning after sunrise as the atmosphere will destabilize a little more. Any TSTMs that do develop could also produce gusty outflow winds, small hail and potentially waterspouts or weak, short-lived, tornadoes due to the amount of turning in the lower levels of the atmosphere.
The latest high rez mdls show the front exiting SBA county just around dawn. The fcst for VTA county calls for the rain and the front from 300am to 700am. LA county should remain mostly dry through 5am (There will be some earlier showers as a little warm sector sets up in front of the main rain band). The main rain band should exit LA county to the east around 11am. It looks pretty dry behind the front with decent clearing, but the April sunshine may well create enough low level instability to allow for some afternoon shower development.
Rainfall rates are still likely to fall in 0.25 to 0.50 in/hr range, but locally higher rates around 0.75 inches/hour are possible under heavy showers or TSTMs. . So, minor nuisance flooding is likely, but major flooding/debris flows remain unlikely. This frontal passage will be rather dynamic (decent CAPE, etc), resulting in a 15-25% chance of thunderstorms.
As for winter weather issues, snow levels will drop to between 4500-6000 foot today. This system will likely drop 5-10 inches of snow above 6000 feet. This snow along with southerly wind gusts from 45 to 50 mph are covered with a WINTER WEATHER ADVISORY which includes the mtns of SBA/VTA/LA counties.
It will also be windy ahead and behind the front in areas other than the mtns. Most gusts, however will come in just under advisory levels. The exception will be the Antelope Vly where a wind advisory is in effect through this evening.
The front will usher in a grip of cool air and as a result max temps will end up mostly in the mid 60s. These temps are 5 to 10 degrees lower than normal.
There will be a few stray showers overnight, but for the most part the night will be partly cloudy with cooler than normal overnight lows.
Monday will start out mostly sunny and dry. In the afternoon, however, a little trof will ripple overhead. This combined with the sfc heating from the high April Sun angle will bring a slight chc (20 percent) of showers to the area (30 to 40 percent chc for the mtns). While there maybe an isolated location or two that see a quarter inch of rain under a heavier shower most of the area will not see much additional rain at all. Max temps will bump up 2 to 4 degrees, but will remain below normal.
Dry NW flow will move over the area on Tuesday. It will be a sunny day with weak offshore flow. The sunny skies, offshore flow and rising hgts will allow max temps to climb 4 to 8 degrees. Cst/vly highs will end up in the mid 60s to lower 70s.
(Wed-Sat), 12/324 AM.
Not much excitement in the xtnd.
Look for a little ridge overhead on Wed. An inside slider will work its way down the state line on Thu. Followed by dry NW flow on Fri and Sat.
At the sfc there will be mostly onshore flow on Wednesday. Persistent offshore flow from the north will begin on Thursday while the E/W grad will diurnally shift back and forth from weak offshore in the morning and moderate onshore in the afternoon.
Cannot rule out some coastal low clouds but other than that and some ocnl upper level clouds skies will be mostly clear.
The passage of the inside slider will bring a two day north wind event with advisory level gusts likely through the I-5 corridor and the Santa Barbara county mountains.
Max temps will rise 2 to 4 degrees Wed and then change little on Thu. The offshore push on Fri and Sat will result in 2 to 4 degrees of warming each day and will push coastal highs into the 70s and vly highs into the 80s on Saturday (3 to 6 degrees over normal)
12/0616z.
At 0522Z at KLAX, there was no marine layer or inversion.
Moderate confidence in the TAFs. A cold front will affect all terminals tonight into Sun morning. Low confidence in cig/vis fcst when the rain is occuring. Winds will be southerly ahead of the front and westerly after. There is a 15-30% chance of thunderstorms, highest for northern airfields, tonight into Sun morning. Any thunderstorms could produce gusty and erratic winds and brief lower vsbys in heavy rain.
KLAX, Moderate confidence in TAF. Rain is expected between 11Z-19Z and cig/vis may be as low at 1SM-2SM during rain. Winds will shift rapidly from southerly to westerly as the front passes. There is a 10% chance of thunderstorms from 20Z Sun to 00Z Mon. No significant east wind component expected except during thunderstorms.
KBUR, Moderate confidence in TAF. Rain is expected between 10Z-18Z and cig/vis may be as low at 1SM-2SM during rain. Winds will shift rapidly from southerly to westerly as the front passes. There is a 15% chance of thunderstorms from 18Z Sun to 00Z Mon.
12/325 AM.
A strong storm system will affect the southwestern CA coastal waters through this afternoon. This system will sweep a cold front across the waters through this morning, bringing Small Craft level southerly winds, showers and a chance of thunderstorms to the area. Potential hazards include: heavy downpours, dangerous cloud to ocean lightning, small hail, and erratic gusty winds. Boaters, especially those with small vessels, should avoid these conditions.
Seas will build to 8-10 feet today across the central and northern Outer Waters. Additionally, Small Craft level west to northwest winds are likely for all the waters Monday afternoon and night. Then northwest SCA winds are possible for much of the time across the outer waters Tuesday through Thursday night, with a 20% chance of Gale Force winds at times Thursday night.
Ca, Winter Weather Advisory remains in effect until 11 AM PDT Monday for zones 353-376>380. (See LAXWSWLOX). Wind Advisory remains in effect until 10 PM PDT this evening for zones 381-382. (See LAXNPWLOX). PZ, NONE.
