Swell Matrix

Area Forecast Discussion

National Weather Service Los Angeles/Oxnard Ca

337 am PDT Tue Mar 26 2019

Synopsis

25/727 PM.

Tonight will be mostly clear ahead of a weak cold front approaching the area. Cloud cover will increase on Tuesday and Wednesday with cooler temperatures and a chance of rain. Dry conditions are expected on Thursday with gusty winds. The dry weather will continue through the weekend with warming temperatures.

Short Term

(tdy-Thu), 26/226 AM.

A cold 534 DM upper low is about 300 NM to the west of Seattle (satellite show actually shows 3 lows all spinning in this general area) 573 DM SW flow sits over SRN CA. A weak cold front bisects the state with rain as far south as Monterey county. Gradients are weakly onshore and the marine layer is about 1200 feet deep. There is enough clouds in the SW flow to make skies at least partly cloudy and probably mostly cloudy over SLO and SBA counties. There will also be some stratus across the Central Coast as well as LA county. The front will not move much but it may bring a light shower or two to SLO county esp the northern section. Due to the increased clouds SLO and most of SBA counties will have slightly blo normal temps while the less cloudy VTA and LA counties will have normal or slightly above normal max temps.

The front gathers a little more steam overnight and rain will likely develop over most of SLO and NW SBA counties. Rain is almost assured north of the city of SLO. Rainfall amounts will be under a quarter inch except the for extreme NW tip of SLO county where greater amounts are likely. Otherwise a coastal marine layer stratus deck will develop under the mostly cloudy mid level skies.

The upper low does not make much progress on Wednesday but an impulse does move through the upper flow and this will spread a chc of showers as far south as VTA county. SLO and SBA counties will likely have scattered showers through the day. The increased clouds along with increased onshore flow will bring 3 to 6 degrees of cooling to the area and this will be the coolest day of the next 7.

Rain amounts Wednesday will be very light and probably not even reach .01" for much of Ventura/LA Counties. In SLO and nrn SB Counties generally a quarter inch or less.

On Thursday the upper low finally spins itself out and moves to the east. There will be a slight chc of showers over the mtns but otherwise look for dry conditions and clearing skies. Max temps will rise a couple degrees but will still be blo normal.

High pressure will build into the center of the state and will set up moderate offshore north flow. There will be some cool air advection as well. These two factors will combine and will likely generate some low end advisory level gusts through the i-5 corridor.

Long Term

(Fri-Mon), 26/234 AM.

Dry NW flow will set up on Friday. Skies will continue to clear and hgts will rise to 576 DM. Max temps will warm to normal or even 1 or 2 degrees above normal.

Northerly offshore gradients will increase to about 7MB Friday night. This strong N push will bring advisory level Northerly gusts to the mtns (except SLO) and the SBA south coast and probably to the area 15 miles either side of the LA/VTA county line.

Weak ridging and diminishing offshore flow will combine to bring three consecutive days of very nice weather with mostly clear skies and warmer than normal temps. On Sunday and Monday there will be a smattering of 80 degree temps and in general max temps will be 4 to 8 degrees warmer than normal. There will be some night through morning canyons but probably not advisory level.

Aviation

26/1036z.

At 1015Z, the marine inversion at KLAX was based around 1500 feet. The top of the inversion was 2000 feet with a temperature of 15 degrees Celsius.

Overall, moderate confidence in 12Z TAF package. BKN-OVC cirrus deck is obscuring ability to monitor low clouds. Moderate confidence that VFR conditions will prevail at all sites through this evening. For tonight, high confidence in development of MVFR CIGs across coastal/valley sites, but low confidence in timing. There will be a chance of light showers north of Point Conception after 08Z.

KLAX, Moderate confidence in 12Z TAF. There is a 30% chance of MVFR CIGs 12Z-20Z. For tonight, high confidence in development of MVFR CIGs, but low confidence in timing (could be +/- 4 hours of current 06Z forecast).

KBUR, Moderate confidence in 12Z TAF. There is a 30% chance of MVFR CIGs 12Z-20Z. For tonight, high confidence in development of MVFR CIGs, but low confidence in timing (could be +/- 4 hours of current 08Z forecast).

Marine

26/1257 AM.

For the Outer Waters, high confidence in current forecast. Today through Wednesday, winds and seas will remain below Small Craft Advisory (SCA) levels. For Thursday, there is a 60% chance of SCA level northwest winds and a 70% chance of SCA level northwest winds Friday and Saturday.

For the Inner Waters north of Point Sal, moderate to high confidence in current forecast. High confidence in winds and seas remaining below SCA levels through Wednesday. For Thursday through Saturday, there is a 50% chance of SCA level northwest winds each afternoon and evening.

For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. High confidence in winds and seas remaining below SCA levels through Wednesday. For Thursday through Saturday, there is a 50% chance of SCA level west winds each afternoon and evening, especially across western portions.

Watches, Warnings, Advisories

Ca, NONE. PZ, NONE.

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