textproduct: Los Angeles

SYNOPSIS

09/836 AM.

A cooling trend will begin today and continue through the weekend. A couple storms will move through the area late Friday through Monday with showers and thunderstorms possible, especially Sunday.

LONG TERM (SUN-WED)

09/220 AM.

On Saturday night a colder and more vigorous upper low will move into nrn CA. It will bring a wetter and much more dynamic front into the area. There is a greater than 80 percent chc that all areas will see rain overnight. The front will likely produce a number of TSTMs. It will have at least advisory level southerly winds in the mtns and interior vlys and perhaps over the Central Coast as well. The south winds will bring enhanced precip totals and rates to the transverse ranges. Any TSTM that forms will also bring enhanced precip totals and rates to areas they pass over.

At this point it looks like the flatter portions of the csts and vlys will see a half to three quarters of an inch of rain overnight with inch plus amounts on the across the foothills and coastal slopes and any area affected by TSTMs. Most rainfall rates will be between 0.25 to 0.75 in/hr but higher rates will be possible under any TSTM that develops.

Snow levels will fall to about 5500 ft and accumulating snow will fall above 6000 ft.

These rainfall and snowfall numbers are still preliminary and are still subject to change. The most likely factor that would change the numbers are the speed of the front (slower = more rain / faster = less rain) and the trajectory of the parent upper low. Still confidence in this forecast is higher than it has been.

The main front will exit LA county sometime between dawn and mid morning on Sunday. There will be some shower activity behind the front but additional rainfall amounts will not amount to much. It will feel more like a rainy January day with max temps only in the lower to mid 60s.

There is a 20 to 30 percent chc of lingering showers Sunday night and a low by non zero chc Monday morning. These showers should just be stray nuisance showers. By mid morning Monday dry NW flow will set up over the area. Sunnier skies and rising hgts will bring 2 to 4 locally 6 degrees of warming to the area. Max temps, however, will be 8 to 12 degrees blo normal.

Tue and Wed will see a nice warming trend as the cold air moves out of the area and high April sun angle combine to bring 4 to 8 degrees of warming Tuesday and 2 to 4 additional degrees on Wednesday. Wednesday's highs across the csts and vlys will almost all be in the 70s.

AVIATION

09/1800Z.

At 1654Z at KLAX, the marine layer was 1600 ft deep. The top of the inversion was at 2000 ft with a temperature of 17 C.

Overall, moderate confidence in 18Z TAF Package. Timing of flight cat changes may be off +/- 2 hours and cig hgts by +/- 300 ft. PROB30 -SHRA chances after 10/14Z for KPRB, KSBP, and KSMX.

KLAX...Moderate confidence in TAF. Low clouds could arrive as early as 09Z or as late at 13Z. Cigs could range between 008 and 015. No significant east wind component expected.

KBUR...Moderate confidence in TAF. There is a 40% chc MVFR CIGs (015) do NOT develop (remaining FEW-SCT) after 10/09Z.

MARINE

09/808 AM.

Current Small Craft Advisories are on track. Refer to MWWLOX and CWFLOX for more details.

A weak Cold Front will move across the coastal waters Friday into Saturday morning bringing showers and a slight chance for a thunderstorm north of point conception.

A second system will arrive later on Saturday into Sunday with a more traditional cold front. This stronger front will bring numerous showers and a slight chance for thunderstorms across all waters. 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.

LOX WATCHES/WARNINGS/ADVISORIES

CA...NONE. PZ...Small Craft Advisory in effect until 11 PM PDT this evening for zone 650. (See LAXMWWLOX).