31/226 AM.
A warming trend will start today and continue through the weekend. Areas of low clouds and fog are possible for coast and valleys each night through morning through the weekend. Light showers are possible north of Santa Barbara over the weekend as the southern end of a storm system moves into the Central Coast. Rain is likely across the entire region late next Tuesday into Wednesday with periods of moderate to heavy rain possible.
(tdy-Sun), 31/305 AM.
Fairly unexciting weather on tap for the three day short term forecast today through Sunday.
At the upper levels ydy's ridge will be flattened down by a cold system pushing out of British Columbia. Hgts actually increase through the period as an upper high pushes up from Baja. At the sfc the gradients will be on the light side between -1 and 1.
Today's marine layer stratus is confined to the Central Coast. The marine inversion is much stronger than it was ydy and the rising hgts will serve to strengthen it further. The stronger inversion will likely produce a most robust night through morning low cloud pattern but the higher hgts will smoosh the marine layer to a depth that will keep the low clouds out of the valleys. The low cloud forecast is not a slam dunk, however, there will be plenty of mid and high level clouds streaming overhead and this could reduce the radiational cooling and inhibit the low cloud formation.
The rising hgts and only weak seabreezes with bring 3 days of warming. 4 to 8 degrees today; 3 to 6 Saturday and 2 to 4 additional degrees Sunday. Sunday's highs will range from the mid 60s to the lower 70s across the csts/vlys. Sunday's temps will mostly be above normal, only the nearshore area will remain below normal.
A fairly impressive atmospheric will develop later day and will affect the Bay Area and northward. The operational GFS and EC and many of their ensemble members are now keeping the AR more to the north and thus lessoning the chc of rain for the Central Coast. There are still enough ensembles with enough of a southerly movement to keep a slight chc to chc of rain over SLO county. Western SBA county now look like it will only see sprinkles at best. While there is a slight chc of rain tonight, the best chc of rain will be late Saturday night and Sunday morning.
Rainfall amounts today tonight through Sunday will mostly be under a tenth of an inch with the usual exception of the coastal slopes along the NW tip of SLO county where a half inch of rain is possible. The wettest ensembles bring about double this amount of rain.
(Mon-Thu), 31/323 AM.
Monday looks dry everywhere as the main AR axis is forecast to push to the north. Still enough mid and high level clouds in the fast moving W to E flow to make the skies mostly cloudy. Betting onshore flow, lowering hgts and thicker clouds will all contribute to a few degrees of cooling everywhere except the LA csts and vlys where clouds will be the thinest.
On Monday night and Tuesday morning a 520 dam upper low that had been spinning over British Columbia will begin to move the SW. As it moves it will tilt the flow pattern into a SW to NE orientation and a cold front will develop. This front will then sweep through Srn CA Tuesday morning (SLO county) to Wednesday afternoon. The 00Z mdls (esp the GFS) have scaled back on the intensity of the storm and this current forecast, but not confident enough to change the rainfall forecast for the area which calls for light to moderate rain amounts (1" coast/valleys, 2-3" foothills/mountains) During the 2 day period.
All of the moisture from this system originates from the warmer ocean waters and this will keep the snow levels at or above 8000 feet.
Most of the rain should be over by Wednesday afternoon with just a slight chc of showers lingering into Thursday.
Look for lots of cooling with Tuesday's temps lowering in the lower to mid 60s and further cooling bring Wednesday's to near 60.
31/1133z.
At 07Z at KLAX, the marine layer was 3300 ft deep. The top of the inversion was at 5200 feet with a temperature of 11 C.
Overall, moderate to high confidence in 12Z TAF Package. There is a 30% chance of MVFR conds after 06Z Sat for KPRB, KSBP, and KSMX. Slightly higher chances for MVFR conds at KLGB after 09Z Sat. Otherwise, VFR conds are generally expected for airfields.
KLAX, Moderate confidence in 12Z TAF. Most uncertain in stratus cig ~BKN/OVC015-025 returning after 09Z Sat (30-40% chance of no return). No significant east wind component expected.
KBUR, High confidence in 12Z TAF.
31/223 AM.
In the Outer Waters, conditions should remain fairly benign before chances increase for Small Craft Advisory (SCA) level winds this weekend. The areas favored will be for the waters around Point Conception and the Northern Channel Islands. There is a 30% chance of SCA level winds Fri afternoon/eve thru the night, with increasing chances (40-50%) for the waters around and between the Northern Channel Islands and San Nicolas on Saturday (PZZ676). Lingering but lower chances on Sunday. Otherwise, conditions should remain below SCA criteria.
In the Inner Waters north of Point Sal, SCA conds are not expected thru Mon, but chances return (30-40%) Tue and Tue night.
For the Inner Waters south of Point Conception, winds will begin to increase Friday afternoon, with a 50-60% chance of SCA level winds Saturday afternoon/eve with lingering chances into Sunday for the SBA channel (PZZ650).
Ca, NONE. PZ, NONE.
