29/829 AM.
Low clouds will linger each night/morning along the coast and in coastal valleys with the potential for some very light drizzle. Falling heights will keep temperatures well below normal through the middle of the week. Temperatures will begin to warm by Thursday, with many valley locations warming into the 90s again by early next week.
(tdy-Wed), 29/833 AM.
***UPDATE***
We will continue to see low clouds along the coast and filling into coastal valleys each morning. Models indicate the marine layer will dissipate over the next several hours this morning. A closed low will track southward through CA today before lifting into NV early Tuesday and transitioning to an open trough. The tighter pressure gradient today is the reason many models reflect the the breeziest conditions being this afternoon, becoming a touch lighter each subsequent afternoon/evening. No wind highlights are planned at this time as they look to remain short of Advisory level in the Antelope Valley and Antelope Valley Foothills. Various high resolution models, as well as the National Blend, maintain broad coverage of 25 to 35 mph wind gusts this afternoon with a relatively smaller region of 35 to 40 or so mph gusts, especially across the Foothills. The National Blend max gust for today and Tuesday is generally 38 to 44 mph across this smaller portion of the aforementioned regions.
Daytime temperatures will remain very stable, running below climatological norms through mid-week. Widespread highs will range the 70s with 80s in the valleys. Temperatures will then warm beginning Thursday into the next week, with upper 80s to low 90s in the forecast again by this time the following week. It is worth noting though that ensembles begin to differ on the upper- level details heading into next weekend and so these values could easily change.
***From Previous Discussion***
The short term forecast issues continue to be gusty winds, cooler than normal temperatures, and extensive night to morning low clouds cover. A Wind Advisory is now in effect for the Antelope Valley (SW winds) and western Foothills, and for SW Santa Barbara County (NW winds) where gusts up to 45 mph are likely. While confidence in this forecast is moderate due to weaker gradients, winds are increasing in the areas under the Advisory this evening and believe they will not have too much trouble reaching criteria within the next few hours. Onshore gradients between LAX to Daggett are forecast by the NAM12 to increase the next few days, so the gusty winds near or above Advisory levels are likely to continue into at least mid-week.
Heights aloft will lower through Tuesday, with below normal temperatures expected to persist through Thursday. High temperatures tomorrow are expected to be in the 70s and 80s, except for some 60s near the coasts. Interior temperatures will be 10 to 15 degrees below normal during this time.
The extensive low clouds will continue to move inland each night, at times reaching the interior valleys and with periods of drizzle possible. The best chances of drizzle will be across the foothills of the San Gabriels, but any lower mountain or foothill locations could see occasional light drizzle.
The upper trough situated over the Great Basin is expected to lift northeast into Monday. In tandem, a shortwave trough will dive due south along the British Columbia coast deepening some into Socal. The upper pattern will slow down with weak troughing continuing across the west into Thursday.
Evening NW winds across SW SB county will continue Monday into Tuesday (Sub-advisory). Better chance for advisory Wed & Thurs, but marginal if it materializes. Gusty winds will continue across the far interior thru the period.
(Thu-Sun), 29/225 AM.
Little change expected into Thursday, with below normal temperatures and June Gloom coastal conditions. High pressure aloft will build over the region Friday and Saturday, with 500 millibar heights going from 582 decameters Thursday morning to 592 decameter on Saturday. This will noticeable warming to the mountains and deserts, with highs in the 90s by Saturday which is up 15 degrees from the first half of this week. For coastal areas however, it all depends on how the marine layer responds. There are no current signals that point to a dissipation of the low clouds and fog, which would favor the marine layer staying around and actually becoming more concentrated as the inversion strengthens well beyond its weak form seen today. With all that in mind, the most likely scenario is more limited warming of around 5 degrees for the coastal plains, with highs in the 70s, and 10 degrees of warming for the valleys with highs in the 80s. Overall, this warming will likely pull us out of the relatively cold end of June and back closer to early July normals.
Ensemble solutions start to diverge on Sunday in terms of the trend of the upper level ridge, but all of them keep some form of high pressure going through at least the first half of next week.
Happy early 4th of July.
29/1008z.
At 10Z at KLAX, the marine layer was 3400 ft deep. The top of the weak inversion was 5000 ft with a temperature of 14 Celsius.
High confidence in VFR TAFs for KPMD KWJF. 20% chance of MVFR ceilings at KPRB 10-16Z today, increasing to a 60% chance Tuesday morning.
Moderate confidence (50+% chance) in ceilings at all other airports and Tuesday morning. Moderate confidence in timing (+/- 3 hours) and flight categories (+/- 1 category.
KLAX, High confidence in ceilings forming tonight and Tuesday morning. Moderate confidence in timing (+/- 3 hours) and flight categories (+/- 1 category). High confidence in any easterly wind staying under 6 knots.
KBUR, High confidence in ceilings forming and Tuesday morning. Moderate confidence in timing (+/- 3 hours) and flight categories (+/- 1 category).
29/225 AM.
High confidence in Small Craft Advisory (SCA) level winds continuing for the outer waters from the Central Coast through San Nicolas Island through this morning, with a 50% chance of forming again later this afternoon and tonight. Chances decrease Tuesday through Thursday.
Other than a 30% chance of SCA winds over the western Santa Barbara Channel each afternoon and evening through Tuesday, high confidence in conditions staying under SCA for the rest of the waters.
All waters will see short-period choppy seas into early next week.
Ca, NONE. PZ, Small Craft Advisory in effect until 3 AM PDT Tuesday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect from 2 PM this afternoon to 3 AM PDT Tuesday for zones 673-676. (See LAXMWWLOX).
