12/815 PM.
A gradual cooling trend is expected through Saturday as high pressure weakens. Areas of dense fog are possible near the coast. Temperatures will trend warmer again Sunday through the middle of next week before cooling returns the end of the week. The next chance of rain is during the week of Christmas.
(tdy-Sun), 12/815 PM.
A classic December dense fog pattern is setting up again along the coast under a very strong and shallow marine inversion and very light pressure gradients in all directions. Latest ACARS data showing a shallow and strong marine inversion with a depth of around 600 feet. As of 8 pm this evening, already seeing visibilities drop to between 1/4 and 1/2 mile at San Luis Obispo, Santa Maria, and Santa Barbara. Expecting many coastal areas to see areas of dense fog tonight, so have expanded the dense fog advisory to now include the inland portions of the Ventura county coastal plain, as well as the inland portions of San Luis Obispo and Santa Barbara Central Coastal areas. The areas of dense fog are expected to persist through the early morning hours, likely creating some delays at coastal airport sites.
Otherwise, the lengthy dry spell continues and not expected to change until the week of Christmas. In the meantime, the shift now to light onshore flow will continue the slight cooling trend, mainly just for coastal areas through Saturday before another high pressure ridge nudges in from the west Sunday into early next week. At that point temperatures will start climbing again with widespread 80s across the coastal valleys south of Pt Conception and 70s to lower 80s in the northern valleys. North to northeast flow will start ramping up Monday which should lead to some gusty offshore winds across southern Santa Barbara County and the I5 corridor, as well as some typical northeast wind prone areas of the LA/Ventura county mountains and valley, possibly reaching portions of the coastal plain.
(Mon-Thu), 12/155 PM.
Around mid week next week the upper level pattern will begin a slow shift towards a more favorable pattern for rain locally. The long standing ridge will begin to break down which will allow storms to drop farther south into California. Virtually all of the AI and ensemble models are indicating a return of rain to southern California before Christmas but there remains a large amount of uncertainty on timing and strength. Likely dry through at least the 21st of Dec and possibly as late as the 24th.
In the meantime, temperatures will remain well above normal through the end of next week but with a slow cooling trend.
13/0612z.
At 0538Z at KLAX, the marine layer was 900 feet deep. The top of the inversion was 3000 feet with a temperatures of 21 Celsius.
High confidence in VFR conds at KWJF and KPMD.
Moderate confidence in VFR conds at KPRB, KBUR, and KVNY, although periods of MVFR vsbys are likely at KBUR and KVNY through the morning. There is a 20-30% chance for VLIFR to LIFR conds through 18Z.
VFR conditions expected at desert airfields (KPMD & KWJF).
VLIFR or LIFR conditions (with vsbys 1/4 to 1 mile) ongoing at coastal sites and will continue into at least Saturday morning, with a return for Saturday night into Sunday morning. Cigs may not clear during the period at all coastal sites. Timing of CIG/VSBY restrictions may be off +/- 3 hours, and flight minimums off by one category.
KLAX, Low to moderate confidence in TAF. Cigs may not clear during the entire period, but if they do, 19Z-01Z is the most likely time frame. VV001 with 1/4SM FG possible at times into into early Saturday morning. No significant east wind component expected through period.
KBUR, Moderate confidence in VFR conds with periods of MVFR vsbys through 18Z. There is a 30% chance for VLIFR to LIFR conds through 18Z if marine layer clouds are able to push into the valleys.
12/930 PM.
Areas of dense fog with very low visibility will affect much of the coastal waters through at least Saturday. Best chances for dense fog will be from the overnight through morning hours with scattered pockets likely through the afternoon and evening.
High confidence in light winds and lowering seas through the weekend. Localized Small Craft Advisory (SCA) level winds are possible Sunday evening with breezy sub SCA level winds for the southern inner waters. Gusty NW-W winds will likely return Monday and Tuesday, with SCA winds most likely across the Outer Waters south of Point Conception.
Winds will become stronger Wednesday and Thursday, bringing a 30% chc for Gale Force winds from near Point Conception to San Nicolas Island including portions of the Santa Barbara Channel. These stronger winds will likely result in choppy seas.
Ca, Dense Fog Advisory in effect until 10 AM PST Saturday for zones 340-341-346-347-349-350-354-355-362-366-367. (See LAXNPWLOX). PZ, NONE.
