22/1156 PM.
A shallower marine layer is expected over the next few days. A significant warming trend will peak on Wednesday, with well above normal afternoon temperatures, and then continue into Thursday. A push of moisture today will bring a low chance of a shower or an isolated storm from Ventura County eastward, and then drier conditions return. Temperatures are then expected to cool heading into the end of the week and the weekend.
(tdy-Thu), 23/1221 AM.
The area will be under the NW quadrant of an upper high to the SE. Hgts will be be 592 dam which is 6 dam higher than normal. At the sfc weak onshore flow this morning becoming moderate in the afternoon. The onshore flow and 1000 ft marine layer will bring low clouds to almost all of the csts and some of the lower vlys. A small eddy is forecast to spin up so the clearing time might be a little later than ydy. PWATs will increase through the day as mid level moisture works its way around the upper high. This increase in moisture will likely create some build ups over the mtns. It will also bring a non zero (~10 percent) chc of a shower or TSTM to portions of LA/VTA this afternoon and evening. The eastern San Gabriel mtns will have the greatest chc of convection. But its much more likely that the convective activity will be focused across Orange County and San Diego County. The higher hgts and weaker onshore flow will bring 3 to 6 degrees of warming to the area which will boost max temps into the lower to mid 90s in the vlys. Heat Advisories are in effect for the interior cst of LA county as well as the LA vlys. Admittedly under normal conditions, these temperatures would not necessitate any heat products. However, given the current influx of visitors and numerous outdoor events across the county, there is a higher risk for heat related problems esp given that humidities will be higher than normal.
Now it looks like the chc of showers will diminish on Wednesday. but there is still a non zero chc. The marine layer clouds should have similar coverage as this morning. There will be stronger onshore flow in the morning and weaker onshore flow in the afternoon, which makes for a tricky temp fcst. The most probable forecast shows 1 or 2 degrees of warming, but it is still possible that max temps will be very similar to Today's.
The ridge will move to the east on Thursday and this will cut off the moisture tap. Look for lower humidities and no chc of showers as a result. Stronger onshore flow will bring more clouds into the vlys. Hgts will fall to ~589 dam. The lower hgts and stronger onshore flow will team up to lower max temps by 2 to 4 degrees. Despite the cooling most max temps away form the nearshore areas will be a few degrees above normal.
(Fri-Mon), 23/225 AM.
A pretty dramatic shift in the upper level pattern is in store for the xtnd period. A large 547 dam Gulf of Alaska upper low will plunge into the PACNW. This low will bring fairly sharp cyclonic flow to the area through the period. Mdt to stg onshore flow to the east will develop. There will be mdt onshore flow to the north in the afternoons but much weaker and perhaps even a little offshore flow is possible in the N/S direction in the mornings.
The increase in cyclonic flow and onshore flow will bring June Gloom conditions back to the csts and many of the vlys. The only coastal exception may be the SBA south coast where some northerly flow may keep portions of it clear.
Most areas will see some cooling Friday through Sunday with temps forecast to hold fairly steady on Monday. Most areas will experience below normal temps with the vlys leading the charge with max temps coming in 4 to 8 degrees under normal.
The offshore push across SBA county and locally in the nrn LA county mtns will produce an increase in northerly winds across the Santa Ynez Range and the I-5 Corridor. Winds across the western half of the Santa Ynez Range could approach advisory levels next weekend.
23/1000z.
At 0812Z at KLAX, the marine layer was 1300 feet deep. The top of the inversion was 2400 feet with a temperature of 21 C.
High confidence in TAFs for KPMD & KWJF.
Moderate confidence in the remainder of TAFs. Timing of CIG/VSBY restrictions may be delayed by up to 2 hours and cig hgt by +/- 200 ft.
KLAX, Moderate confidence in TAF. VFR conds may not arrive until 18Z. No significant east wind component is expected.
KBUR, Moderate confidence in TAF. There is a 30 percent chc of OVC008 conds through 16Z.
23/300 AM.
High confidence in winds and seas remaining below Small Craft Advisory (SCA) levels through Wednesday. Local gusts could reach 21 kts near Point Conception in the evenings. Moderate chances for SCA conditions return to the Outer Waters Thursday afternoon/evening persisting into the weekend. These conditions could reach into the nearshore waters along the Central Coast and the Santa Barbara Channel at times. Main concern is wind although seas could approach SCA levels later into the weekend.
Ca, Heat Advisory remains in effect from 8 AM this morning to 9 PM PDT Thursday for zones 88-368-372-373-379-380-548. (See LAXNPWLOX). PZ, NONE.
