23/1239 PM.
A shallower marine layer is expected over the next few days. Warm weather will peak on Wednesday and continue into Thursday. A push of moisture today will bring a low chance of a shower or an isolated storm from Ventura County eastward. This moisture will linger into Wednesday morning. A cooling trend with temperatures below normal is expected Friday into the weekend.
(tdy-Fri), 23/120 PM.
A 592 dm ridge is currently situated over Socal. This ridging is expected through Wednesday before breaking down to zonal flow on Thursday with significant cooling by Friday.
Heat advisories are in effect through Thursday evening across LA County. Temperatures are expected to be warmest Tuesday (Today) and Wednesday. Feels-like temps will be higher due to humidity. Refer to NPWLOX for more details.
PVA and the influx of mid-level monsoonal moisture will result in a slight chance of thunderstorms (15%) across the eastern San Gabriel mountains and eastern Antelope Valley early this evening into the overnight period. This moisture will linger across LA County into Wednesday morning.
NAM12 cross-section shows a moist layer roughly from 700mb- 500mb on top of a dry PBL which extends westward to Ventura County. However, a pocket of vorticity sufficient enough to trigger convection remains confined to eastern LA county. This can also be seen explicitly in the Omega fields. Fire starts from dry lightning is a concern for any storm that initiates. This is especially true over the eastern San Gabriels where updrafts are most likely to be strong enough for charge separation. Hi-Res guidance shows MUcape values roughly 250-400 J/KG in this area. Some models are weaker with the lifting and struggle to develop any substantial convection, but considering the setup and general consensus - a 15% chance of TSTMs over the aforementioned areas seems reasonable.
Onshore flow will strengthen to the north through Thursday and to the east through Saturday. This will result in gusty SW winds across the interior - strongest across the Antelope Valley/ft hills and portions of LA county mtns. Approaching advisory levels Thursday into Friday. Sundowner potential increases on Friday, with likely advisory level winds especially on Saturday.
With increasing onshore flow, decreasing 500 mb heights, and increasing potential for Catalina Eddy (throughout the week) this will result in the continuation of marine layer stratus across the coasts and valleys.
(Sat-Tue), 23/120 PM.
An upper trough will strengthen and dive into the Great Basin through the weekend. As a result, cyclonic flow will develop over the region. Moderate to strong onshore flow to the east is expected. A bit weaker to the north. ECWMF guidance suggest a short-lived (Saturday & Sunday) reduction in onshore flow to the north followed by returning moderate onshore push. The general pattern is expected to persist thru the end of the forecast period.
Cooling trend is expected through Saturday or Sunday depending on location. Most pronounced on Saturday (5 to 10 degrees) especially across interior areas away from marine layer influence. Temperatures are likely to remain fairly similar thereafter thru Tuesday. June Gloom conditions are expected across the coasts and many of the valleys.
Gusty SW-W winds near advisory levels are likely Saturday and possible Sunday across the Antelope Valley and I-5 Corridor (NW-W). Winds will remain gusty but will decrease some Monday and Tuesday. But especially across the I-5 corridor as the LAX-BFL gradient increases by a few millibars. As mentioned in the short-term, Sundowners will peak on Saturday (advisory likely). Advisory level winds could linger into Sunday. Sundowners will continue through mid-week but for now look mostly below advisory levels. These winds will be focused across western Santa Ynez range.
23/1821z.
At 1800Z at KLAX, the marine layer was 1000 feet deep. The top of the inversion was 3000 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. MVFR CIGs linger late this morning. VFR conditions this afternoon and evening. Timing of flight category changes could be +/- 2 hours of current forecasts. No significant east wind component is expected.
KBUR, Moderate confidence in TAF. There is a 20-40% chance of MVFR/IFR CIGs between 08-16Z Wednesday morning.
23/120 PM.
High confidence in winds and seas remaining below Small Craft Advisory (SCA) levels through Wednesday. Local gusts could reach 21 kts near Point Conception and across the western Santa Barbara Channel in the evenings. Chances for SCA criteria gusts increase Thursday evening. Probabilities increase Thursday evening into Friday morning to 30-60% for PZZ670/673. Chances expand and increase Friday afternoon to the inner waters PZZ645/650 and outer waters PZZ676. SCA conditions are possible through the weekend as a trough continues to move over the region.
Ca, Heat Advisory remains in effect until 9 PM PDT Thursday for zones 88-368-372-373-379-380-548. (See LAXNPWLOX). PZ, NONE.
