Heat will peak today with a cooling trend for Tuesday through Thursday. Night and morning low clouds and fog will be present each day through the forecast period along the coast and into portions of the valleys. A gradual warming expected for the end of the week.
For extreme southwestern California including Orange, San Diego, western Riverside and southwestern San Bernardino counties,
Heat peaks today for inland locations with high temperatures 10 to 20 degrees above average. Highs in low desert are forecast to reach 105 to 110 degrees with widespread highs in the upper 90s to 100 degrees in the Inland Empire. Palomar Mountain and Borrego Springs are in contention to break high temperature records today. Highs Tuesday for inland locations will fall 6 to 12 degrees from their peak today as a shortwave weakens and pushes the upper level ridge to our east.
Guidance is in good agreement that a weak troughing pattern will prevail over the US West Coast Tuesday through Thursday. This will maintain marine layer low clouds and fog for the coast and valleys and take high temperatures back to within a few degrees of normal. For Friday and Saturday, the majority of ensemble clusters keep the upper level pattern zonal, which will bring a few degrees of warming to the area. Highs are forecast to be 5 to 10 degrees above average.
By Sunday most ensemble clusters indicate the return of weak troughing which has the potential to cool conditions a few degrees. There still remains some uncertainty in the temperature forecast for early next week. The current forecast follows the deterministic NBM which continues to be more in line with the warmer end of most other ensemble guidance.
111800z, Coast/Valleys, Low clouds based around 1000 ft MSL are lurking just offshore. Mostly VFR conditions expected through the afternoon, though cannot rule out occasional BKN cigs at coastal TAF sites. Clouds begin to move back inland around 00-02z and should push 15-20 miles inland overnight. 40-50% chance for low clouds to reach into the western Inland Empire (including KONT). Bases should lower some overnight creating minor vis reductions (1-5SM) for elevated coastal terrain and inland valleys. Clouds will be slow to clear out Tuesday morning, though bases will rise back above 1000 ft MSL. Coastal areas may remain under BKN cigs through the afternoon.
Otherwise, SKC and VFR through Tuesday morning.
No hazardous marine conditions are expected through Saturday morning.
Ca, Heat Advisory until 8 PM PDT this evening for San Bernardino and Riverside County Valleys-The Inland Empire.
Extreme Heat Warning until 8 PM PDT this evening for Coachella Valley-San Diego County Deserts-San Gorgonio Pass near Banning.
PZ, None.
