On cue, the heat really ramped up today inland with 100+ temps widespread in that area. Outside of the interior temps also warmed but were still reasonable. Keep in mind, this is day one and the warmest days are still ahead. Not only is warmer weather in the forecast the amount of the area that will experience threatening heat will expand into the weekend.
The forecast is largely unchanged, the confidence in some extreme temperatures is high. That is why the excessive heat warning is in place for the interior and the Southcoast (and a small area in the hills near Avial Beach) into Monday evening. That warning could easily be extended based on the forecast which holds temps above 100 past Wednesday next week.
What is new, but not unexpected, was the addition of an excessive heat watch for areas not in the warning area. The watch is identifying areas where temps of 85-100 are possible Saturday morning thru Monday.
Functionally this means that folks trying to escape the heat will find fewer places of high contrast relief available. I think even beaches warm into the 80s over the weekend but that still beats the 115 inland.
This brings into play how to manage affairs during this forecast.
I hate to say it but common sense rules apply: avoid the peak heat of the day, avoid strenuous activities, hydrate, and think about pets, children and the elderly. There is also a heightened fire risk. There will be a tremendous strain on electrical resources so following advice from your power company to reduce draw at peak hours will help the overall grid remain up.
Relief looks to arrive mid to late next week when a trough rumbles thru the PacNW flattening the upper-level ridge and weakening high pressure significantly. After that, some modeling shows a series of waves in the jet so we might avoid a re-boot of the heat wave. There were questions in yesterday's modeling regarding some muggy air coming north. Looked more likely in yesterday's and today's early runs but a little less likely in afternoon runs. Some E-SE flow at the mid-levels looks to establish and might bring up dew points a little but I don't see anything currently at high confidence levels. Maybe around the 8th or 9th as a tropical system could push up the Baja and bring some moisture north with it but a simultaneous trough in the PacNw could limit or negate much real local impact from that. Again, that is WAY out there. I'll keep you informed.