Synopsis
Very hot temperatures are expected this week with highs 6-12 degrees above normal. Patchy night through morning low clouds and fog will be confined to coastal areas, mainly north of Point Conception.
Plaincast — the National Weather Service forecast, decoded into plain English
What is an Area Forecast Discussion?
Area Forecast Discussions are the real forecasts, written 3 to 4 times daily by NWS meteorologists reading the models and interpreting what they mean for your area. They offer far deeper insight than any weather app, but they're written in dense meteorological shorthand. Plaincast uses Anthropic's Claude to summarize them into plain English, side by side with the annotated original.
Plaincast decodes the National Weather Service's Area Forecast Discussion — the real forecast, written 3 to 4 times a day by the meteorologist on shift — into plain English. The discussion is where a forecaster explains their reasoning: which models disagree, what they are watching, and how confident they are. Below is the current edition for Los Angeles, with its shorthand expanded. The full experience — an AI plain-English summary beside the annotated original — loads with JavaScript, and every one of the 68 forecast offices has its own edition.
Short Term
All signs still pointing towards a very hot week, especially south of Pt Conception. The combination of strong high pressure aloft, weakening onshore flow, and much warmer than normal ocean temperatures will create a long duration heat event, during which several daily records will likely be broken. The warmer than normal SST's will primarily impact the overnight temperatures, keeping those higher than normal and hindering any beneficial cooling. Heat advisories are in affect for most areas south of Pt Conception through Monday night with minimal changes in temperatures Monday over today. However, models have been consistent showing a 2-5 degree increase in highs Tuesday and Wednesday pushing some areas into the major heat risk category. The biggest factor determining which areas get upgraded to an Extreme Heat Warning will be the pressure gradients and will wait to see how those look with Monday's model runs. Currently there is a 30-40% chance of highs of 110 or higher in the San Fernando Valley and a 50% chance of highs of 100 or higher in Downtown LA.
For the Central Coast, the case for heat advisories is not as strong though by Tuesday or Wednesday low end advisories would likely be appropriate for inland coastal areas like Santa Maria and San Luis Obispo as well as the Salinas Valley.
This is the plain-text edition, decoded without AI so it loads anywhere. Read the whole Los Angeles discussion at /o/LOX/, see what changed since the last one, or open The National Desk for where the weather is today.