Plaincast — the National Weather Service forecast, decoded into plain English

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 St. Louis, 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.

Area Forecast Discussion · National Weather Service St. Louis (LSX) · issued Friday, September 11 at 6:42 AM CDT.

Messages

Areas of dense fog is expected through mid-morning, especially across central and northeast Missouri into west central Illinois where a Dense Fog Advisory is in effect.

There are chances (20-30%) for showers and a few thunderstorms through this weekend with better chances next week. Isolated storms late Saturday night could produce gusty winds and heavy downpours over central and northeast Missouri.

Slowly increasing temperatures are expected through early next week.

Short Term

The latest satellite imagery is showing fog persisting across parts of central and northeast Missouri into west central Illinois early this morning. Surface observations are showing multiple observations at 1/4 mile where we already have a Dense Fog Advisory in effect until 10 am. Fog continues to develop southeast of the advisory area where there is thinning in the clouds, with a few locations reporting dense fog in the river valleys. Will continue to monitor for an expansion of the advisory the next few hours if we continue to get more reports. This fog will eventually dissipate when we begin to see some low level mixing later this morning.

The latest run of the RAP is showing a weak upper low moving slowly northeast across the area today and tonight. Forecast soundings are showing weak positive areas, with the only uncapped sounding at FAM. Will keep with a 20-50% chance for showers and thunderstorms today mainly across the southern forecast area and continuing into the southeastern forecast area tonight. With light winds and moist conditions in the boundary layer, the HREF probabilities and model output statistics guidance is pointing for additional fog late tonight over central and southeast Missouri and in river valleys.

I expect more sun today than yesterday, so highs should climb back into the lower to mid 80s. With 850mb temperatures climbing back to around 20C on Saturday, highs are forecast to be in the upper 80s in most areas.

This is the plain-text edition, decoded without AI so it loads anywhere. Read the whole St. Louis discussion at /o/LSX/, see what changed since the last one, or open The National Desk for where the weather is today.