What the forecast actually says — NWS Area Forecast Discussions, 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 Jacksonville, 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 Jacksonville (JAX) · issued Friday, September 11 at 8:53 AM EDT.
Messages
For the latest NE FL and SE GA Daily Key Messages please visit: https:/www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf
Numerous Afternoon and Evening Thunderstorms Expected through Saturday. Strong Storm Potential Along the I-95 Corridor During the Late Afternoon Hours. Stronger Storms May Produce Wind Gusts of 40-55 mph, Frequent Lightning Strikes, and Torrential Downpours that Could Result in Localized Flooding.
Daily Peak Heat Index Values of 104-108 Degrees Expected. through Monday.
Moderate Rip Current Risk Continues at All Area Beaches through Monday. High Risk Likely from Tuesday through Thursday of Next Week.
Short Term
Potential for strong thunderstorms and localized flooding this afternoon and evening, especially along the I-95 corridor.
Moderate Rip Current Risk at All Area Beaches.
Mean layer ridge oriented more or less west-east through 700 mb is located in central FL area. Typically for September this ridge is located further north. Deep layer flow is southwesterly at about 10 knot, and we continue with the deep moisture in place with the 18z JAX Sounding showing 2.29 inches and 500 mb temp of only -4.1C. Fairly confident PWATS will stay the same today, but the 500 mb temperatures may drop another degree or so during the day. Models suggest that some shortwave energy may impinge on the forecast area after 21z today which will likely encourage more cloudiness and probably boost rain chances this evening.
Given the moisture and summer-like pattern, we anticipate scattered to numerous showers and storms to develop during the day. Initial develop of convection likely to be around any lingering boundaries from Thursday, and along the west and east coast sea breezes that develop by the early afternoon. Climatology would suggest the I-75 corridor first, though, near the developing west coast sea breeze. The movement of the west coast sea breeze may meet the east coast sea breeze this afternoon and early evening, and cells mergers may would be near and east of the U.S. Highway 301 area. The moisture laden airmass will be efficient for heavy rainfall/localized flooding. Rain amounts in excess of 3 inches in spots are likely. The DCAPE on the model soundings looks unimpressive at about 500-600 J/kg, similar to yesterday, so for now assuming peak thunderstorm gusts of about 40-50 mph. Cannot totally rule out an isolated severe storm though where strongest convergence occurs.
Daytime highs will be in the lower 90s, and probably around 90 at the east coast as the sea breeze develops. Heat index values will hover under Heat Advisory criteria, with values in the 104-108 F range. Lows tonight in the lower to mid 70s.
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