claude-sonnet-4-6 Analysis · Jul 21, 2026

A Flood Watch is in effect for July 21 through late tonight, with widespread heavy showers and thunderstorms expected throughout the entire day and evening. Rainfall totals of 1–2 inches are possible both during the day and overnight, with torrential rates of 2–3 inches per hour during the worst storms, creating serious flash flood and road hazard risks.

• 01 Active Flood Watch issued by NWS through late tonight (July 22 at 2:00AM EDT), covering a wide region including parts of NJ, PA, and DE, citing flash flooding as possible from excessive rainfall.
• 02 Thunderstorm probability rises sharply from 58% at 8AM to 75–76% between 11AM–1PM, then surges to 84–98% from 6PM–8PM, representing two distinct high-risk windows.
• 03 Torrential rainfall rates of 2 to 3 inches per hour are explicitly cited in the alert, which can cause near-instant road flooding and drastically reduced visibility.
• 04 Daily forecast projects 1–2 inches of new rainfall during the daytime period and an additional 1–2 inches overnight, totaling potentially 2–4 inches for the full day.
• 05 Evening hours (6PM–10PM) carry the highest precipitation probabilities of the day (84–98%), making evening travel especially dangerous.
• 06 High relative humidity throughout the day (79–97%) will worsen visibility conditions and contribute to wet, slippery road surfaces all day.
• 07 Urban and low-lying areas are specifically called out for flooding risk due to poor drainage, making common routes through cities or near waterways particularly hazardous.