Anomalous Tropical and Monsoonal Moisture Drives Flash‑Flood Threat From Intermountain West to Texas and the Mid‑Atlantic

Overview

• Intermountain West, the Mid‑Atlantic and Southern Appalachians, and southeast Texas are under an enhanced flash‑flood threat after Thursday night training storms regenerated and produced multi‑inch swaths that are expected to continue producing heavy totals.
• Forecasters say precipitable water values are well above normal—often in the 90th–99th percentiles and locally near 2.5–2.9 inches—which makes convective cells unusually efficient at producing very high rainfall rates of 1–2 inches per hour with pockets to 3–4 inches per hour.
• Tropical Storm Bertha’s circulation has focused deep tropical moisture over southeast Texas and the Houston metro, where radar and satellite trends show convective bursts capable of 2–4 inches per hour and isolated 4–5 inch totals that threaten urban flash flooding.
• The Storm Prediction Center is also tracking an isolated severe threat for damaging wind gusts, brief tornadoes, and hail in parts of the Mid‑Atlantic and across eastern Colorado into western Kansas with watch probabilities roughly in the 20–40% range.
• Saturated soils, low flash‑flood guidance in previously drenched areas, steep terrain and burn scars, plus poor urban drainage mean runoff can rise rapidly and close roads or flood basements, and forecasters urge following local NWS Weather Forecast Office and River Forecast Center warnings as model placement of exact heavy‑rain corridors remains uncertain.