Monsoonal Moisture Fuels Daily Storms as Flash‑Flood Watch Covers Parts of Montana

Overview

• An entrenched surge of monsoonal moisture is producing daily afternoon and evening showers and thunderstorms across much of Montana, with storm chances expected to continue through at least early next week.
• A Flash Flood Watch is in effect from this afternoon through early Thursday for areas from Sheridan County to Musselshell County and westward because storms may produce rainfall rates exceeding one inch per hour and train over the same locations.
• Widespread severe storms are unlikely due to weak upper‑level winds and limited shear, but isolated cells can still produce large hail, damaging wind gusts and frequent lightning that threaten people and property.
• Temperatures will diverge across the state as an expanding upper‑level ridge warms southeast Montana into the 90s and lower 100s while southwest Montana stays cooler and cloudier under the moist pattern.
• The pattern raises short‑term hazards for outdoor plans, low‑lying roads and poor‑drainage areas, and is rooted in a northward push of tropical‑origin moisture from the Desert Southwest and Gulf of California that favors slow, high‑rain‑rate storms.