Thunderstorms with flash flooding possible

Slow moving thunderstorms, mixed with rapid snowmelt along the highest mountain peaks, will keep us busy with threatening weather. A Flash Flood Watch has been issued for the Potneuf River downstream from the Chesterfield Dam. There is a potential failure of the Portneuf Dam Spillway on the Chesterfield Reservoir.

Overnight, a chance of showers and thunderstorms. An overnight low temperature around 48°.

A chance of showers and thunderstorms for Thursday. Some of the storms could produce small hail, gusty winds, and heavy rain. Increasing clouds, with a high near 76°.

For Friday, a chance of showers, then showers likely and possibly a thunderstorm after noon. Mostly cloudy, with a high near 70°. South wind at 10 mph becoming west in the afternoon. Chance of precipitation is 70%.

FLASH FLOOD WATCH FOR THE POTENTIAL FAILURE OF THE PORTNEUF DAM
SPILLWAY ON CHESTERFIELD RESERVOIR ON THE PORTNEUF RIVER IN EFFECT
THROUGH FRIDAY AFTERNOON…

• WHAT…Flash Flooding caused by a potential spillway failure is
  possible at the Portneuf Dam on Chesterfield Reservoir.
• WHERE…A portion of southeast Idaho, including along the Portneuf
  River downstream of Chesterfield Reservoir through Pebble and
  along Old Highway 30 south to Lava Hot Springs and downstream to
  McCammon.
• WHEN…Through Friday afternoon.
• IMPACTS…Failure of the spillway may result in flash flooding of
  low-lying areas below the dam, including areas that are already
  experiencing flooding along the Portneuf River.