Snowmelt Flooding Possible Through Next Week

Issued by the National Weather Service on Wednesday April 26, 2023


  • Temperatures will warm significantly over the coming days leading to increased snowmelt through at least early next week
  • Some areas will see mid-level snow melt of several inches through the end of the week, and then snowmelt will really increase over the weekend when the warmest temperatures occur
  • Streams and creeks will swell to near bankfull
  • Good news: No significant precipitation is expected through the weekend
  • A broad storm will approach the west coast early next week which could bring slightly cooler temperatures, but could also bring rain back to eastern Idaho

A Flood Watch is in effect through next Tuesday afternoon



  • Temperatures will warm to well above normal by this weekend area wide
  • Areas below 5,000ft have a greater than 95% chance of high temperatures above 70 degrees Sunday and Monday
  • By Sunday morning most locations will see overnight lows stay above freezing, including areas above 5,000ft
  • Temperatures may come down a little into early or middle of next week, but should remain warm enough to continue the snowmelt
  • The 6 to 10 day temperature outlook favors above normal temperatures into next week, so the warm temperatures are here to stay


  • No significant precipitation is expected through the weekend
  • The broad storm arriving along the California coast may move close enough to the Great Basin to increase moisture over central and eastern Idaho
  • That storm is nearly a week away and finer resolution details need to be worked out, but additional rainfall could exacerbate any remaining flood concerns


  • Through Friday we’re expecting up to around 2-4″ of liquid melt in the low and mid elevations across the South Hills, the mountains east of Fort Hall, and into the Lost and Wood River Valleys
  • Lesser amounts will melt in the Bear River Valley, Gem Valley, Teton Valley and Upper Snake Highlands where the snow is not as ripe
  • Beyond Friday, snowmelt will really accelerate as overnight lows and daytime highs maximize


  • Strong rises on area creeks and streams are already occurring
  • The Portneuf River at Pocatello is expected to reach bankfull by Friday afternoon and Minor Flood Stage by Sunday
  • The Bear River at the WY border is forecast to reach bankfull by early next week
  • The Big Wood River at Hailey is forecast to reach bankfull by early next week
  • The Little Wood and Little Lost Rivers will likely spike higher daily through the weekend, reaching bankfull as early as tonight
  • Monitor river and stream gauges here


  • Inflow to area reservoirs will increase dramatically, especially in smaller reservoirs and holding ponds – proactive releases may be necessary to keep up with inflow
  • Locations that still have a lot of snow should move deep snow away from foundations of buildings and move equipment and livestock out of poorly-drained areas
  • Clear snow, ice and debris away from culverts and other flow paths to allow runoff to flow away from buildings and other vulnerable infrastructure
  • Monitor upcoming forecasts and river levels and be alert for possible Flood Warning or Flood Advisories
  • If you observe flooding, please report your observations to the National Weather Service via phone, email, or social media when it is safe to do so.

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United States National Weather Service

1945 Beechcraft Avenue

Pocatello, ID 83221

Phone: (208) 233-0834