511
FGUS75 KBYZ 111718
ESFBYZ
MTC003-009-037-067-095-097-107-111-WYC033-132200-

Hydrologic Outlook
National Weather Service Billings MT
1118 AM MDT Sun May 11 2025

...Warm temperatures and mountain snow melt continue to bring
increased flows on rivers and streams...

Expect very warm temperatures through Monday. Enhanced snowmelt in
the mountains will continue to increase flows on area rivers and
streams through the first part of the week. While flooding is not
anticipated on larger rivers and streams, there is a chance that
some smaller streams could reach bankfull in and near the foothills,
producing minor flooding. At the very least, stream flows will be
much higher with the increased snowmelt.

Water rises will occur first on small streams flowing out of the
foothills, eventually arriving on larger rivers and streams. The
rate and magnitude of the water rises will be determined by how warm
temperatures get over the mountains, as well as whether temperatures
remain above freezing overnight.

Also, there is potential for significant widespread precipitation
from Tuesday night to Thursday. Snow is expected to fall above 7000
feet, ending the high elevation snow melt for the time being, but
rain at lower elevations may cause additional rises on some streams
and rivers. There is still uncertainty regarding exact precipitation
amounts, and we urge people to monitor the forecast over the coming
days.

For those living near waterways, this may be the last chance to
finalize preparations for runoff season. Move any livestock and
equipment to higher ground away from waterways. Any stream bank
stabilization activities should be completed as soon as possible.
For those planning recreation activities on or near waterways, be
prepared for changing conditions and significantly higher flows.

Erosion will also increase as stream flows increase, making
streambanks unstable. Please stay well away from streambanks when
water is running fast, and be especially vigilant with children.
Erosion will undercut the bank and can break off taking the bank and
anyone standing on it into a very cold raging current.

Stay tuned to the forecast for any watches, advisories, or warnings.
Please report any flooding to local law enforcement and have them
relay the report to the National Weather Service.

$$