The National Weather Service issued an advisory Wednesday for possible localized flooding due to melting snow. People living in low-lying areas around the Missoula Valley are advised to move livestock and personal items to higher ground to avoid possible low-level flooding over the next few days.
Daytime temperatures are forecast to warm into the 50s by Monday, so snow is beginning to melt. The ground is still frozen, so melt water will tend to pool rather than seeping into the soil. Some water could flow overland and accumulate in low-lying areas, where it could cause general flooding, water on roadways and seepage into basements.
But nighttime temperatures will still dip below freezing, causing snowbanks to linger and ice to re-constitute. In some areas, large snowdrifts could act to trap water, making it deeper.
Water flowing into streams could also increase the potential for ice-jam formation at night and related flooding. Muddy, slushy roads may be increasingly difficult to travel over the next few days.
Fortunately, the forecast is for a gradual warm-up, so more serious flooding associated with rapid warming is not expected. But that could change into next week.
The National Weather Service advises that now is the time to move personal items, equipment and livestock out of low-lying areas and away from waterways. People should also shovel heavy accumulations of snow away from home foundations, and take steps to prevent water from entering basements.
Some Missoula roadways, such as International Drive near the Missoula Brewing Company off Reserve Street already have large ponds that could drench pedestrians if cars don’t slow down when passing through.
Drivers are advised to take care when driving through high water because they can flood the engine, causing it to stall. Even driving slowly can cause problems if oncoming vehicles push enough water toward your vehicle.