February storms improve precipitation outlook

“February was overall a month of steady snow accumulation in Montana,” said Eric Larson, USDA Natural Resources Conservation Service (NRCS) hydrologist.

The SNOTEL site in the North Fork of the Jocko posted nine inches of precipitation, compared to a median of 7.1 inches for February. The Flathead Basin overall was at 110% of normal as of March 1.

SNOTEL sites across the state reported from one-to-four inches of precipitation equaling about 10-30 inches of snow during the first week of February. Mid-month brought slightly less accumulation, but the snowpack did make gains of about 5-15 inches of snow at mountain elevations.

Overall, the last week of February was characterized by sunshine and precipitation, with storms falling as a mix of rain and snow at many mountain locations. Despite warmer temperatures during the last week of the month, SNOTELs across the state received up to an inch of precipitation with northwest Montana receiving slightly more.

Overall mountain precipitation during February was 90-180% of normal, except in the Tongue River basin where precipitation was only 50% of normal.

Above normal precipitation resulted in increased snowpack percentages since last month in nearly all basins, however early season deficits persist across most of the state. Currently basin-wide snowpack percentages are 80-100% of normal. Exceptions include the Sun-Teton-Marias and St. Mary River basin, where the snowpack is about 70% of normal, and the Gallatin and Smith-Judith-Musselshell, where snowpack is at 110-120% of normal.

“The slightly below normal snowpack in many basins is not overly concerning yet, especially given the stormy outlook for the next two weeks. At least we are doing better than last year at this time when snowpack percentages were 60-70% of normal statewide,” said Larson.

One to two months remain in the typical snowpack accumulation season. The snowpack at Montana’s highest elevations typically reaches peak levels in late-April or early May.

“Even locations that currently have an above normal snowpack need additional snow over the next couple months,” said Larson.

Streamflow forecasts are published in the March-through-June NRCS Water Supply Outlook Reports, with this month’s forecasts providing an initial look at what spring and summer snowmelt and runoff might bring.

“The March 1 water supply forecasts currently trends with total water year precipitation and the resulting snowpack, therefore most forecasts indicate slightly below-normal runoff this season,” said Larson. Continued precipitation over the rest of the winter and spring will be influential in catching up from water year precipitation deficits and below normal runoff predictions at many locations.

A full report of conditions on March 1 can be found in the monthly Water Supply Outlook Report available at nrcs.usda.gov/montana/snow-survey.