“February was, overall, a month of steady snow accumulation in Montana,” said Eric Larson, USDA Natural Resources Conservation Service (NRCS) hydrologist. SNOTEL sites across the state reported 1-4 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 some gains, about 5-15 inches of snow at mountain elevations. 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, basinwide 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. The Gallatin and Smith-Judith-Musselshell 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. March 1 forecasts provide an initial look at what spring and summer snowmelt and runoff might bring this year. Uncertainty in the forecasts published this month comes from uncertainty of what future weather will bring.
“The March 1 water supply forecasts currently trend 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 www.nrcs.usda.gov/montana/snow-survey. In addition, real-time snow survey data can be found at the site. — USDA NRCS
