Contact:
Lucas Zukiewicz
406-587-6843
BOZEMAN, Mont., Feb. 5, 2021 – While January started off on the right foot, with snow falling at many locations in the state, the remainder of the month was hit-or-miss for mountain and valley snowfall.
Atmospheric circulation patterns early in the month were similar to those experienced throughout much of the winter. Moisture and warm air spilled into the state from the Pacific, favoring the Pacific Northwest and river basins along the Idaho border and northwest Montana. “It was abnormally warm during the first two weeks of the month. Fortunately, a return to more winter-like conditions occurred after January 17, when northwest flow brought in cold air and moisture from the north,” said Lucas Zukiewicz, USDA Natural Resources Conservation Service water supply specialist for Montana. Temperatures during the following week dropped below seasonal normal, and central and north-facing mountain ranges received snowfall. Zukiewicz continued, “Another shift in flow occurred during the last week of January with moist southwest flow yielding abundant moisture to southwest and south-central Montana.”
Overall, January snowfall was below normal for all areas of the state, except the central mountain ranges and southwest river basins. This caused snowpack totals to decline for the second month in a row for all river basins except the Madison, Gallatin, and Smith-Judith-Musselshell, which experienced marginal increases.
Padded by the well above average early season October snowfall, many river basins in the state were near to above normal on January 1. “You can only rely on early season totals for so long. If you experience two months of below normal snowfall during the bread and butter snow months, like we just have, those surpluses aren’t going to stand up for long,” said Zukiewicz. January is typically the “wettest” month in northwest Montana with regards to snowfall, but this month’s low snowfall totals caused declines in snowpack in all river basins west of the Divide. Due to those declines, snowpack ranges from 77 to 86 percent of normal on February 1 in west-side river basins.
One area east of the Divide that experienced very dry conditions this month was the Rocky Mountain Front and plains feeding the Sun, Teton, and Marias Rivers. “Snowpack in this region declined 30 percentage points over the month from well above normal on Jan. 1 to 83 percent of normal on Feb. 1,” said Zukiewicz. “It wasn’t just the mountain locations that were dry this month. Plains locations generally reported less than 0.2 inches of precipitation, with the Choteau Airport reporting a paltry 0.01 inches.”
Snowpack east of the Divide ranges from near normal in the south-central, central, and northern tier basins (St. Mary and Milk) to below normal in the Sun-Teton-Marias and southwest river basins. “Snowpack in the southwest has been lacking all year. While it was great to get that big shot of moisture at the end of January in the headwaters of the Gallatin, Madison, and Jefferson River basins, it wasn’t enough to make up for the early season deficits,” explained Zukiewicz.
By February 1, 60 to 70 percent of the peak snowpack has usually accumulated west of the Divide. “The front-loading of snowpack in these western basins means that late season snowpack recovery is less likely to happen by spring runoff, but not impossible,” said Zukiewicz. The amount of snowfall now needed to improve to a normal peak before runoff begins in these areas varies, but in general, ranges from 125 to 145 percent of normal. East of the Divide, where 55 to 65 percent of the peak snowpack has typically accumulated by February 1, the make or break spring and early summer months are yet to come. The amount needed to recover before runoff is slightly lower in these areas, ranging from 120 to 130 percent of normal snowfall.
With more optimistic forecasts for snowfall over the next 14 days and beyond, there are some signs that more favorable weather patterns may return to the state and start this recovery. “You don’t have to look far back in time to find a miracle February 1 to March 1 snowpack recovery,” said Zukiewicz. “On February 1, 2019, the snowpack looked similar to this year, and after the month our office referred to as ‘Februburied,’ the snowpack was in much better shape on March 1. Come on, Februburied!”
From March 1 through May 1, additional manual measurements of snowpack will be conducted across the state. “These additional snow course measurements help us to fill in the critical gaps between our automated network and help to give us a better picture of the overall snowpack distribution as we approach the peak snowpack for the year,” said Zukiewicz. With this additional information, the NRCS will begin to issue streamflow forecasts for the coming spring and summer runoff season. The forecasts will be found in the March 1 Water Supply Outlook Report and on new NRCS water supply webpages.
Find the monthly water supply summaries at the NRCS Montana snow survey webpage under Water Supply at https://www.nrcs.usda.gov/wps/portal/nrcs/mt/snow/.
February 1, 2021
River Basin |
Snow Water Equivalent
% Normal |
Snow Water Equivalent
Monthly Change % |
Monthly Precipitation
% Avg |
Water Year Precipitation
% Avg |
Columbia |
|
|
|
|
Kootenai, Montana |
86 |
-7 |
78 |
100 |
Flathead, Montana |
84 |
-14 |
64 |
103 |
Upper Clark Fork |
77 |
-12 |
52 |
88 |
Bitterroot |
83 |
-11 |
70 |
100 |
Lower Clark Fork |
78 |
-11 |
66 |
88 |
Missouri |
|
|
|
|
Jefferson |
78 |
-1 |
79 |
82 |
Madison |
77 |
+8 |
92 |
87 |
Gallatin |
79 |
+3 |
92 |
87 |
Helena Valley |
92 |
-5 |
72 |
100 |
Smith-Judith-Musselshell |
95 |
+8 |
93 |
90 |
Sun-Teton-Marias |
83 |
-30 |
52 |
112 |
St. Mary |
100 |
-15 |
74 |
106 |
Milk |
98 |
-57 |
61 |
117 |
Yellowstone |
|
|
|
|
Upper Yellowstone |
89 |
-7 |
72 |
100 |
Bighorn |
76 |
-7 |
58 |
75 |
Tongue |
88 |
+2 |
87 |
99 |
Powder |
74 |
-1 |
63 |
74 |
- Less than 50% equates to well below average/normal
- 51 to 70% equates to below average/normal
- 71 to 90% equates to slightly below average/normal
- 91 to 110% equates to near average/normal
- Greater than 111% equates to well above average/normal