Georgetown Lake Update – March 13, 2026

Current Lake Elevation  -  6428.60 ft    

 
(Provisional Data from Georgetown Lake near Philipsburg, MT - USGS Water Data for the Nation)

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The water surface elevation is about average to a little below average for this time of year based on 80 years’ worth of lake elevation data. The lake remains frozen.

Elevation and Inflows
Since the last conditions update in December, 2025 inflows to Georgetown steadily declined until the 2nd week of February when they dropped quite drastically ending February with only about 30% of normal for that time of year. Last month, the lake gained only 30 acre-feet of storage. There were periods in February of declining lake level that is not observed in the historic record before, with no change in outflows it is unclear if these declines were truly variability in inflow to the lake or instrument error with the USGS station reading lake levels (ice and pressure differences can create these errors). The February average monthly outflows were 6 cfs, which were about equal to the inflows, making the total lake inputs equal to about 6.5 cfs. The inflows were 29% of normal for February which was a major decline from January. Daily inflows for the first 2 weeks of March have been staying close to 6 cfs with isolated events of higher inflows. The 1-week average is 18 to 20 cfs for inflows as this past week saw a pronounced increase in lake level.

 

Precipitation
Although snowpack has been up and down in Montana this winter, recent storm patterns have drastically improved conditions in western MT. Snowpack is sitting above average for the Georgetown area. The Peterson Meadows SNOTEL site accumulated 1.6 inches (73% of normal) of precipitation in February. Peterson Meadows is reporting 9.2 inches of snow water equivalent (110% of normal). The Warm Springs SNOTEL site, which gives an idea of the higher elevation precipitation conditions, accumulated 4.1 inches of precipitation (128% of normal). The Warm Springs station is reporting 24.4 inches of snow water equivalent (134% of normal).

 

Climate Forecast
The latest CPC climate forecast for Western Montana (created March 14, 2026) shows a high chance of much warmer than average air temperatures and average precipitation for the rest of March (up to the 27th). The local weather in Philipsburg is predicting the current winter-like conditions to pass and high temperatures to reach into the high 50s with lows in the 40s for the next 10-days.

 

Model Forecast
I used the end of February lake elevation to start this model run. The March NRCS Water Supply Forecast for the USGS Flint Cr at Southern Cross gage was 92% of normal for 2026. Based on current snowpack, and inflows, I used 80% of normal inflows for the runoff months (May, June), 60% for March and April based on current inflow trends, and 75% for the rest of the year. As always, it is still March, forecasts are uncertain at this time of year and outflows may need to deviate from those shown in this model run to account for changing conditions into April and May (the bulk of Georgetown spring runoff usually happens in early June but it seems to have been weeks early in the last few years).