Big Hole River Conditions & Drought Management Plan

From Jacqueline Knutson, Montana Fish, Wildlife and Parks Hydrologist. As of 3/20/2019:

Streamflows: Gages are seasonal and are not currently reporting flows.

Snowpack: Snowpack conditions improved greatly across southwest Montana last month and the boost we got at the end February and beginning of this month nudged us into the (barely) above average category. Currently the snowpack in the Big Hole Basin is average, sitting at 95% of normal. The Jefferson Basin is 108% of normal. As we move into the spring it is still possible to augment our snowpack as March through May often yield a significant portion of the yearly snowpack depending on temperatures. We can also usually expect peak snowpack to occur in late April and the most important piece of the snowpack story is the timing and availability of runoff. Lower elevations are above average due to the February storms but high elevations are still below average which will have a greater effect on late spring availability of runoff.

Precipitation: Precipitation in Montana was above average in February, particularly in parts of southwest Montana. After two months with average to below average precipitation it’s been nice to see snow accumulating at the SNOTEL sites around the state. Between February 26 and March 8 enough snow fell in the Big Hole valley to bring our snowpack up to 100% of average. Warmer temperatures have reduced that to 95% rather quickly but given the dry December and January we had the addition of a strong February for precipitation is very good.

Temperatures: Temperatures in February were the coldest recorded in Montana since 1936 and across the state the average temperature was 4.6F with an average temperature departure of 19.5F from normal. This shift from above average temperature to well below average occurred over the space of a few hours (and in some places a few minutes—temperature changes of 30 degrees in 10 minutes were recorded in some areas) around the 2^nd of February and stayed consistently around 0F from the rest of the month and into the early part of March. As March has pressed on, though, we have swung to the other side of the pendulum and we are seeing warmer than average temperatures over the last few days and this will continue for the foreseeable future (10 day forecast).

Forecast: A weak El Nino formed in January and is persisting through the spring. The effects of this weak El Nino were clear in January but February brought a change in flow and we had good precipitation and bitter cold temperatures. El Nino should stick around (55% chance) through at least May if not through the summer and even though we got some respite from normal El Nino conditions last month don’t be surprised if the faucet turns off and true El Nino conditions return to Montana. The three-month outlook currently favors average precipitation through the rest of the spring and above average temperatures through the early spring.