A powerful La Niña winter has produced one of the harshest winters in Montana in recent memory and reminds me of my childhood growing up in Montana and dealing with long cold and snowy winter seasons.
The combination of a stronger La Niña and a very active MMJ (Madden-Julian Oscillation) pattern has been conducive to producing numerous storms with one good strong storm almost every week in 2018 to date and impacting most areas of Montana with heavy wet snow and strong winds.
SWE (snow water equivalent) percentages have seen a significant increase statewide over the last 60 days. All river basins are above to well above normal on water content in the snowpack and there is a very healthy valley snowpack statewide as well.
There are some concerns for possible flooding issues this Spring if the snow-melt coincides with the spring rainy season.
Some snotel sites near Butte and Anaconda as of March 1st have exceeded their max of record for SWE.
NOAA will issue their Spring Outlook on March 15th and Spring flooding will be one of the topics covered. We will update that forecast here on-line and on-air next week.
The next 90 days will be studied very closely as climate change has been warming our Spring seasons up more quickly than in the past.
Last year we had a healthy March snowpack but it melted out too fast and the Spring rainy season was dismal and temperatures jumped into the 90s in June which produced a flash drought and terrible summer fire season.
Will that happen again this Spring? That is the million dollar question and we will be closely monitoring forecast and climate models to try and answer that question.
Right now the news is good and we are optimistic that with the current high SWE and IF we see a typical cool and wet Spring and come out of the rainy season in May and June near normal that this summer we will have adequate water in rivers, reservoirs and for irrigation.
La Niña continues to show signs of weakening during the month of February according to NOAA but below average sea surface temperatures were observed in the equatorial Pacific.
The atmospheric anomalies associated with La Niña weakened considerably across the topical Pacific. Other signs of weakening show a warming of ocean subsurface water temperatures and suppressed convection near Indonesia into the far western Pacific.
Most forecast models are pointing toward a continuation of decay of the current La Niña heading into the next 90 days. We anticipate a transition to ENSO-neutral by the end of May.
ENSO Forecast Probabilities look interesting. There is a 55% likelihood of the current La Niña will be reaching a neutral state by May.
The chart above shows the percentages of La Niña weakening by May and an uncertain projection of a possible neutral to weak El Niño by October-November-December (OND). During this time period there is an estimated 20% chance for La Niña developing, a 40% of a neutral state and a 40% of El Niño developing.
ENSO Monthly Update Report: CLICK HERE
ENSO Blog: CLICK HERE
Madden-Julian-Oscillation: CLICK HERE
NRCS Monthly Snowpack Report: CLICK HERE
Warming Spring Seasons: CLICK HERE
Spring Flood Potential: CLICK HERE