We are now officially into mid March as of this writing and the official start of Spring will occur next week on March 20th even though we have been in "meteorological spring since March 1st. Many are anxiously awaiting getting out into the garden to begin cleaning up and prepare the soil for planting but here we are in Northwest Montana at over 2000 feet above sea level and around 48 degrees North latitude. In addition there is still a fair amount of snow on the ground even across most valley areas so the wait will have to continue at least for a little while longer. Many are wondering what the upcoming season will hold? I will try to answer that question to the best of my abilities in the article following. Take a look at the two charts below.
These are the official Spring outlook charts produced by the Climate Prediction Center for The National Weather Service. For our region in far Northwest Montana, the first chart shows slightly greater odds (around a 33% chance) that temperatures will remain below normal or colder than normal for April, May and June while the second chart shows that equal chances exist for precipitation to be above normal, near normal or below normal. It is also noteworthy to point out that the Climate Prediction Center (or CPC from here on out) just updated this outlook as of today, March 15, 2018. So what does this all mean for us in Northwest Montana and the Northern Rockies? Well the official outlook from the CPC would indicate that they think that our region will experience a greater likelihood of cooler than normal temperatures for the next 3 months but also that they really don't know what will happen with precipitation for our area which is why they indicate equal chances for precipitation. So how do I see this affecting our area? Well records for Libby and the surrounding area have not been well kept in the past as the consistency has been lacking but I will do my best to break it down for our region.
Statistically we are heading into one of our driest months of the year for most of Lincoln County, that being April which is the second driest month of the year averaging a little over an inch of rain and melted snow for Libby with slightly more for surrounding areas with only August coming in a little less. The exception to this is most of Sanders County to our south and west which does not follow suite as they have more of the wet winter/dry summer bias so April is still a relatively wet time of the year if you live there. This is followed by a sharp increase in precipitation totals for most of Lincoln County in May and June which is often one of the wettest times of the year while again Sanders County continues to see a drying trend at that time. The reason for this is our summer convective season begins and systems passing by along the jet stream tend to steer further north. As for temperatures, using Libby as the basis here with the data that is available, April average high is 61.7 degrees farenheight, May is 71.6 degrees farenheight and June is 78.9 degrees farenheight. So between April and June there is an almost 20 degree increase in average high temperatures during that time. If the CPC prediction is true, then we are likely to see some chilly readings in April and likely May as well, with perhaps some cool readings into June. On the precipitation front, from the data available, the average precipitation for April, May and June for Libby are approximately 1.09 in, 1.62 in, and 1.83 in. respectively. Unfortunately, snowfall data is incomplete for all reporting areas so I don't have access to that. If the CPC prediction for precipitation comes true then a wide range of possibilities exists from very dry, wet, or very wet with the possibility still for some snowfall.
The key deciding factor will be what will the jet stream do this Spring, how strong will the Gulf of Alaska low be and will the Continental 4 Corners Upper ridge build in quicker and stronger than normal? From what past experience has shown me from living here, I believe we are likely to see a normal to slightly cooler than normal Spring temperatures with still the possibility of some light snow on the valley floors into April especially during the night time hours. For precipitation, I would tend to agree with the CPC here too as there is no clear indication of what will happen with the first 3 factors listed above. These 3 are the driving force behind both the temperature trend and the precipitation trend for our region during the Spring. The La Nina across the Pacific is rapidly fading and is expected to become ENSO neutral by early Summer and remain that way until the fall. All it would take is one significant storm system or widespread thunderstorm outbreak to give our region a wetter than normal Spring. If I had to choose, I would lean slightly on the wetter side for our Spring months as the last 5 years have not produced much in the way of Spring rains during May and June like we are accustomed to. In addition patterns have a tendency out west to go in 5 year cycles with the last "wet Spring" cycle occurring in 2012, 6 years ago so we are somewhat overdue. If you are thinking of getting started on that garden, remember the best rule of thumb is not to plant anything outside until Memorial Day weekend. If more information becomes available or changes occur that would warrant an update then I will post that here. In the meantime, I am looking forward to seeing scenes like the one below over the next few months with much lush greenery in the valleys and an abundance of snow in the mountains with days consisting of sunshine and showers.