Dec 17, 2011 5:18 PM by Mike Heard (KBZK Bozeman)
The National Climate Prediction Center (NCPC) updated the long range winter weather forecast and for the 90 day period from January through March there is a strong La Nina connection. To date La Nina has had a very limited impact on the late fall season of 2011 with near normal temperatures and periodic weak storms and certainly not as dramatic as last year at this time.
Meteorologists with the Missoula National Weather Service commented on the lack of snow and cold usually associated with La Nina episodes and they feel that by the time the winter season is over in late March we will see colder than normal temperatures and above average snowpack.
The two graphics attached to this report are from the NCPC and they look at the overall weather pattern in 3 categories, EC or equal chances of above or below normal conditions, Above Normal and Below Normal conditions.
The graphics show Montana has a 30% to 40% chance of seeing below normal temperatures January through March and a 30% to 40% chance for above normal precipitation with a 50% chance of above normal precipitation in NW Montana.
Although this year's La Nina has been a slow start for Montana confidence is still running high for similar conditions to what we saw last year. Heavy mountain snowpack is anticipated by winters end and there is a good likelihood for Spring flooding.
Long range forecast models are also consistent in predicting the current La Nina to remain in place into the April, May and possibly June which could also continue the cooler and wetter than normal weather trends into Spring across Montana.
La Nina is an oceanic oscillation that occurs near the equator off the South American coast and extends out into the central pacific ocean and has a major impact on the overall northern hemisphere weather patterns. There is a considerable amount of upwelling of deep cold oceanic waters that rise to the surface during a typical La Nina event.