Weather changing - but not much

For the past two solid months a broad-scale weather pattern has been anchored over the U.S., causing nearly unprecedented warm and dry conditions in the west and extreme snow and cold in the eastern part of the country.

A large bubble of warm air aloft has persisted along the west coast, pushing the jet stream far to the north into northern British Columbia and Alaska. On the backside of this ridge the jet stream then plunges southward, dragging with it bitterly cold air into the eastern third of the U.S.

This weather pattern has occurred many times before, but it's the extended duration that has captured the attention of many. Drought conditions continue to worsen in California along with very low snowpacks, in some cases no snow, in the mountain west. Conversely, Boston, Massachusetts, has never before had this much snow in the month of February.

Here in Sisters, January precipitation totals were two inches below normal, and a quarter of an inch short so far in February. December actually registered above normal precipitation levels, but warm temperatures caused most of it to fall as rain, even in the mountains. To date, February temperatures are a good seven degrees Fahrenheit above normal.

The big question is how much longer will this warm, dry weather last? The honest answer is no one knows for sure. But early last week medium-range weather models were hinting that by March the strong ridge that's been holding Pacific storm systems at bay might collapse and allow a more normal progression of low-pressure systems to approach from the west.

Since then, however, most of the models are now suggesting that the ridge will maintain its amplitude but retrograde (shift westward) into the eastern Pacific Ocean. Should this happen, Central Oregon would likely be subjected to minor amounts of precipitation as a weak system or two drops down from the north bringing much cooler temperatures and lower snow levels.

By the end of the first week in March, the ridge may indeed break down, paving the way for more substantial moisture to overspread the Pacific Northwest.

The Climate Prediction Center is forecasting warm and dry conditions to persist through March.