Roland Steadham

Idaho is about to embark on a very unsettled weather pattern this week as a hyper-active Jet Stream will bring a high frequency of storms into the region. The snow we had this morning in the Treasure Valley was the first of the series of storms that will move in from the northwest. By the way, our first average snowfall in the Treasure Valley occurs right around November 21st. So the timing was just about right. Some of our ski resorts like Tamarack and Brundage received about 8" with this storm. Bogus Basin had about 1-2".

The most powerful storm of the season is rapidly forming off the coast of Washington and Oregon. The low is so intense that it is actually forming a center of circulation that looks like the eye of a hurricane. This is not a tropical cyclone but it will generate winds of 70+ mph on the west coast. If this storm was plowing toward the state of Idaho, it would be time to batten the hatches. However, the storm is expected to stall on the west coast. That will keep us in a southwest flow. That makes forecasting in the Treasure Valley very difficult because the Owyhee Mountains south of us typically act like a storm blocker causing a rain shadow effect in the valley. Whereas the mountains to the north and west of us can see heavy rain and snow depending on elevation. Plus, the southwest flow is a warm flow and consequently, snow levels are typically above 6-7,000'.

After a stormy first part of the weekend, we've had some amazing weather today. However, the models show another front headed this way on Tuesday and it might b

Expect rain Sunday night into early Monday morning as the next surge of moisture moves through the state. Snow levels will be between 5,500' and 6,000'. That means that the upper half of our ski resorts will see snow. However, many of the mountain valleys will see a rain/snow mix. The window will remain wide open for one surge of moisture after another to move across the region. The only thing these storms are lacking is cold air. As a result, the periods of showers we'll see will be valley rain and mountain snow. Highs this week will remain in the 40's. The moisture headed this way will be composed of a lot of sub-tropical air. These atmospheric rivers will be packing a lot of very mild air through the end of the week.

This is going to be an active week for weather across the state thanks to a persistent atmospheric river that will favor much of Idaho. Look for the next surge of moisture to move into the region on Tuesday. This will bring valley rain and mountain snow. We'll see sunny to partly cloudy skies on Christmas Day. However, the next surge of sub-tropical air will bring periods of valley rain and mountain snow starting Thursday and continue through the weekend. This will not be one solid storm. But, we will see showers on again, off again. The sub-tropical air moving in from the southwest will keep our temperatures above normal for this time of the year with high this week in the 40's. We should be in the 30's. But, at least we'll continue to see mountain snow.

It's time to start looking at the snowpack levels across the region. At first glance, Southern Idaho is off to a good start. For example, the Boise Basin is currently 129% of normal. The Weiser Basin is 163% of normal. These are good numbers but it's not time to relax just yet. This is just the beginning of the snowpack season. A lot of our storms have been very warm and that's why we haven't seen any significant snow in the valley as of yet. However, if this current trend continues, then we'll be in great shape. The only problem is that the active pattern can shut off very easily putting us in a dry spell. That scenario could easily put us in a deficit. For right now, the computer models keep us quite unsettled for the next 10 days. Here's how the forecast is shaping up right now.

For the last few weeks, a persistent flow has ushered in one storm after another across the northwest including Idaho. In the past 7 days alone, some of our ski resorts have had nearly an additional 3' of snow. This has kept our snowpack at very comfortable levels. For example, the Boise Basin is now 133% of normal. The Payette Basin is 139% of normal and the Weiser Basin is 167% of normal. But, things are about to change.

Our pattern has taken a turn toward a drier spell over the last few days. This is typical for the month of January. The end result has been a very slow decrease in our snow pack. Don't get me wrong, we're still ok, but the percentages have dropped by about ten points since last Sunday. The Boise Basin is still above 100% of normal, but I'll bet those numbers get even lower this week with the weather scenario headed this way.

High pressure will keep the sun shinning through Wednesday with highs in the mid to upper 30's. The pattern has been too dry for too long. The last time we had measurable precipitation in the Treasure Valley was January 10th. If the computer models hold true, the high pressure will be replace by a trough of low pressure by the end of the week and that will open the window for storms to return to the state. I'm cautiously optimistic that we'll see valley rain and mountain snow moving in by Friday. Next weekend could be rather unsettled. It's still too early to get excited but this is normal behavior for this time of the year.

A persistent trough of low pressure has parked itself along the Pacific Northwest. As it spins counterclockwise it is pumping in a lot of moisture from the West