About 10 more days to go until the cold in the East snaps back into the West. This is one of the strongest La Ninas on record and the pattern is one of the strangest for La Nina. In the past 100 years only one time has the East had a colder than average winter with the onset of a moderate-strong La Nina. But even that winter (1916-1917) the cold wasn't as extensive as this winter. Will be interesting to watch because historically the East will have even colder winter the next 2-3 years after the onset of the La Nina.
This has all messed with my forecast for this winter because the cold would normally be in the West this first winter of the strong La Nina & so would the trough and jetstream. We got lucky in November & December with blocking that formed in the North Pacific suppressing the jet underneath into CA for a week of 100+ inches of snow in each month. But that is all we have really gotten and it really had nothing to do with a typical La Nina pattern.
Historically we should have a wet & cold winter this first winter of La Nina here and then drier the next couple of winters with a weaker La Nina. So if I'm right we need to have a big second half to our winter here starting in mid-February. Mid-February is about the mid-point of our winter here and the good news is that Northstar has seen 84% of our annual snowfall already, so we have a head start. My original forecast in the fall was for 125% of average snowfall, mostly based on the average of the snowfall we received the last 3 strong La Ninas.
Valentine's Day looks like it will be the most noticeable turning point in the pattern. With the higher sun angle and the warming starting in the atmosphere we should continue to see a break-up of the cold stronghold in the East. We are currently in a +AO, +NAO, & +PNA pattern. 2 out of 3 things we need for a change and the PNA should go negative over the next week so we will have all 3. Once that happens the pattern should become very progressive with any ridges not sticking around too long.
Looking at the model forecasts we see the ridge expand Northward off the coast this week which means the temps will warm going into the weekend. Then next week we see retrogression of the ridge Westard in the Pacific. At first this should drive down some colder air just to our East like we saw yesterday, which will cool our temps. Then as we head into Valentine's Day weekend and the following week watch out! We could see some of the coldest air of the season in CA as the cold in the East snaps back into the West as the ridge is out around 150w in the Pacific. This cold should push pretty far South in CA so look out in L.A. for cold coming as well.
The cold may be a bigger story than the snow, although we will begin to see cold storms move in as well. It looks like we will finally get into our typical La Nina pattern finally. The weather should look like the original winter forecast map from the fall which you can find on the Weather Charts page, with the cold and snow in the Pacific NW.
The biggest thing on everyone's mind is the snowfall. The big question will be exactly how far West in the Pacific will the ridge setup? Out at 160w then we should see some big storms the 3rd week of February. 150w where the long-range charts have it now would mean smaller-moderate sized storms. With the cold in place that could still mean big amounts with the high snow:water ratios. If it is a bit closer around 140w then we may just see lots of cold with small storms like the one this past weekend.
Either way the entire pattern is changing and the rigde in the West and trough in the East pattern of the past month will soon be gone. Plan on lots of cold starting in about 10 days and hope/pray for lots of snow. The East coast has 2-3 more snowstorms in the next 10 days and then their record snowfall pattern will be gone and it's their turn to thaw out as we freeze and get snow. We only need 56 inches of snow to hit our annual average over the next 3 months and 143 inches to hit my forecast. That is about 19 & 47 inches per month respectively.
With this strange pattern so far and what should finally be a flip to normal La Nina, it will be interesting to see where we end up. The good news is that our 200% of average snowpack as of Jan. 1st got us through this drought with plenty of snow still on the ground and with the flip just happening now in Mid-February it doesn't look like winter will be shutting off in March like in the 07/08 La Nina. Stay tuned, January re-cap out later this week once the final numbers are in. BA