Winter 2024/25 Recap

Now that we're well into spring, it's a good time to take a look back and review the winter we just finished up.  Was it cold?  Wet?  Mild?  Dry?

First, as a reminder, the Climate Prediction Center was expecting a weak La Nina to develop and influence our weather.  La Ninas tend to produce cooler and wetter winters (and springs) in the Northwest.  

But after the previous winter's strong El Nino, a weak La Nina was slow to develop.  In fact, we won't know for a few more months, but this winter may not even reach the criteria for calling it a La Nina winter.  The graph below shows the index that is monitored for this determination.  And you can see that it's not until just the last data bar on the far right that the ocean temperature has cooled below the La Nina threshold (horizontal blue line).

In spite of this uncertainty, CPC came out with this winter outlook last fall, which looks much like the typical La Nina pattern:

So for the three months of "winter" (Dec-Jan-Feb), here's how the average temperature ranked compared to the 133 years of historical data.  Temperatures in the Northwest were near-normal to above-normal when averaged over the three months  Not quite the "cold winter" the seasonal outlook expected.  The Southwest was much above normal.  You may have seen news stories stating that this was the coldest winter in 10 years in the lower 48 states, which is correct.  But when compared to the 133 years of historical data, it wasn't a very cold winter at all.

For precipitation, the seasonal outlook was a bit better.  Some areas in the Northwest were wetter than normal.  All of eastern Oregon along with central Washington had more than the usual amount of precipitation, while the Washington Cascades and the Idaho Panhandle mountains were below normal.  This somewhat odd combination is the result of a wet southerly flow pattern.  That pattern lessens the typical rain shadow effect, and doesn't give the mountain ranges as much heavy precipitation.

The current snowpack also reflects this.  Lots of blue dots (above normal snowpack) in Oregon and north-central Washington, but lots of orange and even a few red dots in the Cascades, the Idaho Panhandle, and the Canadian Rockies.  The storm track was often displaced to the south of our area, giving Oregon more precipitation, and British Columbia less.  All that said, the overall snowpack in the Northwest is in pretty good shape.  The flows on the Columbia River this summer will be on the low side.

Looking at the daily temperatures this past winter (blue bars) at Deer Park, we can easily see the mild first half of the winter (December through mid January), followed by cooler temperatures for the remainder of the winter.

Precipitation at Deer Park airport overall was above normal (green line above the brown line), but not by a tremendous amount.

Our recent dry spell helped minimize the spring mud season.  The weather for the next 10 days will moisten things back up.  The bar chart below shows the expected precipitation amount from the next few storms.  As you can see, we'll get more rain today (Wednesday) and tonight, before drying out a bit on Friday.  We should see some snow Friday night and Saturday morning, which will change to off-and-on rain over the rest of the weekend.  At this point it looks like we'll only see some light rain showers next week, with heavier rain possible by the end of next week.