Note: The data presented in this post is accurate as of midday Wednesday.
Snowflakes in weather apps present an annual struggle for meteorologists and weather enthusiasts. Last night, a friend of mine texted me showing exactly that – a major weather app with snow in the forecast for the Tri-Cities.
Before we get too deep, let me give you a brief summary. Yes, there is a chance of snow next week in the Columbia Basin, but as it stands right now, it isn’t anything exciting. That said, if you are traveling for Thanksgiving, you should be prepared for winter travel conditions.
SYNOPSIS
Weather models are becoming increasingly confident that a regional storm will approach the West Coast early next week. What models aren’t confident in is where the storm center will make landfall and how much precipitation it will actually bring. The latest run of the GFS has the low skirting the Oregon Coast before making landfall between San Francisco and Eureka, while the ECMWF has it making landfall due west of Eugene. This is a difference of about 300 miles. Other models plot the landfall as happening in Washington.
Right now I lean more toward an Oregon landfall, but this spread is important in showing the level of uncertainty in the forecast right now. If the landfall does end up happening as far south as the GFS shows, this will be largely a California/Nevada event with some precipitation in and west of the Cascades in Washington and Oregon.
A Washington or Oregon landfall gives us our best shot at precipitation here in the Columbia Basin, but even if this does happen, snow isn’t a guarantee. During the period when we could be seeing precipitation, temperatures look to be within a few degrees of 34°. The low end of that range would give us some snow, but most of that temperature range ends up as rainfall.
Above is the projected snowfall for the next ten days from the ECMWF. This particular model seems to be on the higher end for our snow chances, yet it still gives the Tri-Cities less than two inches. Two inches of snow over a ten-day period is not much. Furthermore, this depicts snow that falls from the sky, not snow that sticks on the ground. Even if all of this snow does fall in the Columbia Basin, it looks to be a wet dusting at best. Here’s how the National Weather Service office in Pendleton put it in their forecast discussion issued this morning:
Tuesday, the higher elevations are looking to have the best chances of snow, with rain in the Columbia Basin. At the moment, the best chances of snow in the Columbia Basin is early Wednesday morning, where snow levels will drop to 1000 feet and below.
This snow level puts snow possibly reaching close to the basin floor, but not until we approach the end of the precipitation. If you’re in Pendleton or Walla Walla, it seems that temperatures could start getting cold enough for some snow to mix with the rain as early as Tuesday evening. A word of caution for Pendleton and Athena, though – I wouldn’t trust that six inches of snow displayed on the map above. While the ECMWF is one of the best global weather models, it still doesn’t have great resolution when it comes to terrain. I’m quite sure that number is higher than it should be because of your proximity to the Blue Mountains.
There is also something to be said about how far out this event is. Forecasting anything a week out is not always an easy task, let alone specifics about where it may or may not snow in a near-freezing scenario like this. The outlooks that weather models provide will change between now and next Tuesday. They could become more favorable for snow, they could remain pretty similar to what we’re seeing now, or they could completely remove the storm altogether. On this topic, I really liked what Meteorologist Monty Webb at KNDU had to say this morning:
UNDERSTANDING WEATHER APPS
One of the pitfalls of many major weather apps like the one my friend sent me a screenshot of last night is that they rely on a very limited set of symbols to communicate the forecast. The snowflake that appeared in the forecast for the Tri-Cities says nothing about how much snow we might get, the chance of snow, whether it will be all snow or some mixture of rain and snow, and how long the snow might last. For all we know, it could have been displaying a snowflake for a 30% chance of snow that only lasts for three hours.
The forecasted temperature provided by most apps is usually pretty dependable and should be the first thing you look at when you see a snowflake appear. In the example from last night, the forecasted low was 34° with a high of 43°. Right away this tells me that this event, as forecasted by the service behind the app, is either going to be short-lived or will involve precipitation mixing with rain. At any rate, it’s unlikely to amount to any sort of major accumulation. The snowflake has since been removed from the app’s forecast, but I wouldn’t be surprised to see it return.
Weather apps are handy to use for basic weather information, but when something exciting like snow starts showing up in their forecast, it is important to take it with a certain level of skepticism. It also doesn’t hurt to get a second opinion.
Ben Randall, owner of Western Oregon Weather in Tillamook, helped provide model data and analysis for this post.
