Weather Blog

Should this map cause concerns for a big snow?

Should this map cause concerns for a big snow?

There's a map that NOAA's Climate Prediction Center put out on Saturday that seems to be creating a little bit of buzz around the Northwest for those eager to see some snow.

But is the buzz really warranted? Maybe a little.

What you are looking at is their 8-14 day temperature and precipitation probability forecast, which is routinely issued several times a week. It's just one of many long range products the CPC issues.

This particular map is showing a "depth of probability" chart of having above or below normal temperatures during the 8-14 day time frame ahead of the issue date. 

What this map is actually saying is there is a very high -- almost extremely high -- probability that temperatures will be below normal along the west coast 8-14 days from now. The darker the colors, the greater the probabilities.

In our case, the darkest purple is a 70 percent chance of below normal temperatures in this time frame.  (Are you a statistics major and want to delve into the technical minutia of what this map really shows? Knock yourself out.)  In a nutshell, this means the computers feel there is only a 27 percent chance of getting normal temperatures and a 3 percent chance of getting warmer than normal temperatures.

As an aside, I will say it is rare to get such a high confidence on this map, either warm or cold.

Now for snow fans, this might look like you need to lick your chops for some lowland snow, but I think some might mistake this map as depicting intensity of a cold snap or a snow accumulation map, since it's sort of in the same color palette that typical snow accumulation maps are shown on TV.

But this doesn't mean it'll be *really* cold, just colder than normal, which is now the upper 40s for most of us. For example, a week of highs in the low 40s would verify this forecast.

There is a companion graphic that is similarly issued for probability of above or below normal precipitation. (On Saturday's map, it had the west coast as equal chances above or below normal -- or basically no discernable signal.)

That said, this at least means if this map is correct, then we probably have at least a decent chance of getting the right conditions for some lowland snow -- although predicting snow is not the intention of this chart; it's mainly for planning purposes.

Now, if lowland snow fans do want to cling to something, This map below shows a typical atmospheric set up for the predicted pattern above.

That does show a big ridge over western Alaska which is a typical pattern to drive the jet stream way up into the arctic and then drive that cold air down the BC coast into Washington. (Hard to see on there, but we are just northwest of that "blue bulls-eye" in the center-left of the image.) All we'd need is the moisture and voila, La Nina can stop hanging her head in shame around here.

But remember, even if there is an 80 percent chance of below normal temps, that means there's 20 percent it'll still end up climate average or warmer, and the way this winter has gone? The underdog is a little more appealing than usual.