Snow on Monday and Tuesday? Here's what to watch in days ahead

Many of you woke up today, looked at your iPhone forecast and saw a snowflake (!) for next Monday and Tuesday.

Since you’re probably wondering what that means and why your phone says it is going to snow, here’s our explanation.

The snowflake on your phone does NOT mean we are going to get snow. Not in the least. In fact, this far out I’m not very confident in the potential at all.

However, the computer models have been showing some border-line cold enough air to potentially get some lowland snow early next week. Most of this article will be why I think we WON'T get much.

Making columns for each, here’s what we can list. Each of these points are explained below.

Yes to snow:

1. Borderline cold enough air for snow

No to snow:

1. The air is just barely cold enough

2. There won't be much moisture left

3. It's not an arctic outbreak of massively colder air

4. South/Southwest wind almost always makes it difficult for snow to fall in western Washington

Right now there is a system scheduled to come in on Sunday. It’ll be a cool and wet system with plenty of mountain snow, not much different from what we have been getting.

Sunday’s system will include a cold front, which is the front edge of a cooler air mass and once it passes enough cold air from the northwest will filter in and drop our snow levels will drop from around 2,000’ to potentially 500' or lower by early Monday morning.

However, the cold air coming behind the front does not appear to be part of a major cold air outbreak and should only put our temps bordering on the level for snow.

When I'm looking at the computer models, I tend to start with the thickness of the atmosphere as a good early indicator that I should dive more deeply into the models for the potential for some snow.

Now, I'm going to get into a little more technical detail, so hang on!

The thickness has to do with how much cold air (lower thickness), or how much warm air (higher thickness) we have in the atmosphere.

I've learned over the years a good early indicator for the potential for lowland snow is the "522" thickness line. For a lot of places in the country, a 540 thickness can be associated with around cold enough temps for snow, for us it's typically around 522. Seeing the 522 line always causes me to look more deeply into the lower levels of the atmosphere, moisture content, wind direction etc.

Having that 522 thickness value DOES NOT MEAN SNOW, it just means we should look more closely at the situation. In this case I do see the 522 thickness line, but there are many other factors going against the chance for snow.

This is the kind of pattern where if the showers were heavy enough we could force the snow level down closer to the surface, much like we often see in the Puget Sound Convergence Zone. As it stands, the showers look very light and would more than likely fall as either rain or a rain/snow mix with snow showers for higher elevations.

At the same time there won’t be much moisture left, but at least one computer model is hinting at some pockets of snow early on Monday. The snow level will be around 500-1,000’ and high temps will warm more than likely into the upper-30s and low-40s.

We don’t have to have freezing temps to get snow, but as long as it’s around or below freezing at 1,000’ the snow can survive to the ground. I don't see much wind, but we will have 5-15 mph wind from the south/southwest, which makes it much harder for snow showers in western Washington.

Overall this is NOT a pattern that would produce copious amounts of snow in the lowlands, it’s possible we could have some snow showers with very spotty accumulations that would not last. There should be enough cold air in place for some scattered mix showers on Tuesday as well, but from there the threat will go away.

All that said, there will be changes to the forecast in the coming days. Anytime you're looking at conditions a week away, there is tremendous uncertainty, especially with lowland snow which requires all the ingredients coming together at just the right time.

In fact, we will likely go into the weekend (yes, days from now) with a very high degree of uncertainty about early next week's snow potential! That's how difficult lowland snow forecasting can be! So, we'll need to be patient until we get close to early next week.

Unfortunately, however, a snowflake on your phone's weather app doesn't give you any detail or explain this uncertainty. That's why a HUMAN meteorologist is so important!

We'll be following the trends carefully and updating you on KIRO 7 News.