More of the Same Only Different

As promised, it has been a mild, wet and windy week.  Thanks to a record Atmospheric River that has dumped a lot of rain on the Northwest.  Several west-side rivers have eclipsed their all-time record levels.  Here is a map of the 4-day rainfall for Washington and North Idaho:

It's the usual story of tons of rain over western Washington, drier in eastern Washington, and then wetter again in the Idaho Panhandle.  But lets look a little closer at the west side.

The Olympic Mountains (west of Seattle) received over a foot of rain.  And the Cascades (east of Seattle) were inundated with more than a foot.  Lynn Lake (in the central Cascades) received over 20" of rain in 4 days.  But look at the green numbers in the middle of the map, north of Seattle.  They are in the lee of the Olympic Mountains, so like Wenatchee and Yakima, they actually don't receive very much rain in a pattern like this.  Heck, some of us in the northeast Washington area got more rain than these folks did.

As your phone app will tell you, we're getting a break in the rain for a few days, but there's more of the same in the forecast for next week: rain, warmth and wind.  Is this another Atmospheric River?  

Technically, just about every weather front that moves through our area has an atmospheric river associated with it.  But most are rather weak, and more importantly, they don't linger over our area for 4 days.  So while you'll likely hear about more atmospheric rivers next week, it won't be the same as what we just had this past week.  Let me show you.

  

Here's the atmospheric river forecast for Monday.  This looks kinda similar to last week, right?  A long plume of moisture from Hawaii pointing right at Washington.

Here's the forecast for 12 hours later.

Uh, the atmospheric river is still there, but now it's pointing at northern California.  What happened?  This is just your average, every day, run of the mill storm on the west coast.  Yes, there's an atmospheric river, but it moves through our area in about 8 hours.  So yes, Washington will get some rain, but nothing out of the ordinary.

And there will be more storms after this one.  So Washington will see a lot of precipitation next week.  And it's possible that by the end of next week we could see a more prolonged event.  Here's what the European model forecasts for next week:

Wow.  That looks like a lot of rain for next week, especially in the Cascades where they don't need it.

But wait, there's another important difference between this past week and next week.  Snow levels will be much lower next week.  So a lot of that precipitation will be falling as snow in the mountains, not rain.  Here's the European computer snow forecast for that same period:

Those bright orange areas in the north Cascades are for more than 70" of snow next week.  There's not too many places that can rain away all their snowpack one week, and then pile up 70" of snow the next week.  But the main point is that with snow instead of rain in the Cascades next week, the flooding threat won't be the same as what we've seen this week.

What about snow in the lower elevations?  As I've mentioned in the past couple of blogs, the climate models have been advertising a pattern change around the holidays.  They're still hanging on to this idea.  So today's weather map looks like this:

Lots of warmth across the western US, with cold over the upper Midwest and the East.  Here's the forecast for next weekend:

Complete reversal.  Cold in the Northwest and mild in the Midwest and East.

Will this mean snow for the holidays?  Too early to answer that question.  Confidence is pretty high that it will at least be colder by Christmas.  Nothing frigid.  Just back down where we should be at this time of year.

So, to recap, 

• Monday and Tuesday:  Look for rain and wind as a couple of strong cold fronts move through our area.  Wind could be stronger than our recent events.
• Wednesday: strong wind in the morning, and cooler.
• Thursday: Possibly some wet snow, but eventually changing to rain.
• Friday: More strong winds possible with temperatures back into the 50s.