Monday Rain

If you read the previous blog, you'll know that we were expecting some showery weather for Tuesday and Wednesday, and that's pretty much what we're getting.  Watch out for frosty temperatures on Thursday morning.

But beyond that, we were talking about the uncertainty of the forecast starting this weekend and continuing into next week. Well, the computers are starting to hone in on that forecast a bit better.  And now Monday is starting to look rather wet.

Let's look back at a graphic I showed you on the previous blog.  It showed about a 20% chance of rain starting Monday night and continuing through Thursday.  After that, chances of rain were rather low, but not zero.

Now let's look at that same graphic two days later.  Notice the differences?  First, the computers are a little more definitive on the showers this week.  But look at how the forecast next week has changed.  Starting Sunday night, the chances of rain really increase, peaking on Monday, and then slowly tapering off by next Wednesday.  

Why the big change in the forecast?  In the previous blog I showed that half of the 150 computer forecasts were expecting a warm high pressure to dominate our area, while the other half were favoring the cold low pressure to our west.  Now, more of the computers are starting to jump on the rain band-wagon.  But not all of them.  In other words, the odds are favoring rain for Monday, but it's far from a sure bet.  Could the computers reverse course and go back to a warm and dry forecast for next week?  Yes, it could happen. Another way to put it is that the odds of rain have increased from 50:50 to 60:40 or even 70:30.  But not enough to wager a bet yet.  

If we do wind up getting rain next Monday, how much are we talking?  The first image below shows the average of the US model ensemble (from 30 different computer forecasts).  The clear message from these models is that there will be westerly winds with this storm, resulting in a rain shadow in the Basin and more rain in the Panhandle and Cascades.

 

The next forecast is an average of the 50 European computer forecasts.  Looks a little wetter than the US forecast.  This is in part due to less westerly winds, so less of a rain shadow for the Basin.

Remember, these are average forecasts, so there are going to be some computers that don't give us a drop of rain.  We'll just have to keep an eye on the new computer forecasts as they arrive and see if the wet forecast for Monday is still being predicted.

Beyond that, the European and US models are both forecasting a large, warm high pressure to develop over the West by the end of next week.  The Canadian models aren't on board with this idea yet.  But the European and US models have been pointing at this for the past couple of days.  We can see this in the cluster forecast below.  Clusters 1 & 2 would bring us warm weather (80s), while Cluster 3 keeps the storm door open.