I just KNEW that if I planned to take a break from weather blogging, then things would suddenly become really active and intriguing.  Now we’re looking at a very active pattern for the end of October & early November, with possible hints of unusually early cold next week.  So a compromise has been reached:

1.  Only short blogs for the time being (less than 500 words)
2. No more than 3 images per blog.

After an unusually warm and foliage-delaying start to fall, it looks like we are plunging straight into a La Niña winter pattern.  Today we have another weak atmospheric river across NW Oregon and SW Washington, making for the wettest Halloween in at least 5 years.  Thankfully my Halloween & Samhain plans were completed over the weekend.  That should push our October rainfall totals at PDX at least within shouting distance of the monthly normal (3.27″).

Tomorrow through Thursday will be less rainy but cooler, with the coldest airmass of the season thus far.  Snow levels drop to at least 3,000 feet, and high temps will struggle to get above 47-50 degrees in the western valleys.  Overnight temps should also dip into the 30s for the first time.  Late summer to early winter temps in just two weeks!

Then midday Friday through midday Saturday, a stronger atmospheric river sweeps south from Vancouver Island through our area, continuing deep into southern Oregon.  Friday night looks extremely wet in our locale, with at least some threat of localized flooding.  Some strong westerly winds are also possible as the frontal AR slides through:

Next Sunday is when things start to get intriguing.  There are signals that frigid arctic air will move into British Columbia & Alberta for the first time this season.  The “proper” pattern could send some of that cold air southward into the BC Fraser Valley and WA Columbia Basin.  The last few GFS runs are going crazy with the cold air next Tuesday/Wednesday, showing snow in the Columbia Gorge and Western Washington, and snow/ice activity for Portland.  But it’s foolish to forecast snow 9 days out on any model, let alone the GFS.

The European model has more “undercutting energy” coming from the WSW, which would keep the cold air bottled up to our immediate north.

Here is the 00z chart for The Dalles, OR.  Notice the disagreement next week:  some members are wet and seasonably mild, while others bring cold arctic air down:

It will be at least another 3-4 days before we have a clearer picture on what next week’s pattern is going to look like.  This is always the case in an active winter pattern, when things can turn on a dime’s notice.

In the meantime, get your rain gear ready!

Karl