First rainy & windy system this fall will be followed by chilly weather next week

It’s about time for a blog post! I’ve been very busy the past few weeks; meetings, school visits, new weather branding (more on that below), and working on graphics. Plus we’ve added some time to our evening broadcasts, so...real busy. I strongly recommend you follow me on Facebook @marknelsenweather and Twitter @marknelsenKPTV because I regularly post on those platforms. Plenty of maps, models, and thoughts when I’m working on those sites. Blogging takes quite a bit longer, I need a good chunk of quiet time to do this...my kids would say that’s “because I’m a boomer”. Whatever.

QUICK RECAP OF RECENT WEEKS

October DID end up as Portland’s warmest on record, as did September, and August. All 3 were Portland’s warmest. Of course August was also the hottest of ANY month. We ended up with 12 days at/above 80 degrees (yellow outlines below) and even with the sharp change to cooler/wet the last 10 days of the month we STILL ended up about 6 degrees above average!

I had some people ask me either on social media or email if “the rain will ever come back this winter”. Most likely new transplants; the rain ALWAYS COMES BACK. And that happened in late October. That’s why I somewhat ignored those that were complaining about the 4 months of mainly dry weather. Yes, fires were starting to pick up again after the showers in late September, but we avoided a big east wind episode that could have led to lots of trouble. We ended up with close to normal rain by Halloween evening. And sorry about that Halloween soaker; those have been rare lately

WHAT’S AHEAD

The cooler weather and lots of rain hasn’t surprised me at all. But now it appears we’re headed toward much cooler than normal weather next week. If models are correct, this will end up being the most dramatic change I’ve seen in the fall; from 80s to highs in the 40s (or colder?) in just a few weeks.

Tonight we’ve got an atmospheric river setting up across the region. That’s due to a strong westerly jet stream approaching the coastline. This is the view from jetliner altitude tomorrow...about 30,000′ or so

Then Saturday...a 200 mph jet stream right over us!

Then by Monday a deep upper-level trough has dipped south out of Canada and is just offshore. That’s cold. So we get lots of rain through tomorrow night, then showers Saturday, a colder/wet system Sunday, then back to scattered (even colder!) showers Monday.

THE RAIN

How much rain? Models have backed off just slightly the past 24 hours. This will be mainly a “nuisance” rainfall in the lowlands, especially south and west of Portland. A collection of model forecasts

And the highest resolution model available to local meteorologists; the UW 1.33 km WRF-GFS (from the Huskies of course!). You can clearly see a very sharp rain shadow in the lee of the Coast Range. Less than 1″ around Hillsboro tomorrow, but up to 2.50″ central/east metro areas. I could see some water over a few roads if we do get 2.00″ or more in spots. Heaviest rain will be in the evening.

Another view of the heavier rain in the aptly named “Waterfall Corridor” in the Gorge.

THE WIND

A gusty southerly wind will accompany the atmospheric river/pineapple express tomorrow. That’s normal for these events and in this case it won’t be TOO strong. I think gusts 30-40 mph are likely in a few spots anytime tomorrow. Wind will come and go all day, but should be strongest in the evening just before the cold front passes through between 8-11pm. Normally that would just give us some isolated outages, but there’s a complication this time. You’ve probably noticed leaves have been very slow to change or drop off this year, due to the record warm 1st half of fall. So we’ve got a bunch of extra “wind-catchers” on the trees and I can see that adding to the outage count tomorrow. Regardless, especially if you are in a rural area, keep in mind the power COULD go off in your neighborhood tomorrow.

FOX12 FIRST ALERT WEATHER

For over 15 years at FOX12 we’ve used the branding “First Live Local” for our weather forecasts. It’s been time for a change for quite awhile, plus we are now part of the Gray Corporation. It’s nice working for a company that owns lots of TV stations and knows what it’s doing. So, we’ve taken on the First Alert Weather branding that most other Gray stations use. And I think it’s a good change. I’ll admit that sometimes I get a bit lost in the “meteorological weeds” during a weathercast and this will help focus things a bit more with most important information right up front. Apparently you can teach an old dog new tricks...

When a specific day shows up that really sticks out weatherwise (tomorrow?) we’ll draw your attention to it by marking it as a “First Alert Weather Day”. If we do it right, these should be days in which weather will significantly disrupt your plans or day. Tomorrow is a bit marginal for that; we’ll see how many outages we get and whether local flooding shows up in spots. We have specifically avoided using the terms WATCH, WARNING, or ADVISORY because those are used by the National Weather Service. This is NOT a replacement for those official watches/warnings/advisories! You can learn a bit more from this 2 minute video: https://www.kptv.com/2022/11/02/first-alert-weather-new-way-stay-ahead-weather/

COLDER WEATHER AHEAD

That cool upper-level trough I mentioned earlier drops down along the West Coast and sits there Monday through Wednesday. 850mb temps bottom out around -4 to -6 C during that time; unusually cold for early November. Typically that’s around 1,500′ to 2,000′ snow levels. That’s with onshore flow. But during that time next week, we get a cool north or northeast wind as a cold arctic high pressure area will be sitting over SW Canada.

The low level airmass will also be unusually cold, including north of us. Here’s a Wednesday morning forecast temperature map; keep in mind anything under about -17 (C) on this map is 0 (F). Very unusual to have temps around zero degrees in early November just north of the U.S. border.

With that chilly air filtering south, snow levels COULD dip all the way to sea level. But at the same time it appears we’ll likely be dry from late Monday through at least Wednesday next week. So I’m thinking sticking snow down to sea level is unlikely Monday through Wednesday. It’s a bit too warm still Monday morning, but then when it WILL be cold enough Tuesday/Wednesday we’ll probably dry out. Now later next week, we could see moisture return. Each model is different with timing so we’ll see what happens. Remember that it IS possible to get snow or freezing rain as we head into mid-November. In 2014 freezing rain made it all the way into the central part of the metro area on the 13th!

That’s it for now. Our forecast looks like this...with high temperatures 10-15 degrees below normal Monday-Thursday next week. Stay Tuned!

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