***Tuesday Afternoon Update*** We’re still expecting a significant storm Saturday night through Sunday. Today’s data is suggesting slightly warmer air aloft arriving Sunday. The change to sleet and possibly freezing late weekend remains a possibility (esp at the coast). We’re still many days out, and lots of time to iron out the fine details. Stay tuned.
It has been a strange winter so far. To this point in the season, Portland is still about 5″ above normal in snowfall, which may seem odd to you. The reason, most of it came in November. The biggest storm was only 8.3″, and that was way back on November 20th before Thanksgiving. As of late though, we’ve been dealing with smaller snow events with many rain/snow/ice lines. Both December and half of January only yielded 12.9″ of snow in Portland, which combined, is less than the entire month of November.
Outdoor winter enthusiast have been asking, Where’s the snow? If you’re a skier, snowboarder, or someone who likes to ride snow mobiles, you’re probably going to like the forecast. Only fly in the ointment is the possible change to sleet late in the weekend.
The pattern will stay quiet through Thursday. The first of two storms will arrive Friday. That one will not be a blockbuster, but should be enough to bring the plows out.
The second storm should bring a longer duration, and potential for heavier snow. The time frame we should highlight is Saturday night through Sunday. On paper, it looks to be the biggest of the season so far. It’s still pretty far out, so we’ll need to see how the forecast evolves in the coming days. A change to sleet is on the table too. Here’s an early look at timing.
5 to 6 days out, many questions remain. We still need to nail down the strength, track, and if there will be any mixing. A change to sleet and freezing rain is a real possibility esp south and coast. Forecast modeling has remained consistent since last week sniffing out the weekend storm. You’ll notice a model spread (which is expected) suggesting the surface low track. Here’s 21 member GFS (US Model) low locations valid 1PM Sunday. Each one of those L’s is the forecast storm center track.
Here’s the European Model and its ensemble 51 member low locations valid same time 1PM Sunday.
Lets go over the mixing potential. This could be one of those storms where we get a solid round of snow followed by ice pellets. Here’s one forecast model suggesting that scenario. Here’s a look at ground level temperatures in degrees Fahrenheit. Note most of the area is expected to be well below freezing.
From the same model, here’s a sample of temperatures in degrees Celsius at around 5000 feet in elevation. This equates to temperatures in the 40s in degrees Fahrenheit at around 5000′.
This scenario would result in snow flakes falling high up, melting and becoming raindrops, and then freezing to ice pellets at the ground level. That’s why sleet, and possibly heavy sleet is on the table with this one.
So what can we take away from all of this on a Monday evening?
- Plan on snow Friday with some accumulations.
- Saturday being the best day of the weekend for travel and outdoor plans.
- Big storm possible Saturday evening through the day Sunday.
- That storm could bring heavy snow to the entire area
- A change to sleet and possibly freezing rain
- Long duration
- Possibly the biggest of the season so far
- Strong gusty winds possible
Stay tuned in the coming days. I’ll have updates all week.
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