As expected, the innocuous, non-sticking snow that was so persistent yesterday quickly ballooned into a full-fledged, crippling lowland snow event last night as heavy band of snow pushed through the Portland metro area. I was out and about with some friends, and it was refreshing to see very few cars out on the roads, as people had obviously learned their lesson from past Portland snowstorms and heeded the Winter Storm Warning put out by the Portland National Weather Service forecasters. Speaking of the Portland National Weather Service, I firmly believe those folks are some of the best forecasters you’ll find anywhere in the country – I’m continuously amazed by both their thorough understanding of the local weather features of the Pacific Northwest and synoptic meteorology in general. And they are super nice people to top it all off!
In addition to strolling ’round downtown, we brought “Hubert” the snowman into existence, and with subfreezing temperatures, the snow was still around by sunrise. Areas in the sun saw their snow quickly melt as the day went on, but there was minimal melting in shady spots, as temperatures only rose into the mid-upper 30s today.
Like last night, tonight’s our snow will be brought to us via a low making landfall to our south (probably near Newport, OR) while spinning moisture into the area, giving us sub-freezing temperatures and snow. However, unlike last night, we aren’t looking at a secondary “follow up” trough right on the heels of this low, fostering frontogenesis and the creation of a narrow but intense band of snow. The Portland NWS forecasters mentioned that tonight’s system has less “moving parts” than last night’s system, and that makes for a significantly easier forecast.
By the way, the large-scale setup that we have is a textbook setup for lowland snow. That huge, anomalous ridge near 150o west forces the jet stream way up into Alaska and the Yukon, and as a result, a giant trough forms right over us, allowing arctic air to surge into the Pacific Northwest. Meanwhile, a shortwave (less than several hundred miles long) trough slides southward from the Yukon over the coast of Vancouver Island and intensifies as it picks up moisture over the relatively warm Pacific. If this shortwave makes landfall just to the south of your area (as tonight’s will), you get both a reinforcing shot of cold air and plenty of moisture. And we all know what happens when you combine those two things!
The storm is now close enough that we can see the precipitation on radar. A giant blob is currently moving ashore the southern Washington Coast, with particularly heavy precipitation occurring near Westport.
This blob will continue to track southeast as the evening goes on. Now that we are so close to the event, I believe the best strategy is just to keep an eye on radar, compare it to any models that come out, and interpolate the precipitation to estimate where it will hit and what time it will do so.
The Forecast
- I’m expecting 1-3 inches for the Portland metro area, all the way down to sea-level. Due to the showery and somewhat convective nature of this precipitation, some areas could receive 5-6 inches, especially areas above 500 feet. Keep your eye on the radar to get an idea of where the heaviest snow is.
- Though we’ve already seen a few flurries this evening and will continue to do so, steady, accumulating snow will occur after 9-10 pm for the Portland metro area. For Salem, the heaviest stuff will begin shortly before midnight, and the Southern Willamette Valley will see their heaviest snow beginning very early Thursday morning.
- Snow should begin to lighten up after 2 am for the Portland metro area, but we may still see some flurries by daybreak as the upper-level trough that is associated with the surface low making landfall on the Oregon Coast sits over the area.
- Any snow that falls on untreated roads will stick, so prepare for a slick commute if you must go to work tomorrow morning. However, the snow will quickly melt as the sun angle rises, and sunny roads will be fine for the commute home. However, temperatures will only reach the mid-upper 30s, so roads in the shade will see very little melting and will still be dicey.
- Finally, we’ll see a hard freeze tomorrow night with temperatures plunging into the low 20s. The main roads will be in much better shape for Friday morning’s commute, but shady side roads will be extremely treacherous.
Links
Portland NWS: http://www.weather.gov/pqr/
Portland NWS Twitter: https://twitter.com/NWSPortland
UW Radar loop: https://www.atmos.washington.edu/weather/radar.shtml
Reports
If you have any snow reports, please write them in the comments below! The folks at the National Weather Service like to have as many reports as possible when tallying up snow totals. Please include your elevation, location, and time of report!
Thanks, and enjoy the snow!
Charlie
