We have one more round of freezing rain and snow in the Columbia River Gorge this weekend before a dramatic warmup (even IN the Gorge) early next week.
Here are the highlights:
- Dry tonight, not much happening except east wind continues to increase in the Western Gorge. Gusts 60+ mph are likely through midday Saturday.
- Light rain showers arrive in the metro area midday tomorrow and continue through Saturday night. It might even turn to steady rain since this next system is a bit wetter than yesterday’s.
- It’ll be at or below 32 degrees during that time from Corbett eastward into the Gorge.
- Freezing rain (glaze ice) again from that area out to around Bonneville.
- 1-3″ snow is likely Saturday afternoon through late night from Cascade Locks to The Dalles.
- I-84 might be okay during the daylight hours then freeze up around sunset since the air mass will be slightly warmer this time (by all of 1-3 degrees).
- The Gorge should be clear (temps 35-40) by midday Sunday. Then a west wind Monday means a jump to around 45-50 degrees!
- Monday & Tuesday will be very mild with high temps into the 50s
Last night’s system knocked down the cold air a bit that’s stuck in the Columbia Basin, but not much. The cold pool is still about 3,000′ thick or so stacked up against the east side of the Cascades. The pressure gradient from Troutdale to The Dalles dropped as low as 4 millibars this morning, but has increased dramatically the past 6 hours to over 8 millibars again! This is maintaining a cold flow of air from east of the Cascades westward into the Portland metro area. Notice PDX made it to 42 today, but Eugene was a “subtropical” 53!
The approaching splitting system sure doesn’t look impressive, but it is a little wetter than yesterday’s system. Forecast soundings definitely say snow from the central Gorge eastward to The Dalles. The cold pool is 3,000′ thick and the actual snow level is around 3,000′, so that means flakes survive all the way down.
West of Bonneville the cold air thins dramatically, only around 1,500′ thick by the time it passes over Crown Point. So just freezing rain (again) in those areas from tomorrow afternoon through early Sunday morning.
Let’s look farther ahead…
All models in general agreement with a mild and wet system over us Monday and Tuesday, then a sharp cold front for Wednesday morning at the latest.
Behind that cold front, we get into the classic “cold showers, how low does the sticking snow go” pattern. So I’ve added the obligatory snowflake to the 7 Day forecast for Wednesday night and Thursday morning. Rarely does this pattern give us anything other than snow in the air and brief AM sticking snow in the lowlands, but sometimes we do a little better than that. We probably won’t have a really good idea until at least Tuesday night as models key in on smaller scale features. This is quite similar to the event in December that brought some morning snow to Portland’s West Hills and a dusting all the way down to sea level in spots.
Beyond Thursday it gets real interesting…
Earlier runs of the GFS had shown us drying out on Thursday with just a cool and dry air mass through Friday. The 12z ECMWF decided to bring one more system down the coastline Friday for very cold rain and snow in the hills. Now the 00z GFS has hopped onboard that idea bringing another wave of moisture south later Friday.
What’s going on? Models are having big issues deciding how close to build an upper level ridge to the coastline in the 7-14 day period. If it builds real close to us, then mainly dry and fog/east wind. If it’s a little farther offshore, weak and cold systems can drop in over us. If it’s out around 145W or farther, that’s the perfect setup to “open the backdoor” for an arctic blast to move south. Here’s an excellent example of the unknowns right now, the 18z GFS ensemble chart for 850mb:
Look at the range on Day12! The operational GFS was +9 (ridging quite close to us). The warmest member was +13 and the coldest was -20 (bitter cold arctic blast). Wow…the 12z ECMWF solutions were quite a bit closer:
Although maybe 5 of the members were cold enough for snow, the general theme seems to be for ridging to get a bit closer (warmer). Hmmm, I think we don’t really know yet. Of course the 00z GFS just came out with a very cold forecast and a nice arctic outbreak around Day 10 (a week from Monday), but is it just one of the cold members? We’ll find out soon when the chart comes in within a half hour.
10:02pm Update…and here it is!
Chief Meteorologist Mark Nelsen