The Mother of All Convergence Zones

Heavy snow began falling in the Seattle area around noon on Dec. 18, 1990, as a strong Puget Sound Convergence Zone developed. By the end of the day, Seattle was buried in 12 inches of snow.

As colder air poured into the region behind last Monday’s windstorm, there was speculation that a strong Puget Sound Convergence Zone could form over the Everett area and head south, whitening cities along the way with several inches of snow before drifting off into the Cascades. Such a scenario, of course, never materialized—with just light snow showers affecting the region later that night.

22 years ago, it was a much different story.

Tuesday, Dec. 18, 1990, began on a relatively calm note in Seattle, with temperatures at the stroke of midnight resting in the low- to mid-40s under overcast skies. To the north, however, there was trouble brewing—with arctic air from Canada slowly sinking toward the Washington border.

As night turned to morning, the cold air began spilling into the state, dropping the temperature around Puget Sound into the upper 30s. Then, right around lunchtime, a powerful—and unpredicted—Puget Sound Convergence Zone formed near Lynnwood, and all hell broke loose.

Heavy, wet snow fell in droves as the Convergence Zone roared south into Seattle in the early afternoon, blanketing freeways and blinding motorists. Accompanied by howling northerly winds, the Zone peaked in intensity right over downtown—dumping a foot of snow in the heart of the city. As if that weren’t enough, lightning flashed overhead as peals of thunder boomed from the sky—treating stunned Seattleites to a spectacular display of thundersnow. (Thundersnow—thunder, lightning and snow, all rolled into one—also hit the region on Mar. 7, 2002 and Dec. 18, 2008, courtesy of the Convergence Zone.)

The Zone also spread its wrath to the other side of Lake Washington, dropping up to 14 inches of snow in places like Bellevue, Kirkland and Redmond as the afternoon wore on. The heavy snow caught the entire region off guard—so much so that over a thousand children in the area, trapped at school when the storm hit, were forced to spend the night in their classrooms.

Eventually, the Zone began fizzling as it meandered south of Renton, bringing only 2.5 inches of snow to Sea-Tac Airport. In the wake of the blizzard, however, the mercury plummeted as cold Canadian air settled in. By 11 p.m., the temperature at Sea-Tac stood at 21 degrees, with bitter north winds gusting to 43 mph. In Bellingham, it was even worse, with a 16-degree temperature and winds blasting above 60 mph.

The biting cold would go on to grip the region for days, with Sea-Tac staying below freezing until Christmas Day, when the temperature mercifully rose to 36 degrees—only to drop back into the 20s once more near the end of the month. Needless to say, the plethora of snow that buried the area on the 18th remained on the ground for more than a week—cementing the December 1990 Convergence Zone’s place in Seattle lore.

And making it the gold standard by which all future epic snowfalls are judged—the mother of all Puget Sound Convergence Zones.


  1. nice post, well written! I discovered your blog a couple of months ago. I think this is my favorite post so far!

    • Thanks, Jon! My best guess for January is that we’ll have a couple more brushes with snow (similar to last week and tomorrow), but no serious arctic air to give Seattle a bona fide snowstorm. That said, I hope I’m wrong!

  2. Just realized the “anniversary” is this Wed, 12/18/13, and I required some validation in regard to my trauma and found this article, thank you! Reposted on my Facebook page ha! I was trying to get home from Northgate to 405 and 520 in Bellevue mid day when snow started and remember friends trapped in parking garages downtown in the gridlock for hours. My husband abandoned his car on I-5 like many others just to get home. I didn’t get home until the next day, my snow boots etc waiting on the dining room table as the forecast was for snow the NEXT DAY! I still remember listening to a recorded weather forecast on the radio as I was sliding off the road while at a stand still, telling us minimal precip that afternoon and snow the next day. Jeff Renner, why are you still working. 😛 😛

    • Crazy story—the forecast really was way off that day. Talk about being in the worst possible place too. Thanks for sharing your memories of that epic (and not necessarily in a good way) day!

  3. Ahh yes, I remember this event. I was attending Bryant Elementary in North Seattle and remember the snow just coming down in buckets! I luckily lived only a few blocks away but I did hear of classmates spending the night in the school. My dad was stuck in the bus tunnel downtown, until he miraculously caught his bus and she somehow guided that thing all the way to Wedgwood. The next day we had to catch a train and my cousin was the only that could take us since all the taxis were caput. It was amazing. I would love to see a dump like that again. Although now, I live in Mount Vernon, and we had a similar event 2 years ago in February when we had nearly 2 feet fall under one cell. Never have seen anything quite like it!

    • Great story! Can’t imagine what it would have been like to sleep at school. (I was in a.m. kindergarten then, so I fortunately got out before the storm hit.) That’s right, Mt. Vernon got really got blasted in February of ’11. Sounds like lightning has struck twice for you!

  4. Hey, Justin, you bring back great memories for this Redmond family. On that day while August 23rd lingered in his classroom in Snoqualmie, February 25th made a foolish trip to a bank in the heart of Redmond, only too be stuck with two wee ones, your bud January 7th and the younger February 21st. They ended up hitching a ride up Education Hill lest they walk the 2.5 miles in their tennis shoes. As you say, it is your generation’s memorable monster storm. Merry Christmas! Drop by on 158th for a meal sometime.

    • What a tale, August 23rd! If only February 25th had realized what was coming–thankfully none of the gang had to hike back. Merry Xmas to the whole crew! July 5th would love to see you guys sometime.

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