MISSOULA — We've seen some serious warmth this season and we can attribute that to a couple of really strong ridges of high pressure and a fairly persistent southwesterly flow.
NWS Missoula Meteorologist Dave Noble says, "This pattern has historical precedent, too, notably during winters like the La Niña 1933–1934, which was the warmest Dec–Feb period on record locally". That time frame even featured robins overwintering & pansies blooming - much like what we’re seeing now.
He continues, "In these cases, a La Niña or La Niña-like Pacific favors a strong, extended jet stream out of Asia, while cold anomalies can exist over Alaska and northwest Canada. That configuration helps anchor a deep trough over the north-central Pacific and maintains a quasi-stationary southwest flow into the West, funneling mild air and occasional subtropical moisture inland. The result is prolonged warmth, higher snow levels, limited valley snow, and strong ridging that can persist for days to weeks, something that’s relatively uncommon, but well documented in the climatology".
"Take a look at the satellite loop over the eastern North Pacific today... first thought this morning was Groundhog Day. Rinse and repeat. That upper trough is HUGE north and west of Hawaii"!
Noble says, "What’s especially interesting is that while we’ve seen early-February ridges like this before, most of those years had snow on the ground, which helped maintain stronger cold pools. In February 1934, there was essentially no snow cover and Missoula warmed to 58°, a useful historical parallel to keep in mind. A caveat is that this 2026 ridge is a lot warmer than the 1934 case.
The largest and longest ridge (highest 500mb heights) in the month of February was Feb 1-8, 1954. The warmest 700mb temperatures in the Spokane soundings were 4.9 C on Feb 7, 1954... that's 41° F at approximately 9,000 feet"!
