Portland Monday weather: Low temps threaten icy commute

So much for that early spring.

Snow and ice are expected to return to Portland Sunday for the second time this winter, the first sighting of the white stuff in the city since Christmas.

The National Weather Service says about an inch of snow could fall across the metro area through the day Sunday, possibly starting as early as morning.

Lower elevations will see a rain-snow mix turning to all snow, said Matthew Cullen, a National Weather Service meteorologist, as moisture passes through the area and colder air moves in, he said.

Expect to see a 1/2 inch to an inch across Portland's lower elevations, Cullen said. "As you get up to the higher hills - the West Hills and higher spots in Southwest Portland and Mount Tabor, those spots could be in the 1-inch range," he said.

Above 500 feet, as much as four inches could fall, he said.

Wondering how we keep the snowfall lined up for the different locations & elevations? Here's a map created this afternoon for Sunday's snow amounts.



As always, visit https://t.co/VCWxwcb3Nx for the forecast for your exact location.#pdxtst #orwx #wawx #pdxsnow pic.twitter.com/D5Ivk1LnI6 — NWS Portland (@NWSPortland) February 18, 2018

Latest on Sunday's snow: From metro Portland north to Kelso/Longview: low-elevation snow expected on Sun morning (generally between 5-8 AM), then again Sun evening. Total accumulation at valley floor: Up to 1 inch. Higher amounts (1-4 inches) likely in higher elevations. #pdxtst — NWS Portland (@NWSPortland) February 17, 2018

Transportation officials are warning about the impacts of an overnight Sunday freeze on Monday commutes.

John Brady, a spokesman for the Portland Bureau of Transportation, said city crews will be out starting Sunday morning to pre-treat roads with magnesium chloride, a deicer, and could use road salt if streets are particularly wet, because salt works better on wet roads.

Temperatures overnight Sunday into Monday morning will be in the mid-20s, Cullen said. "It likely will freeze overnight," he said.

Monday will be above freezing but not particularly warm - a high between 36 and 38 is expected. While icy roads will be worst before sunrise and improve throughout the day, Cullen said shady and sheltered roads could stay slick through the day.

Any moisture lingering on roads will freeze again Monday night, when temperatures are expected to drop to the low 20s. But Cullen said Monday morning - the President's Day commute - "is the primary concern."

Winter Weather Travel Advisory:

Presidents' Day may get off to an icy, slick start and PBOT urges Portlanders to use caution when traveling https://t.co/iI9wyYDrUm #pdxtraffic #pdxtst #pdxsnow pic.twitter.com/WE7CuMJ1nh — Portland Bureau of Transportation (@PBOTinfo) February 17, 2018

-- Rob Davis

rdavis@oregonian.com

503.294.7657; @robwdavis