A Winter Storm Watch Monday through Tuesday morning for elevations near and above 1,000 feet for sticking snow. A Gulf of Alaska cold front arrives early Monday morning with falling snow levels during the day and into Monday night. The map below shows (in blue) a Winter Storm Watch up for the Coast Range, Cascade foothills and the Cascades starting Monday morning through Tuesday morning. Snow amounts are expected to be 4-8” near and above 1000 feet and 8-16” near and above 2,000 feet in the Cascades. Weather models continue to show up to .50” of possible liquid moisture with the storm front arriving from the northwest. Winds will be west to northwest and breezy to gusty Monday and Monday night 15-30 mph with higher gusts to 40 in the Cascades and along the coast.
Here is my valley snow timeline:
MONDAY 4:00 PM: All rain continues below 1,200 feet
MONDAY 6:00 PM: Snow level lowers to 1,000’. Snow amounts in the hills may reach 4” or more through early Tuesday
MONDAY: 8:00 PM: Snow level 500 feet. 3” or more may fall through early morning.
MONDAY: 10:00 PM: Snow level lowers to 200 feet. 2” or more may fall through early Tuesday.
Portland and lowest elevations still expected to hold near 34 degrees with snow showers in the air, but roadways staying wet. Obviously this is a close call, and freezing temps at sea level after midnight into early Tuesday morning are possible, as are light accumulations near sea level. A west wind has a good chance of holding ground temps at 34 as forecast below 200 feet and also along I-84 in the gorge. Weather models show good instability, meaning heavy snow showers or snow rates at times are possible, which can lower temperatures and produce scattered areas of snow accumulation at sea level, meaning downtown Portland. All quickly goes dry Tuesday morning with partial clearing expected. Look for new Winter Advisories to be issued for low elevation snow chances Monday night.