Let’s just dive into what’s going on; plenty of weather action to cover in the days ahead.
We have transitioned into a “chilly” airmass this morning, with snowflakes seen in the air down into the hills. At this time sticking snow appears to still be above 1,500 in most places, nowhere in the metro area.
Take a look at this beautiful satellite loop from the new GOES-17, soon to become GOES-WEST. If you’re on a cell signal you might want to skip it; even on my slow home internet it takes quite awhile to load: http://rammb-slider.cira.colostate.edu/?sat=goes-17&z=4&im=12&ts=1&st=0&et=0&speed=130&motion=loop&map=1&lat=0&opacity%5B0%5D=1&hidden%5B0%5D=0&pause=0&slider=-1&hide_controls=0&mouse_draw=0&follow_feature=0&follow_hide=0&s=rammb-slider&sec=full_disk&p%5B0%5D=geocolor&x=11798&y=2087
There is a cold front offshore and then you see all those “streamers” coming off the British Columbia coastline? That’s cold arctic air pouring out over the ocean. That cold air picks up moisture over the “warm” ocean; those cold showers then move inland over us this evening and overnight. Very similar to Lake Effect Snow back east.
Over the next 48 hours a very cold upper-level trough (The Itty-Bitty Polar Vortex) drops south just offshore, moves down the Oregon Coast, and moves across the California/Oregon/Nevada region. Slideshow gives you the general idea, but this is an unusually cold one
WHAT I’M EXPECTING IN LOWLANDS OF WESTERN OREGON & S.W. WASHINGTON
This includes all I-5 cities from Longview to Eugene and coastal towns as well
THIS EVENING / TONIGHT
- Showers pick up and mix with snow as temperatures drop
- ANYONE could see a light accumulation after midnight, unlikely before that time in lowest elevations. It won’t be cold enough.
- We’re talking off/on showers so there isn’t a whole lot of moisture, tough to get significant snow in this pattern
MONDAY A.M. COMMUTE
NOTHING TO 1″ SNOWFALL, UP TO 2″ NEAR/ABOVE 1,000′
- Anyone in these areas could see up to an inch on the ground (likely the wet/slushy stuff), but since it’s showery some of us will wake up to nothing or just the “white on barkdust” stuff.
- Some school delays are likely, and maybe even closures, especially in hilly areas
- Some roads will be slushy or have light snow on them, especially in hills.
- MAIN HIGHWAYS/FREEWAYS WILL MOSTLY LIKELY BE CLEAR FOR A.M. COMMUTE
- I doubt we’ll see “frozen roads” where showers fell and then skies clear and wet roads freeze
DAYTIME & EARLY EVENING MONDAY
- Continue your normal Monday life…well…it’ll be Monday after the Super Bowl, but you know…
- Roads/highways all clear with high temp around 40 in afternoon, slushy snow left on roads up near/above 1,000′
- Scattered mixed (rain/snow) showers along with sunbreaks
MONDAY NIGHT & TUESDAY AM COMMUTE
- We either just clear out and wake up to mainly dry roads Tuesday…OR
- We do it again if some light snow showers appear during the night with spots of icy roads
TUESDAY & WEDNESDAY
Sunny and chilly, hard freezing at night and temps around 40 both afternoons
COLUMBIA RIVER GORGE, NORTH-CENTRAL, & NORTH-EAST OREGON
There is more moisture to work with, so you folks in the Eastern Gorge and east will see a significant snowy period tonight through Tuesday morning/midday. An upper-level low moving through southern Oregon can be a perfect setup for a snowstorm for many of you.
2-8″ of snow likely during this period and cold/dry arctic air pours south through Eastern Washington and gets overrun by moisture moving up from the south.
Trust me, I looked at EVERYTHING this morning. The big picture is that we’re entering an unusually cold period the next 10+ days. Remember just a week ago it looked like the big upper-level ridge would be quite close to the West Coast? Instead it is going to sit in the Gulf of Alaska and allow cold upper-level troughs (and wet/white surface low pressure systems) to slide down the back side through Western Canada and into the Pacific Northwest. This IS the perfect setup for snow & cold in the Pacific Northwest. Who thought in a (very weak) El Nino year we would get a cold/snowy pattern in February after a very warm winter? Location of that ridge is everything!
A significant change from 24-36 hours ago is the location of a deformation band feature setting up on the north side of the upper-low as it tracks across the region through Tuesday. Models are showing that develops mainly to our east (north-central/north-east Oregon) tomorrow and Tuesday. That’s why my snow forecast for the metro area and western valleys is so low. Not a single morning model is forecasting significant snowfall in the next 36 hours for us. Check out the HDRPS, ECMWF, WRF-GFS, NAM-WRF, & RPM. I see plenty of NO SNOW gaps showing up in the lower elevations, raising my confidence that this isn’t a widespread disruptive event for Monday morning’s commute.
The GEM & ECMWF are still keeping significant cold easterly flow away from us tomorrow and Tuesday. ECMWF just gives us a northerly wind drift. Most likely the other models are overdoing the cold air pouring south into Eastern Washington.
One significant concern I have is the ECMWF giving us more wrap-around snowfall tomorrow night, implying that 1-2″ could fall in western Gorge and east metro area. I’ll keep an eye on that, but for now pretty much focused on the next 24 hours for now.
Assuming skies clear out Wednesday and Thursday mornings, we’ll probably see our coldest temps of the winter season. Not much east wind from the Gorge plus very low dewpoints = low-mid 20s even in urban areas. Probably upper teens outlying spots. That’s sure going to slow down plants that thought it was almost spring!
Another system drops in Thursday evening and lingers maybe through Saturday. This will be another messy forecast. If enough cold air is over us this could produce lowland snow again.
I’ll be on-air tonight at 5pm, then 8-10pm on FOX12PLUS, then 10-11:30pm back on FOX12. New models will be coming in during those 8-9pm shows so it’s always fun to relay that additional info.
During this cold/snowy period make sure you LIKE me on Facebook: https://www.facebook.com/MarkNelsenWeather/
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I tend to post more frequent updates there, but this is always the “long-form” weather.
Chief Meteorologist Mark Nelsen