A Sunny & Warm Weekend; Above the 1,200′ Elevation

January 27, 2019

2:30pm Sunday…

This weekend has been very challenging for forecasters; a classic and very strong wintertime inversion is in place over the most populated parts of Northwest Oregon and Southwest Washington.  The result is a very cool and gloomy day in the lowlands

live cam portland

We expected a mix of fog and sunshine, but assumed the strengthening sunshine would be just enough to “mix out” the lowest elevation moisture and overnight cooling.   “Mix out” means some of the warm and very dry air overhead would mix down into the lowest elevations where many of us live.  Instead the fog/cloud layer is holding strong.

We have a VERY warm atmosphere (for January) overhead.  Take a look at the mountains and beaches.  Temps in the 50s, and a few spots in the Cascade foothills have even made it into the 60s the past two days

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If it was mid-late February (3 weeks from now), we’d see highs make it into the low-mid 60s in this weather pattern in the lowlands and it would feel like spring.  Instead the long nights are still just long enough to keep the chilly air in the lowest elevations locked in place.  Take a look at the satellite image from midday

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Notice you don’t have to go far from the metro area to find bright sunshine.  West of Banks along Hwy 26, anywhere along the coastline or in the Coast Range, or anywhere east of about Corbett in the Gorge.  The Cascades are enjoying blinding sunshine right now.   Both Bend and Redmond have hit at least 66 degrees this afternoon!

What about going uphill?  Check out the spine of Chehalem Mountain sticking out.  That plus the current view from our Skyline Camera

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tells me the fog/cloud layer is about 1200′ thick or so.  Above that elevation you pop out into sunshine.  Unfortunately the vast majority of us west of the Cascades live below that elevation.  This type of forecast (when the fog/clouds break up) is always difficult because models don’t handle the lowest 1,000′ of the atmosphere very well.  In December and January we need some sort of wind, preferably a dry east wind, to blow the fog away and mix that drier air down to sea level.  In February the increasingly strong sun can do it alone.  But in the last 5 days of January it was a tough forecast.

I can GUARANTEE you bright sunshine tomorrow though!  Why?  Cool/dry Canadian air is pushing into Eastern Washington as a strong arctic high surges south into the Great Plains.  By daybreak a strong and dry easterly wind will already be blowing through the Gorge and spreading into the metro area.  If we get any fog/clouds tomorrow morning they will be gone quickly.  Replaced by a windy and sunny day.  The WRF-GFS tends to overdo the metro area wind speeds with east wind, but I think gusts 25-40 mph are likely by midday Monday.

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We’ll get the sunshine and warmer temps, but the wind will make it feel chilly in the shade and early/late in the day.  Find a spot facing south and protected from the wind for lunch Monday; then you should have a great time!

Our next good chance for rain is Wednesday night or Thursday.  More on that in blog post this evening… tomorrow.

Chief Meteorologist Mark Nelsen