Cold Air Is Here…Freezing Rain Threat Decreases

November 29, 2014

The chilly air has moved in…we are 31 at 9pm in Portland compared to 46 just 24 hours ago! East wind is just starting up in the Gorge and that wind will arrive after sunrise for most of us.

As a result of clear skies, low relative humidity, and light wind, temperatures are dropping quickly. We’ll end up around 20 in the coldest parts of the metro area and 20s everywhere else. Not quite as cold as two weeks ago, but close.
FCST_Tonight_Metro

No changes in tomorrow’s forecast with sunshine, a gusty east wind, and chilly temps.

But Monday is sure looking different as of this evening’s model runs.  The last three model runs have been suppressing the precipitation farther south, decreasing the intensity, and slowing it down.   If current runs are correct, much of the day could be dry in the metro area and/or rain will fall with temperatures above freezing.  Take a look at our RPM 7am Monday:

MarkRPM_Cloud_Snow_Fcst and 11am with precipitation just arriving.MarkRPM_Cloud_Snow_Fcst2 That’s too late to get freezing rain with marginal temps and a dying east wind.  The reason the east wind dies off more quickly this time around is because the northern stream of the jet is sending a weather disturbance east across southern British Columbia and Washington.  Flow from the WNW up at 700mb and higher tends to form lee-side troughing on the east side of the Cascades.  This always happens and in this case high pressure weakens quickly over the Columbia Basin on Monday.  Pressure gradient is down to just 2-4 millibars easterly by Monday evening through the Gorge.  So one more reason it won’t be too hard to warm it up above freezing Monday morning.

So does this mean no freezing rain Monday?  No, but the chance of it occurring has dropped quite a bit.  Of course tomorrow’s model runs could bring the rain farther north again, but the trend is usually your friend and the trend since 12z has been to keep it farther south.

By the way, the last 24 hours was a little bit of a disappointment up on the mountain.  At least to me.  I was hoping we could over-achieve and get a foot or more.  Timberline and Meadows had 8-10″ and Skibowl 6″,  But we need a lot more and I don’t see that coming.  Mt. Bachelor is the only ski area in the state that has been able to offer several lifts for Thanksgiving Weekend skiing.  You can see why; they have more than two feet on the ground.  I don’t see a significant snow storm for Mt. Hood in the next 3-4 days at least so next weekend MAY not be much better.

MarkSnow_MtHood_Totals

Chief Meteorologist Mark Nelsen