A Frigid Night & A Cold Winter

January 12, 2017

10:30pm Thursday…

It’s been a long and disruptive week for many of us.  Lots of you have missed days of work and the kids have been out of school.  Meanwhile transportation/utility/emergency/police/media folks have been working overtime.  Today is day #12 for me.  But I actually have two days off!  Looking forward to sitting around doing nothing important for at least that 1st day…

Tonight we have perfect conditions for the coldest night in at least 3 years, and possibly much longer.  Here is my forecast for the metro area:

fcst_tonight_metro

If low clouds or thick fog develops in any one spot, that could keep the temperature 5-8 degrees warmer.  As a result the low temperature forecast is tough in a situation like this.  PDX is right at the edge of the “well-mixed” east wind zone.  Near the Gorge the wind keeps the air mixed up all night, which keeps low temps up around 20 degrees.  Away from that area temps can really drop off (as you see in the map above).  IF we hit 12, that will tie the low during the 2013 cold snap.  IF we get down to 11, it’ll be the coldest temp since the December 1998 arctic blast.  If we somehow get down to 10, it’ll be the coldest in 28 years…since the February 1989 arctic blast.  Hillsboro has already hit 9 as of 10pm!  If Hillsboro gets below 9, that will be the coldest since 2009, and a 6 would be the coldest since 1998.

The next few days we are heading into a cold version of our typical wintertime inversion pattern with the mountains warming up and valleys remaining cold.  We may see increased low/clouds fog since we have a bit of a moisture source too (melting/sublimating snow).  But there won’t be any dramatic change through Sunday/Monday

It turns a bit tricky briefly later Monday as we go into a mild/wet period for three days.  Tuesday-Thursday next week feature a series of warmer than normal systems (first time in many weeks!) flying across the Pacific Northwest.  As we transition into that pattern, there is the possibility of brief freezing rain later Monday or Monday night. All models show the south wind quickly overwhelming the low-level cold air in a situation just like Monday, December 18th.  But the ECMWF gives us some freezing rain Monday night and holds the cold air in the Gorge longer due to south wind holding off until Tuesday AM.  If this is the case, we would have an ice storm in parts of the metro area Monday night and a big ice storm in the Gorge…we’ll sure be keeping a close eye on this one.  Note the ice accumulation forecast from that model:

ecmwf_frz_rain_portland_20

I just checked some temperature numbers this evening and they were surprisingly cold.  Check out the first 12 days of 2017:

marktemp_last13days

The first 12 days of January have been the coldest since 1979…yes, that’s the coldest start to January in 38 years!  For those of you that were around then, what you probably notice is that it hasn’t been EXTREMELY cold this time, but it has been consistently cold.

coldjanuarystart

Combine the chilly December with this, and Portland is enduring the 3rd coldest start (first 43 days) of winter!  Winter would be December 1st-February 28th of course. What a HUGE change from the past few winters.

Looking ahead, we have a mild and rainy week ahead starting Tuesday.  I’m confident we will see at least localized flooding Tuesday/Wednesday with the sudden low-elevation snow melt plus heavy rain.  The ECMWF has been showing 2-3″ in the valleys Tuesday-Thursday which isn’t a big flood by any means, but we’re definitely going to see some issues.  I bet we get some mudslides too due to all that rain on frozen/thawing ground.

Enjoy another snow day kids, and for you parents, we’ll try to get those kids out of the house on Tuesday…

Chief Meteorologist Mark Nelsen