Some Cold Weather Stats

December 10, 2013

The bulk of our cold spell has passed, in fact we climbed above freezing for the first time in 5 days today.  Lots of 34-37 degree temps.  Tomorrow should be a little warmer with an east wind and afternoon sunshine.  Good time to check out some stats.

So how did our cold spell rank?

Mark_Christmas_DecemberStats

Definitely the coldest in the metro area since at least 2009.  I noticed Hillsboro, Portland, Aurora, and McMinnville were the same or colder in December 2009.  Troutdale hasn’t been this cold since the 2004 ice storm.  It appears the 14 degree reading in Downtown Portland was the coldest since 1990.

Once you head out to the coast or down the valley, it became a more historic cold spell.  Tillamook was colder in 2009, but Newport hasn’t been down to 18 since 1998, and Astoria hit 13, the coldest since December 1990. Salem’s 8 degree reading was the coldest since 1990 too.  Eugene’s amazing -10 was the coldest since 1972.

If you’ve been in our area a long time you might think it was a big cold spell, but not THAT bad.  I think I know why.

1.  We had very little of that strong east wind we often see in these cold spells.  Only Friday was windy, then it went calm.

2.  Daytime highs were all very reasonable…28 or higher in Portland each day.

Mark_Christmas_DecemberStats2

Compare this cold spell with 1989, 1990, or 1983.  Those are featured a raging east wind and bitter wind chills.  In February 1989, we had a day in the TEENS with an east wind gusting 40-60 mph across the metro area!  Wow…

We had 0.5″ snow Friday, and 0.2″  today, for a GRAND TOTAL of 0.7″ so far this winter.

It’s very likely this was the coldest weather we will see this winter; to get another cold spell like this would be historic.

OR IS IT???

Models this afternoon/evening are hinting that another shot of cold air may try to drop into the western USA right around the beginning of Christmas Break (NEXT Friday) about 10 days from now.  Here is the 00z GFS ensemble chart showing quite a dip late next week:

tseries_850t_000-384_Portland

The 00z ECMWF is also pushing arctic air south again at day 10 now:

500vty_f240_bg_NA

The air mass is about as cold as what we just went through on the model run!  In 1990 we did have two arctic blasts in a two-week period, so it’s possible, but we’ll see.

ecmwf_apcp_f240_nw

Chief Meteorologist Mark Nelsen

 

 


Transition Day Goes Smoothly…So Far

December 10, 2013

10:00am…

We are slowly transitioning out of the cold arctic air mass this morning.  Temperature stayed in the mid-upper 20s overnight in the metro area due to the cloud cover; practically tropical compared to the previous 4 mornings!

KPTV_Default

We escaped without major issues for the morning commute; models did a great job showing extremely light (or no) precipitation overnight in our area.  Looks like just about no one had more than 1/2″ of snow and just a few pockets of freezing rain.  If we don’t get any freezing rain before noon, we are probably clear for this event.  Remember from past events that for freezing rain to “stick” and cause issues on roads, the temperature needs to be 30 or below, especially during the day since even on a cloudy day we get some energy from the sun to warm road surfaces.  At 10am, ODOT sensors on Highway 30 around Sauvie Island, I-205 at Division, and a couple of others show road surface temps now at freezing or above.  We should top out slightly above freezing today, then with some spots of clearing drop down below freezing again tonight.

As a result, at this point the afternoon commute looks even a bit better than this morning.

There is a chance we get a spot or two of freezing drizzle or a flurry tonight, but most of the energy for lifting the cloud layer to produce precipitation will be gone. 

We did have interesting and unusual weather in the Columbia River Gorge the past 24 hours…it was WARMER than here in the metro area.  I see The Dalles made it up to 38 in the middle of the night, same thing at Hood River.  Wait a minute…isn’t it always colder in the Gorge at the end of a cold spell?  Not this time, we had weak westerly flow through the Gorge, and some warmer air from above mixed down with those west winds.  That will come to an abrupt end tonight when surface high pressure strengthens on the east side of the state.  Thus it will be a significantly colder day in the central/eastern end of the Columbia River Gorge tomorrow and the gusty east wind will return.  Think of it as the colder east side air “sloshing” back into the Gorge overnight.

So what happens beyond tonight?  A very slow weather pattern with a few weak systems.  One on Thursday and another possibly later in the weekend.  I don’t see significant rain, or mountain snow, until the middle/latter part of NEXT week.  Our drier than average weather pattern we’ve seen since October continues with upper-level ridging nearby.  A very persistent pattern this cool season so far…

Will precipitation start as snow or freezing rain Thursday?  Very unlikely for most of us.

Why?

  1. No strong east wind, or even much at all, to supply a reinforcing shot of cold air out of the Gorge.  We will moderate temps quickly with a southerly wind above the surface.  By Thursday afternoon the actual snow level is over 4,000′.
  2. Atmosphere overhead would only support freezing rain, not snow.  That’s pretty clear on forecast soundings.
  3. Precipitation arrival appears to be at midday.  Unless temps are 30 or below late morning to midday Thursday, freezing rain won’t be able to freeze to road surfaces.  If the system were to rush in at 7am I could see pockets of freezing rain Thursday morning after a mainly clear night Wednesday night.

I could see a better chance for a few pockets of freezing rain in the Gorge…maybe.  This is also going to be a weak system without much wind or precipitation.

Chief Meteorologist Mark Nelsen