A Spring Like Day For Thursday

February 8, 2012

While I was working hard posting about the rest of winter, a very nice day tomorrow just about “slipped under my radar” as they say.

We have a warm front moving through tonight, followed by partly cloudy to mostly sunny skies most of tomorrow. Next, add 850mb temps jumping to +6 to +8 in the afternoon with good southerly flow just above the surface. Light south wind will surface in the western valleys by afternoon just about everywhere except right near the Columbia River in the Portland Metro area. One more ingredient, a cloudy and mild night tonight. The result should be the first widespread 58-63 degree highs in the lowlands west of the Cascades. The 1.3km WRF-GFS clearly shows the effect of east wind from central Portland out towards the Gorge…temps are 5+ degrees cooler in those areas.  The 2nd shade of orange/red is the 60 degree line.  It shows that from Washington county through the south metro and over into Clackamas county.

So we’re going 57 at PDX, 55 at Troutdale, but 59 or above all areas west of the West Hills and from Milwaukie south & east. Even Sandy could hit 60 for the first time this year.  Salem?  Maybe 62-64 with that south wind!

A little early taste of spring…for one day.

Chief Meteorologist Mark Nelsen

Is Winter Over? Yes and No

February 8, 2012

It’s that time;  I’m getting emails and questions wondering if “that was it” for our pathetic Winter 2011-2012.  It sure has been a disappointment if you were looking for some crazy weather goodness…

What we have seen:
-significant flooding
-one brief lowland snow (2.2″ at PDX 9pm-1am)
-many weeks of dry or almost dry weather

What we haven’t seen:
-major windstorm
-lowland snow kids could actually sled on
-arctic blast with very cold temps
-several snow events or one big snowstorm

I’m definitely not ready to scream “WINTER IS OVER!” from the top of Rocky Butte, but here are some thoughts of what could still occur over the next month and what we are probably finished with.

It’s important to point out that this is based on what I see on maps and models right now.  It’s clear that there is little or no threat of cold/snow or flooding in the lowlands of western Oregon and western Washington through the next 7-10 days

That takes us all the way to around the 18th of February.   Based on that…

(About 90% confidence on these)

1. An extended period of cold weather (a big arctic blast)
– record low and “low-high” temps jump quite a bit the 2nd half of February.  It’s extremely rare to get down to 20 or below after the 16th.  It’s only happened 3 times (18 degrees the last week of February last year!).  Maybe more notable is the increasing sun angle means it’s hard to keep daytime temps down near freezing even with a very cold air mass.  We don’t get an all-day “frozen roads” storm after mid February for this reason.  After the 16th, only 3-4 times (in 70 years) have we seen high temps stay near freezing.
2. A multi-day snowstorm like 2004 or 2008
– same reasoning, record low maximum temps (coldest daytime highs) are 33-44 for the last 10 days of February.  Hard to keep the streets frozen in that case. 
3. A big flooding event
– we don’t tend to see significant, widespread winter flooding after we get through early February, and no models show wetter than average weather the next 10 days.
4. Freezing rain anywhere outside of the Gorge

(But none of these are expected in the next 7-10 days)

1. Snowfall in the lowest elevations
– everything has to line up just right in our climate to get snow in mid-winter at the lowest elevations.  But to get significant snow the last week or so of February? Everything really has to line up perfectly.  In the last 15 years, we’ve only had 4 measurable snowfalls in Portland in late February or March.  An inch or less each time.  Feb 2011, Feb 2009, March 2009, and March 2006.  That shows everything has to line up just right.
2. Significant snowfall in the Gorge and/or foothills above 1,000′
3. A blast of cold & dry air for a damaging late season freeze
– sure, we may not get a days-long freeze, but we can get a quick blast of winter cold.  Look at last year!  February 25th-26th saw highs 33-34 at PDX and a low down to 18.  That’s extreme & rare, but it CAN happen. 
4. A major windstorm
– we can get these through early March, although they aren’t nearly as common as during the fall and winter months

To summarize, Yes winter is somewhat over, but no, we could still see snow at the lowest elevations in the next 3-4 weeks.

Chief Meteorologist Mark Nelsen