Updraft: January 31, 2013 Archive

Coldest night of winter tonight? Blame the "Arctic Oscillation." Snowier pattern next week?

Posted at 8:04 AM on January 31, 2013 by Paul Huttner (2 Comments)
Filed under: Winter 2012-13

-12F coldest temp at MSP Airport so far this winter on January 22nd

-10F to -16F likely low at MSP early Friday morning

Wind Chill Advisories include the metro until noon Friday

Wind Chill Warnings for western Minnesota and the Dakotas

Midler days ahead 30s possible by next week

Wetter days ahead? pattern change may increase snow chances last next week

Arctic Interlude:

Our narrative in Minnesota is that the cold is just no big deal.

We sleep in heated homes. Drive our (hopefully) heated cars to a heated workplace. Back home again to a cozy fireplace. Repeat.

Talk to an Arizonan about winter cold. When they shudder, remind them that they do the same thing in reverse from May to October when it's 100F+. AC home, AC car, AC office. Where's the pool?

It's all about climate control.

Our latest swipe from the Canadian Arctic is here. We can toss terms like "NWS revised wind chill" around until Friday.

The good news? This may be the "last coldest" air mass of the winter.

March...yes March and "Meteorological Spring" is a mere 29 days away.

If I close my eyes and daydream, I can almost feel that 1st mild March spring day... sitting in the sunshine on my front stoop as the last of the snow drips away and strange colorful birds start showing up in the yard.

Almost.

Blame the "Arctic Oscillation:"

Say what? It sounds like a bad medical condition associated with cold & flu.

The "AO" is actually a good indicator of how cold it will get over parts of North America & Europe a week or two in advance. The Negative Phase AO brings cold incursions south into North America and Europe. The Positive AO tends to produce milder weather over Minnesota & much of the USA.

Here's a more detailed description from NOAA's "Arctic Theme Page."

The Arctic Oscillation (AO) appears to be the cause for much of the recent changes that have occurred in the Arctic. Its effects are not restricted just to the Arctic; it also represents an important source of variability for the Northern Hemisphere as a whole. The AO has been described as "a seesaw pattern in which atmospheric pressure at polar and middle latitudes fluctuates between positive and negative phases. The negative phase brings higher-than-normal pressure over the polar region and lower-than-normal pressure at about 45 degrees north latitude. The positive phase brings the opposite conditions, steering ocean storms farther north and bringing wetter weather to Alaska, Scotland and Scandinavia and drier conditions to areas such as California, Spain and the Middle East."(University of Washington)

The AO was strongly negative during last week's arctic outbreak....but should flip back to positive next week. That should allow some moderation in our temps.

Latest trends are unclear for the direction of the AO after next week. If it stays positive...expect a continuation of milder than average temps. If not...winter may hang tough this February.

Stay tuned.

Coldest night of winter?

The incoming arctic air mass peaks Thursday night into Friday morning. As high pressure settles overhead with calm air early Friday morning, temps will plunge.

We've hit -12F so far at MSP for the coldest this winter last Tuesday morning. The models are cranking out --11F (Euro) to -16F (NAM) to -20F (GFS) Friday morning for MSP.

At this point I'm leaning toward the Euro number of -11F...but the range could be anywhere from -10F to -14F at MSP and the inner urban core Friday morning.

We may fall just shy...or possibly take the "award" for the coldest morning of the winter Friday in the metro.

Image: NOAA data via Iowa State University

We warm into the 20s this weekend, and 30s still appear likely by next Wednesday & Thursday.

It's all uphill from here! (Or is it downhill?)

Signs of snow ahead?

This is still far enough out to be in the "wishful thinking" phase...but I see signs that out persistent northwest flow (cold & dry) may be transitioning into a southwest flow (milder & wetter) by late next week. NOAA's CPC supports the idea of a midler pattern emerging.

Image: NOAA/CPC

The GFS is flipping back and forth as usual...but seems to revisit a pattern that drives 2 significant rain/ice/snow events into the Upper Midwest in the next 2 weeks.

The 1st one seems slated for next Friday & Saturday February 8th & 9th. This one ahs Euro support as well...which lends more credence to the idea of significant snow.

The second chance is a deep storm along about February 12-13th. This one could have a deep Gulf of Mexico moisture tap...and that scenario could inject enough moisture to produce potentially heavy wet snows for Minnesota.

Of course all of this still falls under cautionary modifiers like "possibly" and "potentially" but the trends are encouraging...and fit with CPC's idea of a wetter pattern as we emerge into late winter in the Upper Midwest.

Image: NOAA/CPC

Weather toes and fingers crossed.

PH

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