Monday, January 4, 2010

Potential for a January Thaw

"As the days lengthen the cold doth strengthen..."

- proverb

Yes it doth. Welcome to the Land of Low Weather Expectations. At this latitude, around this time of year, we're secretly relieved when the temperature hits 10 (above!). People dressed only in sweats will wander outside to get the newspaper when the mercury eclipses the 20-degree mark. 30 is a Godsend, a sign that all hope is not lost. We have not become Pluto (with lakes). At 30 F we treat our crusty vehicles to a wash, some of us even fire up the grill. The good news: computer models are increasingly hinting at a thaw within 10 days or so, 32 F possible anytime from January 14-18 as Pacific air crosses the Rockies, wafting into Minnesota on more mellow, westerly breezes. I want to see a few more computer runs before I really get excited, but so far so good - there's a good chance we'll all be able to catch our breath (and exhale) after 3 nearly continuous weeks of Nanook conditions, the next best thing to a Yukon vacation.


Potentially Plowable. The latest GFS run is hinting at some 2-4" snowfall amounts Wednesday PM into midday Thursday. With temperatures ranging from 0 to 5 above the snow will be light, powdery, fluffy - quick to accumulate but relatively easy to scrape off your driveway or sidewalk. One word of caution: when it's this cold MnDOT's salt/sand mix doesn't work well at all - I expect roads to be in pretty bad shape after lunch Wednesday through rush hour Thursday morning.

But first we have to muddle through a little more "weather." The approach of a reinforcing arctic burst will squeeze out a period of light snow from Wednesday afternoon into Thursday morning - the latest NAM and GFS models hinting at 2-4" of powder, just enough to make Thursday morning's commute an icy, tire-spinning, white-knuckle adventure. The farther south/west of I-94 you live, the better the chance of 3-5" of snow, a few towns near Windom, Marshall and Pipestone, in southwestern Minnesota, could pick up a cool 6" of light, powdery snow from this next clipper, while Brainerd, Crosby, Little Falls, Princeton and the northern suburbs of the Twin Cities pick up less than 1-2" of powder. With temperatures falling through single digits into negative numbers on Thursday the ability for MnDOT to melt that new snow is going to be limited at best. It's these ultra-cold weather snowfalls that are often the most perilous; the combination of partial melting (from the salt/sand mix) and repeated traffic, flattening/compressing the snow - can lead to a thin layer of glare ice underneath the snow, producing the worst of all worlds, transportation-wise. I think travel conditions may be a real mess late Wednesday into midday Thursday, a 4 on the dreaded Hassle Factor. I think it'll be a "plowable" event across much of central and southern Minnesota, the combination of bitter cold and snow creating very slippery conditions. Winds won't be too strong (under 15 mph) so I don't anticipate widespread blowing/drifting, nothing approaching blizzard conditions to worry about.

Dueling Models. There is some disagreement over how much snow may fall Wednesday PM into Thursday. Most models are suggesting 2 to 2.5", but the latest NAM is hinting at considerably more, over 5" of fluff. The final amount will probably be somewhere in-between. With a snow:rain ratio close to 30:1 (30" of snow for every 1" of liquid precipitation) I wouldn't be surprised to see some 3-4" amounts, a better chance of 5" toward Willmar, Glencoe and Mankato.

Thursday AM (no) Rush Hour. If the latest models verify we'll be scraping about 2-4" of snow off our driveways Thursday morning as a fast-moving clipper pushes a shield of light, powdery snow across the state. Minor blowing and drifting is possible behind the storm, but winds should stay under 15 mph, ruling out blizzard conditions. The bigger concern: bitter cold, with wind chills near -30 by Thursday morning.

This next Siberian Smack will be followed by an arctic breeze Thursday; the core of the bitter air oozes overhead Friday, when temperatures may remain below zero across much of Minnesota Thursday and Friday, nighttime lows once again in the -15 to -25 range across central Minnesota, nearly as cold as last weekend. This is getting old - I know. I'm sick and tired of the cold, too. The snow is easier to take, right? At least you can play in the snow - thousands of Minnesotans make a living from snow. But subzero temperatures, hour after hour? What's the old saying, "anything that doesn't kill me makes me stronger." Right. At this rate we're all going to be very, very strong.

Hints of a Serious Thaw. Here is some of the raw GFS guidance. Check out the projected temperatures from January 14-18, at least 2-3 days with highs at or near 32 F. An encouraging trend - we'll see if it's real.


There's a better than 50-50 chance of a January Thaw by the middle of the month, a few days with highs flirting with 30. The 9-10" of snow on the ground will limit just how high the mercury can go, but we're due for a break, and I don't think this long-anticipated warmer front is a mirage. The January Thaw is a strange, largely unexplained meteorological phenomena, most frequent east of the Mississippi River. Weather researchers really don't have a good explanation for this upward blip in temperature, usually right after the first of the year, about 2-4 weeks before average temperatures begin to trend upward again, responding to a higher sun angle and more daylight. Whatever the ultimate cause, we'll take it. I'd like 2 weeks of January Thaws please - to go. Call me crazy (we WILL see more subzero weather into February, that goes without saying) but I have a strange hunch that the cold spell from Christmas through about Jan. 10 or so may wind up being the coldest stretch of the winter season - the longest duration of subzero temperatures and nasty wind chill. We'll see. I've been accused of being a naive optimist. We'll see - place your bets.

Paul's Outlook for the Twin Cities

Today: Numbing sunshine, dry - quiet. Winds: NW 5-10. High: 11

Tonight: Partly cloudy, not quite as frigid as recent nights. Low: -9

Wednesday: Cloudy with light snow by afternoon, 1-2" powder by evening with increasingly icy conditions on the highways. High: 9

Thursday: Turning colder as snow tapers, total accumulations of 2-4" possible, even more south/west of I-94. Very icy with dangerous wind chills (-30 F). High: -1 Low: -15

Friday: Yukon sun returns, less wind. High: near 0

Saturday: Better, partly sunny, more tolerable. High: 8

Sunday: Much nicer, some sun through high clouds. High: 23

Monday: Above average (for a change) with patchy clouds, noticeably milder. High: 28

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