Monday, December 14, 2009

Yes, it's cold enough for me

Dreaming of a White Christmas? The northern third of the USA will see a mostly-white Christmas. No major storms are brewing between now and December 25, at least for the Upper Midwest. Temperatures bottom out today, with some moderation likely later this week, highs probably in the 20s to near 30 by Christmas Day.

I was in the Washington D.C. area last weekend to visit my son at the Naval Academy (and take in a chilly Army-Navy football game in Philadelphia on Saturday). Driving back to Annapolis (after a Navy win, 8th in a row over Army) I tune my trusty FM radio to WTOP-FM, 103.5. The forecast calls for "windy and much colder by the middle of the week, with highs in the upper 30s to near 40!" The meteorologist was really excited by this turn of events. I look over at my wife, who is just as dumbfounded as I am. My God - we've entered the Land of the Weather Wimps. Wait, that's 40 ABOVE zero, right? Everything is relative. To a thin-blooded resident of Miami Beach 60 degrees feels "nippy". To be fair, 35 in New York, Washington D.C, Boston or Chicago often feels considerably worse than 35 here in St. Cloud. Why? Relative humidity levels tend to trend higher near the Atlantic Ocean (and just downwind of the Great Lakes). More water in the air makes clothing damp - faster - than here in Minnesota, where a lack of major water sources means lower humidity levels. The cold is conducted much faster when the relative humidity is high - you FEEL the sting much faster in Manhattan or Baltimore or Norfolk. There is some truth to the expression "dry cold" vs. "wet cold". Bottom line: pat yourself on the back. You are a modern-day weather warrior. Only Siberia has more extremes in temperature and moisture than Minnesota. That's to be expected - on average the largest variations in weather come near the center of major continents, far way from the moderating influences of large bodies of water, lakes and oceans.

December Temperature Outlook from CPC. Colder than average weather is likely just south/east of Minnesota, with equal chances for Minnesota and the far northern tier of the USA, only California and Nevada expecting a warmer than average December.

Well, you survived Monday's whopping 1.5" inches of powdery snow. On paper it sure didn't seem like a big deal, but I'm always amazed by how a small amount of snow, coming at exactly the right (or wrong) time, can bring the system down. It's the vehicular equivalent of a heart attack: blockage in a key artery can create a domino effect - the result: massive gridlock. So, in reality, the timing of the snow (and the air temperature) may be more important than the number of inches that fall. When the mercury is below 15 F. the salt/sand mixture used by MnDOT isn't nearly as effective - it takes MUCH longer to melt snow and ice. Also, when conditions are ripe traffic can literally compress or squish freshly fallen snow into a thin, dangerous layer of ice. At 30 degrees the snow and ice melts much faster, but at 10-15 F. it can take 15-45 minutes to melt. The bottom line: even a little bit of snow, falling when it's very cold, can lead to debilitating commutes and much more anguish on area highways. When snow is predicted, even a little, and the mercury is <10 or 15F, expect conditions to be MUCH worse than they would be with an air temperature closer to freezing. For what it's worth.

Good news: this is just about as cold as it's going to get through the end of December. A reinforcing surge of Canadian air arrives next Sunday/Monday with more daytime highs holding in single digits early next week, another stretch of subzero lows. But you'll be pleasantly surprised how good 20s will feel as early as Thursday. Flurries are possible Thursday and Friday, a light nuisance accumulation can't be ruled out. But no mega-storms, no travel-busting storms of any flavor, snow, ice or rain is brewing between now and Christmas, possibly through New Year's (although that's on the fringe of how far we can see with any level of accuracy whatsoever). Temperatures generally moderate the latter half of December - I expect highs mostly in the 20s for Christmas Day. And yes, it bears repeating: whatever snow is in your yard right now (4" as of Monday midday) will pretty much still be there come Christmas Day. Santa's pretty pumped about that - no brown Christmas this year!

Paul's Outlook for greater St. Cloud

Today: Windchill Advisory. A mix of clouds and bitter sun. Winds: W 5-15. High: 3 (windchills of -20 much of the day).

Tonight: Partly cloudy, still much colder than average for mid December. Low: -12

Wednesday: Sun giving way to increasing clouds, not quite as harsh. High: 11

Thursday: More clouds, a few passing flurries. High: 21

Friday: Overcast, a little very light snow/flurries. High: 23

Saturday: Mostly cloudy, a few more flakes around town. High: 18

Sunday: Windy and colder with periods of numbing sunshine. High: 13

Monday: Unseasonably/unreasonably chilly - more clouds than sun. High: 17

Temperatures rebound into the 20s for highs much of Christmas week.

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