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Potential for a cool 1-2 feet by Saturday

* Winter Storm Watch in effect for central and southern Minnesota.
* Less than 1″ today from St. Cloud to Twin Cities, 2-4″ possible near the Iowa border.
* Main event comes Christmas Eve into Christmas Day, may not taper until Saturday AM.
* Potential for 7-8″ by 6 pm Christmas Eve, as much as 12-14″ by 10 am Christmas morning.
* If you’re driving try to hit the roads before Wednesday evening, travel conditions will deteriorate rapidly on Christmas Eve as southern storm spreads moderate/heavy snow across Minnesota from south to north.
* Slow improvement in travel conditions over the weekend. Sunday should be the better day (it may take the better part of 2 days to dig out most of Minnesota).
* 12-16″+ from St. Cloud to the Twin Cities, with a potential for 15-20″ south/west of I-94 by Saturday morning.
* Record-setting snow likely. Old record for 24 hour snowfall in the Twin Cities: 2.7″ (1987) and 5.9″ (1950). There’s a good chance we’ll break both 24 hour snowfall records.
* Bitter air follows the storm by early next week, a few subzero nights likely.

Snowpocalypse? Dreaming of an exceptionally bright, white Christmas this year? It’s still (a little) early to panic (or celebrate) but the upcoming 2009 Christmas Storm may become a monster across the Northern Plains and Upper Midwest. Similar to last Saturday’s east coast blizzard, the late-week storm is forecast to dump more than 16″ of snow across much of Nebraska, South Dakota, northwestern Iowa and the southwestern half of Minnesota. A Winter Storm Watch has already been posted for central and southern Minnesota, even though significant accumulating snow is still 36-48 hours away. A word to the wise: if possible, get your traveling out of the way by Wednesday evening – or wait until Saturday PM/Sunday to get to where you’re going. I’m not convinced it’s going to be a blizzard (with low visibility and sustained 35 mph+ winds) but travel conditions may be very poor Christmas Eve and Christmas Day, with snow mixing with ice east of the Twin Cities into western Wisconsin, as warmer air tries to wrap into the storm’s circulation.

Amazingly Consistent. The computer models are all fairly consistent, a surprising amount of “continuity” from model to model (GFS, NMM and WRF), and from run to run (we analyze 4 separate model runs every day). 12-15-18″? One model is hinting at 20″ of snow just south and west of St. Cloud and the Twin Cities. Yes, it will almost certainly be “plowable”. South and west of I-94 it may wind up being somewhere between “plowable” and crippling. Stay tuned, especially if you plan to do any extensive traveling from late Wednesday into Saturday morning.

I want to see 1 or 2 more computer runs, but the models have been fairly consistent and I think it’s relatively safe to go out on a limb and predict widespread 1-2 foot snowfall amounts from the upcoming late-week storm, with many towns and suburbs south/west of I-94 winding up with 15-18″ of snow. If ice mixes in from the east (possible, but unlikely from the Twin Cities on west) that would keep amounts down. If a “dry tongue”, a surge of dry, desert air at all levels of the atmosphere sweeps in from the south, that could also keep amounts down. By down I mean 8-10″. I honestly don’t see how we can possibly pick up less than 6-8″ at this point.

Quick coating to 1″ today. NMM/WRF model showing expected snowfall from noon to 6 pm today. This is the appetizer, not the main event, which comes Christmas Eve and Christmas Day. A stalled front over southern Minnesota will generate enough upward motion to squeeze out 2-4″ snow near the Iowa border. From St. Cloud to the Twin Cities, up and down the I-94 corridor, I could see a dusting/coating to 1″+ amounts, maybe 2″ over the far southern suburbs of the Twin Cities. But to repeat: the brunt of the storm comes Thursday and Friday, Christmas Eve and Christmas Day. Great timing! Get your shopping done, out of the way, by tomorrow evening if at all possible. It may turn into Christmas Chaos on the highways Thursday and Friday.

Projected storm track showing a classic “Texas Hooker”. All the ingredients are coming together. A fresh supply of chilled Canadian air, a powerful Pacific surge of energy and moisture diving southeastward across the Rockies, forecast to intensify into a powerful storm over Texas/Oklahoma by Christmas Eve, before tracking northeast toward Wisconsin. If the storm hooks right over the Twin Cities enough warm air may surge north for a changeover to freezing rain/sleet, which would keep snow amounts down. A track that close to MSP could also allow the “dreaded dry tongue” to sweep into Minnesota, cutting off the heaviest snow amounts, keeping the most outrageous snowfall amounts over far western Minnesota and the Dakotas. That could still happen, but if the storm track is across Wisconsin then most of Minnesota stays on the cold, snowy side of the storm track, increasing the potential for some 1-2 foot amounts by Saturday morning. Yes, this will be a long-lasting snow event, 72+ hours of light/moderate snow for many towns in the Upper Midwest.

Aftermath. Saturday’s east coast blizzard dumped 10-20+” on a huge swath of the Mid Atlantic and Northeast, from North Carolina and the Virginias to Maryland, Pennsylvania, Long Island and Cape Cod, reports of 3-6 foot drifts! By the end of the week it may be warm enough for rain, leading to the potential of rapid snow melt and potential flash flooding. Image courtesy of NASA; for more information click over to Earth Observatory for more on last weekend’s snow-blitz.

An Unusual Sight. It’s rare to have 3-4 times more snow in Washington, Philadelphia and New York than across the Great Lakes and Upper Midwest, but much of the east coast is still digging out from last Saturday’s Big Dump.

Paul’s Outlook for the Twin Cities

Today: Overcast with flurries, little more than a dusting or coating. Winds: E 5-10. High: 25

Tonight: Cloudy with spotty flurries, no major travel problems – yet. Low: 18

Wednesday: Last good travel day. Gray, light snow arrives Wednesday night. High: 27

Christmas Eve: Snow, becoming heavier and steadier as the day goes on. 6-8″ possible by Thursday evening. High: 29

Christmas Day: More snow, heavy at times. Potential for some snow totals in excess of 12-15″ for parts of central Minnesota. High: 28

Saturday: Windy and colder with snow tapering to flurries, little additional accumulation. High: 17

Sunday: Sunshine returns, numbing breeze. High: 9

Monday: Intervals of sun, bordering on bitter. High: 4 (nighttime lows in the -5 to -15 F range).

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