Thursday, November 11, 2010

From 68 (Wednesday) to a Major Snowstorm (Saturday)

* Potential for a major Saturday snowstorm. Mostly rain east metro and southeastern MN, under 1-2" snow expected, but far west metro could wind up with 3-6" or more by Saturday night, maybe a band of 5-10"+ 30-70 miles west of the Twin Cities. Travel conditions will go downhill as the day goes on tomorrow - stay tuned for updates.

Sun Setting On Autumn. Thanks to WeatherNation meteorologist Bay Scroggins for snapping this photo of the sun setting over Lake Hiawatha, with a vivid "sun dog" visible to the right of the sun, caused by white sunlight being refracted (bent) through millions of tiny, prism-like ice crystals suspended 25,000 feet above the ground. Yes, it was an amazing autumn, a Super-sized Fall this year. But the sun is now as high in the sky as it was the last week of January. That has implications for our weather, as we're all about to discover within
36-48 hours.

Go Big Or Go Home. First accumulating snow of the season - how 'bout a cool foot or more over the far western suburbs and much of south central MN? If I predicted 1-10" the guys with the little white jackets would come to take me away - but that's exactly what the latest models are predicting. I still think (some) rain will mix in on Saturday, keeping amounts down (a bit). But the far west metro could still wind up with 4-8" of slushy, wet snow, while suburbs east of St. Paul pick up less than 1". The downtowns? 2-4" slush seems like a real possibility - the best chance of accumulating snow coming Saturday night. Tomorrow is going to be a VERY interesting day, weatherwise.

Ripe Track For Snow? I saw the latest projected path of the storm (from NOAA's NCEP) and chills went up my spine. If this verifies (and it's still a BIG if) it would be a nearly perfect track for heavy, wet snow in and around the Twin Cities. The big question: will there be enough warm air in the lowest mile of the atmosphere to keep most of the precipitation falling as a cold rain on Saturday? A changeover to snow seems inevitable. If the change happens Saturday night we might pick up a few inches of slush at the tail-end of the storm. If the changeover takes place midday Saturday it's not inconceivable that the immediate metro area could pick up a plowable (3-4"+) accumulation. Let's see what the models say on Friday, but someone is going to wind up with a very significant pile of snow by Sunday morning. See the projected track for yourself here.

Right On The Edge. Why can't a forecast ever be black or white? Why must it always be some nebulous shade of gray? The NAM/WRF model (generally considered the most accurate of the short-range models) has a cold rain most of Saturday, ending as a couple inches of slush in the metro Saturday night and early Sunday, especially western and southwestern suburbs. Confidence level is still low: the GFS and a few other models track the storm farther east, meaning a more rapid changeover to snow Saturday, implying heavier amounts of accumulation in and around the metro area. I want to see a little consistency from model run to model run, and (hopefully) all the models will converge on a single solution. Fat chance. Right now it appears the best chance of a (big pile) of fresh snow will come 30-70 miles west of MSP. But if the storm zigs and zags 50 miles farther east into Wisconsin MSP could wind up that band of heavy snow.

"Skew-T" Here is a cross-section of the atmosphere, valid 5 pm Saturday. The line going straight up is a "sounding", a temperature plot throughout the entire cross-section of the atmosphere above the Twin Cities. To get (all) snow temperatures have to be consistently below 32 F - even a thin layer of air warmer than 32 F. can trigger a changeover to rain. The models are hinting at wet snow mixing with rain late morning Saturday, but temperatures during the afternoon are forecast to warm (ever so slightly) - to just above 32 throughout the lowest 2,500 to 3,000 feet of the atmosphere - which SHOULD mean rain mixing in with the snow. Then again - it's a VERY close call and I'm nervous. The air overhead will be rising rapidly Saturday - which can cool the air, which could be just enough to tip precipitation over to (mostly) snow, especially western suburbs. Bottom line: we're right on the edge - and if the temperature winds up being 1-3 degrees colder overhead, much of the metro could wind up with 5-10" of snow.That is still a very distinct possibility (although I'm leaning more toward 1-2" east suburbs, 2-4" downtowns, with as much as 4-8" far western suburbs, from Chaska, Delano and Excelsior to Medina, Rockford, Elk River and the greater St. Cloud area. There could be a 10" difference in snowfall totals over the span of 50 miles.

Omen Of What's To Come? Check out an impressive "quad-camera-split" approach to covering "breaking weather news" in Regina, Saskatchewan - where it's finally starting to look like winter. The YouTube clip is here.

Unusual November Warmth. From the local Chanhassen office of the National Weather Service: "Many communities across the area saw 60° or warmer from Sunday through Wednesday.  These readings were 15° to nearly 25° above normal in places.  This has been one of the latest four-day stretches of 60° weather in the Twin Cities.  Since 1938, a four day period of 60° or warmer weather had happened in November only seven times in Minneapolis (once every decade or so).  Just last year had five days in a row hit 60° during the same week, from November 6th through the 10th.   The average last 60° day in the Twin Cities is November 6th." More details on why it was so warm - for so long - in this post from the NWS.

Wednesday Warmth. September-like warmth swept northward into the Upper Midwest the first half of the week, boosting temperatures 20-30 degrees above average for the second week of November. The Twin Cities registered a record-setting 68, but there were dozens of records highs (and record warm nighttime mins as well). Click here for an interactive map, courtesy of Ham Weather.

Offshore System Will Stir Up Wind And Big Surf. A major nor'easter has stalled off the coast of New England, whipping up some 30 mph. winds and 8-13 foot seas. The fact that this storm has stalled MAY have an impact on our weekend storm here in Minnesota. It (vaguely) reminds me of the Halloween Superstorm, where "The Perfect Storm" stalled off the coast of New England, causing our storm to stall over Lake Superior, prolonging our snow, piling up over 27" of the white stuff over 3 days. No, I'm not  predicting 27" of snow this weekend - but any time systems slow down and stall meteorologists get even more nervous. The story is here.

Scientists Discover Unknown Lizard Species At Lunch Buffet. Yes, it's one of the stranger headlines I've stumbled upon recently on the web, but scientists made a striking discovery recently -- at a lunch buffet in Vietnam. The story from CNN is rated PG, for pretty gross.

Thursday Recap. Yesterday felt more like fall, no question, but readings were still 5-10 degrees warmer than average. .17" of rain fell Wednesday night as a cool front sailed across town, Thursday highs ranging from 44 at Alexandria to 48 in St. Cloud, 52 in the Twin Cities.

Paul's Conservation MN Outlook for the Twin Cities and all of Minnesota:

TODAY: Gray, PM rain develops. Winds: NE 7-12. High: 43

FRIDAY NIGHT: Cold rain likely. Low: 33

SATURDAY: Rain gradually changes to wet snow (faster changeover west of the metro area). High: 38

SATURDAY NIGHT: Periods of wet snow, couple inches possible in the metro, maybe enough to shovel/plow just west of MSP (band of 5-10" still possible parts of central and south central MN). Low: 30

SUNDAY: Snowy (potentially slippery) start, then slow clearing. High: near 40

MONDAY: Intervals of sun, November-like. High: 41

TUESDAY: Clipper arrives, slushy mix late PM? High: 39

WEDNESDAY: Lingering flakes, cold wind. High: 38

THURSDAY: Cool sun, dry sky. High: 36

Our worst fear as meteorologists? #1). Forget to wear pants in front of the green-screen. #2). Miss the EF-4 tornado because you're home having dessert, and #3). Predicting flurries, only to wake up the next morning to a cool foot of flurries. That's why weather-droids (as a profession) tend to overpredict snow. We live in mortal fear of another Armistice Day Blizzard (weather guys in Chicago predicted flurries - we wound up with 18" flurries with 10 foot drifts). 

I can't remember the last time when we didn't have to "worry" about a changeover from rain to snow - a "pure snowstorm", no unpleasant additives, like sleet or freezing rain. The bottom line: the closer the next storm tracks to home, the better the chance warmer air will get wrapped up into the circulation, tilting precipitation over to rain vs. snow. The farther east the storm tracks, deeper into central Wisconsin, the greater the odds we'll have enough cold air in place for mostly snow. Bottom line: the rain/snow line will set up VERY close to the Twin Cities Saturday, mostly rain for southeastern MN and the St. Croix Valley, the far west metro (west of Chaska and Medina) may see mostly snow. Some 5-10" snowfall amounts are possible from Mankato and Glencoe to Delano, Willmar, Monticello and St. Cloud. The farther west you travel tomorrow, the better the chance of snow.

Tune in later today as we factor in the latest computer runs - I want to see if there are any trends, any consistency in how the models are nudging the storm track. The most accurate model: the NAM/WRF, is printing out close to 1.7" of liquid precipitation. if that were to all fall as snow we'd wind up with 13-18" of snow in the Twin Cities. I don't think that's going to happen. I think there will be some rain mixing in much of the day Saturday, especially from the downtowns on east toward Stillwater and Red Wing.

Travel conditions will get worse as the day goes on tomorrow. If you're thinking of driving to St. Cloud or Alexandria consider leaving later today, or maybe first thing tomorrow. The worst conditions will be after dark Saturday evening, as temperatures fall below 32 and wet/slushy roads become very icy. I do expect the NWS to issue Winter Storm Watches, possibly even Winter Storm Warnings by this evening. Stay tuned - we'll keep you posted with the very latest right here.

Slushy Possibilities

Rarely is a forecast ever black or white. It's usually some nebulous/frustrating shade of gray. So it is today: events are conspiring to dump a significant amount of snow on much of Minnesota; some towns could easily see a "plowable" snowfall of 5-10". The question: where will the heavy snow band set up? The most reliable model, the "NAM/WRF", keeps the lowest mile of the atmosphere above 32 F, hinting at a cold rain much of Saturday, maybe a couple of sloppy inches of slush at the tail-end of the storm Saturday night & early Sunday. Other models take the storm farther east, keeping us in the "cold sector", implying a faster changeover to snow. Ugh. Bottom line: confidence level is low. I want to see a few more model runs; see if there is continuity & consistency before going too far out on a (shaky) limb.

Right now the best chance of 5-10" comes from Mille Lacs & St. Cloud to Monticello, Willmar, even Mankato. A jog of just 50 miles in the storm track could make the difference between a cold rain & a cool half foot of slush. Time to stake the driveway and get serious about snow tires. Next week will feel like November; no mega-storms brewing for Thanksgiving week right now.

Is Water The Oil Of The 21st Century? As the atmosphere continues to warm rainfall is becoming more sporadic and unpredictable across much of the planet - most of the supercomputer simulations show an increase in the frequency and intensity of drought in the decades to come. Something many of us take for granted - water - may become even more precious, especially across Asia and Africa. An interesting video from CNBC is here.

Atlantic Hurricane Season Is Getting Longer. Is it a glitch, an aberration, or a trend? Jeff Masters, in his excellent Wunderblog post, has some very interesting observations: "It seems like there have been an unusual number of early and late season tropical storms and hurricanes in the Atlantic in recent years. In 2008, we had four named storms in July, and the second most powerful November hurricane on record. Both 2007 and 2005 had rare December storms, and 2003 featured Tropical Storm Anna, the first April tropical storm ever recorded. This year, Hurricane Tomas made 2010 the fourth straight year with a November hurricane, something that has never occurred in the Atlantic since accurate records began in 1851."

Rapid Warming Boosted Ancient Rainforest. From an interesting article at "Most scientists have assumed that, as carbon dioxide levels increase and the Earth warms, plant species diversity in the rainforests will start to dwindle, with plants unable to adapt to the heat. But a new study suggests that the opposite may be true. In the past, rising atmospheric carbon dioxide and higher temperatures actually drove the evolution of far greater numbers of new rainforest plant species than were wiped out."

Climate Scientists Plan Campaign Against Global Warming Skeptics. From an article in the L.A. Times: "The American Geophysical Union plans to announce that 700 researchers have agreed to speak out on the issue. Other scientists plan a pushback against congressional conservatives who have vowed to kill the regulations on greenhouse gas emissions."

EPA Issues Guidelines For Cutting Greenhouse Gases. From an article in USA Today: "Increasing energy efficiency is the focus of the first-ever federal guidelines for reducing greenhouse gas emissions from industrial sources issued Wednesday by the U.S. Environmental Protection Agency. Among the suggestions: replacing dirty fuels used to power oil refineries with cleaner sources and requiring more efficient electricity and energy use with existing power plants to reduce emissions — while not requiring expensive technology upgrades. EPA's new guidance is meant to help states understand how to implement new greenhouse gas reduction requirements while mitigating costs for industry in a bad economy. Most states will use EPA's new guidelines when processing new air pollution permits for power plants, cement factories and other big pollution sources under the federal Clean Air Act."

What? Only AM's 1965-era ad-legend Donald Draper could make the word "what?" into something interesting and memorable. If you're a fan of Mad Men (as I am) you'll like this clip.

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