Tuesday, October 27, 2009

A potentially scary Halloween (weatherwise)

No cause for panic in the streets. We're not talking 1991 here. No 30" of snow over 3 days. With any luck that was a once-in-a-lifetime weather event (one that none of us who lived through those days will ever forget). My oldest son, Walt, was 1 - this was his first Trick-or-Treat memory, he was dressed up like a pirate. My camera was ready - this would be an exciting adventure! Not quite. All I remember is walking back in the house - the entire left side of his costume was plastered under 2" of snow - my boy wanted no part of Halloween. Frankly, I was starting to feel the same way. I remember going on the air at KARE-TV, going out on a limb, predicting 4-8" of snow from this unusual, early-season snowstorm.

25" later the flakes finally - mercifully - stopped flying. Travel was impossible, roads impassable - the heavy, wet snow (2-3 feet across most of the metro) dropped tree limbs, cutting off power. There were still leaves on the trees (!) and that made a bad situation even worse. The final indignity: there was so much snow in my driveway that the chief engineer at Channel 11 had to drive out to Orono in his Suburban to pick me up to do the shows. My poor Saab couldn't even make it out the garage door. 4-wheel drive? Didn't matter. There was THAT much snow. By this time I was convinced the whole thing was a dream, it all seemed surreal, otherworldly. You just can't get 30" of snow in late October and the the first 2 days of November. That just doesn't happen, even in Minnesota, where we see every kind of weather extreme imaginable. The storm smashed records left and right - it was THE story for weeks to come.

What happened? How could the forecasts be off by that much? "Paul, what the heck happened to your computer models. Are you playing Pong on the computer instead of looking at the weather?" Hahaha! Good one. Hindsight is always 20-20. But here's what (apparently) went down. Off the coast of New England "The Perfect Storm" (yes, the one immortalized by author Sebastian Junger) had unexpectedly stalled, whipping up hurricane force gusts and 50 foot seas. That stalled storm forced the storm over the Great Lakes to stall - again, unexpectedly, and that's why we picked up a cool 2-3 FEET of snow in a little over 2 days. The computer models all insisted that the pattern was "progressive" (ie. weather systems would continue to move along). In reality, the storm over the Great Lakes wobbled over the same location for nearly 36 hours, long enough to drop several hundred million TONS of snow on Minnesota. It was a storm for the ages, and there is a high probability we'll never see another storm of that ferocity and duration that early in the winter season ever again. I say that will all due respect and humility. That storm taught meteorologists a painful lesson: the limits of computer technology - that in spite of massive supercomputers and the best intentions there will always be (extreme) weather events that are still unpredictable - fickle - unknowable. Yes, Mother Nature always get the last laugh.

Getting Closer. Here is the latest GFS Outlook for accumulated snow. This tends to overpredict snowfall amounts, but 3-6" of snow may pile up over the central Dakotas by Friday afternoon, a couple inches for far northern Minnesota by Saturday PM - just in time for Halloween.

84 Hour GFS Outlook. The heaviest rain bands are forecast to set up over the southeastern third of Minnesota Thursday, some 1"+ amounts can't be ruled out, especially south/east of the Twin Cities. The very latest model run backs off on the amounts a bit, closer to 2/3rds of an inch of rain for MSP. Thursday still looks like the wettest day of the week.

Yesterday was a sight for sore (gray) eyes - nice to see the sun is still capable of shining on Minnesota - a fine fall day with highs poking into the mid 50s, a couple degrees ABOVE average for a change. Today won't be quite as bright as clouds lower and thicken, but dry weather should prevail throughout the day, a few light showers brushing far western Minnesota by the dinner hour. If you have something planned outside later today - no worries. It will look (and smell) like rain with gusty south winds, but I think most of the puddles will hold off until Thursday, when commute times may double, even triple, with considerable water on the highways. By Friday winds swing around to the west and northwest, temperatures tumble through the 40s into the 30s - it may be cold enough aloft for a little wet snow by late afternoon. The good news (if you're not quite ready for a coating of white on your lawn) is that by the time it's cold enough for snow, most of the moisture will be pinwheeling to our east into Wisconsin. A surge of chilling air follows the storm, daytime temperatures stranded in the 30s most of Saturday, just breaking 40 over the southern third of the state. It promises to be a chilly Halloween, temperatures at least 10 degrees colder than average with some leftover flurries over the Minnesota Arrowhead.

Meteogram for MSP. This future temperature trend shows temperatures peaking Thursday (with gusty, rain-whipped southerly winds), followed by a sharp temperature drop Friday. Trick or Treat temperatures are forecast to be somewhere between 35-40 degrees. Factor in a 15 mph wind and you have a wind chill dipping into the low 20s at times. Make sure there's a hefty jacket or a few extra layers underneath those crazy costumes.

Expect a mostly cloudy, blustery Saturday - the sun may peek through over far southern Minnesota, while flurries coat lawns/fields over far northern Minnesota (an inch or two may even pile up). Sunday will start out with some sunshine, but clouds increase, a good chance of PM showers (probably rain south, but mixed with wet snow over the northern third of Minnesota, north of Brainerd). Temperatures will trend cooler than average into next week, highs mostly in the 40s and low 50s. Still no imminent sign of Indian Summer. Still waiting. At this rate it may be a long wait...

Observed Snow. I was surprised to see 2-4+" of snow on the ground over parts of the Minnesota Arrowhead - enough snow on the ground for some cross country skiing up in the BWCA this weekend? The ski season is starting a few weeks early this year, no question.

To see the latest snowfall reports for the USA (or zoom into the northern Plains and Great Lakes) click over to the National Operational Hydrologic Remote Sensing Center. Some good stuff here.

Paul's Outlook for the Twin Cities

Today: Clouds increase and thicken, windy - but dry. Winds: SE 10-20. High: 52

Tonight: Cloudy, a growing chance of a shower. Low: 46

Thursday: Gray with rain likely. High: 55

Friday: Gusty, turning colder with showers tapering (possibly ending as a few wet snowflakes Friday PM). High: near 53, but falling through the 40s during the day.

Halloween: More clouds than sun, a chilly breeze. High: 42 (Trick or Treat temperatures near 35).

Sunday: Sunny start, then clouds increase, PM showers possible. High: 44

Monday: Lingering clouds, a few sprinkles possible. High: 46

Tuesday: Sun reappears (finally!). A bit milder. High: 52

No comments:

Post a Comment