Model Wars: Winter storm watch south, big metro range
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They say all weather is local. Wednesday's inbound storm system looks like a perfect example. The forecast for Red Wing looks very different than Rogers.
There is still major model disagreement in storm track and placement of snowfall totals for this system. NOAA's GFS and NAM models predict you'll be shoveling snow in the Twin Cities Thursday. The Euro and Canadian models predict NOAA's models are shoveling something entirely different.
One thing all models seem to agree on; there's a good chance you'll be shoveling potentially heavy snow totals in Albert Lea, Rochester and Winona. Your local NWS office has hoisted winter storm watches for a big swath of southern Minnesota.
My advice? Prepare for winter storm conditions in southern Minnesota, northern Iowa and central Wisconsin. Keep a close eye out for possible forecast changes in the Twin Cities metro Tuesday.
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Weather headlines
Mild again Tuesday with temps in the 50s.
Winter storm watches for southern Minnesota starting Wednesday night.
Still uncertainty in storm track, and specifically Twin Cities snowfall totals.
INCLUDING THE CITIES OF...LE SUEUR...FARIBAULT...RED WING...ST JAMES...MANKATO...WASECA...OWATONNA...FAIRMONT...BLUE EARTH...ALBERT LEA...DURAND...EAU CLAIRE
348 PM CDT MON MAR 21 2016
...WINTER STORM WATCH IN EFFECT FROM WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING...
THE NATIONAL WEATHER SERVICE IN TWIN CITIES/CHANHASSEN HAS ISSUED A WINTER STORM WATCH...WHICH IS IN EFFECT FROM WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING.
* TIMING...WEDNESDAY AFTERNOON UNTIL THURSDAY MORNING.
* MAIN IMPACT...6 TO 12 INCHES OF SNOW. A FEW LOCATIONS COULD SEE MORE THAN 12 INCHES.
* OTHER IMPACTS...BLOWING AND DRIFTING SNOW WEDNESDAY EVENING AND WEDNESDAY NIGHT.
The system
A deepening low pressure system pushes east from the Rockies Wednesday. The eventual storm track is still in question. Here's NOAA's latest version of the storm track and precipitation shield. Heavy snow in southern Minnesota. The Twin Cities rides the northern edge of the significant snow zone according to NOAA.
NOAA: Metro snowfall likely
Give this to NOAA's newly upgraded GFS model. It's staying the course on the northern track solution, and the notion of snow for the Twin Cities. NOAA's NAM model agrees, laying out shovelable, potentially plowable totals for MSP.
Here's NOAA's NAM 4 km solution. Heavy snowfall totals over a foot from Mankato through Rochester and Eau Claire. 6" at MSP, with a razor sharp cutoff in the metro to the north.
The old school forecast wisdom on the NAM is it has a northward bias on winter storms. We'll see.
Ensemble forecasts?
One approach to forecasting is to take a wide range of models and use the average for the "most accurate" outcome. The problem with ensemble forecasts is they're only as good as their members. Just because you ask 20 people what the right answer is doesn't mean the average of their answers is more accurate. Chances are one or two of those "ensemble members" is right on the money. The rest drag the average farther from reality.
NOAA's suite of models in the Short Range Ensemble Forecast yields a wide range of potential snowfall outcomes for the Twin Cities.
A trace to 15 inches? Now there's an 'actionable' forecast you can plan for. That's why our job as meteorologists is to sift through this and give our best "human" forecaster input. The weather forecast parlor trick? To pick out the signal from the forecast noise. Easier said than done.
The southern solution
The Euro model's southern storm track has been as steadfast as NOAA's northern solution. The Euro literally forecasts zero precipitation for the Twin Cities as the storm slides south.
The Canadian model has budged slightly north, and now brings the edge of snowfall just into the Twin Cities metro.
For the record, I am leaning toward the Euro and Canadian solution at this point with the south metro riding the edge of snow with this system. But any shift north in the overnight Euro run could change that thinking. I'll be closely watching NOAA's next major GFS run between 10 pm and midnight, that could be illuminating.
Bottom line
Expect winter storm conditions Wednesday into Thursday morning for southern Minnesota.
Heavy snow totals to a foot or more and high winds will cause near blizzard conditions at times.
There's still high uncertainty in precise storm track and Twin Cities snowfall totals.
Stay tuned.
