SE ridge and NW trend cause major snowfall busts in Midwest storm

I have noted many times in this blog over the past year that the models have consistently done a poor job in capturing the strength of the SE ridge and its role in deflecting storms to the northwest of where models predict. This phenomenon happened yet again Thursday/Friday as the surface low from the potent Midwest storm tracked a couple of hundred miles northwest of the track predicted by both the GFS and NAM.

NWS offices in central IN, northern IN, and central IL predicted an 8-15 inch snowstorm for those regions with the heaviest snow on an axis running through Lafayette, IN and into SE Michigan. The end result was that central IN, including Indianapolis received an inch of slush while northern IN and central IL received about 5-7 inches of snow. The heaviest snowfall totals occurred in the western suburbs of Illinois, where 8-12 inches of snow was common.

It is always fun to read the newspaper articles that always follow a busted forecast to see who gets the blame. See if you can find the faulty logic from this article from the Indianapolis Star…

The storm system that was supposed to dump 6 to 8 inches of snow on the area instead left a little more than an inch of slush — enough to make roads slippery but nothing that required plowing heroics. A low pressure system that was supposed to cross the state near the Ohio River shifted north and shoved the major snowfall away from Central Indiana. “The 6 to 8 inches we were supposed to get ended up being 100 miles farther north,” said Logan Johnson, a meteorologist with the National Weather Service in Indianapolis. Weather service forecaster Michael Koch said thunderstorms in the Gulf states walled off the moisture that could have fallen here as snow. Winter storms are hard to predict because the storm track decides the intensity of the snow, he said.

I suppose it is bad PR for an NWS forecaster to say that NOAA computer models botched the forecast, so instead thunderstorms in the Gulf states got the blame. But if thunderstorms down south took away all the moisture, then why did the heaviest snow occur 100 miles farther north? If the thunderstorms were truly to blame, then why did Chicago get 8-12″ of snow?

Even the Louisville NWS office was duped by the GFS. They issued a winter weather advisory for northern KY that predicted 0.1 – 0.3 inch freezing rain accumulations overnight on Thursday with temperatures below freezing. Instead, as the storm tracked farther NW, temperatures in Louisville rose to the lower 40s with a steady rain.

As I have said before in this blog, the SE ridge, which has been responsible in part for the mostly snowless winters in the Mid-South for the past two winters, the drought of 2007, and the August 2007 heatwave, is the meteorological equivalent of the New England Patriots. And just like it is foolish to bet against the undefeated Patriots, I will always bet on the SE ridge to have the final say in any storm that ejects out of the Southwest. Until, the SE ridge is beaten, all forecasters should consider its impact on shortwaves and expect storms to end up NW of model projections, even if the storm less than a day away.

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