A follow up: this blizzard did come out like I expected for northeastern Colorado. Blizzard conditions were observed in Burlington, Colorado, and probably some other places nearby (unfortunately some sites stopped working).
Snow totals were generally what was expected across northeastern CO and western NE/KS (my focus area) and the forecast verified well across the Upper Mississippi Valley / Great Lakes.
But there was one area where the forecast was a bit off. Late Tuesday afternoon, the NWS upgraded the Denver metro area from a Winter Weather Advisory to a Blizzard Warning with…
* SNOW ACCUMULATIONS...6 TO 12 INCHES. THE DENVER AREA IS EXPECTED TO SEE 4 TO 8 INCHES WITH HEAVIEST AMOUNTS AND STRONGEST WINDS FOUND ACROSS EASTERN PARTS OF THE METRO AREA.
What actually fell… more than double that, with generally 18-30 inches in the Denver metro! (No disrespect meant to the NWS as this storm surprised nearly everyone.) Denver also had blizzard conditions for more than 5 hours!
So what happened? Well, the storm track shifted slightly west and moisture increased. Additionally, some characteristics of Denver’s geography — namely its location just east of the Rockies — allowed for strong upslope winds. This enhanced atmospheric lift — in other words, it led to much more snow. (For more details check out this excellent blog entry.)
Thus, while the storm was slightly different than expected, the unique geographical characteristics of the Front Range enhanced those differences and created a crippling blizzard. While the mechanics are very different, this is not unlike “surprise” snowstorms along the East Coast, where minor changes in a storm are enhanced by the unique geography of the region. Bottom line: in places like Denver or the Boston-Washington corridor, the line separating minor snowstorms and major blizzards is often subtle. While weather forecasting has greatly improved in the past few decades, forecasting extreme storms remains a big challenge.