So what have been the extreme snowfall amounts for past NWS Marquette Halloweens?
The previous records haven't been that impressive:
For Halloween 2012, we had 2.9 inches! This breaks the previous record snowfalls here at our office!
So what caused this excess snowfall and blustery weather for Trick Or Treaters?
The former Hurricane Sandy brought abundant moisture to Upper Michigan, and led to northerly winds off of Lake Superior. Upslope flow (associated with the higher terrain) and Lake Effect kicked in, allowing for scattered to numerous rain and snow showers to develop across the area.
Here are a few images from around 830 AM EDT on Halloween. The top left shows radar reflectivity, with the highest values (best precipitation) along Lake Superior and the high terrain. The observations in the top left picture also show the gusty northerly winds that were observed along the Lake Superior Shore. The image on the top right shows a topographic map, with the red values being the highest terrain. Notice how the highest reflectivities on the radar match the highest terrain! The bottom left shows the Relative Humidity in the lower layers of the atmosphere around the same time, which was 90% or so in the North Central and Eastern U.P.-courtesy of Sandy and Lake Superior. The last image, bottom right, shows the tight pressure gradient (leading to gusty winds) and forecasted winds for that time period (around 8 am EDT).
The image below shows the low pressure center that was Hurricane Sandy over the Lower Great Lakes, complete with infrared satellite imagery. The brightest colors on the infrared indicate colder cloud tops. This image was taken around 12 pm EST.