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Friday January 18, 2019

Assignment: Predict the snow depth at the end of the day (inches) for Omaha, NE (KOMA)

A big storm will be forming to the east of the Rocky Mountains later today, and it's expected to bring heavy snow to the Northeast over the weekend. But before that, it will bring some significant snow to the Great Plains. The National Weather Service is reporting 3 inches of snow currently on the ground in Omaha, Nebraska, and the models are predicting from about 0 to 6 inches (predicting the exact amount of snowfall isn't easy!) of new snow during the day Friday -- for example, here's one forecast map of 24-hr snowfall. So let's forecast the snow on the ground at the end of the day Friday for Omaha and see what happens.

Question: To predict the future snow cover, it makes sense to start with the snow currently on the ground and then add the predicted new snowfall. But that ignores one possible factor that could make a big difference -- what is it?

What Happened?

The snow for Omaha really fizzled out. There were several hours of light snow, but the amount was not even measurable (reported as "trace"). Here's what the NWS said: "Snow yesterday was less than initially expected due to lack of ice aloft/lack of deep moisture, so the precipitation type remain freezing drizzle for more of the area and was of longer duration." So the snow on the ground reported at the end of the day was the same as before the day: 3 inches.

Forecasts for Omaha, NE (KOMA)
Forecaster Snow depth, inches (error) Comment Day Score
GFS-MOS-12-DAY02 3 (0) 3.3
NAM-MOS-12-DAY02 3 (0) 3.3
GFS-MOS-06-DAY02 3 (0) 3.3
GFS-MOS-00-DAY00 3.7 (0.7) 2.9
NAM-MOS-00-DAY00 3.7 (0.7) 2.9
GFS-MOS-18-DAY01 5.2 (2.2) 2.1
1. lkirkman 0 (-3) There is no snow in our forecast. It is 45 degrees and sunny in Randleman, NC. 1.6
GFS-MOS-12-DAY01 6.8 (3.8) 1.2
NAM-MOS-12-DAY01 6.8 (3.8) 1.2
GFS-MOS-06-DAY01 6.8 (3.8) 1.2
GFS-MOS-00-DAY01 6.8 (3.8) 1.2
GFS-MOS-18-DAY02 6.8 (3.8) 1.2
NAM-MOS-00-DAY01 8.2 (5.2) 0.4