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March 12, 2018. Below is the stage IV precipitation analysis (verification data) for the event. The color scale is the same as used for the model runs. Below are the 00z and 12z model runs up to the event. The Euro is top left, GFS is top right, GGEM is bottom left, and ICON is bottom right. This gif starts 96 hours before the last run. Before that there was another event, and weather.us doesn't have a way to distinguish between the precip totals. We're missing some of the earlier ICON runs below because I didn't realize that weather.us only archives them for about 7 days. I'm still looking for a consistent way to compare model output for snowfall. Instead of snow depth maps, below I show different snow total maps. They include 10:1 maps for the GFS (top right) and GGEM (bottom left), qpf as snow for the Euro (top left), and the snowfall map for the ICON (bottom right) using its own ratios. This gif starts 108 hours before the last run. Before that there was another event. (Some snow from that event can be seen in NE MD in the earliest panels.) For comparison with the above plots, here are the reported snowfall totals from LWX. This map doesn't cover the entire state of Virginia, so I've also added a map of CoCoRaHS reports from 03/13.

A few thoughts on model performance for 03/07/2018: 1. The Euro did very well in the long run. It consistently showed some sort of snow event for the nothern tier from 10 days out. I hadn't noticed that until I put these maps together. 2. At about 6-7 days out, the GFS showed some good widespread hits, like this one: They had support from the GEFS, but not from the other models or ensembles. We didn't get a widespread hit, but it wasn't as bad as what the Euro showed at that time. 3. The GGEM lost the storm about 72 hours out, sending it out to sea. It gradually came back over the next two runs. It was interesting that the extended RGEM still had the storm when the GGEM had lost it. 4. All of the globals struggled with western edge of the precip. The Euro went from giving Lancaster, PA nearly no precip to about 1.5" in four runs within 72 hours of the storm. They got about 0.3". After the 18z runs the day of the storm, the HRRR started picking up on an eastward shift in the precip shield that ended up verifying. The 03/06 12z RGEM ensemble mean also overdid the western extent of the precip But a small fraction of members (about 10%) showed the risk of the shift. I'm still trying to figure out how useful the RGEM ensemble is, and one of the things I've been wondering is whether we should pay attention to the spread in the members at game time. This above plot suggests the answer is yes.

March 7, 2018. Below is the stage IV precipitation analysis (verification data) for the event. The color scale is the same as used for the model runs. Below are the 00z and 12z model runs up to the event. The Euro is top left, GFS is top right, GGEM is bottom left, and ICON is bottom right. This gif starts 84 hours before the last run. Before that there was a rain event, and weather.us doesn't have a way to distinguish between the precip totals. To get a better sense on how the models did in predicting snow, I plot the snow depth maps below. Snow depth is not a great metric because 1) Every model seems to calculate "snow depth" differently. (The Euro appears to use a more generous algorithm than the other models.) 2) There is something wrong with the snow depth maps for the GGEM on weather.us. It appears to ignore all depths below 2", which makes it look like the GGEM predicted no snow in areas where it predicted low snow depths. Unfortunately, it's the only metric of snowfall available for all four models on weather.us. The Euro is top left, GFS is top right, GGEM is bottom left, and ICON is bottom right. This gif starts 192 hours before the last run. For comparison with the above plots, here are the reported snowfall totals from LWX.

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Moved this post to the second page so we don't have too many graphics on the first page. https://www.americanwx.com/bb/topic/50849-post-event-model-discussion/?do=findComment&comment=4871375

Moved this post to the second page so we don't have too many graphics on the first page. https://www.americanwx.com/bb/topic/50849-post-event-model-discussion/?do=findComment&comment=4871363