SNOWFALL FORECAST: How winter weather predictions stacked up to reality on Friday
Meteorologists are scientists, and in the world of science, comparing expectations to reality is key. FOX 5's Matthew Cappucci looks back at his predictions for Thursday's snowfall to see how his predictions stacked up.
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Officially we recorded 2.6 inches at Reagan National Airport. Combined with the 6.7 inches that fell Monday, we’re actually just shy of an average season’s worth of snowfall — and we’re not even halfway done with winter. There are reasons to believe that more wintry weather could be on the way, with a chance of some icing as early as Sunday.
When Matthew entered the weather office on Thursday morning, FOX 5's Mike Thomas had already made a templated snow graphic after reviewing data from the night before. Matthew says he pored over morning model runs and looked at what had happened upstream in Nashville, Tenn., where 6.3 inches came down. It was Music City’s greatest snowfall since January 22, 2016. Lexington, Ky. picked up 9.9 inches, their seventh-greatest single-day snowfall since records began in 1887. The storm had a history of overachieving.
Matthew says he maintained the expectation of 2 to 4 inches in D.C., but expanded the 3 to 5 inch zone to our west and added a new category of 5 to 7 inches in the Alleghenies and into the Panhandle of Maryland. He also believed that a tightly-focused filament of moisture north of the rain/snow line resulting from frontogenesis, or the formation of a cold front at the mid-levels of the atmosphere, would enhance snowfall over St. Mary’s and Calvert Counties, as well as over the Delmarva Peninsula. He added a 3 to 5-inch category there.
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With the offshore storm usurping some of our moisture, Matthew says he anticipated a sharp northwest snowfall gradient/cutoff, and kept low amounts near and north of the Mason-Dixon Line.
All told, Matthew says he would give his forecast a B. Here’s what went right:
- We were spot-on in D.C. to keep 2 to 4 inches. Widespread 2 to 3 inch reports with a few reports in the 3 to 3.5 inch range were realized within the Beltway. That panned out beautifully.
- Matthew says he was correct in bumping up snowfall to our west. There wound up being more moisture to work with (evidenced by what happened in Kentucky) on the northern periphery of the system, and I anticipated it being forced upwards where it would cool, condense and deposit snow.
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Here’s what Matthew says he missed:
- He believes he should have been more aggressive with snow totals off to our west. In addition to the 5 to 7 inch category, he says he should have added a 6 to 10 or a 6 to 12. Even Hagerstown saw 6.2 inches.
- In retrospect, he says he should have been more bullish with snow near the Pennsylvania border, where a persistent band of snow had become established by evening. Thurmont, east of Hagerstown, saw 8 inches, though Gettysburg, just a half-hour to the north, saw 2.5 inches.
- Matthew says he mis-forecasted where the frontogenetic band of snow would become established. In the end, the Delmarva Peninsula and regions in the Virginia Tidewater/St. Mary’s and Calvert Counties didn’t see the 3 to 5 inches he called for. On the contrary, they experienced much less. Instead, that band of snow occurred in northern Delaware, New Jersey and New York State, where the storm overachieved in a big way. Up to 8 inches fell in the Big Apple, doubling estimates.
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- Matthew notes that FOX 5's Caitlin Roth, very smartly, removed his eastern 3 to 5 inch category in the afternoon when models began to depict that zone of snowfall not materializing. She also adroitly expanded the 2 to 4 inch zone northwards. Caitlin's afternoon forecast, made with the benefit of midday model data, deserves an A, according to Matthew.
On the western flank of systems, there are usually two areas of enhanced snowfall — one northwest of the band of "frontogenesis," and one on the far western side in a region of "deformation," or stretching, in the atmosphere. This time around, the deformation zone caused overperforming snowfall in northwestern parts of our viewing area, while the frontogenetic band didn’t get going until it was northeast of our area. Pinpointing those bands is never easy.
No meteorologist is ever going to get things 100 percent right, and Matthew says he's pleased with how things panned out, especially in D.C. Scientists can only get better through an open and honest self-reflection and an assessment of what went right and wrong.
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