On an unexpectedly snowy day Thursday — Baltimore’s snowiest in November since at least 1989 — the region unofficially set a record for its wettest year in the books.
As of 5 p.m., an inch of precipitation had fallen at Baltimore-Washington International Thurgood Marshall Airport, enough to surpass an annual precipitation record of 62.66 inches, set in 2003.
It came down as snow and then a mix of sleet and rain at the airport, but elsewhere, cold air kept temperatures stubbornly close to freezing. That drove up snow totals to as much as 5 inches in parts of Carroll, Baltimore and Harford counties along the Mason-Dixon Line.
The mess of precipitation closed schools across the region and threatened to cause further disruptions Friday morning. Rain and snow were possible overnight, with temperatures forecast in the lower to mid-30s.
National Weather Service meteorologist Jason Witt said a high pressure system off the coast of Maine was to blame for steering a steady stream of cold air from eastern Canada into the region. He said it’s unusual for those conditions to come together and produce significant snow in the mid-Atlantic in November.
“This was one of those rarities in November where cold air happened to be in place, and it wasn’t going anywhere fast,” Witt said.
November snowfall is relatively common in Baltimore but usually leaves just a trace of flakes. With at least 1.7 inches of snow at BWI, though, Thursday became the snowiest November day there since 3.8 inches fell over two days, Nov. 22-23, 1989. If updated airport snowfall totals expected to be released later Thursday night surpass 2 inches, then it would be the most snow on a November day since 1987, when 6 inches fell Nov. 11.
The arrival of accumulating snow was also earlier than normal. The last time measurable snowfall — defined as a tenth of an inch or more — fell at BWI earlier than Nov. 15 was in 1996, when 0.3 inches fell Nov. 12, according to weather service records.
The annual rainfall record was not unexpected — it has loomed inevitably for weeks — but was nonetheless dramatic given that there are six weeks left in 2018.
It was largely the product of a persistently wet weather pattern over the late spring and summer, which brought deadly flooding to Ellicott City in May and Abingdon in August. Baltimore set five daily rainfall records so far this year, two of them surpassing 4 inches, and July was the wettest on record for that month, with 16.73 inches of rain.
While the remnants of Hurricane Florence and Hurricane Michael brought some rain in September and October, the rain record stands in contrast to many of Baltimore’s other wettest years on record. They are often associated with memorable hurricanes, or “nor’easter” winter storms — but there weren’t any of those in this year, either.
2018 may be Baltimore’s wettest calendar year on record, unofficially, but the region is still a few inches away from a record for its wettest 365-day period — 65.95 inches in the period ending Aug. 4, 1889.
Dry weather is forecast to arrive Friday, and through the weekend, with high temperatures expected in the upper 40s and lows in the lower 30s.