Is it me, or did it feel like March just whipped by? We’re about to head into the first full month of astronomical spring, and there’s loads to look forward to! Flowers in full bloom. The Boston Marathon, Red Sox baseball, and the Bruins and Celtics playoffs. And literally anything outdoors, where, of course, chaotic spring weather always makes you think twice before you firm up plans.
Here are some takeaways from our April forecast and what they mean for the kind of weather we can anticipate.
1. Closer to seasonal temperatures and precipitation
Despite facing one of our snowiest winters in years, March has been pacing warmer than average with roughly normal amounts of precipitation, and much less snow.
April is likely going to see closer to seasonal temperatures and precipitation across Boston and New England. It’s a different story elsewhere, where folks south and west of here may see much warmer temperatures with varying amounts of precipitation.
2. A nudge cooler and wetter to start, however
If I had to tip the scale one way or the other, aside from average temps and rain, I’d say our region holds better chances to nudge cooler and wetter than normal, at least to start the month — and that’s not an April Fool’s joke.
That’s because lately the coastal waters have been cooler than average, and our larger-scale pattern suggests a wavy jet stream is probable, which, of course, can bring colder air from the north to enter the region more than usual.
3. Without a pronounced El Niño, a disrupted polar vortex
Without a pronounced El Niño or La Niña in place, which influences the type of weather we experience across the country, I looked elsewhere to try to find any signals of whether or not April will run wet, dry, warm, and/or cold.
With winter and early spring experiencing quite an active jet stream pattern, I peeked at the Arctic Oscillation (AO) climate pattern — essentially the fluctuating pressure difference between the Arctic and mid-latitudes. The AO directly impacts the temperatures we feel and subsequent precipitation. A positive phase signals a strong polar vortex with cold air held to the north, while a negative phase reveals a weaker polar vortex with cold air usually locked up north, likely to stretch, break up, and travel south.
Almost the entire winter experienced a negative phase of the Arctic Oscillation, and hence, we saw more cold days and snow. The latest trends show a decent chance for the AO to turn negative for perhaps the first half of April. Should this happen, again, we may see more cold days than warm to start the month.
4. Cooler sea-surface temperatures
There have also been cooler sea-surface temperatures along the immediate East Coast as of late, which would keep the atmosphere, especially along the coast, including Boston, a touch cooler than normal, negating some of the isolation or heating from the increasing sun angle throughout the month.
We’ll see a dramatically increasing sun angle with 70 to 80 minutes of sunlight gained throughout the month. Boston’s sunset will grow from 7:10 p.m. on April 1 to 7:42 p.m. by the time we hit May. Our sunrise will expand from 6:26 a.m. to 5:40 a.m.
5. What recent weather history tells us
All in all, Boston has seen five straight years in which the average April temperature ran warmer than the 30-year average (1991-2020), regardless of what climate patterns were in place. During that timespan, the last four years were drier than average.
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Ken Mahan can be reached at ken.mahan@globe.com. Follow him on Instagram @kenmahantheweatherman.