As One Disturbance Departs, New England Readies for the Next
April 27, 2023
The large jet stream level disturbance that’s been meandering east out of the Great Lakes all week, increasing our chance of showers each day in New England, is finally passing through our New England sky Thursday. Though not exceptionally strong anymore, this disturbance carries a pool of cold air aloft, thousands of feet above our heads, which will prove important in our Thursday forecast. Cold air aloft, with near-surface temperatures rising into the 50s as has been the case the last few days, will create a temperature contrast that will result in building, puffy, cumulus clouds that, during the late morning through early evening, will grow tall enough to produce rain showers. In fact, there’s enough cold air aloft that we will likely see a decent amount of ice form in the top of these clouds, which means embedded downpours, a few lightning strikes and even some small hailstones – balls of ice at the core of the downpours – are possible Thursday afternoon into early evening. While none of these are expected to become damaging, keep in mind the old adage, “When thunder roars, go indoors!” This is a reminder if you can hear thunder, the lightning strikes are close enough you should seek shelter. By late day and early evening, even Cape Cod – exempt from most of the showers that cropped up over recent afternoons – should find a few showers crossing the Canal, but near and after sunset, any showers will quickly diminish, giving way to a clearing overnight sky with a few spots of fog, particularly in valleys. Friday brings a welcome break between atmospheric disturbances that won’t last long, but does deliver a great day – early pockets of clouds quickly give way to morning sun, then clouds increase during the afternoon to evening, but the day stays dry, regionwide. Most of New England should remain dry through Saturday morning, even as clouds take over starting late Friday – a swath of rain with the next approaching storm system will be slowly moving through the Mid-Atlantic Friday night to Saturday morning, though a few very isolated and light showers are possible for a brief time Saturday morning. Far more likely is the arrival of rain from southwest to northeast across New England, during the afternoon and late day for Southern and Western New England and evening to night in much of NH and ME. Rain should continue Saturday night into Sunday morning. Though it’s possible there’s a relative lull in rain intensity at some point Sunday, our First Alert Team is very hesitant to put a lot of weight in that from this juncture – at least some showers remain likely, an onshore wind very well may lock in low clouds and drizzle, and a new shot of rain will be moving into the region sometime later Sunday through Sunday night, anyway, so at this point we believe a damp day of off and on showers is the best way to plan. Next week brings a very similar pattern to this past week, but the slow-moving upper level disturbance stalling over the Great Lakes before nudging east over the course of the week will be larger and stronger, meaning the coverage of showers cropping up each day will likely be greater than most days this past week. That said, there may be a brief period of time, centered on Monday, where we enjoy mild air and fair weather from dry air in the wake of Sunday night’s rain, before those repetitive scattered showers return, anew, from Tuesday onward.