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September 2009

As cool air settles in, clouds become a familiar feature

Another surge of cool air underway Wednesday morning produces lots of clouds as the contrast between a cold sky and relatively warm ground sets cumulus cloud growth into motion.  Some of these clouds will grow heavy enough to drop a few light rain showers or sprinkles from time to time across New England Wednesday afternoon, though most communities will stay dry through most of the day.  There's no question the air is plenty chilly, though, with communities like Rutland and Montpelier, Vermont, struggling to get past 50 degrees for an afternoon high!  For as cool as Wednesday may be, the chilliest air will arrive Wednesday night and Thursday on a northwest wind.  Pushing up against the northern faces of North Country mountains, this wind will be forced up the mountainslopes and create clouds that very well may produce some snow showers in the higher terrain of far Northern New England!  Farther south, partly cloudy and cool conditions are expected to lead us into the coolest day of the week on Thursday, with more bubbling clouds to limit how much sun we see.  The weather pattern begins to shift by Friday, as winds turn to blow from the south, carrying warmer air toward New England.  Aloft, the jet stream starts to shift north, as well, and this also favors deeper warmth pressing toward New England, which is likely to create lots of Friday clouds, and perhaps even a few showers in far Western and Northern New England by late in the day.  More substantial rain, however, will wait until a more solid push of warm and moist air from the south, expected to develop from west to east early Saturday, and bring periods of rain, heavy at times.  Though a few surges of warmer and more moist air will create a few rounds of rainfall, it's unlikely that we'll see rain non-stop this weekend.  The trick, therefore, is timing the breaks in the action, and right now one of those breaks looks like it may come Saturday evening, with just scattered showers rather than steady rain.  It's still early, though, and this will become clearer with time.  Sunday should bring moring rain, then gradual drying and partial clearing from west to east during the afternoon, with eastern areas seeing the rain ending last.

Video Forecast: As cold pool aloft moves into New England, showers, thunderstorms and hailstones result

Cool air has begun its move into New England behind damaging thunderstorms that moved through Southern New England Monday evening and night.  A large and energetic storm center located north of Lake Ontario is associated with strong and cold Canadian energy, and has carried a slug of cool Canadian air southward with it.  The cyclonic wind circulation around the storm - a counter-clockwise turning of wind around the storm center - has carried that cool air across the Great Lakes, east across the Ohio Valley, and now into New England, slowly but surely.  At the surface, the cool air will continue to build through Thursday, which will likely be the chilliest of the week.  Aloft, the pool of cold air associated with the incoming storm will move into New England on Tuesday, and the difference between lingering *relatively* mild air near the ground and much colder air aloft will result in bubbling afternoon clouds after morning sunshine, and a cluster of showers, downpours and thunderstorms is likely beneath the cold pool of air Tuesday afternoon.  Greatest coverage of showers and thunderstorms will be in Central and Northern New England, though scattered showers are possible in Southern New England, as well.  Because the air is so cold just a few thousand feet off of the ground, hailstones (balls of ice) are possible with any thunderstorms that develop.  Thursday and Friday will bring cooler air to the lower levels of the atmosphere, meaning the difference in temperature from ground to sky will be less pronounced, and therefore showers will be less numerous and less intense.  In fact, Friday is likely to be mostly dry, though clouds may increase as warmer air aloft tries moving in from the south.  Eventually, this incoming warmth will clash with our cool air, creating rain - which right now looks unfortunately timed for our weekend...starting from west to east during the daylight hours of Saturday and continuing periodically through Sunday.  I'll hope to be able to improve this forecast as we near the weekend!!

Video Forecast: Indian Summer for many on Monday, then a slap from reality the rest of this week

Showers that swept through New England on Sunday were representative of the leading edge of warm air returning to New England, doing battle with the cooler, drier air that began the weekend.  With the showers departed, warmth is left behind as sunshine emerges, and high temperatures will near 80 degrees Monday afternoon - true Indian Summer conditions for folks who've seen their first frost (the requisite to term Indian Summer is a frost antecedent to 70+ degree temperatures).  A fast moving, energetic disturbance aloft will charge east across the Great Lakes and thrust a surface cold front east, as well.  In advance of this front, showers and thunderstorms have been sweeping across Western NY and PA even early Monday morning, and should continue moving east, bringing a round of windswept showers and possible thunder from west to east across New England Monday mid-afternoon through evening.  This won't be the only round of showers, as the energetic system emerging from the Great Lakes serves to instigate more showers through the overnight, culminating in nearly an inch of new rain for Eastern Maine by Tuesday morning.  Though drier air is expected to bring sun for a time Tuesday, cold air aloft will allow lots of bubbling clouds to develop with scattered showers and even a few thunderstorms back into the picture Tuesday midday and afternoon.  With such cold air just a few thousand feet off the ground, a few storms may contain hailstones!  Wednesday and Thursday will continue to bring bubbling clouds with a few showers and cool temperatures before a drier, brighter but still brisk day on Friday.  An early call on the weekend is for most of Saturday to be dry before rain moves back in late, perhaps leaving showers into Sunday.

Video Forecast: Split decision weekend - Saturday gem, Sunday soaker

For now, a dome of high pressure building southeast out of Canada is forcing a plume of moisture from the Pacific Ocean and Gulf of Mexico to split in two, with some moisture moving west into an energetic disturbance over the Eastern Rockies (responsible for Rocky Mountain snow earlier this week) and some moisture migrating east across the Mid-Atlantic.  As long as high pressure is in charge, we're protected.  Clear skies and nearly calm wind is expected Friday night as the center of the fair weather cell moves over New England, and this will mean frost as far south as Northern, Central and Western MA, and a hard freeze for all of Northern New England.  Saturday will bring a light wind and lots of sun for a very comfortable day, but by Sunday a surge of warmth and moisture from the aforementioned moisture plume will mean rain - likely developing late Saturday night from west to east - lasting until late afternoon Sunday.  Heavy downpours and even some rumbles of thunder are possible with a couple of inches of rain for some of Central and Southern New England!  If the sun comes out Monday, temperatures will rise to near 80 before a strong cold front sends windswept showers and potentially strong thunderstorms sailing from west to east late Monday, paving the way for cool air to move in through the remainder of next week.

Video Forecast: Autumnal battle of airmasses to bring changing weather to New England

A major storm will develop over the Great Lakes in the next several days, and will have a large impact on the weather here at home.  After a dome of cool high pressure crosses New England Friday and Saturday, the counter-clockwise spin of air around the Great Lakes storm will thrust warmth and moisture back toward New England, with a tap from the Gulf of Mexico.  The collision of warm and cool air overhead will create rain, likely to be heavy at times, on Sunday.  Though the timing may change as we near the event, right now I'm thinking the rain will come smack dab in the middle of the day, so I'm encouraging outdoor plans be made for Saturday, which looks delightful.  Behind this rain, the incoming warmth will be in place, so Monday may turn quite mild before strong thunderstorms are possible as a strong cold front and energetic system aloft team up to usher in what should be the coolest air of this young season by the middle of next week.

Video Forecast: Summer today, fall by Friday

Although sunshine will, at times, be dimmed by clouds of varying altitudes Wednesday, a southwest wind will do the job of bringing warmth and even returning humidity to New England.  This boosts temperatures above 80 in many Central and Southern New England communities before a cold front producing showers and embedded downpours/thunder drops southward across New England from late Wednesday north, to overnight Wednesday night south.  Early showers and clouds in far Southern New England Thursday will continue moving south and give way to clearing skies and pleasant air, before the core of cool, autumn air arrives on Friday.  By Sunday, the attempted return of warmth to New England may provide enough of a clash between airmasses to produce scattered showers.

Video Forecast: Temperature roller coaster for the days ahead

My apologies for no post yesterday!  I actually wrote the post and never remembered to hit the publish button!

Nonetheless, we'll pick up where we left off on Tuesday - high pressure has moved into New England with a surge of cool and dry Canadian air, and a northeast wind that's been picking up moisture from the Atlantic and carrying it into Central and Southern New England.  This input of moisture has resulted in plenty of clouds, and after reports of waterspouts near Martha's Vineyard yesterday afternoon, today won't bring nearly as much vertical development to the clouds, owing to the center of high pressure - sinking air - moving over New England.  This dome of cool air will break down as winds shift to blow from the west Thursday night, and continue to increase on Friday, warming the atmosphere into the 70s in the Southern half of New England.  An approaching cold front out of Canada will bring thickening clouds to Northern New England early Friday, with showers not far behind, and this will hold temperatures down in almost the entire Northern half of New England on Friday.  Behind the cold front, brisk fall air moves in for Saturday with wind gusts that may reach 45 mph Saturday morning and midday!  Nonetheless, milder air returns by Sunday, and the entire weekend looks mostly dry with plenty of sun!

Video Forecast: For some, highs reach 80 today...and will be 20 degrees colder on Wednesday

The change in weather over the coming 24 hours will be dramatic, taking some communities from a perfect late summer Tuesday near 80 degrees, to a harsh reminder that autumn is setting in beneath clouds and drizzle while struggling to break 60 degrees on Wednesday.  This abrupt change comes as a strong dome of high pressure builds across Southeastern Canada, carrying a shot of chilly air with it.  Not only is the air that's moving into New England for the latter half of the week cool by nature, but it will also move in on a northeast wind, meaning that cool air will traverse the Gulf of Maine, picking up moisture along the way and resulting in a deck of low altitude, gray clouds and drizzle for most of Wednesday.  The exception will be in the North Country, where a northeast wind doesn't carry an ocean component, but even with breaks of sun, Northern New England residents will still be plenty cool!  Thursday has consistently been looking like a relatively dry day with some breaks of sun (but still cool with a northeast wind), before Friday brings a chance of showers.  The weekend looks promising as a dome of high pressure settles overhead.

Video Forecast: Mid-Atlantic coast battered by hybrid storm...New England to get breezy leftovers

First, for those interested in the hybrid storm that ramped up off of the New Jersey coastline, and slammed the Jersey shore with damaging wind and flooding, I posted an analysis on the Northeast Regional Page of - click here to link to the regional page.

Meanwhile, back home in New England we'll find bands of rain associated with the storm pinwheeling northward into Southern New England Friday into Saturday, much weaker in nature and with just enough wind at the South Coast to produce some tidal flooding on the west end of Long Island Sound Friday afternoon.  Otherwise, rain will be accompanied by active breezes across Southern New England, but nothing too extraordinary (some coastal gusts to 35 mph), while Northern New England stays mostly dry.  Though Saturday looks gray and dreary the farther south you are, it also doesn't look like a day that will rain all day long - rather, periodic showers and drizzle.  Sunday still looks fabulous.

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Video Forecast: Sluggish rain holds off until Friday for most areas

A strong dome of high pressure crested over Northern Maine early Thursday morning, allowing for a hard freeze in a few valleys of Northern Maine, and a frost in our deeper valleys all the way south into Northern New Hampshire.  Nevertheless, a cool start will give way to a pleasant day with sunshine strongest in the North Country as high and middle altitude clouds spread back into Southern New England.  Coolest afternoon temperatures will be found along the coastlines as a wind comes in off of the water.  Showers will wait until high pressure starts to break down before they move in - arriving to far Southern New England Thursday night, and spreading to Southern New Hampshire gradually during the day on Friday, then moving farther north Friday evening and night.  Periodic showers are likely on Saturday before improving conditions move in Sunday through early next week.