Welcome to the weather blog - a regular Monday through Friday discussion of the weather! While the discussions usually will only come on days I'm working, I'll issue special updates when the weather warrants. I will always post to let you know when no discussion is expected if I'm away on vacation, etc. - if no update is here and no info is available, that likely means the server has temporarily gone on the fritz and I will update as soon as technically possible. You'll find a quick weather synopsis linked to the daily forecast at the top of the page, a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow by mid-afternoon. My email is contact@mattnoyes.net. This blog is for you, so I hope you enjoy it! -Matt Noyes
General Weather Summary:
The cold front that moved across New England on Tuesday has stalled across the Mid-Atlantic, separating warmth and moisture over the Southeastern quarter of the country from cooler and drier Canadian air that's been sneaking south across the Northeastern U.S. This battle zone will serve as a pathway for pieces of the strong storm across the nation's midsection, as bundles of energy and moisture break away from the main circulation and run to the Eastern Seaboard.
One of these energetic disturbances has been producing plenty of clouds across especially Central and Northern New England on Wednesday, though dry air in the lower several thousand feet of the atmosphere has been preventing precipitation from falling for most of the day. Though this moisture is riding overhead, at the surface a fair weather cell (high pressure) is in place, meaning the dry air continues to hold tough, and winds are light around the center of this high pressure system. These light winds have been shifting in direction through the interior, but have allowed steady sea breezes to develop at the coastlines, holding temperatures in the 50s for our coastal locales while inland counterparts warm a bit more. As described in the past few days of discussions, last year's dead vegetation and brush has dried out extremely quickly with our recent dry airmass, and the past few days have brought sunshine and very low relative humidity thanks to the lack of moisture in the air combined with rising temperatures. Rapid drying of old brush and undercover raises the concern for brush fires, and after a couple of days of battling blazes, the highest fire danger on Wednesday is found across most of Northern New England. Of course, fires in dry weather cannot start without an incindiary device, so the challenge is not to provide anything that could breed a fire - controlled burns must be very closely managed and constantly monitored, and even cigarette butts can serve to start fires in conditions like these.
Meanwhile, the jet stream pattern across the Lower 48 has taken on the signature of what's referred to as a "split flow" - that is, northern stream energy and cool air operating rather independently of southern stream energy and significant moisture. When the two streams combine, a large and moisture-loaded storm is often the result, but in the near future, such a volatile merger is not anticipated. Instead, the "trough" or dip in the jet stream is forecasted to relax over Eastern Canada, gradually relaxing the input of dry Canadian air, while the southern stream sends sprialing energy gradually migrating east out of the Rockies and Plains. This energy resulted in a rare combined event of Colorado Rocky Mountain snows and foothill tornadoes - in some cases only a couple of counties apart - on Tuesday, with severe weather that rumbled through the Plains. The same storm will touch off severe weather outbreaks from the Midwest and Western Gulf States on Wednesday, then the Central/Eastern Gulf States and Ohio Valley on Thursday. This weather pattern change all gradually shifts moisture toward New England, on the northern side of the responsible southern stream disturbance. After prolonging the arrival of rain through Wednesday, the first formidable disturbance to carry a chunk of moisture east will pass south of New England Wednesday night. With Connecticut, Rhode Island and Cape Cod near the northern fringe of this disturbance, light rain showers are possible from west to east in these locales from Wednesday evening through the first part of the overnight. Later Wednesday night, though, another push of dry Canadian air will settle south behind this disturbance, clearing skies and providing a sunny start to our Thursday.
This new installment of dry air will be impressive enough to continue holding even most cloud cover at bay to our southwest on Thursday, and though our air may not be warm in origin, strong mid-April sunshine will modify temperatures above normal in all locales Thursday afternoon. Once again, winds will be relatively light and a sea breeze will result for our coastlines. By later Thursday, the same primary storm will be winding into the Great Lakes, with its counter-clockwise flow of air around it, and yet again it will eject a disturbance toward the Eastern Seaboard. This time, however, the incoming disturbance will come with a stronger flow of warmth and moisture on an increasing southerly wind aloft, and that will thrust clouds and precipitation farther north than its predecessor.
Because this incoming precipitation is driven by a southern stream disturbance with a tropical tap to the Gulf of Mexico, and because the tap of Canadian cold will have diminished, rain is by far the most likely precipitation type for all locales. The rain will blossom in the predawn hours of Friday as miosture and warmth charge into New England, and will fall heavily at times on Friday morning, when the strongest push of warmth moves in, and may even be accompanied by a rumble of thunder. In fact, amist all of this and the respective airmass change, a wave of low pressure is likely to develop near the New England coastline. While this weak storm center will help to focus rainfall through the morning, and will also bring rain ahead of its passage and taper steady rain to showers behind it Friday afternoon, the weak counter-clockwise surface wind flow will keep a cool northeast flow in most of Northern New England, and especially New Hampshire through Maine, where highs may not exceed the 40s. Farther south, the passage of the warm thrust and attendant low pressure center will mark the leading edge to deeper warm air that will bring temperatures into the 50s and perhaps even near 60 the farther south one is. Thereafter, it's likely that a sizeable chunk of the energy driving these changes from the southern stream will actually park over the Great Lakes, where it will slowly degrade while awating a push from the northerly jet stream winds to jumpstart it again. As it spins, it will bring drier air into its circulation, and that's likely to arrive to New England on Saturday and Sunday, bringing back some sunshine. Still, with spokes of energy rotating around the main disturbance, a few showers are likely Saturday afternoon in scattered form across New England.
By Sunday, what's left of this disturbance will move over New England with another round of scattered showers amidst sunshine and perhaps a thunderstorm with the passage of a weak cold front. In the extended pattern, a general pattern of a jet stream "trough" or dip will linger into the start of May, keeping us vulnerable to shots of cool air, and shots of energy that can bring occasional precipitation events of moderate intensity. Nonetheless, it doesn't appear as though any period of dramatically below normal temperatures is in the extended range forecast, even though some bouts of cool air may push us below normal for one or two days at a time.
Enjoy your Hump Day.
Matt
