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:
Clouds overspreading New England Monday are indicators of change in the atmosphere - a new airmass spreading northeast from the Ohio Valley, where early morning temperatures began the workweek in the 60s! Though I'm not expecting a start quite that warm here in New England this week, I do think a sliver of this mild air will move into Central and Southern New England on Tuesday, before cooler but very pleasant air sweeps south for the middle and end of the week.
Any black ice early Monday morning melted quickly as temperatures rose with the combined help of sunshine through increasing high altitude clouds and an increasing southwest wind. This wind will remain active through Monday as New England is sandwiched between a surface high pressure cell drifting east off the Atlantic Seaboard, and a series of weak low pressure systems rippling along an eastward moving cold front through the Great Lakes. Because winds blow in a clockwise direction around a high pressure center, and counter-clockwise around low pressure, this forces an increasing southwest wind across New England, and in north-south oriented valleys like the Champlain Valley of northwest Vermont, this wind will be redirected from the south and may gust as high as 40 mph.
Meanwhile, an energetic disturbance is moving across the Upper Penninsula of Michigan, with a weaker bundle of energy preceding it across New York State Monday morning. It's the leading, weaker disturbance that will move across New England on Monday with showers coming across the New York State border around lunchtime and spreading east through most of the rest of New England except Central and Eastern Maine between 2 and 5 PM, and this will mean that communities experiencing rain will find a slowed evening commute. You can, of course, follow the showers on radar through the links at right. It's been interesting to follow the radar imagery through Monday, as the "bark" has been worse than the "bite" with these showers, showing up as strong "reflectivities" that would imply heavy downpours or thunderstorms. During Monday morning, this radar signature was deceptive, as only light rain was being reported beneath the echoes, yet numerous cloud to ground lightning strikes were present with some of the heavier storm cells. This phenomenon results when lots of moisture and warmth is moving into a region, and because warm, moist air is less dense, this air rises quickly, creating deep clouds chock full of water droplets and ice crystals. In the lowest few thousand feet of the atmosphere, however, dry enough air is present that the raindrops falling from these vigorous cloud formations mostly evaporate before reaching the ground, leaving behind light rain at the surface, but still experiencing the frequent lightning strikes associated with the more vigorous storm occurring thousands of feet above the ground. This will be a similar case across much of New England for a brief time when the rain commences, thanks to our own supply of dry air at the surface, though as more moisture piles into the system, rain will become heavier and these bursts will begin to reach the surface as heavy downpours, at times. Though conditions will not be quite as favorable for thunderstorms in New England as they were in New York State, isolated thunder is still possible for Western Massachusetts and Connecticut Monday afternoon through the first half of Monday night. As warm and moist air erodes the lingering surface cool and dry airmass, fog will develop and a combination of low clouds and fog is expected to linger into Tuesday morning, even after the showers have dwindled pre-dawn.
Through the day Tuesday, a weak wind shift will drop south across New England. Though this wind shift will have a history as a weakening cold front, there will be very few cold frontal characteristics left with it when it moves through, instead simply representing a wind shift that will bring winds out of the northwest - a "downsloping" wind that slopes down off the mountainfaces and hillsides for a lot of lower elevation communities of New England. With mild air in place, very little cool air streaming in, and a steady downsloping wind that will push air into lower elevations, thereby allowing it to warm and dry upon descent, sunshine will break through the deck of low altitude clouds for most of Central and Southern New England from late morning onward. The combination of warming strong late-March sunshine with downsloping winds will push Southern New England locales into the 70s Tuesday afternoon while Central New England rises into the 60s. Farther north, sunshine will come in the form of breaks between clouds as Northern New England straddles the boundary of warm and cool air, awaiting the arrival of new Canadian cold, and the limited sun will hold temperatures in the 50s. Though there will be little to focus showers or thunderstorms at the surface by Tuesday afternoon, there will be a warm airmass in place at the same time a moderate strength upper level energy center rides over Southern New England, and this may trigger a few Tuesday afternoon showers and thunderstorms in Southern New England.
The next big feature on the weather map will be a southward sagging cold front across Quebec, heading south toward New England. This front will represent the leading edge to a hearty shot of cool air in place across Central Canada, associated with a large and strong high pressure cell that will be expanding over Hudson Bay, Canada, and moving gradually southeast. As the high pressure cell grows, its reach of clockwise airflow - and therefore northerly winds on the east side of the cell - will increase, driving the next installment of cold air into New England from north to south overnight Tuesday night. Though this air will have a better hold of New England on Wednesday, it will truly be a slow bleed southward, and therefore temperatures probably won't reach their coolest period until Thursday. This will leave a gorgeous day of sunshine for midweek thanks to the steady supply of dry air from Canada and a northerly wind, with temperatures certainly cooler than Tuesday but still running above normal for the date, which would be close to 50 degrees as a New England average. After a cool night Wednesday night, expect the coolest day of the week's end to come Thursday, as Canadian air will be squarely in place across the six-state region with winds picking up in speed from the northwest as a strong storm cranks up in extreme Eastern Canada while the nearby high pressure cell weakens, though still remains strong enough to exert its influence, especially when resulting in a big pressure difference from the Eastern Canada storm.
The expansive high pressure cell will lock dry and cool but pleasant conditions into New England through Friday, when a few high altitude clouds will increase late. All the while, the jet stream pattern aloft for the end of the week will feature one major upper level storm over Eastern Canada - associated with the aforementioned surface storm that will help to keep cool, dry air in and our winds cranking later in the week - and another slug of significant energy moving east out of the Eastern Pacific and across the Rocky Mountains into the Central United States. This type of a pattern, with two very strong disturbances over a relatively short distance (Rockies to Eastern Canada isn't far in the scope of the global atmospheric scale), is referred to as an "amplified pattern" because the dip in the jet stream with each disturbance is quite pronounced, creating large undulations in the jet stream winds that steer our storm systems and act as a thermostat for the atmosphere, leaving deep troughs of unsettled and cool weather very nearby to cresting ridges of warmer and fair weather. With such an amplified pattern by the end of the week, this will mean a rapid transition to a milder regime by Saturday, likely followed by at least some showers if not a more meaningful rain for the end of the weekend. This amplified pattern, however, will likely lead to its own demise, as cool air dragged down from Canada by each strong disturbance will beat down the ridging warmth, resulting in the development of a more stable, flatter pattern for the United States next week, though a pattern that's likely to bring cooler air to the northern tier of the country, and especially to the Northeast for part of the first week of April.
Looking forward to the warmth tomorrow afternoon - see you back here tomorrow!
Matt
Matt's Technical Meteorological Discussion: Updated Monday, March 26 at 1:15 PM
Clouds and precip come courtesy of isentropic lift coupled with leading vort max ahead of primary vort moving across Great Lakes. First vort max brought multiple CG lightning strikes even tho light rain for a time, then the boundary layer moistened. We're in a similar situation tho without the lightning for Nrn NewEng as I write, which makes sense given decreased llvl speed convergence and decreasing theta-e gradient. Still, as air becomes more saturated, elevated instability increases and Wrn NewEng may see thunder before the day is out. Farther south, slug of warm and moist advection has been less focused thus far but still will be sufficient to generate sct shra and then dynamic lift assoc with and ahead of main vort max this eve and tonight will be enuf to generate widespread shra, downpours and isolated tsra perhaps from Wrn MA to CT. Wind shift early Tue truly is a trof rather than a cold front at its leading edge, tho I suppose technically it's still a cold front, just with the temp gradient lagging far behind. The airmass change is lax in coming south because it must wait for the eastward movement of the high over Hudson Bay, which happens but not until later. This actually means the passage of the wind shift favors more warming than otherwise in Srn NewEng as winds turn from the northwest and downsloping kicks in, warming many locales of Srn NewEng into the 70s as this downsloping helps to break up deck enuf for sun. I know RH progs are very high, but that's similar to what we're seeing upstream in OH Valley today and tho clouds are numerous, sunshine is effective and temps have been soaring. We're likely to see the same result in Srn NewEng on Tue afternoon after morning fog and low clouds that will be stubborn, with deck hanging until late morning when wind shift kicks in a bit. Still, we're looking at a wind shift line/front that doesn't completely clear Srn NewEng, and a few extremely weak mesoscale waves of low pressure will develop along it. This slight lowering of pressure, along with the warming interior, is likely to favor a sea breeze for almost all Southern NewEng coastal locales, whereas BOS may not get over 56 or so degrees before the sea breeze initiates, while LWM hits 70. A bit trickier on the SCoast of CT where GON may go to 62 or so and then fall back, but stronger NW gradient flow in HVN argues for mid 70s! Weak vort max Tue afternoon/eve may spark a thunderstorm in CT with sfc based LIs approaching 0.
Wed thru Fri brings installment of fresh, clean, dry and cool Canadian air. High amplitude pattern flow suggests quick warming on Sat, and perhaps several degrees above normal, before rain event to end the weekend and cooler air to begin April.
Matt
