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 coolest and windiest day of the bunch will be in New England on Thursday, as we remain under the influence of a huge high pressure cell that extends though nearly all of the Canadian Province of Quebec, southward to the northern Mid-Atlantic coastline. A slight rebound of mild air is expected on Friday, then a reinforcing surge of cool and dry air will be in place for most of the upcoming weekend.
This dry Canadian air is quite protective for the Northeastern United States, as the clockwise flow of air around the sprawling area of high pressure in Eastern Canada is keeping deep spring warmth, moisture, and Pacific energy at bay. To our west, across the nation's midsection, the intersection of cool, warm and moist air all created an amazing spectacle of severe thunderstorms along and ahead of a sluggish cold front, spawning 65 reports of tornadoes stretched from Texas to Nebraska on Wednesday, sadly resulting in two fatalities in Oklahoma. For the next few days, flooding rains and bouts of severe weather will continue to plague the Central United States, a snowstorm will move through the Eastern Rockies of Wyoming, while New England remains fair and dry, thanks to continued northwesterly flow deep through the atmosphere.
Our large and protective fair weather center, like all high pressure cells in the Northern Hemisphere, has air flowing clockwise around its center, and this means a northerly and northwesterly wind across New England in advance of it. Further increasing wind speed is the squeeze between this high pressure center, and a strong low pressure center (storm) located in extreme Eastern Canada - a difference in atmospheric pressure means a consistent motion of air, and this setup will contribute to gusts of up to 45 mph Thursday afternoon. Winds of this force are capable of downing a few small tree limbs and branches, perhaps resulting in an isolated power outage, but are more likely to blow around small objects like trash cans and other loose items that you'll want to secure if you don't feel like hunting them down in the neighbor's yard! The cool nature of our Canadian airmass will team with these winds to produce widespread wind chill values in the 40s - a brisk day for one and all - though the strong late March sun angle will make for a delightful day if you're reading this from a windowed office or you'll be out driving, sheltered from the wind. Wind combined with the dry nature of this air - relative humidity values of below 20 percent in some spots - will have an extremely strong drying effect across New England. One of these effects is felt on the body - have you noticed your skin drying out and a few more static electric shocks lately? Though we don't often think about a cool spring day as an important day to be hydrated, the air on a day like today is drier than it is during the summer months, and though the body may not be sweating profusely, this airmass will take the water right out of us - keep the liquids coming! In addition to the body, the combination of dry air, sunshine and fast winds are also taking any water right out of vegetation on the ground, allowing dead vegetation from last growing season to become dry and brittle. Active winds provide a good exchange of air from the ground to a few thousand feet in the sky, and in combination with dry ground cover, this can serve as good fuel for fires, and fire danger is high for the second day in a row Thursday for non-snowcovered locales of Southern New England and Eastern New England, from Eastern Maine through Eastern Massachusetts to the South Coast of Connecticut.
A dry airmass warms quickly with the help of sunshine, but also cools quickly when sunshine is removed. We saw this phenomenon Wednesday night, and will see it again Thursday night to a lesser extent as winds shift to blow from the west, rather than the northwest, allowing cold air to retreat just slightly. This west wind will be the prevailing wind direction on Friday in advance of another approaching cold front from Southern Canada, and temperatures will warm with the combination of this new wind direction, relinquishing cold, and another dose of significant sunshine. Adding to most of New England's potential for warming will be a "downsloping" wind - a wind that slopes down the hills and mountains, compressed as it descends (owing to higher atmospheric pressure at lower altitudes) and undergoing both warming and drying as a result of that compression. The combination of slightly milder air, sunshine, and this downsloping flow will push some Southern New England locales over 60 degrees for the final day of the work week. Meanwhile, a cold front will be settling southward out of Quebec, representing yet another installment of cool and dry air from the sprawling Canadian high pressure cell. With such dry air already in place, the only areas that may see a shower with the passage of this front Friday afternoon would be north-facing mountainslopes of the North Country where air will be forced upward a bit more vigorously as the incoming wind shift encounters high terrain, but most of us will find only a period of clouds later Friday marking the passage of the front.
Behind the front, cool and dry air will take residence through the weekend, bringing beautiful spring weather through most of the weekend. By later Sunday, the dry air will break down gradually, but steadilly, resulting in thickening clouds and the likelihood for showers to develop later in the day. Rain will move across New England Sunday night into early Monday with one low pressure center passing to our north, and another to our south. There will be at least a pocket of mild air following this disturbance for a 24-48 hour window, but it will only come after the disturbance moves through, and is available only for a limited time before another shot of cool air comes in. What I'm getting at here is that Monday's high temperatures may range greatly, from 30s in Maine to 50s or maybe even 60s in Connecticut, depending upon how quickly this disturbance exits and the milder air moves in, with many areas likely to land in the 40s and 50s even after lingering rain ends early Monday, as clouds and an onshore flow may linger for awhile. By Tuesday, milder air will attempt to ride through New England, but this comes during a closing window as a new cold front steadily moves east, destined to bring a shot of cool air back for midweek.
Technical Discussion: None today.
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
