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
Tuesday Podcast: Issued
General Weather Summary:
Rapid moderation of yesterday's arctic air began in the late night hours of Monday night, with temperatures rising in many Southern New England locales with the approach of dawn. The southwest wind responsible for this temperature rise will continue through the day on Tuesday, bringing temperatures above 40 degrees in Southern New England for the first time in a few weeks.
Morning surface weather analysis places a weakening storm center north of the Upper Great Lakes and a high pressure, fair weather cell off the coast of the Southeastern United States. With a counter-clockwise flow of air around the former, and a clockwise flow of air around the latter, this has induced a steady southwest wind from the Ohio Valley into the Northeast, and a few noticeable surges of warmth are evident both at the surface and aloft. Aloft, the influx of warm and moist air has resulted in seemingly random patches of stubborn clouds that can be seen through satellite imagery links in the left sidebar of this page, though, of course, the cloud formations aren't quite as random as they appear. Instead, what's happening is something seen often when mild air dislodges a well-established cold air dome - clashes of airmasses result in stubborn development of cloud decks at varying levels of the atmosphere. Some of these clusters of clouds will produce a few disorganized light showers of rain and snow through the day, most of which won't amount to more than a few stray raindrops and snowflakes, though a fresh inch or two of snow is possible in Northern Maine. Otherwise, breezes will remain active from the southwest for one and all - gusting up to 30 mph on the Cape and Islands and up to 25 mph elsewhere - and at least some sunshine, especially in the warm sector across Southern New England, will help to boost temperatures some 5-7 degrees above normal south. An amazing contrast in temperatures will continue through the afternoon, set up in Central New England as the dense, tough-to-displace arctic cold hovers near the surface of northeastern New England. On the cold side of the boundary, snow has been falling intermittently across Northern Maine, and by the end of the day a fresh inch or two is possible in some of these spots ahead of an approaching upper level disturbance.
With the passage of this disturbance Tuesday night, quieter weather will settle in for Wednesday, along with a cooler shot of air for the midweek with enough moisture in the lower levels to pop clouds amist sunshine. This cool shot will be short-lived, however, as the parade of disturbances out of the Great Lakes continues, meaning another round of southwesterly winds to warm New England once again. This steady parade of atmospheric disturbances comes as each rides the jet stream winds aloft - the fast river of air high in altitude that steers our storm systems and acts as a thermostat for the atmosphere, separating cold air to the north from warmer air to the south. With deep cold surging into New England but ready to quickly retreat on Tuesday, the jet stream wind corridor will also be lifting north, meaning each disturbance that races out of one upper level storm over Western Canada will scoot along the Northern Tier of the U.S. until it is absorbed by another upper level storm east of New England. These disturbances will, at times, bring only increased clouds, though the heartier of them will deliver more focused areas of precipitation - mostly in the form of snow, and mostly focused across Northern New England. The next of these disturbances with focus will come Thursday afternoon into Thursday night, and though milder air will once again be transported northward ahead of its passage, the airmass should be dry enough to cool as precipitation falls into it, allowing for snow in many locales, though perhaps rain in Connecticut, Rhode Island and Southeastern Massachusetts. The question is just how much snow we can anticipate. While this disturbance is going to be quite strong, and carries a great deal of energy, it will accelerate rapidly from the Upper Great Lakes to a position near Cape Cod from early Thursday to Thursday evening. This rate of forward speed is very quick, and favors what's called a "center jump" at the surface - that is, because the surface low pressure center can't move at the same pace as the upper level energy, the first is left behind as another forms ahead of the energy, in this case near Cape Cod. This usuallly results in a precipitation minimum under the area where the "jump" occurs, and in this case that may be right here in New England. Still, the combination of available moisture and energy aloft will yield at least some snow, but it may be limited to a few inches in even the hardest hit areas as a result of the fast forward speed. A few factors that could still change this would be a slower speed, and certainly mountains and hilly terrain can result in locally higher snowfall totals.
Behind this disturbance, another shot of chill will pour south for Friday - much less intense than it's Monday counterpart. Thereafter, a stronger storm will develop over the Central United States in response to a digging jet stream "trough" coming east from the Western U.S. Remember from past discussions that these troughs represent dips in the jet stream where cold air penetrates southward, and often can breed storms along the battlezones of protruding cold air with antecedent warmth. This will be the case over the Mississippi River Valley next weekend, and with a storm track to our west and counter-clockwise flow of air around the storm, warm air will surge northward along with Gulf moisture, meaning rain is the most likely precipitation type for many of us. An active storm pattern may shift gradually east thereafter, but this first rain event may not be the last if the jog eastward in storm path turns out to be gradual enough.
So, winter lovers should make hay while the sun is shining, so to
speak. Though, history dictates that March will bring plenty of
excitement and surprises.
Matt
Matt's Technical Meteorological Discussion: Updated Tuesday, February 20 at 1:55 PM
Amazing sfc temp contrast across NewEng today as boundary layer thermal gradient encourages isentropic lift to perpetuate clouds in lowest few thousand feet across Central/Nrn NewEng while sunshine has broken out for a time in warm sector across Srn NewEng. Used low level thickness fcst combined with early AM temps that were already near 40 to put fcst into the 40s for Srn NewEng. The tight baroclinic zone comes as cold dense air remains locked in place across Nrn and esp NE NewEng, preventing mixing and promoting lift. Shortwave heading for NewEng tonight is producing active CG lightning strikes over IL this afternoon and will produce convective elements over NewEng overnight Tue night. Doubt we'll be looking at any lightning, but healthy convective downpours that will quickly incorporate big, fat flakes esp as the shortwave axis swings thru and we capitalize on cold enuf air thru all levels but the boundary layer, which will cool evaporatively, dynamically and thru advection late tonight. The result will be a setup for some black ice in Srn VT/NH/Nrn MA, tho the strip affected by this will probably be rather narrow because farther north it's been cold today and farther south it'll still be above freezing Wed AM.
The remainder of Wed looks relatively quiet tho high RH progged in the lowest 100-150 mb has me on guard for widespread cold advective stratocu in esp Nrn/Central NewEng, broken up by downsloping flow and less intense CAA farther south. Our next shortwave will be compact and very impressive as it moves across or just north of the Upper Great Lakes. The problem for NewEng snowlovers is what it does thereafter. If this thing simply turned southeast and held its integrity, we could try to wring something decent out of it. Instead, it's going to become caught in very fast northwest flow over NewEng - confluent flow between the upper low north of Nova Scotia and the ridge axis over the Southern and Central Plains. This very fast motion will not only degrade the compact nature of the vort by stretching it out, but also will increase the speed of the compromised vort. The former means that vorticity advection will be channeled, and not coming tangential to the geostrophic flow, thereby creating a limited duration and areal scope of dynamic lift. The latter means an even more limited duration of CVA/PVA, thereby favoring a center jump scenario where the Srn Ontario low dies as the energy prompts new low development over Cape Cod, but in between we get a relative precip min. There are two factors to watch: 1) Confluent flow is less intense, meaning the vort maintains more consistency and a more favorable speed - this would increase the intensity and duration of squally bands and clusters, and 2) When the vort prepares to gather itself and surface cyclogenesis results, it does so a bit farther west or a bit earlier in the game, or slows a bit earlier before moving east, this would give more time for an easterly flow to develop in the lower and middle levels, thereby allowing enhanced snowfall earlier in the game. Though this doesn't appear highly likely, it is one thing to watch.
Cold air streams south on Friday with active wind and good mixing but enuf cold air aloft for instability Cu and snow showers in the mountains. Though the weekend starts quiet, Sunday brings warm and moist advection and good agreement on a spike in 850 mb temp anomalies that should mean snow changing to rain for most areas unless we can find a way to get lingering confluent flow aloft to hold in low level cold for some Northern locales. Doesn't look great right now, but there is plenty of antecedent cold, which means all we'll need is a weak bubble sfc high to hold it in for snow in the North Country - so enjoy this stretch while it's here, but don't give up all hope on pulling some snow out of Sunday/Monday system.
Have a great Tuesday.
Matt
