Gradually a Bit Wamer and a Bit Less Windy...Plowable Snow for Many on Thursday...Cold Returns for Weekend Before Another Potential Storm Next Week
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 and a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. My email is firstname.lastname@example.org. This blog is for you, so I hope you enjoy it! -Matt Noyes
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Matt's Quick Weather Synopsis: Another day of chilly sunshine across most of New England as a storm system parked well to our northeast continues to spin in place while gradually weakening. The result will be continued busy winds, though less intense than Monday, with gusts to 25-30 mph, teaming up with continued cold temperatures for a nippy feel. Most areas will enjoy sunshine, though most of Maine will be in and out of clouds as we were yesterday, with these clouds spinning southward from the aforementioned storm in Eastern Canada. A fast-moving but moisture starved disturbance will eject southward out of Canada Tuesday night, bringing variable cloud cover south, and mountain flurries north. Another quiet day is in store for New England on Wednesday, as we'll be sandwiched between Tuesday night's departing disturbance, and a much stronger storm moving east across the Midwest. This approaching storm comes from roots in the Pacific Ocean, and has dumped several inches of rain and several feet of snow on the West Coast over the last two days. This moisture-laden and energetic storm will cross New England on Thursday, with snow developing Wednesday night after midnight, and continuing into Thursday. At this point, a widespread plowable snow (3" or greater) appears likely in many areas by the time the storm winds down, with a band of higher amounts possible, especially through interior locales (see map below). There is also the possibility of lesser amounts farther south in New England, where enough mild air may nose in to mix with or change to sleet and rain for a time. By Friday, northerly breezes behind the departing storm will bring in one installment of cooler air, and another arctic surge appears en route for the weekend. Have a great Fat Tuesday! -Matt
Early Thoughts on Thursday Snow (check in for updates, though...still some time to go on this one):
Weather Summary coming later, as usual.
General Weather Summary: With a stalled and gradually weakening storm loadged northeast of New England, winds will continue to be active from the west-northwest on Tuesday, and cold air will remain locked in place. While the gradually weakening state of this storm will mean slightly less wind than Monday with gusts to 25 or 30 mph rather than 35 mph, and slightly warmer temperatures nearing 30 in a few communities, a chill will certainly still be felt for all who spend an extended period of time outdoors. Northwest winds extend upward, deep into the atmosphere above us, and this means that any disturbances to affect New England - for now - will be dropping south out of Canada. A morning analysis shows one of these energetic disturbances "upstream" to our northwest, ready to dive over New England Tuesday night as it becomes caught in the fast flow from the northwest. Because it's originating in Canada, this disturbance is moisture-starved, and will bring little more than passing clouds and mountain snow showers as it moves overhead Tuesday night.
With one disturbance moving away from us, and the next still hundreds of miles to our west, Wednesday will bring much lighter winds and a continued gradual moderation in temperatures. Meanwhile, several inches of rain and several feet of snow have been falling the past two days along the Pacific Coast and mountains of the Western United States. Heavy rains have fallen in Los Angeles with this storm, and residents of Phoenix, Arizona, will be turned skyward in search of the first raindrops in 132 days on Tuesday as a strong Pacific storm system barrels its way inland. This moisture-laden system will eject a piece of energy eastward across the U.S., and the associated surface storm center will move through New England on Thursday.
As with this past weekend's disturbance, the exact track of the storm will make a large difference regarding where the heaviest precipitation falls. Regardless, as warmer and more moist air surges north in association with this approaching storm and collides with our cold airmass, snow is likely to develop for many areas after midnight Wednesday night. Given the surge of warmth and moisture associated with this system of Pacific Ocean origins, it's likely to snow heavily at times in many areas late Wednesday night through Thursday morning. Though some variation is still possible, the most likely scenario takes a strengthening storm center into Southeast New York State by Thursday morning, then shifts energy to a new storm center that will take shape immediately south of Cape Cod. At the surface, this means winds will blow from the southeast in advance of the approaching storm, which will slowly bring warmer air in from the Atlantic Ocean. Eventually, if enough warm air comes into play, a mix or change to sleet or rain would be possible in far Southern New England, though right now I wouldn't count on a widespread mix or changeover. Unlike the last storm, fluffy snow will be confined mainly to Northern New England, while the remainder of us will see a heavier, wetter snowfall. - and this also will cut back on amounts. I've posted a map of my initial thoughts in the Synopsis above, but keep in mind a few things: 1) Storm track still is subject to change, which would bodily shift the corridor of highest amounts, though I don't see a significant shift in track as likely at this point, and 2) The amount of warm air that moves in will be critical to snowfall amounts. Areas of Southern NH, Southern VT, and Northern MA stand the best chance of seeing the combination of somewhat fluffier snow with plentiful moisture, and these are the areas most at risk for either side of a 6" snowfall, but there is still plenty of time to fine tune this.
After our Thursday snow, cold northerly winds take hold behind the departing and strengthening storm, and these winds will usher in cold and dry air - helpful in bringing the sun out for Friday, but also likely to hold daytime high temperatures in the upper 20's to around 30 for most areas. By Saturday, a stronger northerly flow will set in behind a reinforcing cold front, and the result will likely be weather equally cold to the beginning of this week, in place just in time for the weekend.
Looking farther out in time, the weather pattern continues to indicate potential strong storm development in the early to middle part of next week, as a strong storm south of Alaska - over the Aleutian Islands - breaks down this weekend and ejects east and across the nation. At the same time, the stalled storm to our northeast that's been keeping a northwest flow of wind relaxes, and this would allow the new energetic storm to move to the East Coast, where it would be likely to develop into a more potent system - chock full of wind and likely to spell at least a week-long temporary end to deep cold here in the Northeast, which would mean milder weather after the storm...from roughly March 8 to March 14. Thereafter, early signs are that at least somewhat colder than normal weather may return for a time.
Have a great Tuesday!
Technical Discussion: Probably not today with lots going on here at the station, but I'm reposting below what I posted late yesterday afternoon, in case you missed it due to the late post.
Matt's Technical Meteorological Discussion: Reposted from Monday, February 27 at 3:20 PM
Warm advection clouds across ME/NH/parts of NE MA today are the result of warm air wrapped all the way around the north side of storm circulation to our northeast and another burst of these is possible later Tuesday as polar vortex throws warmer air southward aloft. A strange reality, I know, but this is what happens when you get a wound up storm bombing northeast of NewEng during a strong Greenland block and developing strong negative NAO.
I'm going to broadbrush the short-term in favor of focusing on the medium range and longer range forecasts today...and the broad strokes paint an eastward moving shortwave moving over NewEng Mon Ngt and bringing snow showers with it - esp Nrn MA point N - with a dusting of accum possible given a couple of hundreths that output on esp SUNYSB MM5 and WRF.
Good mixing Tuesday will team with downslope flow and sunshine for at least most of the day away from warm advection clouds from the north to bring temps into the 20's most areas Central and South. Wed features a westward retrogression of the polar vortex and this is an important shift as it dictates where the storm currently slamming the west coast with copious amounts of rain and snow will be steered.
In fact, using this pattern shift, we could determine that the NAM solution for the track of Thursday's shortwave - our first stopping point in the medium range - was initially likely much too far north as it took the shortwave over Central and Northern NewEng, but the new 12Z position is more in line with the remainder of the operational models and likely more on target. There are a few things to keep in mind with this shortwave: 1) It is the composite of northern and southern stream energy, but really is a reincarnation of the storm over the West Coast Monday afternoon, which splits north and south and then comes together again over the Western Great Lakes, 2) When the new merged vorticity maximum moves through the northeast on Thu, remember its origin - it has come from moisture-laden beginnings bringing rain from SEA to LAX on Monday, and feet of snow to the CA mountains, 3) It is cresting a thermal ridge of tremendous warmth - some 20 to 25 C at 850 mb over the Central and Southern Plains, and this sets up a tremendous baroclinic zone with the cold air shoved south of the polar vortex, 4) The surface low will be strengthening as it moves in a path that...according to progged 500 mb and 700 mb flow...should take it immediately south of NewEng as it races E.
Once again this leaves us with a storm that we wonder whether it will be able to generate a closed circulation and add ocean moisture, but this time it's not nearly as important to do this as it was with the weekend system. Remember that in this discussion you and I considered the importance of this ocean inflow for the past weekend storm, and we knew that where an easterly flow could establish, the higher snowfall and QPF would be, and that was likely to set up on the northern side of the circulation. We needed that moisture this weekend to offset what was otherwise a bone-dry atmosphere. Though the air is dry currently, by Thursday the situation will be quite different, as this storm comes of Pacific origin - carrying its own moisture. For snow lovers, that's a good thing because indications right now are somewhat iffy on whether it could get its act together quickly enough to incorporate Atlantic moisture, largely owing to its very fast progression eastward. Nonetheless, this system of moist origins will carry a southerly llvl jet east into NewEng late Wed Ngt into Thu, and this will again result in a band of snow, heavy at times, into Thu across most of Southern and Central NewEng, and likely spreading into Nrn NewEng as well, esp given lingering trough and SE sfc flow in place. Remember that with this past weekend's event, there was a fairly well-defined southern cutoff to the plowable snowfall amounts - that is the nature of a system that is relying heavily upon a surge of warmth and moisture colliding with a cold airmass - south of the collision there will be a sharp drop in precip amounts. This will be the case again with the upcoming storm, but indications are that most areas should end up under this enhanced baroclinicity. So, once again a shot of plowable snows appears en route for NewEng late Wed Ngt into Thu.
Thereafter, with northwest flow the weather may quiet down for a few days, but this is likely to only be the calm before the storm that will break the back of the deep cold for a time, if not for the rest of winter. Consistent indications for several days have been coming back for a few things to happen around March 6-7. The first is that the polar vortex lets go of Eastern Canada and shifts north and northeast, diminishing the confluent flow that has kept disturbances moving so quickly across us. The second is that...in response to this shift and a weakening of the Greenland Block, the NAO approaches neutral. Historically, when we see the NAO shift from strongly negative to near-neutral or slightly positive, this can signal a large storm development near the Northeastern US. Add to this the fact that a strong Pacific shortwave will be traversing the country - the leftover heart of the Aleutian low spinning south of Alaska today - into a less confluent flow over the Northeastern US but still confluent enough over Nova Scotia to hold cold high pressure to our NE, and we have a recipe for a strong storm. Additionally, the operational models continue to key in on this time period for storm development, which can add further confidence to a forecast of a large storm in this time period. Behind the storm, it does appear heights rise dramatically, which tells me two things: 1) The storm will likely be a strong one, as this is evidence of the amount of warmth and moisture available to it from the southern stream and the resultant baroclinicity, and 2) This strong storm will lead the northeast into a spring-like pattern for what is likely to be at least a week, taking us to around March 13-14. Thereafter, while the deep cold will be exhausted, cold locked in Siberia that will have been cut off from migrating eastward (truly it's this bridge to Siberian cold that's been feeding our current cold streak) will be able to slide east into Western and Central Canada again, and renewed cold appears possible sometime after March 14, though not as deep and not for as long a period, it still will be watched carefully as baroclinicity would be a big factor at that point, owing to a significantly higher sun angle.
Needless to say, plenty watch for one and all. That's all for today.