Welcome to the weather blog - a regular Monday through Friday discussion of the weather! You'll find a general non-technical weather summary below, and when available (most days) a detailed technical meteorological discussion will follow. If no technical discussion is available when you check in during the morning, check back later as it often comes after the Weather Summary - I try to indicate at the end of the general weather summary when/if a technical discussion is coming. My email is [email protected]. While the discussions usually will only come on days I'm working, I'll occasionally issue special updates when the weather warrants. This blog is for you, so I hope you enjoy it! -Matt Noyes
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Matt's Weather Summary: Furious winds resulted in widespread damage on Wednesday and if you'd like to get a taste of just some of the damage reports, the National Weather Service compiles them at the following web address: http://www.erh.noaa.gov/box/lsr.shtml The highest wind gust I received a report of here in the NECN Weather Center came from the Blue Hill Observing team at the Blue Hill Observatory in Milton, MA - just southwest of Boston. Peak wind gust was 92 mph shortly after midday.
Thursday's weather map sandwiches New England between this departing storm center well to our northeast, and a bubble of high pressure over the Ohio Valley. The result is another windy day - though child's play compared to Wednesday - with sustained winds of 15-30 mph and gusts to 40 or 45 mph...not strong enough to cause additional damage. Enough moisture lingered in the lowest levels of the atmosphere for Thursday morning snow showers in the mountains of Northern and Western New England, though as dry air continues to spill in at the surface, these snow showers will dwindle, and breaks of sun will emerge in the mountains. Elsewhere in New England, abundant sunshine begins the day as we make the most of the dry air that's in place.
Our very active weather pattern, however, won't allow us to enjoy a dry atmosphere for long. Satellite imagery shows a small energy center racing northeast toward New England that will arrive Thursday afternoon. This disturbance carries very little moisture at ground level, but is accompanied by a patch of high and middle altitude clouds that will filter out the sunshine from southwest to northeast later Thursday. These clouds will also help to keep temperatures relatively mild during Thursday night in conjunction with a light southwest wind, while there may be just enough moisture to squeeze out a few flurries and sprinkles across the mountains of Northern New England.
A mild start Friday morning will provide a platform to build from as the day progresses, and even with limited sunshine, temperatures should still climb into the upper 40's in Southern New England by day's end. This comes as a continued southwest wind ushers in the northern edge of a warmer airmass laid across the Southeastern quarter of the nation, and with the change in airmass, expect any morning sunshine to fade behind quickly increasing clouds, and most of our Friday will end up overcast, with a few flurries and sprinkles continuing in the mountainous terrain as a weak disturbance at the jet stream level moves across Northern New England, dragging an associated surface cold front very gently southward across the North Country.
There's more than meets the eye, however, to this scenario. The combination of this southward ooze of cold air into New England from Canada, and the northward nudge of warmth nosing into Southern New England later Friday, will help to set the stage for storm development - establishing a sharp contrast in airmasses over our six-state region. In fact, the cold air oozing southward is part of an airmass that's meant business - a chunk of this air that has been pouring into the Northern Tier of the United States has brought low temperatures below zero in the Upper Midwest and Upper Great Lakes, as well as across Southern Canada! Remember that storms feed off of a temperature contrast like this, and energetic disturbances, when moving through sharply contrasting temperatures, can result in storm formation. With our active weather pattern, there's no shortage of these energetic disturbances sweeping east, caught in the jet stream winds aloft, and another of these disturbances will eject from the Midwest and across the Ohio Valley Friday night.
Ahead of the incoming disturbance, winds aloft will increase from the southwest, carrying a continued supply of warm and moist air toward New England. Remember, however, that colder air will be draining into the North Country, and this process of gliding warm air over a cold dome is the perfect scenario for clouds and precipitation. My expectation, therefore, is for precipitation to develop on the cool side of this temperature boundary on Friday night - Northern VT, NH and Central and Northern ME - and the air in these northern locales will likely be just cold enough for precipitation to fall as accumulating snow that develops late Friday night and lingers into early Saturday afternoon. Amounts are likely to range between three and six inches of snow from valley to hilltop, respectively, by the time snow winds down Saturday afternoon. A very narrow corridor of rain showers will be possible during this same time frame from Rutland County, VT, to the Central Lakes Region of NH, to the Central Maine Coast, with snow found north of these areas and no precipitation south of them. This means that Saturday should be a day of clouds, some sun, windy, mild and relatively dry conditions with just the chance of a few showers for the Southern half of New England. The reason for this? It's really the clash of airmasses that will be driving precipitation and cloud production in this case - so as we head south...squarely into the milder air and away from the battle zone...we head away from the mechanism allowing for precipitation. As the weak and progressive center of low pressure helping to focus this precipitation moves through Northern New England, it will shift surface winds out of the north, and this will drain colder air southward on Saturday, likely carrying some of the clouds and a few rain showers southward Saturday afternoon, and ushering in cooler and drier air for Saturday night and Sunday.
Again, this southward drain of cold air is a subtle change in the weather, but one that may become quite important down the line. Sunday should bring dry and cool conditions to all of New England under plenty of sunshine. But to our west, yet another upper level disturbance and its associated area of low pressure will be racing toward the East Coast. With colder air in place for most of New England, the increasing clouds this system throws our way Monday morning will give way to precipitation as warm and moist air from the south once again collides with a cooler airmass in place. In essence, the mechanism behind this will be similar - though stronger - that what brings Northern New England snow early in the weekend, and with colder air in place farther south through New England, this certainly raises the likelihood of accumulating snow through interior New England later Monday or Monday night, though a rain/snow line is likely to exist, and may penetrate inland quite a way in Southern NewEng.
The overall pattern still appears to favor a very gradual cooling of the atmosphere over the next couple of weeks. Of course, this is with regard to the average state of the atmosphere...there will surely be large deviations either side of the average trend. But one thing that's important to keep in mind is that all of this heat that's been across the U.S. is a form of energy. This energy was spilled east with each successive storm that's battered the West Coast. Eventually, these storms battering us will succeed in carrying the energy east into the Atlantic, and this could allow for a colder and snowier pattern to develop in February. Food for thought, anyway...
Enjoy your Thursday,
Matt's Technical Meteorological Discussion: Updated Thursday, January 19 at 2:25 PM
Quick Note: Day off for me on Friday, so no techie discussion, though Weather Summary will go out, FYI.
Middle and high altitude clouds spreading toward NewEng from moisture starved vort racing northeast across Ohio Valley. Warm advection aloft is keeping this cloud mass intact but fast flow keeps the culpable vorticity maximum progressive. This carries clouds thru NewEng overnight and some sun is likely Fri AM after a relatively mild night thanks to the cloud cover and an active SW wind keeping the boundary layer mixed.
Input of low level moisture from Gulf of Mexico to low pressure center farther north in Eastern IL is already evident and well forecasted by low level RH progs of NAM. Trend has been a bit slower with bringing this moisture into NewEng from the west and this matches up with reality fairly well. So, bottom line is a sunny start to a cloudy finish on Friday, but active southwest winds keep mild airmass advecting in as surface wave of low pressure rides north of NewEng border.
From that point forward we monitor subtle weather changes that will have big impacts. The first subtle feature is the cold front that will nudge southward behind the passing low pressure center on Friday. With strengthening southwest flow in the middle and upper levels, and increasing SW 850 winds into Southern NewEng, this front will be fighting to push south and won't make it much farther south that Central VT/NH/Srn ME. It's important to realize the effects of this front, however - the height falls that occur north of Georgian Bay (Eastern Great Lakes) allow deeper Southern Canada cold to spill south and east Friday, and confluent flow north of NY/VT helps to hold this cold in as it seeps southward. At the same time, you can't argue with the deep southwest flow, and this should set up a very impressive 850 mb baroclinic zone over Northern NewEng. As warm advection moves east ahead of the approaching shortwave, precipitation will develop late Friday night and last into Saturday afternoon. Differences in the placement of the precip axis between GFS and NAM but superior handling of cold air in low levels by NAM will be bought here and going to take a NAM weighted solution to precip placement and therefore ptype. This Canadian cold can be equated to a heavy slow liquid sloshing out of a bowl (that bowl is Canada for the cold) and it's going to be hard to keep it from dripping south into Northern NewEng. Result is snow - and QPF amounts are increasing in all model guidance as event nears and more Gulf moisture tap is indicated. Band of heavy and steady precip should be narrow thanks not only to the tight baroclinic zone and confined area of isentropic lift, but also thanks to channeled nature of vorticity and relatively limited area of cyclonic vorticity advection as vort max is funnelled through fast flow. Total QPF likely to fall just above .5" which will equate to over half a foot in the mountains...probably closer to a 10:1 ratio or even a bit lower in the valleys given marginal thermodynamic profile. Southern extend of precip band likely to fall as periodic rain showers outside of intense lift and on southern end of thermal gradient.
Southern NewEng will not entirely escape this event, though active SW wind feeding into the frontogenetic process across the north will mean mild air keeps coming into Southern areas through the day and even with plenty of clouds temps should be able to climb to around 50! But one big limiting factor will be cloud cover, as attendant cold front will be quite eager to swing south Saturday afternoon with passage of low pressure wave and clouds will increase ahead of and along front, with scattered showers of rain in Southern NewEng with passage of this low level forcing mechanism.
Sunday brings drier and cooler shot of air which allows for sunshine and downsloping flow but low Td's set the stage for Monday storm. Most guidance trend is to keep this storm south of NewEng but I really don't buy that solution for a few reasons, focused primarily on the fact that midlevel flow is shifting toward NewEng, baroclinic zone will be eager to wave northward ahead of low given lack of deep dense cold air, and finally, overall steering flow doesn't favor a storm that comes in at Oregon going off the coast south of DC. So, I think this late Monday or Monday night storm is a distinct possibility for NewEng and enough cold and more importantly dry (which can offset the effects of downsloping that will be witnessed on Sunday) air is in place to allow for evaporational cooling. The challenge here will be holding the cold with high center shifting east of NewEng as storm approaches, while 1015-1020 mb low deepens passing S of NewEng as will turn ageostrophic flow E and then NE. End result may be an inland and mountain snow with a significantly inland displaced coastal front...but let's get a few more runs under our belt before we start hashing out rain/snow lines!
Have a great day.