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
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General Weather Summary:
With a rapidly strengthening storm system moving east of New England over the Atlantic waters, snow rapidly diminished in both coverage and intensity early Friday morning. This fresh snow created some slick spots early Friday thanks to a greasy consistency of the snow, and lingering snow and slush on roadways will freeze by Friday night as colder air streams south. This colder air will bring a chilly start to the weekend before a near-perfect winter day on Sunday. The next chance of snow comes by early Monday.
In the meantime, snowfall reports were heavily dependent upon elevation with Thursday night's event, totaling over four inches in higher terrain of Bennington County, VT, Worcester County, MA, the Berkshires, and Northern Connecticut, but only a trace to a dusting in some deeper valley locales across the Southern half of New England. The snow developed in only a marginally cold airmass, which made it a warm and sticky snow, able to clump into very large flakes, and able to stick to almost everything, creating a winter wonderland for many! The greasy consistency of the snow made walkways and driveways slick, though the near-freezing temperatures ensured road treatments worked well in most areas. Though snowfall amounts varied, the weather will become more uniform from Friday afternoon through the upcoming weekend. As the powerful ocean storm continues to strengthen while pulling east, winds will freshen from the north and northwest, gusting up to 40 mph at times, regionwide. This wind will not only carry colder air southward from Northern New England into Central and Southern areas, knocking temperatures down a few degrees over the course of the day, but will also serve to blow most of the glistening snow from trees and also will add a chill to the air - creating wind chill values in the teens south and around 10 north. The colder air is also drier air, and will continue to bring sun out for many, leaving a Friday afternoon blend of sun and clouds with bubbling mountain clouds producing a few snow showers in the higher terrain of Northern and Western New England.
Winds will remain active out of the northwest under a partly cloudy sky on Friday night, keeping temperatures milder than they'd otherwise be under clear skies and calm winds, though wind chill courtesy of gusts to 25 and 30 mph will likely make up the difference. These winds will remain active from the northwest for an otherwise quiet, and mostly sunny Saturday, gusting to 35 mph at times. Meanwhile, a stronger storm developing over the Central United States in response to a digging jet stream "trough" coming east from the Western U.S. will breed a weekend severe weather outbreak through the Plains States and into the Mississippi River Valley. 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, and with a primary storm track to our west and counter-clockwise flow of air around the storm, warm air will surge northward along with Gulf moisture. It will be a suspense-filled battle of incoming warmth and another dome of Canadian cold later Sunday through Monday, as the fine details of this clash will determine both storm track and precipitation type. It continues to appear as though increasing moisture and warmth aloft will bring thickening clouds late Sunday after mostly sunny skies for a good chunk of the day. Originally, I'd been thinking precipitation would develop late Sunday, but we continue to see a sluggish jet stream pattern over and immediately east of New England, and this alters the forecasted setup somewhat for New England. What happens instead, is that fast moving winds aloft over the Northeast will likely tug pieces of energy from the Central U.S. storm, chunk by chunk, rather than all at once. These fast moving winds also will help to hold cold air in for the lowest several thousand feet of the atmosphere thanks to a southern nudge of cold Canadian high pressure by Hudson Bay, and both of these factors together imply we'll be dealing with a slower and colder scenario, more likely to bring waves of precipitation as each chunk of energy floats by, rather than one formidable storm.
The first potential swath of precipitation would come through on Monday morning - slower than thought earlier in the week, but running into enough cold air to produce a swath of snow across Southern New England. Amounts will hinge tremendously on how far north this swath of moisture can penetrate, and the exact direction of winds aloft that will determine how far north this first chunk of energy can ride. As an early estimate, at least a few inches of snow seems like a possibility, with perhaps a stripe of higher amounts, and this could make for a difficult Monday.
By Tuesday and Wednesday it's difficult to really bring appreciable clearing through since the primary slug of energy will linger to our west and feed weak disturbances east, each capable of carrying light snow overhead.
Have a great weekend. Back at it Monday morning.
Matt
Matt's Technical Meteorological Discussion: Updated Thursday, February 22 at 1:20 PM
Precip has officially begun in NewEng with the first raindrops in Danbury, CT. Wet bulb temps are mostly above zero in far Srn NewEng with mostly below zero Tws across the remainder of the area. The lower CT river valley has warmed to above 40 while the Litchfield Hills and Berks have stayed colder, and this will play itself out thru varying ptypes at the onset of this afternoon/tonight's event. Mostly a snow event for the Berks and NW CT higher terrain where inverted trof assoc with dying primary low and connecting to new coastal low E of NJ will swing slowly E during the overnight and serve as the impetus for band of heavier snowfall amounts. The farther one goes from this inverted trof, the more difficult it will be to see anything appreciable fall from this event as the strengthening low to our south steals the show in this anticipated center jump event. Nonetheless, there will be a swath of warm advection and upper level diffluence on the north and northeast side of the vort max as it dives southeast across NY/PA/NJ and that will allow for a swath of light precip with embedded mesoscale bands of moderate to heavy precip to develop. Good consensus on half an inch of liquid equivalent assoc with the inverted trof, but much of that will be "wasted" on rainfall in lower elevations including and especially the Lower CT river valley. Farther W, however, just outside the valley, rain/snow combo will be quicker to change to snow with mostly snow higher terrain, and this is where amounts will increase, as shown in accums map in General Wx Summary above. Highest terrain certainly may exceed half a foot of snow but where most folks live will verify closer to amounts given. Other wild card is Cape Cod, closest to where low center winds up. Make no mistake that even tho I think this low is not going to deal a strong blow to NewEng, it becomes a very powerful storm, strengthening to 971 mb by Friday midday as it pulls even farther E of Cape Cod. In this strengthening process, moist influx will increase on east and then wrap around to north of storm, and that will force heavier precip onto Cape and Islands. So, how hard to we bite on heavy snow potential here? I had trouble bringing snow onto the Cape until a wind shift, and I feel better about that as I see obs that have wet bulbs above freezing as of midday and the wind is southeast. Not much chance of cooling or drying the airmass that way, even with the effects of dynamic cooling working in your favor, so I'm still not thinking of a changeover in these areas until after 06Z when the ageostrophic flow takes over and swings sfc winds to a northerly component. After that transition, somewhere between .1 and .2 inches of precip on Nantucket, and have gone with locally higher amounts there, accordingly.
Biggest concern is freezing of roads for early Fri. Presumably numerous treatments will be on the major roads, but secondary and back roads should be very icy with wintry mix melting on road surfaces then freezing with onset of new shot of cold predawn Fri. This shot of chill comes with 850 mb temps between -8 and -18 C from S to N, but 925 mb temps plummet and this keeps most of NewEng chilled - combined with gusts to 40 mph as low bombs to our east and wind chill will be a factor.
Quiet Sat. Sunday quiet most of the day - would like to bring in precip a bit earlier than models are suggesting with WAA tending to run ahead of schedule, and ECMWF does a decent job with this, but even still, we're looking at just about the entire daylight hours mostly dry. Thrust of warmth and moisture looking more and more like it will be cut off at the pass by SErn nose of high pressure over Hudson Bay that inches cold air southward, and is aided by confluent flow that will be quite sluggish to go anywhere east of NewEng. The result will be a rain/snow line that very well may stay suppressed over far Srn NewEng. Doesn't look like one big converged energy center, however - more like chunks of energy that slide S of NewEng, but this energy comes with warm and moist advection and therefore brings a slug of decent precip with a band of mesoscale snows likely in Southern NewEng.
Matt
Tuesday's Discussion:
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
