Update On Wednesday Night Storm

11:00pm

Hi all!

This blog will be short, because I don’t need to go over the technical aspects of the upcoming storm. My reasoning has not changed, so it would just be a re-run. ūüėČ

I’ll just get to the time frame and the snow amounts, and here it is…

Snow starts in Boston between 6pm & 9pm, a bit earlier to the south, later to the north. The reason for the 3  hour window of start time is that the air above us will be very dry and it will take some time for the snow, which will be falling above us for several hours, to stop evaporating into the dry air and start reaching the ground. The heaviest snow will occur sometime between midnight & 6am Thursday. After this we should see a rapid ending to the snow from southwest to northeast during the morning commute Thursday.

Snow amounts should be 2-5 inches from southern NH southward to the northern part of the 128 belt (just north of Boston), and 5-9 inches from Boston southward into Plymouth County. I still think that amounts of 8 or 9 inches will not be that common, but are certainly possible, in those areas. Further south, except 4-7 inches near the Cape Cod Canal and dropping off to 2-4 inches over the Cape except 1-3 inches on the outer Cape, which will mix with and probably change to rain for a time for the first half of the precipitation event.

Another blog will be posted in a while with an outlook for the last 5 days of January. This includes a snow threat Saturday and a potentially very cold Monday.

Mini Storm, Bigger Storm?

150am

The extreme cold of Monday is now easing, and even though some readings were still near zero Monday evening, temperatures have started to rise as clouds have moved in. These clouds are associated with a weak storm system that will bring a period of light snow to MA & southern NH from the early morning to midday hours of Tuesday. Accumulations will range from 1/2 to 1 1/2 inch, with a spot 2 inch amount possible, especially in the hilly terrain. Once this system departs Tuesday afternoon, we may see breaks in the clouds and even a little sun before the day is through. Temperatures will continue to moderate and may approach 30 in some areas Tuesday afternoon.

Partly cloudy skies are expected Tuesday night with low temperatures falling back to around 20. Clouds will return and thicken during the day Wednesday ahead of the next storm system, which is currently developing near the Gulf of Mexico. This system will have plenty of moisture with it, and one might be tempted to think it’s set to unload all of it over New England since it is forecast to move up the East Coast by most of the computer models. But I still feel that this may not quite be how it plays out. If you read recent blogs you see that I have been concered about a boundary southeast of New England causing the Gulf of Mexico storm to start getting pulled further east, rather than coming north. I still think this scenario will play out. However, the moisture from the storm should still get far enough north to make it into much of southern and parts of central New England.

A last punch of energy coming along¬†will cross CT & RI as well as south central to eastern MA. This area will be responsible for most of the snow that falls, which will occur early Thursday morning. I don’t think any snow will make it into Boston from the south until after sunset on¬† Wednesday.

Somewhat warmer air aloft and at the surface may result in mixing and a possible change to rain over Cape Cod & the Islands and a portion of southeastern MA. But I think the immediate Boston area & points north and west will see snow from this system. The question then becomes, how much snow?

I think it will break down this way in terms of snow amounts: A general¬†2 to¬†5 inches over most of eastern MA, and I’m leaning toward the lower half of that range (2 or 3) being the rule. The first burst of snow after dark on Wednesday evening should be responsible for a coating to 1 inch, with some mixing possible well SE of Boston. There should then be a lull in the precipitation toward midnight, with a second area of snow moving through and peaking during the 2am to 8am timeframe. This would be when most of the remaining accumulation would take place. Mixing to the southeast should go back to snow as colder air works southeastward across the region. As you head to the northwest, snow amounts may drop off very quickly, so that by the time you get to northern Worcester County you may see very little snow. Places like Springfield may sit on the fence as well but should be in on the Thursday morning snow enough to pick up a few inches.

Keep in mind, there is still a chance that this system is surpressed even further south, and much of the area misses out on precipitation.

By Thursday night, partial clearing & colder weather can be expected, and Friday should be a brighter, chilly, but dry day.

Looking ahead briefly, a couple of weak weather systems may bring a few periods of snow showers or light snow to the region over the weekend. We may see another shot of very cold air by later Sunday or Monday, as we close out the month of January.

The next blog update will be about 4pm Tuesday.

Update on Extreme Cold & Storm Threat

1045pm

Hi everyone! Just a couple quick updates.

First, the most recent 3 runs of the NAM (short range model) are supporting my idea of a storm track further offshore and less of a chance of a major impact. I still feel that it will be close enough to bring some threat of snow/mix to part of southeastern New England, but we’ll fine tune that as soon as possible.

More importantly, an extremely cold night is underway and will lead to a very cold Monday. The NWS Boston has issued wind chill warnings & advisories for the area. Bottom line is, if you plan on spending any time outside through Monday evening, bundle up, because the risk of frostbite is real, and can occur in as little as 10 minutes if you are not properly protected! So be safe out there!

Extreme Cold / The Week Ahead

400pm

Hi everyone! Thanks for visiting!

It’s time for a¬†look at the week ahead, highlighted by an extremely cold start to the week and a midweek storm threat. The weather this week will be determined by the interaction, or lack of interaction, of a split jet stream (a northern one over southern Canada and the northern US, and¬†a southern one over the central and southern US).

It’s been a cold & dry weekend across the region, and it’s about to get even colder. An Arctic cold front¬†has been¬†moving southeastward across New England today and will push south of the area tonight. This has opened the door for some slightly modified arctic air to move into the area. Boston may fall below zero tonight for the first time since 2005. I’m forecasting a -1F low temperature tonight. Most of the areas outside the city and away from the immediate coast will see low temperatures of -2 to -10. A few isolated colder readings are possible in valley areas where winds could be a little lighter. Winds will be strong enough from the northwest, gusting around 25 mph at times, to produce wind chills of lower than -20 at times tonight into Monday! Under bright sunshine, temperatures will barely recover back to near 10 in most locations.

By Monday night, clouds will be moving in ahead of a weak weather system approaching from the west. This, along with the fact the core of the coldest air will be exiting, will mean that we will not see a repeat of the extreme cold of tonight. Low temperatures in most areas should remain slightly above zero, still very cold certainly, since we will already be nearly at those levels by the end of the day Monday.

On Tuesday, expect clouds to dominate the day. There may be some light snow showers or even a period of light snow as a weak low pressure area with the northern jet stream moves through the region. This is not associated with the potential storm for midweek.

Once this system gets by us, attention will be on the storm threat¬†during the Wednesday-Thursday timeframe. There are alot of factors to consider when forecasting the development and movement of this storm. I have been in great disagreement with the approach taken by many of the¬†media outlets regarding this potential system, and you can see I use the word “potential” for a good reason.¬†We’re talking about computer forecasts of a storm that has yet to develop and is largely going to be made up of energy that JUST entered the northwestern US from the Pacific during the past 12 to 24 hours. Hearing people talking about 1 to 2 feet of snow Wednesday is disturbing to me, because it plants seeds for overreaction of the public, preparing for yet another “storm of the century” as well as anger, if the advertised storm does not deliver. Regardless of how major I think this system has the potential to be, I would never start throwing those kinds of numbers out so far in advance. It’s irresponsible.

That said, I have reason to believe that the impact from this potential storm may range from minimal to moderate, and that we will be spared a direct hit from another monster storm. My favorite and what I feel to be the most reliable computer guidance has been advertising to me that the northern and southern jet streams are going to have a difficult time phasing, or getting together, which is something we usually need to produce a big storm and give it an avenue to come up this way. In this case, I feel that Tuesday’s weaker northern stream system will be well offshore and out of the way, as the southern stream system tries to develop over the southeastern US. There is a boundary forecast to be located off the East Coast on Wednesday. It is my expectation that the new low pressure area developing with the southern jet stream, not being influenced by energy to the north, will tend to develop along this boundary and try to follow it. And since this boundary is not forecast to move a great deal, that will tend to steer the southern stream storm on a more northeastward course, rather than turning it straight north up the coast. A track like this would put southern New England on the northwest flank of the storm, with results being anywhere from a light to borderline moderate snowfall (except mix/rain over far southeastern MA & Cape Cod due to warmer air aloft), or even just a brushing and a lower probability of a complete miss. My leaning at this point is for the first scenario mentioned just above. There is plenty that can go wrong with this forecast, so of course I will be watching and upating as we get closer, as has been needed over and over lately with these storms. For now, I wouldn’t be too worried about getting belted with a massive storm at midweek. And timing-wise, whatever we do get would likely occur mainly Wednesday night.

Later this week, expect a continued cold weather pattern, with the next chance of any storminess coming around Saturday. At this stage, that does not look like a major storm, but could produce quite a bit of wind as it is forecast by most guidance to be a pretty strong northern jet stream system. Looking way ahead, there are signs of another visit from very cold Arctic air behind that system, to end January & start February.

Harsh Winter 2010-2011

410pm

Well now that I’ve accepted the fact that I blew the winter forecast this year, it’s just time to enjoy trying to forecast what the rest of the winter has in store. Pardon my absence for a couple of days. I was feeling under the weather (no pun intended… ok, pun intended..sorry). ūüôā

A quick word on the storm that was. This storm turned out pretty much as expected. I missed the high end of the snow but a little bit, but the snow to water ratio ended up at nearly 20 to 1, which is even drier and fluffier snow than I expected in the Boston area. 7.5 inches fell here. You’ll see that along with snowfall reports from across southern New England here (from my friends at the National Weather Service in Taunton MA):

http://forecast.weather.gov/product.php?site=NWS&format=CI&version=1&glossary=0&highlight=off&issuedby=BOX&product=PNS

So, now the snow is done, though there is still blowing snow around as NW winds pick up a little behind the storm. Cold air is rushing in, and temperatures tonight across the Boston area will fall to the lower to middle teens, recovering only slightly to near 20 tomorrow under a sunny to partly cloudy sky.

Saturday night, some clouds will roll across the sky from the northwest as an arctic cold front approaches. This front will cross the region overnight or first thing Sunday morning, and may produce a brief burst or 2 of snow. Any of these bursts could be briefly heavy with gusty winds, otherwise known as a snow squall (fairly common occurrance with Arctic cold fronts). If you do see one, it will not last very long.

This front will usher in the coldest air that most of the region has seen in about 6 years. Temperatures should spend Sunday in the teens, but will fall to near or a little below zero in Boston Sunday night, and possibly as cold as -10 across some suburban and certainly rural locations in eastern and central MA, as well as southern NH. If the wind is light enough, some valley locations could see even colder temperatures. On Monday, under bright but ineffective sunshine, the temperature may never make it to 10 degrees in much of the region.

The cold will ease slightly as it makes it back to the 20s Tuesday, feeling relatively mild compared to Sunday & Monday.

The next storm threat seems to be coming along for the middle of next week. And though based on medium range computer models this storm has some significant potential to produce alot of precipitation, it is far too early to be sure in any detail how this system will impact this area.  Something to follow for sure, but in the shorter term be ready for very cold weather!

Cold & a bit more snow…

225am

The next 4 days…

 Dry & chilly weather will dominate today, with clouds & sunshine. The most clouds will be early in the day as the system that brought rain & snow Wednesday departs & again late in the day as the next storm system approaches from the southwest. This storm will pass through the region on Friday, with about a 12-hour period of snow, starting between 1am & 3am, ending between 1pm & 3pm, and depositing a general 2 to 5 inches of light, dry, fluffy snow. Somewhat less snow can be expected to the northwest of Route 495, and a few spotty amounts over 5 inches may occur over southeastern MA. Amounts should be on the light side in southern NH & west of Worcester MA, that is, under 2 inches.

This weekend, expect dry & very cold weather, with lots of sun but also windy conditions Saturday. There may be some more clouds on Sunday, especially across far southern New England, with even a few snow showers developing, but most of the region will remain dry. Low temperatures of 0-10 will be common and high temperatures of 15-25 can be expected both Saturday & Sunday.

Active Pattern!

1100pm

Tuesday Storm Summary… Things unfolded pretty much as advertised. The snowfall ranges and specific city/town snowfall amount forecasts verified nicely. The amounts on the list were all within 2 inches, and several of them verified right on. I’m proud of those numbers, given that it was not quite what Harvey was forecasting (I had to go higher based on what I was looking at) and because I underestimated the snow amounts on the last 2 significant storms. But enough of that. The main area of precipitation, which was mostly rain and freezing rain tonight, has moved out, leaving drizzle & freezing drizzle behind. Most of the icing continues to occur in the 495 belt into southern NH. The drizzle will come to an end as the night goes on, but temperatures not far from freezing over most of the region will result in some continued slick spots, which will also be the case as we head into the early morning of Wednesday.

Wednesday snow? … Yes, I believe we are going to see a period of snow Wednesday afternoon. A small but potent area of energy will be moving across the region from west to east, and should be enough to trigger numerous snow showers or even a general area of snow, which could fall at a moderate clip for a time. The most likely time to see this will be after 1pm into the early evening hours (7pm or 8pm). Accumulations of 1/2 to locally 2 inches can be expected.

Wednesday night & Thursday tranquility… The disturbance is out of here, and high pressure builds in with cold & dry weather. Like Monday, sunshine will dominate Thursday, but some high clouds will be showing up from the southwest later in the day. Unlike Monday, it will not be quite as cold, with high temps topping off near freezing, some 10 degrees warmer than those of Monday.

Thursday night & Friday storm threat… With a couple days go to before this event, there is still some uncertainty. Some of the computer models have hinted at a quick-hitting but rather significant snowfall, while a couple other fairly reliable ones have taken the system on a faster, more southerly track, with lighter snow. The certainty is that it will be quite cold Thursday night (low in the teens) and Friday (high in the 20s). My feeling right now is that we will see a period of snow during the day on Friday, with the potential for a few to several inches of fluff. I’ll fine-tune this as we get closer.

Weekend cold blast… Arctic air will flow in behind whatever storm we get on Friday, making the weekend bright but very cold! Low temps will probably fall below 10 in most areas for Saturday & Sunday morning, with a few below zero readings possible. Daytime highs will barely make 20 Saturday along with some gusty wind which will make it feel even colder. It will remain quite cold through Sunday, with high temps again well below freezing. Just one note for Sunday… There may be a very small wave of low pressure that presents a slight threat of snow for a portion of southern New England at some point Sunday or Sunday evening … just something to keep in mind as you won’t see that on anybody’s forecasts right now.

More storms & cold? … I don’t have a great feel on the storm threat(s) for the last week of January, but I am fairly confident we will see at least 1 if not 2 more shots of very cold air, especially toward the final few days of the month.

Beyond Tuesday

1220am

Now that we covered Tuesday’s winter storm, let’s look a little beyond that.

Wednesday will feature lots of clouds, but also some breaking of those clouds. There may also be some scattered rain & snow showers as lingering energy passes across the area. It will be relatively “mild” as compared to recently, with a high temperature in the upper 30s to perhaps 40 in a few areas, before it starts to cool down later in the day, along with increasing northwest winds as low pressure finally pulls away to the northeast of the region.

Thursday will be a bright, cold day, with  a high temperature near or a little below freezing.  This will set the stage for the next storm threat, which the computer models have had trouble timing during the past few days. The best guess now suggests that this system will arrive during Friday morning, and with plenty of cold air in place will be in the form of snow. How much snow will be determined by the exact track and speed of low pressure, which will pass south of New England. Early indications are for a decent shot at a moderate amount of snow from this storm system.

Behind the Friday storm threat lurks the coldest air of the winter so far, and that will be making a weekend visit, along with at least one day of gusty wind to make it feel even colder (Saturday).

Tuesday Winter Storm

1030pm

Good evening everyone! Sorry this is being posted later than I wanted. But a busy day will do that…

We have yet another bout of winter weather on the doorstep, moving in from the southwest for Tuesday. This storm, though not nearly as powerful and heavy precipitation-wise as the last, is slated to bring more of a variety of precipitation over a larger area. Whereas the last storm’s rainfall was confined mainly to the immediate coast and Cape Cod, this one will send a sleet/freezing rain/rain swath over a fairly large area of eastern MA and coastal NH.

Instead of getting into technical aspects of the storm, all that really needs to be said is that this particular setup will allow warmer air in above us, resulting in the mix and change in many areas, after starting as snow. The surface remains very cold thanks to a cold airmass in place and a deep snowcover from the recent storm. This results in a rather messy setup.

What to expect, and when…

This storm should start as snow everywhere in eastern MA and southern NH. The snow area is expected to advance north across the region during the morning, starting around 6am south of Boston and by 8am to the north, lastly in southern NH, and of course + or – about an hour either side of these times. The amount of snow that falls will depend on how quickly an area of moderate precipitation moves up into the cold air in place, while it is still cold enough above us to support snow. My best guess for snow before any mix/change occurs is around 1 inch to¬† locally 2 inches along the immediate coast, including the city of Boston, 2 to 4 inches just inland from here including the 128 belt, 3 to 6 inches from just outside 128 into the 495 belt, and 4 to 8 inches northwest of here in northwestern Middlesex County, southern NH away from the coast, and Worcester County.¬† There is an outside chance of an isolated heavier snow amount somewhere in the hills of Worcester County to nearby southwestern NH. Some selected cities and towns and what I expect their snowfall to be, plus or minus 1 inch either side (and if you live in one of these places let me know what you get please!)…

Boston MA: 2″

Woburn MA: 4″

Waltham MA: 3″

Londonderry NH: 6″

Nashua NH: 6″

Chelmsford MA: 6″

Worcester MA: 5″

Fitchburg MA: 7″

Milford MA: 3″

Hampton NH: 3″

If you want a¬†number for your city or town, comment here and I’ll give you my best guess.

The snow will be the least of the problems from this storm for some people. Rain will become an issue for some, due to potential localized flooding in poor drainage areas if it should be heavy enough, and also the issue of snow/rain weight on flat roofs. Icing will be the other story, and trying to pinpoint the area of most significant icing (that is up to 1/2 inch or slightly more of ice buildup from freezing rain) will prove very difficult.

As the warmer air comes in aloft and starts to put an end to the snow from south to north, it will flip to sleet for a time (frozen raindrops, or ice pellets), which generally do not cause major problems) then plain rain closer to the coast and south of Boston where the surface temperature is above freezing, but freezing rain (or rain that comes down and freezes to a glaze of ice upon contact with the ground, or the snowcover). The glazing takes place in areas where the surface temperature is at or below freezing. I’m still not sure where this changeover line is going to make it to. A best guess at the moment is that it will make it into coastal NH and most areas along and southeast of Route 95 in MA fairly easily. The areas near 95 will probably see a period of sleet & freezing rain with some minimal glazing before it goes to plain rain during the afternoon Tuesday. As you go further west and north, the changeover will occur later and the sleet to freezing rain will occur longer. As I see it, the most likely areas to see icing of 1/4 to 1/2 inch or slightly more will run from the MA/NH border through Lowell/Chelmsford, southwestward through the central part of Middlesex¬†County including the Concord area and further southwest from here down toward Worcester. This significant icing belt may be only about 10 miles wide, so we’ll have to watch radar and surface observations to see where it sets up. North and west of this area, precipitation will remain mostly snow & sleet, but may turn to freezing rain for a brief time.

The main precipitation area should begin to taper off and exit from southwest to northeast during Tuesday night, and be all but over by midnight. Temperatures over areas that get ice & snow will remain fairly chilly and untreated surfaces will be slippery throughout the night. Further south and east, areas that get less ice and more rain may develop some slick spots as temperatures fall to near or slightly below freezing, especially if there are any breaks in the clouds, which would allow it to cool more quickly.

Caution should be used in all areas for any travel Wednesday morning.

Quick 7-day Forecast for Boston Area

215am Monday January 17 2011

Today… Bright sunshine, fading at the end of the day as high clouds show up in the southwestern sky. Very cold with highest temperatures from the upper 10s to very low 20s. Light winds.

Tonight… Mostly cloudy. Temperature holding near 20 early then rising through the 20s. Light east wind.

Tuesday… Overcast. Snow developing from south to north between sunrise and 900am, accumulating from a coating to 2 inches in the Boston area except 2 to 4 inches outside Route 128 in areas north of the Mass Pike and possibly 4 to 6 inches outside Route 495 mainly north of the Mass Pike. Snow changing to sleet & rain from southeast to northwest across the region midday through afternoon, but a period of freezing rain is possible especially in the Merrimack & Nashoba Valleys. Highs will climb into the 30s but may remain right near the freezing mark in valley areas northwest of Boston.

Tuesday night… Overcast with periods of rain. Icing should come to an end where it occurs as temperatures range from the middle to upper 30s.

Wednesday… Mostly cloudy with some lingering rain showers or drizzle in the morning. Becoming partly sunny in the afternoon with increasing northwest winds. High temperatures right around 40 through the morning, then cooling through the 30s during the afternoon.

Thursday… Mostly sunny & chilly with a high near 30.

Friday… Chance of light snow or flurries in the morning followed by clearing. High in the upper 20s.

Saturday… Mostly sunny. High in the upper 20s.

Sunday… Chance of snow. High in the middle 20s.

Half Way

1010am

We have reached the half way point of meteorological winter (December-February). Sometimes the whole concept of meteorological winter is rather silly, given how many of our larger snowstorms and some significant cold outbreaks have occurred in March and even sometimes April. But there are the limitations of definition. Weather doesn’t really care about such limitations.

The weather continues to prove my long range winter forecast pretty much wrong this season. Everything has been happening 2 to 4 weeks later than I expected, with persistent blocking being the main reason. Only this coming week is going to resemble the type of weather I expected to dominate January, that is, storms of mixed or transitioning precipitation preceeded & followed by cold. Such a mixed storm is expected on Tuesday, preceeded by cold Monday & followed by late-week cold again. In addition, we’ll be watching for one more storm threat around Friday, but there’s about a 50/50 chance of this system being too far east to have any significant impact on New England.

After the passage of a weak Alberta Clipper system which brought some light snow shower activity, we’ll have a bright & cold Sunday, but otherwise fine to run those last minute snack errands before the Patriots & Jets kick off at 430pm. For those going to the game, it will be quite cold, with a game time temperature in the middle 20s, falling into the upper teens by game’s end. But with a clear sky above and diminishing west winds, it will not be as harsh as it has been during some playoff games.

Looking ahead…

Monday (MLK Jr Day) which some of you have off (I don’t) will feature bright sun & very cold air with a high temp barely reaching 20!

A storm system moving through on Tuesday will bring snow that will then likely change to rain. However, a period of icing is possible especially inland and over valley areas where cold air remains trapped.

The storm will be moving out on Wednesday. There are some questions about some lingering moisture moving up from the southwest to produce additional precipitation, which could be in the form of snow as colder air moves back in. At the moment, I don’t expect this to be a big deal in terms of snow amounts, but it could make things slippery. By the end of the day, wind & cold will likely become the main story.

Thursday looks like a bright but very cold day, and by Friday we may be dealing with the next storm threat. Right now, most indications are that we will get a glancing blow from an offshore storm, with a threat of some snow. But as always, this far out there are too many uncertainties and this potential will be monitored.

Looking way out to next weekend, there are signs of some very cold weather, perhaps the coldest of the winter so far.

Short & Sweet … More later…

355pm

Hi all!

Well I underforecast snow amounts, obviously, in a good part of inland locations. My coastal forecast was better this time. I wish I had bought the precipitation being cranked out by my favorite forecasting model, but I thought it was overdone, and it turned out for the 2nd time in a row I made the same mistake. I have learned my lesson. Also, the storm was in quicker than I thought, by about 2 hours. So if anybody was inconvenienced by my info that didn’t work out, SORRY! ūüôā The main thing is, I hope everybody is safe!

I am running out for a while, lots of cleanup and some driving to do, but I will be back later with some more details on what happened, and what’s to come in the next several days. Is there another storm on the horizon? You’ll have to wait to see. ūüôā

Quick Update!

For the moment I’m going to lean toward the lower side of my totals, that is, closer to 10 versus 16. Snow has come in earlier than expected, but I’m also observing trends that make me a bit nervous. Temperatures right along the coast from Cape Cod all the way up through Boston to Gloucester as of 1am are 36 to 40 with winds straight out of the east. This is being fueled by the relatively mild ocean water. No doubt later in the storm as the low pressure area wraps up, colder air will push back into these areas, but this boundary that seems to be setting up in that area (a coastal front) may limit snow totals near and just east of it.

For the most part the forecast I made is still something I’m comfortable with, but watch these areas near the coast early in the storm for wetter snow and less accumulation. One thing we really have to watch for is that sometimes the low pressure areas can try to track along these coastal fronts, and this could result in a slightly more westward shift to the track. That may allow a dry slot to work in from the south and southeast, and could shut down the snow earlier than expected. Another thing to watch for that could limit totals.

145am Wednesday 1-12-2011

Closing In…

The second major snowstorm in just over 2 weeks is now on final approach to New England. The beast is being born off the Mid Atlantic Coast now, and a very rapidly-deepening low pressure center will result, tracking northeastward, passing just southeast of Cape Cod Wednesday morning. This continues to look like a progressive system, that is, one that is not going to slow down or stall. Nevertheless, the rate of strengthening, track, and available moisture will be enough to crank out major snow for just about all of Massachusetts and southern New Hampshire.

Again, the wildcard remains the issue of how much mixing and rain will occur over Cape Cod. It still looks like most of the mix/rain will be confined to the Outer Cape, including Chatham. Snow amounts could range from as little as an inch or 2 near Chatham building up rapidly to around 10 inches near the Cape Cod Canal. For the remainder of Massachusetts and southern New Hampshire, it is now a pretty safe bet that all areas will see 10 or more inches of snow. The upper limit of accumulation expected has been hard for me to determine, as I have been concerned about the speed of the storm being too fast to allow the amounts you may have seen in some places to verify. That said, there is enough potential with this system that I will set my widespread upper accumulation limit at 16 inches.

Some specifics…

Once snow gets underway, look for a fairly rapid drop in visibility from south to north across the region, southern MA first, southern NH last, between 1am & just before dawn.

There should be up to a few inches of snow on the ground in many areas, especially in MA, by dawn.

Thundersnow remains possible during the heaviest snow in the morning hours. Snowfall rates of 1 to 2 inches per hour can be expected for much of the morning, but can reach 2 to 3 or even 4 inches per hour during thundersnow. These extreme rates do not usually last too long, however.

Blizzard conditions? 3 or more hours of sustained 1/4 mile or less visibility is possible, especially near the MA East Coast, as winds there will be steadiest and strongest (northeast to north 25-40 mph with higher gusts). Winds will be gusty inland, but not as strong as near the coast. Winds closer to Cape Cod may gust over 50 mph to even near 60 mph at times.

Tides… Astronomically low tides should limit flooding problems this time, in contrast to the storm of December 26-27. There will be some splashover and mostly minor flooding. But it also appears that the high tide and the strongest part of the storm will not coincide, which will further limit flooding.

What can go wrong with snow amounts? 2 things: If convective snowbands (thundersnow) are more prominent, snow amounts can be higher than forecast in some locations (isolated amounts over 16 inches). Also, this low pressure area will be deepening so rapidly, it may act almost like a tropical cyclone for a while. When this occurs, you sometimes see drying in the mid levels of the troposphere. That is, the air around where the snow forms can dry out, and you see lighter areas or even holes in the snow areas on the radar. Something similar to this happened in the last major storm, cutting down on snow amounts in central MA. This is something to watch for as the low pressure area makes its closest pass.

Any way you look at it, most of us are in for a good belting of snow and wind. Travel is not recommended, at least Wednesday morning through mid afternoon. Anyone that has to be out should allow alot of extra time and use extreme caution.

930pm Tuesday 1-11-2011

Storm Update

The National Weather Service has issued a Winter Storm Warning & Blizzard Warning from 2am thru 8pm Wednesday. The timing of this storm looks similar to what I discussed in the previous blog, so I won’t get into that again.

I have added a little to the snow totals, due to a slightly colder solution and a fluff factor of accumulating snow. Total snow across eastern MA, except Cape Cod, should be in the 10-16 inch range. It’s not out of the question that a few isolated 17 or 18 inch amounts are seen. I still think the majority of the amounts will come in at 14 inches or less, due to the quick movement of the storm.

Also, do not be surprised to hear thunder during the heaviest snow Wednesday morning. It is during these periods of heavier snow that blizzard conditions are most likely.

Another update will follow this evening!

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