Snowfall maps/forecasts for 1/7/11-1/8/11 snow event

[weatherwiz]

Technical writeup:

As we move towards the end of the week and into the weekend the potential will exist for a minor to moderate snowfall event to impact portions of southern New England. Normally when we are looking at snowfall threats we are looking at coastal storms or fast moving clipper type systems. This event will feature something a bit different that what we normally see.

A southerly displaced polar vortex has placed itself right around the Great Lakes area, on the Canadian side of the border, over the next few days this polar vortex will be responsible for swinging pieces of energy around it. Due to increase upper-level divergence and surface convergence a weak area (or multiple) of low pressure will develop and swing across the region. Now where this low pressure develops and tracks, as well as where the pieces of energy aloft track will have a major say in how big of an event becomes and how much snow it will ultimately produce. As of now the consensus is for development/track to favor an event that is more on the light to moderate side rather than a major event.

As mentioned above this is not going to be a coastal type storm nor is it really a clipper type event. If were looking at neither of these than what are we looking at? Well any snowfall will be produced by something called an inverted trough (also briefly mentioned above)...in this case we are looking at a Norlun "instability" trough. As mentioned above there is a system (polar vortex with associated upper-level low) off to our west, off to our east, well off to our east out across the Atlantic is a strengthening ocean storm. While this storm is pretty far away from land to have any direct impacts on us, it will provide a focal point for our snowfall.

Going back to what was mentioned in the second paragraph regarding the increasing upper-level divergence and surface convergence these two developments will play a great role in the development of the norlun trough. As the upper-levels of the atmosphere are favoring cyclogenesis basically right over our region we take a look to that ocean storm that is off to our east. As cyclogenesis begins to occur and we start seeing weak low pressure development right around CT we will also see the ocean storm start to help us out. If you look at a 1000-500mb map (which will be posted below) you'll notice the isobars on the ocean storm start getting tugged westward towards southern New England...this is the inverted/norlun trough. What this will do is begin to advect moisture both from the ocean storm and off the ocean into the region as winds at the surface and lower levels of the atmosphere turn towards a more easterly direction.

Now that we have this explained this is where things become rather difficult. Where this trough sets itself up will have MAJOR implications on where the heaviest band of snowfall sets up and how long it sets up will determine how much snowfall we are looking at. Both these questions at this time are extremely difficult to answer with 100% confidence, however, given some of the signals we have seen up through now there may be a general idea of where we see it set up and who may potentially end up with the most snowfall.

When reviewing tonight's 0z GFS/NAM as well as the 21z SREF's (I would have loved to incorporate more of the Euro/Ukie but since I don't have access to most of the data I'm not able too) I paid very close attention to the following features;

1) The low-level wind trajectory and the strength of the winds. This is where I looked to get more of an idea on how the inverted trough was looking, how long it looks to hold up, and where to potentially see it set up. Looking at the direction of the winds was to see if they were coming off of the ocean or not and for hong long they would be doing so...this was used to get an idea of how much moisture we would see get slung into the region. Finally here the strength of the winds were looked at, if winds were on the weaker side this meant there would be a good probability that if the trough setup in a particular location it would probably stall out over that particular area which means there would be a higher potential for heavier snowfall totals.

Using the NAM/GFS it appeared that this trough may set itself up across portions of far southeastern MA/RI/CT and down towards the NYC area. It would be these areas that would have the best potential to see accumulating snowfalls.

2) 700mb vertical velocities. This was looked at to get a better idea of where some of the strongest and where the stronger lift would occur.

Looking at the NAM/GFS looks like there could be a few areas of potential enhanced lift, one of those areas being in the vicinity of SW CT and another one out across parts of SE MA and N. RI.

3) Convergence (surface/850-700mb and 700mb-500mb). Where the best convergence is along with the best vertical velocities these are the areas that are likely to see the heaviest snowfall occur.

According to the NAM/GFS this appears the best convergence looks to set up over SW CT as well as parts of RI and parts of SE MA.

Forecast:

Based on what was written above, at this point in time I believe the highest snowfall totals were across a major chunk of SW CT with a second max of high totals occurring out across RI and portions of SE MA. This is where I believe that best convergence will setup along with the strongest lift. Given high relative-humidity values and an ample supply of moisture I believe this will be enough to produce a widespread 3-6'' but the potential does exist for higher amounts, possibly in excess of 10'' where the stronger bands setup for a prolonged period of time.

Elsewhere I believe snowfall totals will not only be lower but also more hit and miss type. Lift/convergence in these areas does not appear to be overly impressive and relative humidity values are not all that high, in face bufkit soundings show quite a bit of dry air into the mid-levels of the atmosphere. Snowfall may not be all that widespread either which means while some locations are seeing snow other locations may not. This may create somewhat of a tight snowfall gradient which also complicates things a bit.

[ORH_wxman]

I think your T-1" north of the pike is going to bust bad. It seems like you ripped the NAM and then cut its qpf at least in half. I think NE MA and SE NH end up doing pretty well in this, they usually do.

[weatherwiz]

I think your T-1" north of the pike is going to bust bad. It seems like you ripped the NAM and then cut its qpf at least in half. I think NE MA and SE NH end up doing pretty well in this, they usually do.

Yeah I can't lie, I mostly went with the NAM for that area...one of these days I'll rid of my NAM fetish. If they have done well in these events in the past then that obviously doesn't bode well for my call, but since I have very little knowledge in the climo department this is something that will probably hurt me until I am able to boost my knowledge.

What I did as well though is virtually look at where the NAM/GFS had the highest low-level relative humidity values as well as where the strongest forcing/convergence/lift setup.

I fully expect to get roasted somewhere with this call.

[Wx4cast]

Technical writeup:

As we move towards the end of the week and into the weekend the potential will exist for a minor to moderate snowfall event to impact portions of southern New England. Normally when we are looking at snowfall threats we are looking at coastal storms or fast moving clipper type systems. This event will feature something a bit different that what we normally see.

A southerly displaced polar vortex has placed itself right around the Great Lakes area, on the Canadian side of the border, over the next few days this polar vortex will be responsible for swinging pieces of energy around it. Due to increase upper-level divergence and surface convergence a weak area (or multiple) of low pressure will develop and swing across the region. Now where this low pressure develops and tracks, as well as where the pieces of energy aloft track will have a major say in how big of an event becomes and how much snow it will ultimately produce. As of now the consensus is for development/track to favor an event that is more on the light to moderate side rather than a major event.

As mentioned above this is not going to be a coastal type storm nor is it really a clipper type event. If were looking at neither of these than what are we looking at? Well any snowfall will be produced by something called an inverted trough (also briefly mentioned above)...in this case we are looking at a Norlun "instability" trough. As mentioned above there is a system (polar vortex with associated upper-level low) off to our west, off to our east, well off to our east out across the Atlantic is a strengthening ocean storm. While this storm is pretty far away from land to have any direct impacts on us, it will provide a focal point for our snowfall.

Going back to what was mentioned in the second paragraph regarding the increasing upper-level divergence and surface convergence these two developments will play a great role in the development of the norlun trough. As the upper-levels of the atmosphere are favoring cyclogenesis basically right over our region we take a look to that ocean storm that is off to our east. As cyclogenesis begins to occur and we start seeing weak low pressure development right around CT we will also see the ocean storm start to help us out. If you look at a 1000-500mb map (which will be posted below) you'll notice the isobars on the ocean storm start getting tugged westward towards southern New England...this is the inverted/norlun trough. What this will do is begin to advect moisture both from the ocean storm and off the ocean into the region as winds at the surface and lower levels of the atmosphere turn towards a more easterly direction.

Now that we have this explained this is where things become rather difficult. Where this trough sets itself up will have MAJOR implications on where the heaviest band of snowfall sets up and how long it sets up will determine how much snowfall we are looking at. Both these questions at this time are extremely difficult to answer with 100% confidence, however, given some of the signals we have seen up through now there may be a general idea of where we see it set up and who may potentially end up with the most snowfall.

When reviewing tonight's 0z GFS/NAM as well as the 21z SREF's (I would have loved to incorporate more of the Euro/Ukie but since I don't have access to most of the data I'm not able too) I paid very close attention to the following features;

1) The low-level wind trajectory and the strength of the winds. This is where I looked to get more of an idea on how the inverted trough was looking, how long it looks to hold up, and where to potentially see it set up. Looking at the direction of the winds was to see if they were coming off of the ocean or not and for hong long they would be doing so...this was used to get an idea of how much moisture we would see get slung into the region. Finally here the strength of the winds were looked at, if winds were on the weaker side this meant there would be a good probability that if the trough setup in a particular location it would probably stall out over that particular area which means there would be a higher potential for heavier snowfall totals.

Using the NAM/GFS it appeared that this trough may set itself up across portions of far southeastern MA/RI/CT and down towards the NYC area. It would be these areas that would have the best potential to see accumulating snowfalls.

2) 700mb vertical velocities. This was looked at to get a better idea of where some of the strongest and where the stronger lift would occur.

Looking at the NAM/GFS looks like there could be a few areas of potential enhanced lift, one of those areas being in the vicinity of SW CT and another one out across parts of SE MA and N. RI.

3) Convergence (surface/850-700mb and 700mb-500mb). Where the best convergence is along with the best vertical velocities these are the areas that are likely to see the heaviest snowfall occur.

According to the NAM/GFS this appears the best convergence looks to set up over SW CT as well as parts of RI and parts of SE MA.

Forecast:

Based on what was written above, at this point in time I believe the highest snowfall totals were across a major chunk of SW CT with a second max of high totals occurring out across RI and portions of SE MA. This is where I believe that best convergence will setup along with the strongest lift. Given high relative-humidity values and an ample supply of moisture I believe this will be enough to produce a widespread 3-6'' but the potential does exist for higher amounts, possibly in excess of 10'' where the stronger bands setup for a prolonged period of time.

Elsewhere I believe snowfall totals will not only be lower but also more hit and miss type. Lift/convergence in these areas does not appear to be overly impressive and relative humidity values are not all that high, in face bufkit soundings show quite a bit of dry air into the mid-levels of the atmosphere. Snowfall may not be all that widespread either which means while some locations are seeing snow other locations may not. This may create somewhat of a tight snowfall gradient which also complicates things a bit.

Here's my 2nd call. adjusted based on upslope, instability, where strongest UVM expected. Leaned heavily on NAM and 06z-12z in house meso-models.

[Logan11]

Obviously I like your depiction Andy ...for selfish reasons.

Just a thought on local topography in general ..... I have noticed when crossing Rensselaer County that there is a central ridge of hills (no name I guess) that you cross between the HV and the valley along route 22. I wonder if they get shadowed as much or if they do better in this event (or others). Maybe not many people live in that n/s upland anyway.

BTW ...talked to a guy yesterday from Hoosick Falls and he got 18" from the Boxing Day event.

Here's my 2nd call. adjusted based on upslope, instability, where strongest UVM expected. Leaned heavily on NAM and 06z-12z in house meso-models.

[Quincy]

a full update coming later tonight, but felt that something needed to be posted. things appear to be coming into more agreement, although I'm still a little bit cautious to go too specific with higher amounts.

[CTNoreaster]

a full update coming later tonight, but felt that something needed to be posted. things appear to be coming into more agreement, although I'm still a little bit cautious to go too specific with higher amounts.

An interesting north of the parkway dividing line!

[Quincy]

An interesting north of the parkway dividing line!

all the heat from the Parkway and 95 traffic will keep that area further north (;

[grinch1989]

a full update coming later tonight, but felt that something needed to be posted. things appear to be coming into more agreement, although I'm still a little bit cautious to go too specific with higher amounts.

I think this is a very good call at this point, seems to be a good blend of the 12z runs.

[CTNoreaster]

all the heat from the Parkway and 95 traffic will keep that area further north (;

Falling into the that same trap that local mets here love!!

We will see!

[Confuzzled]

Found that on DT's FB posted by Justin Berk

[ROOSTA]

Alright I'll nibble at this just for PT. I'll be throwing a map up soon....

I can tell everyones holding there breathe...LOL

[shadow]

wow you guys are all over the place i can get any were from 1 to12 inches thats nailing in down

[rivers]

all the heat from the Parkway and 95 traffic will keep that area further north (;

lol new haven is always on the fence on almost every map..

[Quincy]

wow you guys are all over the place i can get any were from 1 to12 inches thats nailing in down

a typical storm in Connecticut (;

[weatherwiz]

Going to wait until the 0z runs to make the adjustments but what I think I'll end up doing is cutting back on the totals across RI from a widespread 3-6'' and increase totals a bit in parts of northern MA. Might just end up doing widespread 2-4'' with isolated higher amounts possible but keep these higher amounts focused across western CT and western MA.

[cpickett79]

Going to wait until the 0z runs to make the adjustments but what I think I'll end up doing is cutting back on the totals across RI from a widespread 3-6'' and increase totals a bit in parts of northern MA. Might just end up doing widespread 2-4'' with isolated higher amounts possible but keep these higher amounts focused across western CT and western MA.

don't let others influence you thou ....like last storm. just go on your own no regrets.

[weatherwiz]

don't let others influence you thou ....like last storm. just go on your own no regrets.

I'm kind of torn on what to do there in RI...first look it appeared there may be some sort of enhanced lift across this area and obviously that would do wonders snowfall wise. I might just go 2-4'' here instead.

Yeah for once I'm not going to try to let my thoughts get influenced

I'm always willing to take meteorological advice and if I'm using wording that is incorrect or not understanding something correctly that please let me know but I kind of hate when people just say "you're too low" "you're going to bust" blah, blah...give me a reason as to why you think I'm low, and don't just say b/c there is alot of QPF and that doesn't match your totals.

[ChrisM]

Found that on DT's FB posted by Justin Berk

that guy is an actual meteorologist?

[ChrisM]

Found that on DT's FB posted by Justin Berk

that guy is an actual meteorologist?

[ROOSTA]

Alright I'll nibble at this just for PT. I'll be throwing a map up soon....

I can tell everyones holding there breathe...LOL

[weatherMA]

Found that on DT's FB posted by Justin Berk

LOL is this a joke? 1-3" for the berks and Northen Ct gets 12+? :lol:

[Confuzzled]

LOL is this a joke? 1-3" for the berks and Northen Ct gets 12+? :lol:

That is why I posted it. I was made aware of it by someone on my FB and I was like is he smoking crack or does he have some secret knowledge about this NIT?

Oddly, it was a first guess and the time was wrong on it so I am uncertain. It was posted by a MET on his FB though as his.....I couldn't find anything on it on his site...

[Quincy]

final forecast:

[mulen]

They call him the Virginia vigilante he's good at what he does you guys must be new but he's a little off at times see ya.

[weatherwiz]

Final call:

Changes:

Going over latest computer data since the previous forecast I have decided to increase snowfall totals across a good portion of western MA down through western CT as it appears this area will also get an extra boost from upslope which should further increase lift in this areas thus making way for potentially higher snowfall totals.

The next change was to decrease snowfall totals across much of south-central RI from 3-6'' to 1-3''. At this current time I believe the stronger lift will setup further to the north and to the west of this area.

The third and final change was to also slightly increase snowfall totals across northern MA.

Discussion:

An ocean storm off to the east along with a upper level low to our west will work together to produce a norlun trough setup across the region later this afternoon into tonight. This inverted trough feature will aid in the advection of moisture off the the Atlantic Ocean and will be a key factor in the development of snowfall as we go through the day. As the upper level low migrates it's way eastward, we will also begin to see some weak surface low development as upper level divergence and surface convergence favor this development. This will be a huge focal point in the lift needed in order to produce the snowfall.

It doesn't appear the inverted trough feature will last very long though and there are signals that once this feature weakens as winds shift more to the north the supply of moisture will begin to shut off and the system will begin to weaken. We also begin to lose alot of our lift as well. Given these points I don't think we will see a period of heavy snowfall last long enough to produce widespread moderate snowfall totals, thus most of the region should end up somewhere between 2-4'' on average with some isolated higher amounts possible depending on where the heaviest bands setup the longest.

[Damage In Tolland]

Still too low

[Mr Torchey]

final forecast:

Great call, looks spot on to me, hopefully we get an inch down here at the coast.

[weatherwiz]

Still too low

We'll see what happens, was thinking of using 2-4'' instead of 1-3'' but decided against it. Can't wait to see what happens. I just hope it's not alot b/c I don't want work getting cancelled for me tomorrow, 8 hour day coming up.

[weatherMA]

Found that on DT's FB posted by Justin Berk

Still not the best map, probably under in the Berks, but he had the right idea with some of those high totals in CT. Some areas are not done and have 10".