Coastal storm to bring accumulating snowfall to much of CT 2/23-2/24/13

Our active weather pattern continues as yet another coastal storm will be impacting the state of CT during the later half of Saturday lasting through the first half of Sunday.  Unlike past storm this year, this system will be a bit more typical of what we usually experience in CT as the famous rain/snow line will be dissecting the state.  Where this line sets up will have significant impacts on where we see the most snowfall occur and as always this will pose a challenge.

Impacts:

• Precipitation will begin early to mid-afternoon on Saturday and may begin as a rain/snow mix, especially down towards the shoreline where precipitation may actually even start off as plain rain.
•   As we move through the afternoon and evening hours as some colder air works back in place, mix precipitation will begin to transition over to all snow away from the shoreline. 
•  The heaviest precip should be ongoing during the overnight hours of Saturday into Sunday.
• The snow will be very wet and heavy, causing snow to stick to power lines and trees, however, any limb damage or power outages should be on the isolated side and aren't expected to be a major issue. 

Weekend system to bring accumulating snows to southern New England

An active weather pattern looks to produce once again as yet another off-shore storm system will track close enough to the region to bring accumulating snows to everyone.  Sort of like the system we saw the other night, it appears the highest totals will once again be confined to eastern MA and the Cape region, although this axis should extend a bit further to the west.

Computer forecast models have had major difficulties with handling our our weather would evolve this weekend.  At the beginning of the week a few computer models were suggesting the potential for yet another significant coastal storm, then the models "lost this" for a few days only to start bringing this system back.  What's the explaining for this?  Well it all has to do with the models handling of atmospheric waves or pieces of energy that work through our atmosphere.  We also call these disturbances.  During an active jet stream period several disturbances can work through the jet stream on a daily basis and it all comes down to how the models handle these disturbances.  Early on, some models were zoning in on a few disturbances and phasing them, or combining them, with the jet stream on the east coast, when this happens we see explosive cyclogenesis, or rapid coastal storm development.  For a few days the models than began to back off on these disturbances phasing with the jet, therefore, it didn't look like we would see any type of storm.  Well as of a few nights ago, the computer models began on zoning in on another disturbance which would phase with the jet and some models continue to hint at this process occurring late tomorrow into Sunday.  It's just a question as to how far west/east the system will track.

Snow should begin breaking out in the later afternoon hours and should begin winding down during the pre-dawn hours of Sunday, except across eastern MA where the snowfall will wind down by the late morning hours.  At the height of the storm, snowfall rates could approach 1''/HR, especially across eastern areas and travel will be slick and hazardous.

Snowfall map:

Storm system to bring light snow accumulations to portion of southern New England 2-13/13-2/14-13

Not even a week after the Great Blizzard of '13 and we're dealing with another storm system.  However, this  time around we will not see record breaking snowfalls like we did last week.  While this storm system will be strengthening fairly rapidly, the storm will be passing just far enough to our southeast to where we will avoid any significant accumulations.

All computer model guidance seems to be in fairly good agreement that a strengthening and developing storm system will pass close enough to the region to where a period of light/moderate snowfall will overspread portions of the region but far enough to our southeast to where we avoid any significant impacts from the storm.

Snowfall should overspread the region during the late evening/overnight hours and be out of the region by the early AM hours.  Morning travel could be slow and some delay's can be expected but in the end the impacts from this system will be on the low side.  Expect the highest snowfall totals to occur across southeastern CT, RI, far SE Map/Cape/Islands.

Below is the snowfall map:

Historic Blizzard CT Snowfall Update

Given the snowfall totals being reported thus far along with a deformation band setting up right over much of CT with no signs of moving out or weakening over the next several hours we can expect widespread snowfall totals of 24-36'' (2'-3')....there will be some locations though that fall shy of the 2' mark, however, the majority will be passing that.  WE can't even rule out some isolated totals nearing or perhaps slightly exceeding 40'' depending on exactly how long this deformation band stays in tact.

Updated Snowfall Map for Historic Blizzard 2/8-2/9/13

Snowfall has already began across much of the region and conditions will rapidly deteriorate as me move through the afternoon and into the evening hours.  Now that we are in "now-casting" mode, which basically means we toss the models aside (with the exception of the rapid-refresh models) and just watch how the storm unfolds, we can start pinpointing where the axis of heavier snowfall will setup.

Given with what we know and what we see it appears that the axis of heaviest snowfall will setup across northeastern and eastern MA and this area looks to get crushed.  We can expect the deformation band (band of heaviest snowfall) to setup across this area later this afternoon/evening and perhaps just sit over this area for at least 4-6 hours.  During this band snowfall rates will approach 4''/HR along with thunder/lighting.

Now we still have to closely watch the exact track the system takes b/c any wobbles left or right could impact where that axis of heavier banding sets-up.  We also have to watch any jobs to the east b/c if we see any jogs to the east snowfall totals across far western zones will end up being on the lesser side than forecasted.

Let's just break this down one last time on what to expect:

• Snowfall region wide of 1 to 3 feet (with a few spots perhaps nearing 40'', especially in eastern MA)
• Thunder/Lightning with the heaviest bands
• Strong/Damaging Winds late this afternoon and through the overnight.  Sustained winds across far eastern MA/Cape of 45-60 mph with gusts 70-80 mph.  Elsewhere winds sustained 35-50 mph with gusts 55-60 mph.  
• Widespread power outages across much of eastern MA/RI and working into eastern CT but becoming more scattered as you work west.  
• Major coastal flooding along the east facing shores of eastern MA/RI

Below is updated snowfall map:

Below is wind map:

Historic Blizzard to Impact All of southern New England 2/8-13-2/9-13

Computer model guidance continues to be in major agreement that an historic blizzard will have extreme impacts on all of southern New England as a long duration event is a little less than 24-hours away from unfolding.  This storm will have the potential to dump 1.5 to 2 feet of snow region wide along with the possibility of up to 3 feet of snow for some.  We will also be experiencing strong/damaging winds leading to blizzard conditions and whiteout conditions at times, widespread power outages, especially with the weight of snow on tree limbs and power lines, extreme coastal flooding, and the possibility of thunder/lightning.  This will also be a life threatening situation for the homeless and anyone who is trapped outside.  Below we will look into all the hazards associated with what looks to be an historic blizzard.

-Potential for Substantial Snowfall Accumulations Region Wide.

Computer model guidance is in major agreement that we will be seeing substantial (widespread 12''+) snowfall accumulations region wide as many places will pick up as much as 18-24'' of snow.  In fact, we could be looking at as much as 24-30'' of snow for quite a few with even some spots getting as much as 36''.  This will be a fairly slow moving storm and it's associated with a great deal of moisture, with moisture being fed into the storm from both the Gulf of Mexico and the Atlantic Ocean.  There will be a vigorous amount of lift associated with this system along with excellent snow growth.  All of these factors will lead to very heavy snowfall rates with rates as high as 2-4''/HR, especially if there is any thunder/lightning associated with the heavier bands.  Snowfall ratios could also be as high as 13:1 to 15:1, especially across the interior away from the coast.

-Potential for Strong/Damaging Winds Region Wide

With the storm undergoing rapid intensification and a large pressure gradient developing over the region we will see a major increase in the winds, especially out across far eastern MA/Cape region.  Here we could be looking at a prolong period with winds sustained as high as 45-60 mph with wind gusts as high as 75-85 mph.  This is equivalent to category 1 hurricane force winds.  With substantial snowfall accumulations out across this area and snow sticking to tree limbs and power lines widespread power outages can be expected with the possibility for power outages to last for several days.  Elsewhere across southern New England, we are looking at the possibility for sustained winds of 25-35 mph with wind gusts as high as 55 mph.  This, along with substantial amounts of snow should lead to widespread power outages as well with some of the outages lasting for several days.  These winds will lead to a several hour period of blizzard/whiteout conditions making visibility values close to 0 at times.  This will make travel extremely difficult and very life threatening.  Travel during the storm is strongly not recommended.  Strong winds will also lead to drifting snow and we could see snow drifts as high as 4-6 feet!

-Potential for Extreme Coastal Flooding

With such an intense storm system just off the coast and an easterly component to the winds this will lead to extreme coastal flooding across the east facing shores of the ocean across eastern MA/Cape.  Currently we are in a new moon phase so high tides will be running much higher than average and high tide will be occurring during the height of the storm.  This could pose a life threatening situation to anyone near the immediate coast, especially if you're outdoors.  Looking at wave heights as high as 7-10' and perhaps a bit higher.

-Potential for Thunder/Lightning

With such a strong system and vigorous lift associated with it, the possibility of thunder/lightning is possible with this system.  If there is any thunder/lightning that would locally lead to snowfall rates as high as 4'' per hour.

-Storm Timing/Travel Hazards

As the morning hours progress on Friday we should see periods of snow showers as an initial piece of energy moves overhead.  It's possible that these snow showers could lead to a quick coating or an inch for some but the brunt of the storm starts occurring during the early to mid-afternoon hours and then conditions will rapidly deteriorate.  Throughout the duration of the storm travel is not recommended at all as this will be a very dangerous storm and anyone caught or trapped outside could be in a life threatening situation as it could take a while for safety officials to reach you.  Plows will have a very difficult time keeping the roads clear, given snowfall rates could exceed 2-4'' per hour.  The snow should begin winding down sometime late morning Saturday with on and off snow showers the remainder of the afternoon, especially across eastern MA.

This is a very dangerous and perhaps life threatening storm for anyone who risks travel.  We are looking at the possibility of an historic storm with substantial snowfall totals, strong/damaging winds/widespread power outages/extreme coastal flooding.

Below is the snowfall map:

Below is Wind Forecast:

     

Significant/Substantial Coastal Storm to pose significant impacts across southern New England

We are beginning to see some very strong consensus with computer model guidance that a significant/substantial coastal storm will have major/significant impacts across all of southern New England during the day on Friday and continuing through a large part of Saturday.  The impacts will range from snowfall, potential with widespread significant (6-12'' totals) to perhaps substantial (12''+) snowfall accumulations region wide, the possibility of sleet mixing in, especially across the coastal plain, the possibility of thunder/lightning, potential for very strong/damaging winds leading to blizzard conditions and widespread power outages, and coastal flooding/erosion.  All of these hazards and more will be addressed in great detail below.  First off, we will take a look at the meteorology behind the scenes.

-Meteorology behind the storm.

The above image is a 500mb geopotential height/vorticity map from the ECMWF computer model, one of the best and most accurate computer models out there.  This image is from today's 12z (7:00 AM) run and for 48-hours out, meaning this is what is projected for 7:00 AM EST Friday.  I highlighted two areas here as these are the two main features of importance.  In the enclosed blue circles are pieces of energy which are moving through in the mid-level jet stream aloft, roughly 18,000ft ASL.  Energy #1 is looking very strong and intense here and we are beginning to see the energy dig more, allowing for a trough to develop within the jet stream, this is otherwise known as amplification and will allow for this piece of energy to remain strong.  Looking towards energy #2, we notice it is a little more weak in nature as it's working up the coast.  As these pieces of energy continue working through the jet stream flow the northern piece of energy and southern piece of energy will combine, or in meteorological terms we call this phasing.  Once this process occurs we will begin the process of transferring all of it's energy towards the energy moving up the coast, as this process occurs we will begin to see the rapid development of cyclogenesis, or in other words, the development of our coastal storm.  Once this process starts to occur we will be looking at rapid and very intense cyclogenesis.

The above graphic is a chart showing mean sea-level pressure (MSLP) along with 6-HR precipitation from the 12z run of the GFS computer model also for 48-HR out.  I have circled the area with the "H".  This area depicts an area of high pressure and the GFS has the high pressure at about 1036mb which is pretty high.  The GFS, along with several other computer models all show a fairly strong area of high pressure to our north and only drift it eastward very slowly throughout the duration of this storm.  This high is referred to as a "blocking" high and will be of significant importance with this storm as this will make for a very slow moving system, enhancing the impacts we will see.  This area of high pressure along with the rapid deepening of the coastal storm will also play a major significance in the wind potential, as you'll have rapid changes in pressure over a very small distance.

When dealing with the potential for impacts as large as we are looking at the key here will be with regards to the phasing.  As noted above, right now computer models are showing a perfect phase, this means the storm is phasing early enough to where we would see the most significant impacts and the storm will be phasing late enough to where we don't see the storm move inland but stay off the coast keeping the cold air locked in.
Now that we took a little look into the meteorology aspect of things let's take a look at the hazards we may be facing.

Significant/Substantial snowfall accumulations possible:

When using the terms significant/substantial we will define the following as:

Significant - Widespread area of 6-12'' of snowfall with isolated higher amounts
Substantial - Widespread area of at least 12''+ of snowfall with isolated higher amounts

Right now the likelihood of at least 6-12'' of snowfall over just about the entire region is exceptionally high and the potential for a widespread swath of 12''+ is also very high  In fact, the possibility exists for a swatch of snowfall totals ranging from 18-24'' of snow and some isolated higher amounts close to 30'' are certainly possible.  However, right now it's still a little too early to pin down exactly where this will occur.  We could be looking at the potential for snowfall rates to reach 2-3''/HR with even some 4''/HR amounts possible, especially if we see any bands of snow which are associated with thunder.  What also complicates things with regards to where the higher totals will occur is the potential for a dry slot.  With all intense storms they are usually accompanied by a dry slot and to pinpoint if/where the dryslot will occur is a bit difficult right now.  The possibility of mixing will also complicate forecasts a bit, especially closer to the coast.  Snowfall could also be wet in nature, especially for the further south you go leading to heavy wet snow sticking on tree limbs and power lines.

Since this system will be associated with some very potent lift (strong upward vertical motion) along with steepening lapse rates aloft (change of temperature with height) the potential for thunder/lightning will also be possible with this system.  If there is any thunder/lightning that will further enhance snowfall rates locally and this is where 4''/HR snowfall rates are possible.

Several computer models are also showing the potential for some very strong and damaging winds associated with this storm thanks in part to a very strong pressure gradient that will be going over the region thanks to the high pressure to our north and the coastal storm passing just off the coast to our SE.  In fact, some computer models are showing a prolonged period of very intense winds across much of the region and especially the southeast coast.  We could be looking at winds of 25-45 mph sustained with winds gusts as high as 55-65 mph, especially along the coast.  Winds along the coast could even be sustained as high as 45-55 mph.  If future runs don't back off on what we are looking now than wind gusts of 70-80 mph would be possible out across far SE MA along the Cape area. This would lead to blizzard and near whiteout conditions at times and also lead to widespread power outages across the region.

With such an intense coastal storm and strong winds coming in off the ocean this will lead to some major flooding across some of the coastal plane across RI/SE MA and perhaps even across coastal CT.

All in all this is looking like a very dangerous storm.  Snow should begin during the morning hours of Friday with conditions rapidly deteriorating as the afternoon goes on with very hazardous and dangerous travel lasting throughout the night and into the first part of Saturday.  We are looking at the possibility of widespread substantial snowfall accumulations, along with wet snow sticking to limbs/power poles, the possibility of tropical storm to hurricane force winds leading to blizzard conditions and widespread power outages along with major coastal flooding.

Below is a graphic displaying what we could be looking at for snowfall totals.  Keep in mind it is still early so this isn't a fine tuned map and as we get closer and details continue to get resolved the map can be more fined tuned: