Saturday, December 29, 2012
Snowfall forecast update
Now that the mesoscale features are becoming more clear and based on latest trends here is updated snowfall map:
Quick hitting storm system to bring snow to southern New England 12/29-12/30/12
An area of low pressure is currently working up the east coast and will be undergoing fairly rapid cyclogenesis over the next 12-18 hours. This storm will have a solid amount of moisture associated with it, however, the storm will be a fast mover and the strongest lift will only be over the region for a brief amount of time. Because of these two factors this will help to prevent this storm from dropping much more significant snowfall totals across the region. If this storm were to move slower we could be looking at widespread amounts of 8''+ across much of the region.
The storm will be tracking just to the south of southern New England and sliding northeastward towards the southeastern Canadian coastline. This track will ensure cold air stays locked in place for pretty much the entire region meaning precipitation will be all snow. It's possible, however, that locations along the CT/RI coastline and along the Cape begin as either a mix of rain/snow or a mix with sleet. With this potential for mixing across these locations snowfall totals may be held back a bit.
Snowfall will begin breaking out anytime after noon-1 PM as snow flurries/showers ahead of the system move through the region. While this will be a quick hitting system the height of the storm conditions will be very messy. Snowfall rates of 1-2'' per hour are likely, perhaps even isolated 3''/HR rates where the strongest banding sets up. The timeframe for the heaviest snowfall should be between 6 PM-12 AM. This is when most of the accumulations will occur. While snowfall will continue through the rest of the evening and overnight hours snowfall rates should be much more modest, below 1''/HR rates. Snowfall will begin exiting the region from SW to NE beginning around 1-2 AM.
Winds may become a bit gusty as well across portions of the region, especially the southeast coast where winds could gust upwards of 25-35 mph. While not significant this could lead to some isolated pockets of tree damage or perhaps power outages but this is not expected to be a significant issue.
Below is the forecasted snowfall map. The area of 5-9'' is where the strongest lift/banding is expected to setup. It's possible we could see some isolated amounts of 10'' somewhere within this area.
The storm will be tracking just to the south of southern New England and sliding northeastward towards the southeastern Canadian coastline. This track will ensure cold air stays locked in place for pretty much the entire region meaning precipitation will be all snow. It's possible, however, that locations along the CT/RI coastline and along the Cape begin as either a mix of rain/snow or a mix with sleet. With this potential for mixing across these locations snowfall totals may be held back a bit.
Snowfall will begin breaking out anytime after noon-1 PM as snow flurries/showers ahead of the system move through the region. While this will be a quick hitting system the height of the storm conditions will be very messy. Snowfall rates of 1-2'' per hour are likely, perhaps even isolated 3''/HR rates where the strongest banding sets up. The timeframe for the heaviest snowfall should be between 6 PM-12 AM. This is when most of the accumulations will occur. While snowfall will continue through the rest of the evening and overnight hours snowfall rates should be much more modest, below 1''/HR rates. Snowfall will begin exiting the region from SW to NE beginning around 1-2 AM.
Winds may become a bit gusty as well across portions of the region, especially the southeast coast where winds could gust upwards of 25-35 mph. While not significant this could lead to some isolated pockets of tree damage or perhaps power outages but this is not expected to be a significant issue.
Below is the forecasted snowfall map. The area of 5-9'' is where the strongest lift/banding is expected to setup. It's possible we could see some isolated amounts of 10'' somewhere within this area.
Tuesday, December 25, 2012
Significant Storm to Impact New England 12/26/12-12/27/12
Currently there is an area of low pressure located across the Gulf coast states right around LA. This area of low pressure has been slowly strengthening throughout the afternoon. This system is already rather potent as it has been responsible for producing severe weather and tornadoes from eastern TX through LA/MS/AL and will continue to produce severe weather across these areas overnight as well as FL and then CS/NC/VA tomorrow as the system continues to deepen.
As the area of low pressure begins to track more northeastward following the spine of the Appalachian Mountains and the main piece of energy associated with the system strengthens we will begin to see a trough developing within the mid and upper level jet streams as depicted by the image below:
When looking at the orientation of the developing trough we notice that the trough isn't developing in a north-south fashion but a more northwesterly to southeasterly fashion and looking at the image on the right we see a sharply negatively-tilted trough. The combination of these two features means that there will be very little room for a storm track off-shore. The rising heights will also allow for the winds in the middle and lower levels of the atmosphere out ahead of the system to shift more southerly and southeasterly. With the system expected to undergo rapid cyclogenesis (strengthening) allowing for a rapid increase in the mid and low level wind fields this will allow for warmer air to quickly advect into portions of southern New England meaning many locations will see a quick transition from snow to sleet/freezing rain and then eventually rain. Area to the north and west of the low pressure's center should pretty much remain all snow or see some mixing of sleet/freezing rain. With this said the heaviest snowfall totals will be located across central/northern New England.
In addition to the mess of precipitation we will be dealing with this system is also expected to produce a period of strong/damaging winds, especially across the coastal areas of CT/RI/SE MA where a warmer low-level airmass will allow for better mixing of the lower atmosphere and where the wind fields will be much stronger. There will be some very intense lift associated with this system as well so some rumbles of thunder certainly can't be ruled out either.
As usual with out winter storms this forecast will be very, very tricky as many of the thermal profiles, especially during the onset of the storm are very close to either being all snow or a mix of snow/sleet. High temperatures tomorrow across the region are only expected to get into the mid-30's with dewpoints slowly creeping through the mid-20's. As the onset of the precip shield starts progressing into the region evaporative cooling will 1) work to increase the moisture content of the atmosphere and 2) Allow for the surface temperatures to drop. So essentially how warm the temperatures get tomorrow will play a big role in the precip type at the onset across many locations. We then take a look at the thermal structure of the lower atmosphere. Out ahead of the system we really don't have a great deal of cold air in place across our region or to our north. Temperatures from about 925-700mb are only around -3C to -5C and there isn't any strong high pressure system to our north to allow for colder air to stay in place or drain down into our region. This means that as the system continues to work towards the coast eventually warm air will overspread areas to the south and east of the storm's center allowing for a transition from snow-sleet-freezing rain-rain. With this let's break down each aspect of the storm into further details and for each state:
Snowfall:
CT:
Precipitation is expected to first start working into CT between 1-3 PM with activity first occurring across the southwest corner of the state and spreading north and east through the remainder of the afternoon. As of now, thermal profiles are rather tricky as several forecast soundings are very close to being either all snow or a mix of snow/sleet, especially across southern CT. While surface temperatures are expected to range in the mid-30's or so temperatures aloft from 925-700mb are expected to range from -3C to -5C or so. This really isn't all that impressive and should make for any snow that is falling to be rather wet. This also poises difficulties with the forecast as if the precip is on the light side we could be looking more at more of a mixture. Going with this I would expect everyone to begin as either snow or a mix of snow/sleet (with the mix more likely the closer to the coast you go). As mentioned above the level of cold air in place isn't all that great and there is no high pressure to our north to reinforce colder air into the region. We will begin to see warmer air work into the state rather quickly, especially across the coast and this will work to keep snowfall totals across the coast to a minimum and only about a few inches across the interior. Some locations across the northwest corner of the state where cold air may hang in longer could pick up several inches of snow.
RI:
Snowfall totals across RI should be kept to a minimum as well and accumulations are expected to remain under 1'' for the entire state.
MA:
As we work into MA this is where snowfall totals will begin to vastly increase, especially across the western and central portions of the state and outside of the CT River Valley in southern Hamden County. Areas to the east of Worcester county in eastern MA are expected to receive little in the way of snowfall as warmer air will quickly work into these areas. Areas to the west of Worcester County will have the potential to receive significant snowfall accumulations and snowfall could be on the wet side. There will also be areas of sleet/freezing rain but we'll look at this hazard a bit further down.
NH/VT/ME
These states will be getting hit the hardest by snowfall accumulations as they will be to the north and west of the storm's center. Snowfall accumulations here will be rather significant, however, b/c the aitrmass will be a touch colder snow should be more on the dry side.
Freezing rain/icing potential:
CT:
Some locations across interior CT could face a brief period of freezing rain between the transition of snow to rain. As of now this hazard doesn't look to be a major issue, however, there could be a glaze of accumulation to perhaps just under a tenth of an inch of ice accretion. With perhaps a few inches of wet snow accumulating, this could add a little extra weight to the snow allowing for the possibility of downed limbs or power lines.
MA:
There could be a corridor across central/southern MA where there is a several hour period of freezing rain, however, at this point it's tough to say if this will actually occur. If this does occur the potential would exist for a few tenths of an inch of ice accretion. With the potential for higher snowfall accumulations across these areas the risk for downed limbs/power lines would certainly be increased. This will have to be watched as we get closer.
Rainfall:
For areas across southern CT/RI/eastern MA rainfall will be the main precipitation concern. Rainfall totals of 1-2'' can be expected and this could lead to pockets of flash flooding/poor drainage flooding.
Strong/Damaging Winds:
With a very strong low-level jet working into the region we will be looking at a period of very strong winds, especially across southern CT/RI/SE MA where the core of the low-level jet will be located and where a warmer low-level airmass will lead to a little more in the way of mixing. Across these areas winds will be sustained between 25-35 mph with wind gusts as high as 55 mph. With heavy rains and a somewhat saturated ground this could lead to pockets of tree damage/power outages. Elsewhere across the region winds should be sustained from 15-25 mph with wind gusts as high as 35-45 mph possible, especially across the higher elevations.
The height of the storm will be occurring during the overnight hours of Wednesday into Thursday lasting through mid-AM before the storm finally begins to taper down. Below are graphics of what to expect:
As the area of low pressure begins to track more northeastward following the spine of the Appalachian Mountains and the main piece of energy associated with the system strengthens we will begin to see a trough developing within the mid and upper level jet streams as depicted by the image below:
When looking at the orientation of the developing trough we notice that the trough isn't developing in a north-south fashion but a more northwesterly to southeasterly fashion and looking at the image on the right we see a sharply negatively-tilted trough. The combination of these two features means that there will be very little room for a storm track off-shore. The rising heights will also allow for the winds in the middle and lower levels of the atmosphere out ahead of the system to shift more southerly and southeasterly. With the system expected to undergo rapid cyclogenesis (strengthening) allowing for a rapid increase in the mid and low level wind fields this will allow for warmer air to quickly advect into portions of southern New England meaning many locations will see a quick transition from snow to sleet/freezing rain and then eventually rain. Area to the north and west of the low pressure's center should pretty much remain all snow or see some mixing of sleet/freezing rain. With this said the heaviest snowfall totals will be located across central/northern New England.
In addition to the mess of precipitation we will be dealing with this system is also expected to produce a period of strong/damaging winds, especially across the coastal areas of CT/RI/SE MA where a warmer low-level airmass will allow for better mixing of the lower atmosphere and where the wind fields will be much stronger. There will be some very intense lift associated with this system as well so some rumbles of thunder certainly can't be ruled out either.
As usual with out winter storms this forecast will be very, very tricky as many of the thermal profiles, especially during the onset of the storm are very close to either being all snow or a mix of snow/sleet. High temperatures tomorrow across the region are only expected to get into the mid-30's with dewpoints slowly creeping through the mid-20's. As the onset of the precip shield starts progressing into the region evaporative cooling will 1) work to increase the moisture content of the atmosphere and 2) Allow for the surface temperatures to drop. So essentially how warm the temperatures get tomorrow will play a big role in the precip type at the onset across many locations. We then take a look at the thermal structure of the lower atmosphere. Out ahead of the system we really don't have a great deal of cold air in place across our region or to our north. Temperatures from about 925-700mb are only around -3C to -5C and there isn't any strong high pressure system to our north to allow for colder air to stay in place or drain down into our region. This means that as the system continues to work towards the coast eventually warm air will overspread areas to the south and east of the storm's center allowing for a transition from snow-sleet-freezing rain-rain. With this let's break down each aspect of the storm into further details and for each state:
Snowfall:
CT:
Precipitation is expected to first start working into CT between 1-3 PM with activity first occurring across the southwest corner of the state and spreading north and east through the remainder of the afternoon. As of now, thermal profiles are rather tricky as several forecast soundings are very close to being either all snow or a mix of snow/sleet, especially across southern CT. While surface temperatures are expected to range in the mid-30's or so temperatures aloft from 925-700mb are expected to range from -3C to -5C or so. This really isn't all that impressive and should make for any snow that is falling to be rather wet. This also poises difficulties with the forecast as if the precip is on the light side we could be looking more at more of a mixture. Going with this I would expect everyone to begin as either snow or a mix of snow/sleet (with the mix more likely the closer to the coast you go). As mentioned above the level of cold air in place isn't all that great and there is no high pressure to our north to reinforce colder air into the region. We will begin to see warmer air work into the state rather quickly, especially across the coast and this will work to keep snowfall totals across the coast to a minimum and only about a few inches across the interior. Some locations across the northwest corner of the state where cold air may hang in longer could pick up several inches of snow.
RI:
Snowfall totals across RI should be kept to a minimum as well and accumulations are expected to remain under 1'' for the entire state.
MA:
As we work into MA this is where snowfall totals will begin to vastly increase, especially across the western and central portions of the state and outside of the CT River Valley in southern Hamden County. Areas to the east of Worcester county in eastern MA are expected to receive little in the way of snowfall as warmer air will quickly work into these areas. Areas to the west of Worcester County will have the potential to receive significant snowfall accumulations and snowfall could be on the wet side. There will also be areas of sleet/freezing rain but we'll look at this hazard a bit further down.
NH/VT/ME
These states will be getting hit the hardest by snowfall accumulations as they will be to the north and west of the storm's center. Snowfall accumulations here will be rather significant, however, b/c the aitrmass will be a touch colder snow should be more on the dry side.
Freezing rain/icing potential:
CT:
Some locations across interior CT could face a brief period of freezing rain between the transition of snow to rain. As of now this hazard doesn't look to be a major issue, however, there could be a glaze of accumulation to perhaps just under a tenth of an inch of ice accretion. With perhaps a few inches of wet snow accumulating, this could add a little extra weight to the snow allowing for the possibility of downed limbs or power lines.
MA:
There could be a corridor across central/southern MA where there is a several hour period of freezing rain, however, at this point it's tough to say if this will actually occur. If this does occur the potential would exist for a few tenths of an inch of ice accretion. With the potential for higher snowfall accumulations across these areas the risk for downed limbs/power lines would certainly be increased. This will have to be watched as we get closer.
Rainfall:
For areas across southern CT/RI/eastern MA rainfall will be the main precipitation concern. Rainfall totals of 1-2'' can be expected and this could lead to pockets of flash flooding/poor drainage flooding.
Strong/Damaging Winds:
With a very strong low-level jet working into the region we will be looking at a period of very strong winds, especially across southern CT/RI/SE MA where the core of the low-level jet will be located and where a warmer low-level airmass will lead to a little more in the way of mixing. Across these areas winds will be sustained between 25-35 mph with wind gusts as high as 55 mph. With heavy rains and a somewhat saturated ground this could lead to pockets of tree damage/power outages. Elsewhere across the region winds should be sustained from 15-25 mph with wind gusts as high as 35-45 mph possible, especially across the higher elevations.
The height of the storm will be occurring during the overnight hours of Wednesday into Thursday lasting through mid-AM before the storm finally begins to taper down. Below are graphics of what to expect:
Subscribe to:
Posts (Atom)