10:30 AM EST 01/29/2022 Connecticut Storm Update

Well it is time to declare my forecast a bust for a large portion of Connecticut. What led me to go with such an aggressive forecast for much of Connecticut was the idea that I believed we would see the low pressure (storm) end up with a more westward tracking putting Connecticut in line for some of the heaviest snow. 

Over the past 2-3 days, computer forecast model guidance continued to waiver and diverge between a more west and east track. Evolution of the mid and upper levels of the storm favored a more westward track, however, the evolution of the storm at the surface favored a more east track...so what was going to give? Unfortunately, there was really no way to full know this. So for forecasters, this left two options: 1) Be aggressive or 2) Be much less aggressive. There was no middle ground. The only way to know what would transpire was to watch the storm evolve in real time.

Latest mesoanalysis data shows the surface low pressure has consolidated on the eastward track (indicated by the red L and red arrow). This has resulted in the heaviest snows only getting into far eastern Connecticut. Connecticut is outlined in blue. The green arrow represents the track I thought we would see:

Eastern Massachusetts through Rhode Island and far eastern Connecticut are getting absolutely crushed with an extremely band of heavy snow and very strong winds as advertised by the radar below. This is where the highest snowfall totals will occur with totals likely exceeding 2 feet in the hardest hit places. 

For Connecticut, the highest totals will occur within the purple shaded area and these will include 2+ foot amounts. As you work west across Connecticut, snowfall totals will become significantly less. 

The gradient from west-to-east across the state will be wild. That is quite impressive for such a small state, but this just goes to show how slight deviations in a west/east track can mean substantial differences in snow totals! Whether you're getting slammed or a much more tame event, enjoy the storm!

Saturday, January 29, 2022 Potentially Historic Winter Storm Update

 My confidence continues to increase that a potentially historic winter storm is set to unfold across Connecticut Saturday, January 29, 2022. This has been a very difficult 24+ hours in the world of weather models with various solutions ranging from near-historic impact to very little impact. However, given what I've assessed I am leaning towards the historic side of things. 

Regarding this potential storm, there were four key piece to monitor:

1. Shortwave energy within the northern branch of the jet stream

2. Shortwave energy within the southern branch of the jet stream 

3. Confluence associated with the tropospheric polar vortex in southeast Canada 

4. Ridging across the West Coast 

The biggest challenge these past few days has been the handling and evolution of each of the above-mentioned features by the computer forecast models. All (major) forecast models were in strong agreement that a significant storm was going to materialize off the East Coast, however, differences resulted regarding how the storm would evolve and where the storm would track. There were essentially two camps, a western track (closer to the coast) resulting in significant impact to Connecticut and an eastward track which would a much more mundane impact here in Connecticut, although eastern Connecticut may have been hit hard. 

My first forecast call was extremely aggressive which is very unlike me, however, I felt very confident in the westward solution. Since this forecast, some forecast models had thrown a "wrench" into that call by showing a farther east track. However, continuing to heavily assess and analyze how each forecast model was handling the above features, I remained very confident in the west solution. As we now move into Thursday evening, my confidence isn't only higher, but some of the forecast models with the east solution are now beginning to correct west. 

Given my expectation of a west track, this will result in a ferocious band of extremely heavy snowfall traversing a significant portion of Connecticut as evident by this exceptional frontogenesis band:

The 18z NAM bufkit at Windsor Locks, CT (BDL) was indicating as much as 30-40 units of omega (red contoured circles) which indicates extreme upward vertical motion within the dendritic snow growth zone (yellow/purple contours) which is the zone where the best snow crystals and growth occurs. This is also advertising snow ratios as high as ~17:1 (average is typically 8:1 to 10:1), however, the caveat here is the winds from the surface through the troposphere will be very strong and this will likely result in ratios potentially closer to 12:1 to 13:1:

These two above indicate the likelihood of extremely heavy snowfall for perhaps a 3-5 hour period. During this period snowfall rates of 3-5'' per hour will be likely along with the risk for some thunder and lightning given the degree of lift and some instability aloft! 

While the GFS forecast model is nowhere near as robust as the NAM or European forecast model, the strides within the features outlined at the start of this discussion make me confident the GFS will continue heading into the direction of the NAM/GFS. So let's get into storm impacts:

• Heavy-to-extremely-heavy snow overspreads a large portion of the state moving through Saturday morning and continuing into late afternoon before gradually beginning to taper off. 
• Under the heaviest banding snowfall rates could approach 3-5'' per hour!!!
• Thundersnow possible.
• Strong-to-damaging winds are expected statewide with sustained winds of 20-30 mph and wind gusts of 40-50 mph along the immediate shoreline. Sustained winds of 15-20 mph with gusts 30-40 mph inland. This will create blizzard conditions, significant drifting of snow, and extremely low visibility. (I have lowered my wind forecast from Wednesday's forecast).
• Scattered power outages are likely, especially along the shoreline. Power outages may last a few days in some areas. 
• Major coastal flooding along the immediate shoreline. 
• Travel will be very dangerous and perhaps near impossible Saturday. due to the extreme snowfall rates, plow operators will not be able to keep up with the snow. While travel is highly not recommended, if having to travel, prepare a necessity kit in the event you become stuck or stranded.

Below is my updated forecast:

Significant Blizzard Shaping Up for Saturday, January 29, 2022

 Computer forecast models continue to show strong consistency and strong agreement that a significant blizzard is about to unfold across a large portion of southern New England and yes, this includes Connecticut. A low pressure system developing off the Southeast coast through the day Friday will undergo very rapid cyclogenesis (strengthening) as it works up the mid-Atlantic coast. The biggest question is/was exact track, however, this is starting to become more clear, but not yet set in stone so deviations in the track will result in deviations within the forecast. Adjustments will be made as needed. Note: Just because I am using output from a particular forecast model does NOT mean I am favoring that model or creating a forecast solely based on that model. The output is just used for illustrative purposes. 

Low pressure is expected to form right along the baroclinic zone Friday evening just off the Southeast coast. During this time an amplifying (strengthening) trough, southern stream shortwave energy, and strong upper-level jet dynamics will favor rapid cyclogenesis of the low pressure as it moves north-northeast just off the coast:

From this point, the one million dollar question is, how does northern stream shortwave energy interact with this system. This will play a substantial role in the evolution and overall track the low pressure system takes. There are some differences in this within forecast models. Some forecast models indicate a greater and earlier involvement of this northern stream shortwave energy, resulting in an earlier rapid strengthening and a closer to the coast track while some forecast models have this occurring a bit later, resulting in a slightly more east track. One of these models is the GFS forecast model. Given how close the baroclinic zone is to the Southeast coast, I believe the GFS is developing the surface low too far east and as a result, tracks the storm farther east (even though the interaction of the northern stream being later favors an already east track). 

Given the combination of upper-level dynamics and interaction of all pieces mentioned above, surface low pressure should strengthen incredibly rapidly as it moves north-northeast just off the mid-Atlantic coast, likely bringing major snow totals to portions of the mid-Atlantic. Forecast models are also indicating as much as 80+ knots of wind at 850mb (about 5,000 feet off the ground) feeding into the storm. This will result in copious amounts of moisture being fed into the storm:

As the low pressure system rapidly strengthens, low pressure centers develop at 850mb and 700mb (about 10,000 feet above the ground) indicating a very strong, mature system. Where these low pressure begin to develop, strengthen, and track are extremely important as historically, the bands of heaviest snowfall occur northwest of these low centers. In more developed lows this is about 30-50 miles northwest of the centers, in more poorly organized or just developing centers this can be as much as 60-70 miles northwest. This will also be tied into exact storm track, but the indication is this process will occur south and east of Connecticut and close enough to result in a band of extremely heavy snow traversing much of the state. The NAM forecast model (along with the European model) are very aggressive with this. The NAM in fact indicates an extremely powerful band of snow across the state 

Given the very cold airmass with this storm, snow ratios should be fairly high, perhaps on order of 18:1 to 20:1 (1'' of liquid would equal about 18-20'' of snow). Our average is about 8:1 to 10:1! This would be especially true under the band of heaviest snowfall where the degree of upward vertical motion into the dendritic snow growth zone would be maximized. The 12z/26 NAM bufkit for IJD (Willimantic, CT) indicates as much as 40-50 units of omega tapping into the dendritic snow growth zone (purple/yellow contours). That is incredible lift. This would indicate the potential for snowfall rates of...3-5'' per hour!!!! along with the potential for thundersnow:

With such an intense low pressure not far off to the southeast, this will translate to very strong winds thanks to a very strong pressure gradient. Winds along the shoreline could become sustained as high as 25-35 mph with gusts 60-70 mph. Winds just inland could become sustained as high as 15-25 mph with gusts 40-60 mph. 12z NAM/26 bufkit for Groton, CT shows very high wind potential. This would result in blizzard conditions, significant drifting of snow, very low visibility, and scattered-to-numerous power outages:

So with the meteorology/science fun out of the way let's break the storm impacts and timeline down:

What to Expect: 

• Light snow showers throughout the day Friday. 
• Light snow may develop during the evening and overnight well ahead of the storm. This snow will have potential to produce 1-3'' of snow locally. 
• Saturday...
• Heavy-to-extremely-heavy snow overspreads a large portion of the state moving through Saturday morning and continuing into late afternoon before gradually beginning to taper off. 
• Under the heaviest banding snowfall rates could approach 3-5'' per hour!!!
• Thundersnow possible.
• Strong-to-damaging winds are expected statewide with sustained winds of 25-35 mph and wind gusts of 60-70+ mph along the immediate shoreline. Sustained winds of 15-25 mph with gusts 40-60 mph inland. This will create blizzard conditions, significant drifting of snow, and extremely low visibility. 
• Scattered-to-numerous power outages are likely, especially along the shoreline. Power outages may last a few days in some areas. 
• Major-to-devastating coastal flooding along the immediate shoreline. 
• Travel will be very dangerous and perhaps near impossible Saturday. due to the extreme snowfall rates, plow operators will not be able to keep up with the snow. While travel is highly not recommended, if having to travel, prepare a necessity kit in the event you become stuck or stranded.

Below is my initial snowfall forecast. Please keep in mind, given the high uncertainty and low predictability which exists with determining where the heaviest banding will set up and traverse, it's very difficult to highlight that on a map right now. Also, anytime you see such an intense band of heavy snow you get an area of subsidence (sinking air) this will result in less totals in areas under subsidence and that is also very difficult to illustrate on a map. As we get closer, these details can be ironed out:

 

Prospects for a Significant Winter Storm Increasing (Saturday, January 29, 2022)

Computer forecast models continue to come into strong agreement (with consistency) that a significant storm will evolve moving into the upcoming weekend. After a challenging past few winters in the forecasting department which makes me skeptical about raising awareness for storms several-days out, the evolution of the pattern and pieces involved give me enough confidence to communicate the idea of a rather significant storm. The past few winters have been characterized by a rather fast jet stream with many embedded pieces of shortwave energy. This results in chaos and high model uncertainty as more pieces involved, the longer (and more challenging) it takes for forecast models to resolve. A comparable example is that of a puzzle. If you're doing a puzzle which is only 50-pieces, you have less pieces to work with and it's going to be easier to (re)solve the puzzle. However, if you have a puzzle that's 500-pieces or 1,000-pieces, you have more pieces to resolve and it will take longer to complete. 

For the upcoming potential this weekend, there are really two MAIN pieces of shortwave energy we're watching. (Note: While I am using GFS model output in below images this does NOT mean I am favoring the GFS or forecasting solely off the GFS. I am just using for illustrative purposes).

As we progress through the week a large ridge of high pressure builds into the western United States with a vigorous trough amplifies (strengthens) across the eastern-third of the United States. Forecast models indicate a piece of shortwave energy traverses the eastern periphery of the ridge with this shortwave energy (becoming associated with the southern branch of the jet stream) amplifying as it digs into the Gulf Coast states (shortwave #1). Moving towards the end of the week, forecast models indicate shortwave energy diving through the upper-Great Lakes region in association with the northern branch of the jet stream (shortwave #2):

Forecast models indicate a positively-tilted trough (with the trough axis digging into Mississippi/Georgia) becoming more neutrally-tilted to slightly negatively-tiled  as it traverses the southeast. This is a very favorable scenario for rapid low pressure development just off the southeast coast and also favors a storm track closer to the coast. Shortwave #2 is very important here because depending on the interaction, shortwave 2 can further enhance rapid development and it can act as a means to keep this storm closer to the coast as well:

In addition to these two pieces of shortwave energy the evolution and structure of the ridge within the West may have huge implications, especially with how the trough evolves in the East. A stronger ridge could result in the trough axis shifting east a bit increasing the likelihood of a farther west track (coast or just inland) while a bit weaker or more flat ridge could push the trough axis east, increasing the potential for a track off the coast. In this scenario, phasing of the two shortwaves will be huge as this could open the window for a missed phase and storm track well off the coast. At this stage that is appearing more unlikely. 

As low pressure develops and moves up the coast (this is a big vague here as the exact track is far from certain. Up the coast in this sense means anywhere from just inland to anywhere just offshore enough to still bring impacts inland) rapid cyclogenesis (deepening) is expected thanks to incredibly favorable upper-level dynamics. Forecast models indicate a powerful 150+ knot upper-level jet streak may transpire across northern New England moving into Saturday. This jet stream structure and jet streak would favor tremendous upper-level divergence over the Northeast into the mid-Atlantic with the result being rapid deepening of the ow pressure and blossoming of precipitation:

Forecast model ensembles (as well as operational runs) are suggesting storm tracks and potential for favorable evolution which would bring significant storm impacts. This includes extremely heavy snowfall and significant totals, high winds with the risk for power outages, rain along immediate coastal areas (particularly eastern Massachusetts), and devastating coastal flooding. Below is the 12z European Forecast Model Ensemble with each "L" (Low Pressure) the forecast of a specific model-member. At this stage, there is strong agreement in a track very close to the benchmark and that historically can result in very heavy snows for much of Connecticut:

Depending on exact storm track and evolution, there will likely be a very step temperature gradient established between warmer east east of the storm and colder air west of the storm. This will likely favor a corridor of extremely heavy upward vertical motion and subsequent heft precipitation rates. This will occur perhaps 50-75 miles northwest of the surface, 850mb, and 700mb low tracks. One second area to watch (more so getting into eastern Massachusetts) will be a very strong surface temperature gradient where the coastal front sets up. That boundary will be the difference between zero snow and perhaps quite a bit.

Given we are 4-5 days out it is impossible to get into specifics and details such as exact storm track, exact storm evolution (where the 850mb and 700mb lows develop, track, and how they evolve), and potential amounts. However, at this juncture, based on the signals, the potential is rapidly growing for a very significant storm. 

An updated blog post will come forth early Tuesday evening. This will provide a storm update along with getting into a bit more of the specifics (positives and negatives). 

 

Thursday, January 20, 2022 Light Morning Snow

 A strong Arctic cold front is set to cross the state late Wednesday evening. Ahead of the Arctic front, temperatures will be several-plus degrees above-freezing, thus precipitation at the onset will be in the form of rain. However, much colder air rapidly filters in on the backside of the front. Typically with these Arctic cold front, there is a race between the ending of the precipitation and the advection of drier air vs. the advection of colder air (cold enough for precipitation to transition from rain to snow). In this instance, however, forecast models are advertising an abundance of moisture on the backside of the front (coined an anafront). 

As a result of a very tight pressure gradient between the airmass ahead of the Arctic front and the Arctic air behind the front, there will be a very narrow corridor of enhanced low-level convergence and forcing which forecast models are in great agreement on this narrow corridor traversing southern Connecticut. This indicates at least a few hour period of light-to-moderate snow (perhaps even briefly on the heavier side) traversing portions of southern Connecticut:

Temperatures along the immediate shoreline will take a bit longer to drop below-freezing as the Arctic front may actually slow down just before clearing the state. This will keep precipitation falling as rain a bit longer along the immediate shoreline, however, even here rain should end as a bit of snow. 

This mini event could have implications on a potential storm this weekend, however, there is very little consistency or agreement within the forecast models at this time, however, the potential certainly exists for a storm to work up the coast bringing the potential for snow and/or a wintry mix. More on that later in the week :)

What to expect:

• Showers begin working into the state anywhere between 1:00 AM - 4:00 AM EST Thursday.
• Showers will quickly transition to light snow statewide (exception being right along the immediate shoreline) with some more moderate snow across southern Connecticut just away from the immediate shoreline. 
• Snow begins to taper off between 9:00 AM -11:00 AM Thursday morning.
• Expect a slow Thursday morning commute and anticipate icy conditions due to snow and temperatures falling below-freezing. 

Monday, January 17, 2022 Connecticut "Snowfall" Forecast

 Computer forecast models have been incredible agreement the past several days on a significant low pressure system blossoming within the Tennessee Valley and Southeast and then turning up the mid-Atlantic. The question was whether we would be looking at a significant winter storm or not here in Connecticut. If you're a snow lover, unfortunately the news is not very good. Disclaimer: Just because I am posting images from a particular forecast model below does not mean I am siding with that model or solely using that model in the deriving of my forecast. It is just being used for illustrative purposes.

A piece of shortwave energy currently diving southeast through the central Plains rapidly strengthens and amplifies as it moves into the Southeast. This system will have already reached maturity within this region early Sunday. This is evident by a tighly closed 500mb low and jet streak already having rounded the base of the trough:

To begin the day Sunday, high pressure will initially be present over New England with the strengthening low pressure system across the Southeast. High pressure over New England is expected to depart off to the northeast moving into Monday while the low pressure turns up the mid-Atlantic:

With the system strengthening so rapidly and so far to our southwest this will result in a very strong onshore flow developing within the lower-levels of the atmosphere. This combined with the retreating high pressure is going to allow for much warmer air to rapidly advect into Connecticut. This will ultimately result in snow quickly changing over to some sleet, freezing rain, and then heavy rain:

Despite a lackluster storm in the snowfall department, this will be a fairly impactful storm. Heavy rain with a frozen ground could result in runoff and localized flash flooding potential. Strong winds are expected across the state with gusts 50-60 mph along the shoreline and gusts 35-50 mph inland resulting in scattered power outages. Very strong onshore winds combined with astronomical high tides may bring about major coastal flooding as well. 

What to Expect:

• Precipitation likely begins as snow across the entire state between 11:00 PM Sunday - 2:00 AM EST Monday. The only exception may be right along the immediate shoreline where precipitation may be a bit of a sleet/freezing rain mix (if not plain rain).
• Snow overspread inland areas during the overnight with snow coming down moderate at times (even heavy in the northwest and northeast hills). 
• Warmer air rapidly moves into the state causing snow to briefly change over to sleet and freezing rain and then heavy rain. The northwest hills will be the last to change over. 
• Winds will begin to ramp up as well with gusts 35-50 mph inland and 50-60 mph along the shoreline. Scattered power outages are likely. 
• Strong onshore flow and astronomical high tides may yield major coastal flooding. 
• Rain tapers off during the morning and may actually end with some scattered snow showers across the state.
• Below is my current thoughts for snow accumulations:

Friday, January 7, 2022 Connecticut Snowfall Forecast Update

 It is time to bring 'em up! After assessing forecast model data from overnight Wednesday through Thursday afternoon, there have been trends towards more snow across Connecticut. Why is this? Forecast models are becoming in stronger agreement that the storm will intensify more quickly with this occurring closer to the coast. The end result in a greater abundance of precipitation over Connecticut, hence, higher snowfall totals. This will be a fast-moving storm which will limit totals to a degree.

Given the earlier development, forecast models are in general agreement low pressure at 850mb (roughly 5,000 feet above the ground) will become better defined as it is passing southeast of Connecticut. This is a historically favorable track for moderate-to-heavy snow to overspread Connecticut:

As the low is tracking northeast just south of Connecticut, a band of very strong frontogenesis will traverse the state. This is indicative of heavy snow and this should occur for the majority of the state:

12z NAM Bufkit for Windsor Locks, CT (BDL) indicates upwards of 20 units of omega (the negative-valued red contour indicate upward vertical motion) just touch the top of the dendritic snow growth zone (purple/yellow contours). This further indicates a period of heavy snow will occur:

So this what can ex expect:

• Snow begins between midnight - 3:00 AM across the state. 
• Snow quickly becomes moderate-to-heavy across the state with peak snow intensities occurring between 5:00 AM - 9:00 AM EST. 
• During this time snowfall rates could approach 1.5'' per hour. 
• Snow ratios approaching 13:1 to 14:1 so snow will be rather light and fluffy.
• Snow rapidly begins to subside moving into the late morning and is out of the state by early afternoon outside of some residual flurries. The sun may even make an appearance by mid-afternoon. 
• Winds will be light during the storm, however, increase as the storm pulls away with gusts 20-30 during the afternoon. Wind chills Friday evening and overnight into the single digits and teens. 

Friday, January 7, 2022 Connecticut Snowfall Forecast

For snow lovers, unfortunately, this storm will just get going a bit too late and a bit too far southeast to deliver a big hit to Connecticut. While computer forecast models have struggled (and continue to do so a bit) with the exact evolution of the storm, there is a consensus things just won't transpire in time for a bigger hit. 

Forecast models do brush some decent lift across Connecticut as the low pressure passes well to the south and east. Given the strong upper-level jet dynamics and favorable jet placement, the state will be under the presence of upper-lever divergence which will help enhance the development of snow as the low passes by. This will bring a several hour period of light-to-moderate snow through the state.

What to Expect:

• Snow starts: Midnight - 3:00 AM EST Friday 
• Snow ends: By noon 
• Heaviest snow: 4:00 - 7:00 AM EST (rates up to 0.50'' per hour). 
• Expect delays to the morning commute. Plan for delays.

Friday, January 7, 2022 Connecticut Snowstorm Potential

 For snow lovers, the start of the 2021-2022 winter season has been nothing but subpar. While the weather pattern has been on the active side, we just haven't been able to muster up a good, solid snow event. There is a chance that could change as we move towards the end of the week. 

As of Tuesday evening, a low pressure system was rapidly strengthening across the northern Plains with a strong Arctic cold front plunging through the northern-tier of the country. This Arctic cold front is then slated to move across the Northeast Thursday and that will usher in Arctic air into the state, planting the more than sufficient cold air needed for snow:

There are two things we will be watching over the next few days:

1) Wednesday night and early Thursday morning, an area of low pressure develops across northern Texas and moves east across the Southeast Thursday bringing wintry precipitation across that region. This low pressure continues to emerge east-northeast into the mid-Atlantic states, towards the coast. 

2) A sharp longwave upper-level trough amplifying as it moves across the Ohio Valley into the Northeast:

As the upper-level trough catches and phases with the surface low pressure, this, combined with strong upper-level divergence thanks to the jet stream structure, should result in rapid cyclogenesis of the low pressure system. The BIGGEST key here is how quickly does this process happen? While all the cards are there for a significant snow event, this is far from certainty. 

As it stands right now, the timing of these key features may be a bit off. This would result in storm intensification happening just a bit too far offshore to bring significant snows, BUT we would likely still see at least snow with the chance for minor accumulations. 

Given this is tied into phasing that aspect is very tough to pindown and nail even getting past a few days out. This is because the likelihood of phasing and subsequently, a storm is all tied into the timing of the key pieces involved. 

We should get a much clearer idea on this picture moving into Wednesday afternoon!