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: