Good evening to you from Southern Connecticut Weather!
Yesterday, Spencer explained the general setup could put Connecticut in a place to receive snow, sleet, freezing rain, and rain early next week. Another day has passed, and we are closer to Connecticut’s first significant winter weather event of the season. How significant remains to be seen.
This update will provide a brief update on where computer guidance stands, and, more importantly, what we think is the most likely scenario over the next 72 hours. We will put out our first call map, showing our thoughts on snow and ice accumulations across the state, tomorrow afternoon.
Recap
For those that are just beginning to pay attention to this winter weather threat, the system that is coming is the result of two important things working in tandem to provide wintry precipitation. First, a strong surface low forming in Texas, and second, a strong Canadian high-pressure system that passes to our north.
Yesterday, Spencer explained the general setup could put Connecticut in a place to receive snow, sleet, freezing rain, and rain early next week. Another day has passed, and we are closer to Connecticut’s first significant winter weather event of the season. How significant remains to be seen.
This update will provide a brief update on where computer guidance stands, and, more importantly, what we think is the most likely scenario over the next 72 hours. We will put out our first call map, showing our thoughts on snow and ice accumulations across the state, tomorrow afternoon.
Recap
For those that are just beginning to pay attention to this winter weather threat, the system that is coming is the result of two important things working in tandem to provide wintry precipitation. First, a strong surface low forming in Texas, and second, a strong Canadian high-pressure system that passes to our north.
Image courtesy of Weatherbell Analytics
On this latest run of the GFS, you can see the high pressure to our north and low pressure system to our west. This will serve to hold in the cold air, at least initially, as precipitation and warm air aloft from the southwest arrives in association with an area of low pressure that passes to our west. Guidance has shown a secondary area of low pressure forming off the coastline, which could also assist in driving precipitation and colder air into the region.
The Guidance
At the start of this event, guidance continues to show the potential for a period of snow throughout the state, when temperatures both at the surface and throughout the column of air aloft are below freezing.
As was said yesterday, the strength and placement of the high to our north, the push of warm air over the surface and upper levels, and the onset time of precipitation will be critical to determining who gets what. The guidance has begun settling down on large scale changes to the time period, such as whether a storm will actually form, but small scale changes are the ones to watch. Location and timing will have a substantial impact on what we experience.
Let’s look at the GFS model quickly and the changes we still see between two runs. On the first run, you will see that the midday run (12z) has a slower onset of precipitation which results in less snow before the air aloft warms to bring sleet that transitions to a period of freezing rain or drizzle. In the latest run, onset occurs sooner, resulting in a significant thump of snow before a change to sleet and freezing rain/drizzle before the precipitation ends. This looks like a situation where, as usual, areas along the coast change over the fastest and are most likely to change to rain.
On this latest run of the GFS, you can see the high pressure to our north and low pressure system to our west. This will serve to hold in the cold air, at least initially, as precipitation and warm air aloft from the southwest arrives in association with an area of low pressure that passes to our west. Guidance has shown a secondary area of low pressure forming off the coastline, which could also assist in driving precipitation and colder air into the region.
The Guidance
At the start of this event, guidance continues to show the potential for a period of snow throughout the state, when temperatures both at the surface and throughout the column of air aloft are below freezing.
As was said yesterday, the strength and placement of the high to our north, the push of warm air over the surface and upper levels, and the onset time of precipitation will be critical to determining who gets what. The guidance has begun settling down on large scale changes to the time period, such as whether a storm will actually form, but small scale changes are the ones to watch. Location and timing will have a substantial impact on what we experience.
Let’s look at the GFS model quickly and the changes we still see between two runs. On the first run, you will see that the midday run (12z) has a slower onset of precipitation which results in less snow before the air aloft warms to bring sleet that transitions to a period of freezing rain or drizzle. In the latest run, onset occurs sooner, resulting in a significant thump of snow before a change to sleet and freezing rain/drizzle before the precipitation ends. This looks like a situation where, as usual, areas along the coast change over the fastest and are most likely to change to rain.
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12z (midday) GFS run for 1am on Tuesday (left) and 7am Tuesday (right)
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Latest run of the GFS (18z) for the same time period. Note how the precipitation overtakes the state earlier, and the heavier snow in northern sections of Connecticut at 7am on Tuesday. This is only one run of one model, but this continues the idea of a snow to mixed precipitation to rain scenario.
The GFS is one of the colder models showing this evolution, earlier the European model came in a bit colder than its prior overnight run, but showed more sleet than snow before a change to plain rain for much of the state.
The Forecast – Latest Thoughts
The GFS is one of the colder models showing this evolution, earlier the European model came in a bit colder than its prior overnight run, but showed more sleet than snow before a change to plain rain for much of the state.
The Forecast – Latest Thoughts
There remains a significant amount of uncertainty in the forecast—especially with regard to final accumulations. I believe that there will be a storm, but timing and location are critical and we want to see more consistency in guidance before being able to make a deterministic forecast.
Today, the models have trended a bit colder, and when factoring in the tendency for SWFE (Southwest Flow Events) to warm quickly in the midlevels, faster precipitation onset, and surface temperatures staying colder than projected generally, especially in interior Connecticut, we believe a winter weather event is likely, and that this will not be a system consisting of mostly rain.
Precipitation is expected at this time to begin very late Monday evening and lasting into early Tuesday afternoon. The Tuesday AM commute is likely to be impacted.
Takeaways
Thank you for reading. Please like, share, and follow us on Facebook and Twitter @SouthernCTWX as we provide continuing updates on this winter weather threat.
Until tomorrow, thanks for reading SCW!
-DB
Today, the models have trended a bit colder, and when factoring in the tendency for SWFE (Southwest Flow Events) to warm quickly in the midlevels, faster precipitation onset, and surface temperatures staying colder than projected generally, especially in interior Connecticut, we believe a winter weather event is likely, and that this will not be a system consisting of mostly rain.
Precipitation is expected at this time to begin very late Monday evening and lasting into early Tuesday afternoon. The Tuesday AM commute is likely to be impacted.
Takeaways
- Connecticut’s first legitimate winter weather event is becoming more likely on Monday evening into Tuesday
- Small changes in high pressure strength, location, and secondary low development that substantially impact on our final forecast remain possible
- Sleet remains the most significant winter weather threat, but with the models trending slightly colder today there could be a period of accumulating snow at the start. How significant this period is remains unknown
- Interior locations are most favored to receive a significant event, though everyone in the state could begin with frozen precipitation
Thank you for reading. Please like, share, and follow us on Facebook and Twitter @SouthernCTWX as we provide continuing updates on this winter weather threat.
Until tomorrow, thanks for reading SCW!
-DB
