Good evening from Southern Connecticut Weather!
It’s the most wonderful time of the year! Or worst, if you hate winter. Today marked the start of meteorological winter, and as a result, the two week outlooks, which were a new feature to SCW last year, are back!
I started this project to try to answer questions for folks who wanted to know our thoughts on the extended pattern, and last year, I did pretty well for a first timer. Hopefully I can build on that success this season.
A couple of caveats:
First—unlike the usual forecasts which use operational models, the main tool used here for forecasting is the ensembles. For those of you new to these discussions, ensembles are the operational runs of the major models which are tweaked with different conditions. This (ideally) helps resolve the inherent uncertainties that grow in time during a forecast period.
Second—although I’m not making the usual sensible daily weather forecast, it is my hope that I’ll be able to provide enough detail about potential to help you plan ahead.
With that said…let’s get to work!
December Climo
For our purposes, when I discuss climo I am simply referring to weather conditions averaged over a period of time, usually using the data between 1981-2010. Climo gives you a sense of what you could expect on average, but we all know that things can and do fluctuate, sometimes wildly as conditions and patterns change.
If you remember last year, climo was blown away by a torch of epic proportions. Winter got a late start to say the least. This year, many locations have already seen snow, and in some cases significantly so. We are at the month where historically CT sees its first significant snowfall (greater than 1”), though it is not always guaranteed and the second half tends to be the best shot for wintry weather than the first.
BDL (Bradley Airport)
Dec 1 avg high—45
Dec 1 avg low—28
Dec 31 avg high—35
Dec 31 avg low—19
Dec avg snow—7.4”
Dec record snow—45.3” (1945)
BDR (Bridgeport)
Dec 1 avg high—47
Dec 1 avg low—33
Dec 31 avg high—38
Dec 31 avg low—24
Dec avg snow—5.1”
Dec record snow—16.0” (1948, when records are first available at this location)
The last few years have been a dream to those that like warm weather and an extension of fall. This December I expect winter to dominate.
Two Week Outlook Summary
It’s the most wonderful time of the year! Or worst, if you hate winter. Today marked the start of meteorological winter, and as a result, the two week outlooks, which were a new feature to SCW last year, are back!
I started this project to try to answer questions for folks who wanted to know our thoughts on the extended pattern, and last year, I did pretty well for a first timer. Hopefully I can build on that success this season.
A couple of caveats:
First—unlike the usual forecasts which use operational models, the main tool used here for forecasting is the ensembles. For those of you new to these discussions, ensembles are the operational runs of the major models which are tweaked with different conditions. This (ideally) helps resolve the inherent uncertainties that grow in time during a forecast period.
Second—although I’m not making the usual sensible daily weather forecast, it is my hope that I’ll be able to provide enough detail about potential to help you plan ahead.
With that said…let’s get to work!
December Climo
For our purposes, when I discuss climo I am simply referring to weather conditions averaged over a period of time, usually using the data between 1981-2010. Climo gives you a sense of what you could expect on average, but we all know that things can and do fluctuate, sometimes wildly as conditions and patterns change.
If you remember last year, climo was blown away by a torch of epic proportions. Winter got a late start to say the least. This year, many locations have already seen snow, and in some cases significantly so. We are at the month where historically CT sees its first significant snowfall (greater than 1”), though it is not always guaranteed and the second half tends to be the best shot for wintry weather than the first.
BDL (Bradley Airport)
Dec 1 avg high—45
Dec 1 avg low—28
Dec 31 avg high—35
Dec 31 avg low—19
Dec avg snow—7.4”
Dec record snow—45.3” (1945)
BDR (Bridgeport)
Dec 1 avg high—47
Dec 1 avg low—33
Dec 31 avg high—38
Dec 31 avg low—24
Dec avg snow—5.1”
Dec record snow—16.0” (1948, when records are first available at this location)
The last few years have been a dream to those that like warm weather and an extension of fall. This December I expect winter to dominate.
Two Week Outlook Summary
* Note—high confidence (70% or greater belief of event occurring), moderate confidence (36-69%), low confidence (0-35%); nothing significant (less than 1” snowfall and .25” ice)
Week one—Thursday December 1 to Wednesday December 7
Temperatures—below average (moderate confidence)
Precipitation—average (moderate confidence)
Wintry Precipitation—average (moderate confidence)
The first week of December will be a bit of a see-saw, with a relatively quiet pattern that will change as we watch a storm toward the end of the period (5th to 7th). I think there is a chance of some minor wintry precipitation, but much of what we see as a state should be rain. Temperatures look near average to ever so slightly above.
Week two—Thursday December 8 to Thursday December 15
Temperatures—below average (high confidence)
Precipitation—above average (moderate confidence)
Wintry Precipitation—above average (moderate confidence)
By week two, indications currently are that winter drops a big time hammer across parts of the US, including New England. This far out, all I can see is that it could be stormy. Storm tracks may continue to favor cutters (storms that cut to our west and warm sector us) but with cold in place and potentially big cold, we could see a strong front, overrunning, or clipper put down a legitimate widespread snowfall.
Technical Discussion
Week one
I would best characterize much of the first week of December as quiet. This is a time where we see the gradual stepdown toward winter continues in earnest with high pressure in place until early next week. The “warmest” days of the week are today and tomorrow, and I expect to see slightly below normal temperatures, with cool days and colder nights during the rest of the period.
As for precipitation, I think high pressure keeps the lid on our precipitation chances, though I won’t rule out a slight chance of snow showers this weekend as a weak shortwave pushes through. The main show comes early next week, as a wave of low pressure is expected to approach our region from the west. The guidance is split on the evolution of this low—whether a weak low develops in the south or if this is a strong cutter—but I think that enough cold air is in place where the timing and evolution of the low could allow for some wintry precipitation at the start. At the moment, I don’t see anything major, but the period between the 5th and 7th is worth watching.
Week one—Thursday December 1 to Wednesday December 7
Temperatures—below average (moderate confidence)
Precipitation—average (moderate confidence)
Wintry Precipitation—average (moderate confidence)
The first week of December will be a bit of a see-saw, with a relatively quiet pattern that will change as we watch a storm toward the end of the period (5th to 7th). I think there is a chance of some minor wintry precipitation, but much of what we see as a state should be rain. Temperatures look near average to ever so slightly above.
Week two—Thursday December 8 to Thursday December 15
Temperatures—below average (high confidence)
Precipitation—above average (moderate confidence)
Wintry Precipitation—above average (moderate confidence)
By week two, indications currently are that winter drops a big time hammer across parts of the US, including New England. This far out, all I can see is that it could be stormy. Storm tracks may continue to favor cutters (storms that cut to our west and warm sector us) but with cold in place and potentially big cold, we could see a strong front, overrunning, or clipper put down a legitimate widespread snowfall.
Technical Discussion
Week one
I would best characterize much of the first week of December as quiet. This is a time where we see the gradual stepdown toward winter continues in earnest with high pressure in place until early next week. The “warmest” days of the week are today and tomorrow, and I expect to see slightly below normal temperatures, with cool days and colder nights during the rest of the period.
As for precipitation, I think high pressure keeps the lid on our precipitation chances, though I won’t rule out a slight chance of snow showers this weekend as a weak shortwave pushes through. The main show comes early next week, as a wave of low pressure is expected to approach our region from the west. The guidance is split on the evolution of this low—whether a weak low develops in the south or if this is a strong cutter—but I think that enough cold air is in place where the timing and evolution of the low could allow for some wintry precipitation at the start. At the moment, I don’t see anything major, but the period between the 5th and 7th is worth watching.
Above, you will see the GEFS 7 day precipitation anomaly. With high pressure in place, I’m expecting a mostly quiet period, until we get to early next week…
Week two
As you can see above, by the second week of the forecast period we are poised to have winter bring some of the best it has to offer so far. There is a relatively strong of a pattern conducive for delivering cold into the region. In addition, it looks like the trough may make things active in the eastern US.
You can see why we end up here with the Euro ensemble (EPS) plot below. By the second week, we see a strong signal for ridging over Alaska, in contrast to the lower heights and vortex at the start of the run. In the west, we see more ridging as well, creating a very strong mechanism for deep Arctic air to penetrate the US. I expect the biggest departures from normal to be in the Midwest, but I think we’ll see our fair share of cold days.
This signal opens the door potentially for frequent opportunities for storminess, whether through northern stream systems like clippers, or fronts and strong cutters that bump against the cold. With that, we have to watch for enhanced chances of wintry precipitation. If the cold delivers, and I think it will, I think we see our fair share of winter weather chances during the second part of this forecast period.
This signal opens the door potentially for frequent opportunities for storminess, whether through northern stream systems like clippers, or fronts and strong cutters that bump against the cold. With that, we have to watch for enhanced chances of wintry precipitation. If the cold delivers, and I think it will, I think we see our fair share of winter weather chances during the second part of this forecast period.
Overall, this looks like a decent pattern for near to below normal temperatures, and with at least the second portion of the period, wintry precipitation chances. Who knows what happens afterward, but for now, I expect December to act like December early on.
As always, don’t forget to like us on Facebook and share our discussions, and follow us on Twitter @southernctwx and retweet our posts!
Thanks for reading SCW.
-DB
As always, don’t forget to like us on Facebook and share our discussions, and follow us on Twitter @southernctwx and retweet our posts!
Thanks for reading SCW.
-DB
