Good evening to you from Southern Connecticut Weather!
Well, the calendar says Spring is supposed to start on Friday, but we’re looking at a very un spring-like forecast for the upcoming period, with consistently below normal temperatures expected throughout the period along with a round of snow for Friday and Friday evening.
Tomorrow looks to be clear and while still below normal, warmer than today was, with highs generally in the mid to upper 30s. Some wind gusts of up to 25 miles per hour are possible, but winds will not reach the potentially damaging levels that they did today and yesterday. All in all, a bit chilly, but definitely a pleasant day compared to our last few.
That pleasantry will be short lived however as a wave of precipitation from the northern flank of a coastal low exiting into the Atlantic off the southeast coast approaches our region from the SW late Thursday night and overspreads it Friday afternoon from SW to NE. There is fairly good consensus between the various models for a period of moderate snow from Friday afternoon into early Saturday morning from a combination of the initial overrunning wave and coastal redevelopment as the storm hits the Atlantic Friday evening. The afternoon rush would be impacted in this scenario, as would travel Friday evening.
The one outlier on the guidance is the NAM model, which keeps the confluence to our north much stronger than the other guidance and as a result brings only light and scattered precipitation to the state. Given that it is for the most part an outlier, we are essentially discounting it for the purposes of this forecast at this time, but raise it as a potential “red flag” in the forecast that could cause us to have to lower amounts if it in fact were correct.
Here’s a look at the various forecast models for this event.
Well, the calendar says Spring is supposed to start on Friday, but we’re looking at a very un spring-like forecast for the upcoming period, with consistently below normal temperatures expected throughout the period along with a round of snow for Friday and Friday evening.
Tomorrow looks to be clear and while still below normal, warmer than today was, with highs generally in the mid to upper 30s. Some wind gusts of up to 25 miles per hour are possible, but winds will not reach the potentially damaging levels that they did today and yesterday. All in all, a bit chilly, but definitely a pleasant day compared to our last few.
That pleasantry will be short lived however as a wave of precipitation from the northern flank of a coastal low exiting into the Atlantic off the southeast coast approaches our region from the SW late Thursday night and overspreads it Friday afternoon from SW to NE. There is fairly good consensus between the various models for a period of moderate snow from Friday afternoon into early Saturday morning from a combination of the initial overrunning wave and coastal redevelopment as the storm hits the Atlantic Friday evening. The afternoon rush would be impacted in this scenario, as would travel Friday evening.
The one outlier on the guidance is the NAM model, which keeps the confluence to our north much stronger than the other guidance and as a result brings only light and scattered precipitation to the state. Given that it is for the most part an outlier, we are essentially discounting it for the purposes of this forecast at this time, but raise it as a potential “red flag” in the forecast that could cause us to have to lower amounts if it in fact were correct.
Here’s a look at the various forecast models for this event.
As you can see, there is a strong consensus between the GFS, UKMET and GGEM(The Euro is in agreement as well, although we can’t share it here due to copyright issues) for 7.5 to 15 mm of liquid equivalent across most of the state, which when converted to snow at a 10:1 ratio would be 7.5-15 cm or 3-6”, which is a solidly impactful event. However, the NAM only has 2.5-5mm of liquid equivelant across most of the state, which would convert to 2.5-5 cm of snow or 1-2”, which in the grand scheme of things is really no big deal. Our forecast map below essentially discounts the NAM for southern areas in favor of the consensus, and gives it one half weight compared to the other models in northern areas.
Given that a compromise between the consensus and the NAM would still include southern areas of the state in the 3-6” zone, we felt comfortable forecasting the full 3-6” that a non-NAM consensus argues for there. In the northern zone, the consensus is more in the 3-5” range, and given that the non-NAM consensus would result in a lot more 3”s than 6”s and that a compromise between the NAM and other guidance would result in a mainly NAM like solution given the limited wiggle room, we didn’t feel comfortable completely relying on the non-NAM solution there and have hence given the NAM one half weight compared to the consensus, dropping the expected forecast to 2-4” in the northern half of the state.
One final potential wildcard to watch for is the possibility of some snow on Saturday from the redeveloped coastal low depending on how close it can track to the coast. As of now, only the ECMWF and to a lesser extent the GGEM have accumulating snows across the state on Saturday, but it’s worth keeping an eye on, especially in eastern areas as they will be closer to the low and hence closer to the center of the precipitation shield. Depending on how Saturday plays out, we may have to separate the zones by longitude as well as latitude, but for now will hold off due to lead time and low confidence.
As far as timing goes, snow moves in from west to east Friday morning, overspreading the area from mid-morning on and snowing across the state by early afternoon. The heaviest precipitation looks to be during the late afternoon and early evening hours of Friday, where for a time isolated areas of 1” per hour snow are possible, especially along the south coast. Snow begins to wind down after dark and should clear the state by very early Saturday morning, well before daybreak. There is a chance of some additional snow or rain on Saturday from the coastal system that forms to our east, but will not include any accumulations from that in the forecast for now.
Otherwise, expecting gradually clearing skies and slightly warmer temperatures on Saturday(Although temps will be heavily dependent on the eventual track of the coastal), with highs making it up into the 40s. Sunday will be right back into the freezer, however, with highs only in the upper 20s to lower 30s. An arctic cold shot then arrives for Sunday night into the start of the week, sending lows into the teens Monday morning, fifteen to twenty five degrees below normal!
One final potential wildcard to watch for is the possibility of some snow on Saturday from the redeveloped coastal low depending on how close it can track to the coast. As of now, only the ECMWF and to a lesser extent the GGEM have accumulating snows across the state on Saturday, but it’s worth keeping an eye on, especially in eastern areas as they will be closer to the low and hence closer to the center of the precipitation shield. Depending on how Saturday plays out, we may have to separate the zones by longitude as well as latitude, but for now will hold off due to lead time and low confidence.
As far as timing goes, snow moves in from west to east Friday morning, overspreading the area from mid-morning on and snowing across the state by early afternoon. The heaviest precipitation looks to be during the late afternoon and early evening hours of Friday, where for a time isolated areas of 1” per hour snow are possible, especially along the south coast. Snow begins to wind down after dark and should clear the state by very early Saturday morning, well before daybreak. There is a chance of some additional snow or rain on Saturday from the coastal system that forms to our east, but will not include any accumulations from that in the forecast for now.
Otherwise, expecting gradually clearing skies and slightly warmer temperatures on Saturday(Although temps will be heavily dependent on the eventual track of the coastal), with highs making it up into the 40s. Sunday will be right back into the freezer, however, with highs only in the upper 20s to lower 30s. An arctic cold shot then arrives for Sunday night into the start of the week, sending lows into the teens Monday morning, fifteen to twenty five degrees below normal!
Highs won’t be much better, as temps will struggle to get out of the 20s on Monday before warming to the upper 30s and lower 40s Tuesday. There is a signal for a possible system in this timeframe, but the only model showing a storm as of now is the GGEM and it’s solution is unsupported by other guidance at this time, therefore will only highlight a chance of precipitation. Precipitation type, should precipitation occur, would be dependent on the track of the low.
We’ll have another update tomorrow evening with a revised map if needed and more detailed timeline and as always will be updating throughout the storm on Friday with radar grabs, rapid-fire forecasts, and your observations. Until then, thank you for reading SCW!
-SA
We’ll have another update tomorrow evening with a revised map if needed and more detailed timeline and as always will be updating throughout the storm on Friday with radar grabs, rapid-fire forecasts, and your observations. Until then, thank you for reading SCW!
-SA
