Good afternoon from SCW!
We talked last night about a system that, after being soundly out to sea for the past several days, came substantially west yesterday, bringing accumulating snow to eastern portions of the state. That trend continued overnight, with all of guidance coming into agreement for at least a light snowfall across most of the state, with signficant amounts expected in eastern areas. After leading the trend west yesterday, the NAM is now the SE outlier compared to the other global models; while it is worth taking into account, I am inclined to believe the consensus that has developed between the globals and the RGEM and discount the NAM.
However, even without the NAM, there is still some disagreement among the models, and the margin for error is very small; a slight shift to the east would take substantial snows out of most of the state, while a slight shift to the west would being a warning level snowfall to most if not all of the state. As it stands now, we ride the line, with eastern areas in line for a warning level event. The trend with the 12z suite so far has been to go slightly west; I took this into account when making the forecast, but if it were to continue to move west, this would result in higher totals in western areas.
Here's a look at the forecast QPF from the 12z NAM, GFS, RGEM, GGEM and UKMET.
We talked last night about a system that, after being soundly out to sea for the past several days, came substantially west yesterday, bringing accumulating snow to eastern portions of the state. That trend continued overnight, with all of guidance coming into agreement for at least a light snowfall across most of the state, with signficant amounts expected in eastern areas. After leading the trend west yesterday, the NAM is now the SE outlier compared to the other global models; while it is worth taking into account, I am inclined to believe the consensus that has developed between the globals and the RGEM and discount the NAM.
However, even without the NAM, there is still some disagreement among the models, and the margin for error is very small; a slight shift to the east would take substantial snows out of most of the state, while a slight shift to the west would being a warning level snowfall to most if not all of the state. As it stands now, we ride the line, with eastern areas in line for a warning level event. The trend with the 12z suite so far has been to go slightly west; I took this into account when making the forecast, but if it were to continue to move west, this would result in higher totals in western areas.
Here's a look at the forecast QPF from the 12z NAM, GFS, RGEM, GGEM and UKMET.
As far as model preference goes, this forecast is based on a blend of the 12z RGEM, 12z GFS, 12z GGEM and 0z Euro, discounting the NAM as the eastern outlier and the UKMET as the western outlier. I used around 15:1 for a snow ratio, as like we saw this morning, we will see cold temps and good snowgrowth in the midlevels. I also brought heavier QPF slightly west of the model consensus to account for the strong midlevel look and the possibility of a strong frontogenesis band well to the NW of the low and the main core of precipitation.
Here's our forecast snowmap for the event.
Here's our forecast snowmap for the event.
Confidence is highest in the far southeast portion of the state, where all guidance is in good agreement on at least a plowable snowfall. Model consensus is for around four tenths of an inch of of QPF in this zone, which translates to around 6" of snow at a 15:1 ratio. As such, will go ahead and call for 4-8" there to allow for localized banding.
The forecast becomes trickier as we move further north and west. As snow rates will likely be quite high in whatever banding does form, it's possible that this area could rack up a substantial snow total if a band ends up over it for even just a couple of hours. However, it's equally likely that the banding focuses slightly further east and the end result is only some light snowfall from the edges of the storm. I am leaning towards banding making it a little further northwest than the modeled consensus due to the strong midlevel look and the tendency for a band of lift and frontogenesis to develop well to the northwest of the main banding, and so will be a bit bullish with this zone and pencil in around a third of an inch of QPF, translating to 3-6" of snow.
Finally, in the western portion of the state, I expect only light snow from the main event. While there is the isolated chance of some localized banding developing, which would result in higher totals, I'm not confident enough in that chance to go for any more than a light event. I do think ratios will play a role here though, with some light snow hanging back even after the main event has moved east, and ratios there could be very high! Therefore, I'm going to lean a little higher than 15:1 here, and as such, I will forecast two to four inches for most of the rest of the state, with just a coating to two inches in the northwest hills, and will closely nowcast this area to see if any banding is developing.
As far as timing goes, expect snow to move into the state from south to north around mid-morning tomorrow. Snow should persist and make it's way north throughout the afternoon, with the best chance for moderate to heavy snow from late afternoon into the evening hours. Snow will exit west to east later in the evening and through the overnight, with snow out of the state well before dawn on Sunday.
As far as impacts go, expect a plowable snow for eastern portions of the state, with a lighter event in western areas. Travel may be difficult Saturday afternoon and evening, especially east of I91 where the heavier snow is expected. Given the "fluff factor" and the winds in the forecast, we will likely see some blowing and drifting as well, again focusing on eastern areas. Visibilities could briefly be reduced to near zero in areas where the heaviest banding develops along with strong wind gusts. Some isolated power outages could be possible, but given the high snow ratios and low water content, I don't expect them to be a major issue.
We will be keeping a very close eye on the trends this evening and overnight, and if needed will issue a revised map tomorrow morning. Otherwise, we'll be nowcasting throughout the day tomorrow, so make sure to keep an eye out for updates and send us your reports! Thanks for reading, share with your family and friends, and enjoy the storm!
-SA
The forecast becomes trickier as we move further north and west. As snow rates will likely be quite high in whatever banding does form, it's possible that this area could rack up a substantial snow total if a band ends up over it for even just a couple of hours. However, it's equally likely that the banding focuses slightly further east and the end result is only some light snowfall from the edges of the storm. I am leaning towards banding making it a little further northwest than the modeled consensus due to the strong midlevel look and the tendency for a band of lift and frontogenesis to develop well to the northwest of the main banding, and so will be a bit bullish with this zone and pencil in around a third of an inch of QPF, translating to 3-6" of snow.
Finally, in the western portion of the state, I expect only light snow from the main event. While there is the isolated chance of some localized banding developing, which would result in higher totals, I'm not confident enough in that chance to go for any more than a light event. I do think ratios will play a role here though, with some light snow hanging back even after the main event has moved east, and ratios there could be very high! Therefore, I'm going to lean a little higher than 15:1 here, and as such, I will forecast two to four inches for most of the rest of the state, with just a coating to two inches in the northwest hills, and will closely nowcast this area to see if any banding is developing.
As far as timing goes, expect snow to move into the state from south to north around mid-morning tomorrow. Snow should persist and make it's way north throughout the afternoon, with the best chance for moderate to heavy snow from late afternoon into the evening hours. Snow will exit west to east later in the evening and through the overnight, with snow out of the state well before dawn on Sunday.
As far as impacts go, expect a plowable snow for eastern portions of the state, with a lighter event in western areas. Travel may be difficult Saturday afternoon and evening, especially east of I91 where the heavier snow is expected. Given the "fluff factor" and the winds in the forecast, we will likely see some blowing and drifting as well, again focusing on eastern areas. Visibilities could briefly be reduced to near zero in areas where the heaviest banding develops along with strong wind gusts. Some isolated power outages could be possible, but given the high snow ratios and low water content, I don't expect them to be a major issue.
We will be keeping a very close eye on the trends this evening and overnight, and if needed will issue a revised map tomorrow morning. Otherwise, we'll be nowcasting throughout the day tomorrow, so make sure to keep an eye out for updates and send us your reports! Thanks for reading, share with your family and friends, and enjoy the storm!
-SA
