Good evening to you from SCW!
There’s a lot of buzz out there about a strong coastal storm for Friday into Saturday. While it’s true that there is a significant system shown on a lot of the models, it’s equally true that there is a ton of spread among the models, and it’s still too early to make any definitive claims as to what is going to happen. That said, we can still take a look at the setup and the different possibilities.
Wednesday-Thursday
The calm leading up to the storm. High pressure remains in control through tomorrow before weak low pressure brings a slight chance of a sprinkle tomorrow night. Mostly sunny skies tomorrow give way to increasing clouds on Thursday, with chances for rain increasing as we head towards Thursday evening. Any precipitation that falls on Thursday will almost certainly be rain; it’s not until later in the storm that we could start to see some wintry weather in the region as temps crash through dynamic cooling.
Temps for tomorrow and Thursday should be well above normal, with highs in the 50s both days.
Friday-Saturday
Main event in the forecast period is a strong, slow moving coastal storm that will impact the region from Thursday night through Friday and possibly into Saturday as well.
Broadly speaking, low pressure moves northeast from the Midwest into the lakes, but due to strong NAO blocking to the north of us, instead of cutting into the lakes and bringing us a rainstorm, we see the system shunted southeast until it eventually transfers its energy to a coastal low. The blocking in place means that unlike many of the storms we’ve seen recently, this one won’t be in any hurry to move out, and therefore it will remain offshore or just inland for quite some time before eventually moving out to sea.
Large systems are often our most consistent on the model guidance, but that is not the case here. All of the major global models have their own set of solutions, and as of now, we haven’t yet seen a defined trend towards one camp or the other that makes me comfortable endorsing one set over the other. As we go through the models, keep in mind that all of these outcomes are very possible, and equally as possible is some hybrid of these solutions or a totally different one all together. At this point, pretty much all I’m comfortable with saying is that there will be a large storm somewhere on the eastern seaboard this weekend.
GFS
Here’s an animation of the system from the most recent GFS model.
There’s a lot of buzz out there about a strong coastal storm for Friday into Saturday. While it’s true that there is a significant system shown on a lot of the models, it’s equally true that there is a ton of spread among the models, and it’s still too early to make any definitive claims as to what is going to happen. That said, we can still take a look at the setup and the different possibilities.
Wednesday-Thursday
The calm leading up to the storm. High pressure remains in control through tomorrow before weak low pressure brings a slight chance of a sprinkle tomorrow night. Mostly sunny skies tomorrow give way to increasing clouds on Thursday, with chances for rain increasing as we head towards Thursday evening. Any precipitation that falls on Thursday will almost certainly be rain; it’s not until later in the storm that we could start to see some wintry weather in the region as temps crash through dynamic cooling.
Temps for tomorrow and Thursday should be well above normal, with highs in the 50s both days.
Friday-Saturday
Main event in the forecast period is a strong, slow moving coastal storm that will impact the region from Thursday night through Friday and possibly into Saturday as well.
Broadly speaking, low pressure moves northeast from the Midwest into the lakes, but due to strong NAO blocking to the north of us, instead of cutting into the lakes and bringing us a rainstorm, we see the system shunted southeast until it eventually transfers its energy to a coastal low. The blocking in place means that unlike many of the storms we’ve seen recently, this one won’t be in any hurry to move out, and therefore it will remain offshore or just inland for quite some time before eventually moving out to sea.
Large systems are often our most consistent on the model guidance, but that is not the case here. All of the major global models have their own set of solutions, and as of now, we haven’t yet seen a defined trend towards one camp or the other that makes me comfortable endorsing one set over the other. As we go through the models, keep in mind that all of these outcomes are very possible, and equally as possible is some hybrid of these solutions or a totally different one all together. At this point, pretty much all I’m comfortable with saying is that there will be a large storm somewhere on the eastern seaboard this weekend.
GFS
Here’s an animation of the system from the most recent GFS model.
The GFS is the most northerly of the solutions, but also the strongest. Initially, we’d see heavy precip across the state Thursday night into Friday morning, and the column would be warm at least through the midlevels as the system is far enough north that the midlevel lows pass over us, making precipitation type all rain. However, as the system begins to move out to sea, we see colder air begin to get wrapped in at the higher elevations, and should precipitation rates be strong enough, we could see dynamic cooling take over and flash areas over to a heavy wet snow. As shown verbatim on the model, we don’t flip over to snow until after most of the QPF has already fallen, but as the GFS has a tendency for being warm at the lower levels, it wouldn’t surprise me if we saw a bit more snow in this solution than the model shows at first glance, but that’s not a guarantee by any means.
NAM
NAM
The NAM is a similar evolution to the GFS, but the whole system is pushed further south due to a stronger block and so we switch to snow much faster. The result is a significant snowstorm for the whole state; verbatim it’s spitting out some crazy numbers (2’+ in the mountains with snow continuing at the end of the run), but given it’s the NAM which is known to have a wet bias I would be very hesitant to believe those values right now. Nonetheless, in a more wintry situation like the NAM shows, significant snowfall would be a near certainty.
Euro
Unlike the American guidance, the Euro is much less enthused with the idea of significant precipitation in our area. Stronger blocking and less phasing shunts the whole system south of us, and while we would still see some rain Thursday night into Friday morning, we would see much less QPF than under the previous two scenarios. While we can’t post the full Euro due to copyright issues, these maps should give you a good idea of the difference between the Euro and the GFS. On the left is MSLP on the Euro valid for 7 AM Friday morning, while on the right is the same image from the GFS. Look how much further north the low is on the GFS!
Euro
Unlike the American guidance, the Euro is much less enthused with the idea of significant precipitation in our area. Stronger blocking and less phasing shunts the whole system south of us, and while we would still see some rain Thursday night into Friday morning, we would see much less QPF than under the previous two scenarios. While we can’t post the full Euro due to copyright issues, these maps should give you a good idea of the difference between the Euro and the GFS. On the left is MSLP on the Euro valid for 7 AM Friday morning, while on the right is the same image from the GFS. Look how much further north the low is on the GFS!
So what does this all mean?
As I said above, I have no idea. Usually, I’d look for trends in the camps of guidance, with one camp making concessions towards another, but we haven’t really seen that yet with this system. Next, I’d look to ensemble guidance, but here the ensembles are similar to their op runs and don’t offer us a lot of help. That leaves us with climatology and intuition. Climo with a strong -NAO is often to develop blocking and push things south, which would argue for the more suppressed solution that the Euro shows, but the storm is extremely impressive and I’m having a hard time believing that it will be pushed east as easily as the Euro shows it happening. Gun to head, I’d expect a mostly rain event for the state, with some snow on the backend (highest amounts at elevation), but the odds of a foot of snow or nothing at all are probably just as high as what I just outlined, so please don’t be surprised if we come back tomorrow with a snowmap for warning snows or an updated forecast for nothing at all J
What we do know is that regardless of what the eventual impact is to the state, there will be a powerful storm in the Atlantic this weekend, and that means that winds will likely be high and coastal flooding is a possibility. Combine that with the peak of a tide cycle this weekend and coastal areas have reason to be concerned; while I think eastern MA will take the brunt of the impact, it is still likely that we will at least see low-end coastal flooding here, with more significant impacts possible depending on the ultimate track of the system.
All in all, a complex storm that certainly hasn’t shown us its last cards yet. Stay tuned!
Sunday-Wednesday
High pressure moves in behind the storm leading to much improved conditions for Sunday into next week. Next chance of precip is midweek with the passage of a cold front, some models have phasing between the two streams which could produce a larger event, but at this lead time just going with a chance of rain and snow for now until we get through the short term as its likely that the track of the next system will be based on the track of this one.
The Dailies
Wednesday: Mostly sunny, with highs in the mid 50s.
Thursday: A chance of showers, then rain becoming likely late. Highs in the mid 50s. Chance of precipitation is 70%.
Friday: Rain, then rain or snow. Highs in the mid to upper 40s. Chance of precipitation is 95%.
Saturday: A chance of showers, otherwise, mostly cloudy, with highs in the mid 40s. Chance of precipitation is 50%.
Sunday: Mostly sunny, with highs in the upper 30s to lower 40s.
Monday: Mostly sunny, with highs in the lower 40s.
Tuesday: A chance of rain or snow, otherwise, mostly cloudy, with highs in the lower 40s. Chance of precipitation is 40%.
Wednesday: A chance of rain or snow, otherwise, mostly cloudy, with highs in the upper 30s. Chance of precipitation is 40%.
We’ll keep you updated as the models continue to hash out this storm system – stay tuned!
-SA
As I said above, I have no idea. Usually, I’d look for trends in the camps of guidance, with one camp making concessions towards another, but we haven’t really seen that yet with this system. Next, I’d look to ensemble guidance, but here the ensembles are similar to their op runs and don’t offer us a lot of help. That leaves us with climatology and intuition. Climo with a strong -NAO is often to develop blocking and push things south, which would argue for the more suppressed solution that the Euro shows, but the storm is extremely impressive and I’m having a hard time believing that it will be pushed east as easily as the Euro shows it happening. Gun to head, I’d expect a mostly rain event for the state, with some snow on the backend (highest amounts at elevation), but the odds of a foot of snow or nothing at all are probably just as high as what I just outlined, so please don’t be surprised if we come back tomorrow with a snowmap for warning snows or an updated forecast for nothing at all J
What we do know is that regardless of what the eventual impact is to the state, there will be a powerful storm in the Atlantic this weekend, and that means that winds will likely be high and coastal flooding is a possibility. Combine that with the peak of a tide cycle this weekend and coastal areas have reason to be concerned; while I think eastern MA will take the brunt of the impact, it is still likely that we will at least see low-end coastal flooding here, with more significant impacts possible depending on the ultimate track of the system.
All in all, a complex storm that certainly hasn’t shown us its last cards yet. Stay tuned!
Sunday-Wednesday
High pressure moves in behind the storm leading to much improved conditions for Sunday into next week. Next chance of precip is midweek with the passage of a cold front, some models have phasing between the two streams which could produce a larger event, but at this lead time just going with a chance of rain and snow for now until we get through the short term as its likely that the track of the next system will be based on the track of this one.
The Dailies
Wednesday: Mostly sunny, with highs in the mid 50s.
Thursday: A chance of showers, then rain becoming likely late. Highs in the mid 50s. Chance of precipitation is 70%.
Friday: Rain, then rain or snow. Highs in the mid to upper 40s. Chance of precipitation is 95%.
Saturday: A chance of showers, otherwise, mostly cloudy, with highs in the mid 40s. Chance of precipitation is 50%.
Sunday: Mostly sunny, with highs in the upper 30s to lower 40s.
Monday: Mostly sunny, with highs in the lower 40s.
Tuesday: A chance of rain or snow, otherwise, mostly cloudy, with highs in the lower 40s. Chance of precipitation is 40%.
Wednesday: A chance of rain or snow, otherwise, mostly cloudy, with highs in the upper 30s. Chance of precipitation is 40%.
We’ll keep you updated as the models continue to hash out this storm system – stay tuned!
-SA
