Major Blizzard Approaching SWCT/NY

A major to potentially historic blizzard is set to move towards the region tomorrow night into Tuesday.  A wide range of forecasts have already been published showing numerous different accumulation expectations.  Our Premium clients have received word of the storm for upwards of a week, and despite it looking less likely on Friday, it stormed back onto the grid yesterday.  They recently received a large forecast update, and attached below is the free version of the detailed Tuesday storm.  Should you wish to subscribe to the Premium service to receive email updates whenever a Premium post is published summarizing the latest storm threats, you may do so here.  Similarly, should you wish to purchase the one-off forecast update, including school percentages for the week, you may do so here.  Parts of that forecast are what are attached below, while our Premium impact analysis is in that forecast.  If not interested in either of those, here is the official forecast:

Given ratios, expected moisture transport, and storm track, a general 16-28+ inches of snow is expected across the region through the storm.  Yes, this is a very wide range, but as I go through the post I’ll explain exactly why it is necessary, and why it is possible that someone sees both the low end and the high end in the region.  Snow-blown drifts could pile up to 4-5+ feet due to the lighter nature of the snow and the wind gusts.  At the peak of the storm, winds are now likely to gust in the 50-60 mph range in Fairfield and Westchester Counties and in the 50-65+ mph range in New Haven County.  This will be enough for isolated to scattered power outages with downed trees/tree limbs and isolated road closures.

Our models indicate that a strong convective band will set up somewhere near the region overnight Monday night.  Where this sets up someone could easily see 3+ feet of snow, like what happened back in 2013.  However, we don’t know where this will be, so instead the forecast is just 28+ inches for now.  If it looks like the band will set up close to the region, then that forecast will increase even more.  It is looking more likely but is not yet a guarantee, and I don’t really want to hype the 3-feet level for snow unless I’m quite confident that someone in the region hits it.  It’s also very possible that someone in, say, New Haven County gets 30 inches and somewhere in Westchester only gets 14-16 inches.  Just how things could shake out, but without knowing the exact banding structures it is hard for me to pick one county as likely to have the heaviest snow over the other.  Late tonight and likely tomorrow I will divide by county and make forecasts accordingly for the smaller mesoscale features for Premium clients, but there is just not yet enough model agreement for me to do that at this point.

As early as 7 or 8 AM tomorrow we could see some light flurries begin to fly across the region.  Seen here on the NAM (in range for this now) the accumulating snow is off to the west, but we could see flurries at 7 AM.  It’s not until 1 PM, here, that the snow looks to begin to accumulate much.  But by 4 PM, here, it should begin to slowly pick up in intensity.  There is some disagreement on the front-end timing, however, with the GFS showing here 2-3 inches by 1 PM already.  Due to the model’s recent poor performance, that is not weighted too heavily in the forecast, especially as most models do not have more than an inch by 1 PM.  Interestingly enough, one of the lowest confidence parts of this forecast are the impacts tomorrow, which are available in the Premium forecast, as it is hard to know exactly when this light snow starts as it will be associated with the first wave of snow in the Clipper as it transfers energy offshore.  Regardless, the consensus is that around 4 PM is when things really start to go downhill with 2-3 inches of snow having fallen and snow beginning to pick up in intensity then.  Snow very slowly picks up in intensity through the night, with the heaviest snow generally between 1 and 10 AM.  In that timeframe from 1-10 AM, I am worried about snowfall rates anywhere from 3-5 inches per hour, thundersnow, and the strongest wind gusts.  According to the NAM weather model, the strongest winds are between midnight and 6 AM, which makes sense given the expected track of the storm.  However, the ECMWF weather model throws in an added twist where the storm would move up towards Cape Cod before retrograding west slowly and bringing damaging wind gusts up to 70 mph into New Haven County through the morning of Tuesday and into Tuesday afternoon.  The precipitation timing with the heaviest snow in that 1-10 AM range is pretty high confidence, but when winds are the worst is varied depending on exact storm track.  Wind gusts will begin picking up by midnight for sure, but whether they peak overnight or last into the morning on Tuesday is still up for debate and something I will continue to track very closely.  Snow becomes more spotty and banded in coverage through Tuesday afternoon, with just light snow showers by 5-8 PM across the region.  All precipitation should move out of the region by 11 PM tomorrow night at the latest, although isolated flurries could continue, and winds will still be fairly gusty into Tuesday night so that there will be a lot of blowing snow.  Wednesday the sun comes out and the clean-up begins, but attention will then turn to yet another storm on Thursday.

As for travel, travel before noon tomorrow should not be significantly impeded by snow as I doubt we really see anything accumulate.  Roads could get a little slippery around 1 PM as snow will definitely be falling, although it may not reach far inland areas until closer to 2 PM or so.  By 4 PM is when travel conditions significantly deteriorate, and past 7 PM any travel is discouraged to the highest degree.  Travel between 7 PM Monday and 7 PM Tuesday should only be done for true emergencies, as it will be near impossible to keep roads safe overnight Monday night into Tuesday morning.  Crews will then need most of the day on Tuesday to clear up the roads so that major roadways can even be passable by Wednesday.  Thus, if preparing for this storm (which is advised), attempt to get most preparations done today and finalize all preparations by 4 PM tomorrow.  After that, do your best to avoid the roads and just hunker down.  When road conditions get good again is more up to the road crews than the weather, but is more likely to be a matter of days than hours.

In conclusion, a dangerous to life-threatening storm is approaching the region.  Please make all necessary preparations in the coming 24 hours and prepare for the potential to spend days without power.  Power outages are more likely to be scattered than widespread, but are a very real possibility.  An additional brief free update will be posted late tonight, so please stay tuned for the latest.


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