The track of the imminent nor’easter and blizzard has continue to trend west of earlier model runs. This has introduced increasing uncertainty as to overall snowfall totals along the immediate coastal areas along with possible wintry mix/freezing rain. On the other hand, confidence is increasing in heavy snow for areas north and west of the city, with snowfall totals 18″+ looking likely.
Impacts – heavy snow north and west of the city, snowfall accumulations in the interior 16-20″+ looking likely. Sharp gradient in the heaviest snowfall totals approaching the coast where wintry mix, freezing rain, and even plain rain could mix in during the early afternoon Tuesday. The exact location of the extent of warm air intrusion off the ocean will ultimately determine the difference between routine totals over 1 foot and areas that receive much lower snowfall totals. The difference in some cases could be a matter of mere miles. This line could fall in and around NYC itself. Still expecting a period of blizzard or near blizzard conditions for NYC during the course of this storm even if a transition to mixed precipitation does occur. Snowfall totals could still pile up close to a foot or over prior to this transition. The possibility of freezing rain and ice introduces an additional hazard on the roads and when coupled with strong winds of 30-35mph and gusts 45mph+ could result in power outages.
Timing – light snow should begin to fall early into the overnight hours, progressively growing in intensity. In the city, overnight accumulations of 3-6″ possible, with a sharp increase in totals north and west. Heavy snow with sleet and wintry mix during the morning and early afternoon in the city, all snow in points north and west. Blowing and drifting snow with blizzard conditions possible. Snow begins to wind down during the evening hours.
Caveats – any further movement of the storm track west would result in drastically lower snowfall totals for NYC and points east along the coast. Correspondingly, an eastward shift of the storm track would put NYC itself squarely in the bullseye for the heaviest snows.
Classic major nor’easter to bring blizzard conditions to a large swath of the Northeast Tuesday just days from the official start of spring. Areas in and around NYC likely to see snowfall accumulations of over 1 foot, locally higher. This may end up being one of the biggest snowstorms/blizzards in history for the month of March in NYC.
Rest of today – the proverbial calm before the storm. Mostly sunny, cold, with high temperatures in the low-30s.
Tuesday – a major late season nor’easter will bring heavy snow and blizzard conditions to the area. Blizzard warning in effect for the entirety of Tuesday. Snow starts falling overnight into Tuesday. Heaviest snows forecast to begin around the morning rush and continue through most of the day. Blizzard conditions expected on the coast with steady north to northeast winds 30-35mph and gusts over 45mph. Visibility near zero at times. High temperatures at or below freezing. Widespread accumulations over 1 foot and approaching or exceeding 18″ expected around the NYC metro area. Details on the storm at the end of this post.
Wednesday – lingering chance for snow showers early with wrap around moisture on the backside of the departing nor’easter. Mostly cloudy with a high near freezing.
Thursday – skies clearing, high temperatures in the low-mid 30s.
Major Blizzard to Impact the NYC Region
Winter Storm Stella, as the Weather Channel refers to it, is set to bring widespread heavy snow to the area beginning overnight Monday and continuing throughout the day Tuesday.
Impacts – Snow accumulations over 1 foot, in many cases approaching 18″. Locally higher amounts, with some areas possibly approaching 2 feet. Heavy snow and blowing snow during the day Tuesday. Snowfall rates 2-4″ per hour and possibly higher in the heaviest snow bands possible. Thundersnow may accompany the strongest snow bands. Blowing and drifting snow with steady northeast winds 30-35mph and gusts 45-50mph will contribute to blizzard conditions with near zero visibility at times. East and northeast facing shorelines may experience moderate coastal flooding during high tide cycles. Heavy, wet snow at the coast combined with high winds may lead to power outages. Hazardous travel conditions, severe disruptions to aviation likely. High confidence in storm total snowfall at this point, but there is still uncertainty about whether and where mixing could occur.
Timing – Snow begins early in the overnight hours Tuesday. Light accumulations of 2-4″ possible by daybreak. Heavy snow likely beginning during the morning rush hour and continuing through most of the work day, as well as into the evening rush hour. Winds quickly intensifying from the morning and staying steady through the evening hours. Heaviest snow tapers off in the early evening hours, but snow showers could continue overnight. Winds remain strong overnight into Wednesday. Conditions improve going into the morning Wednesday.
Discussion – an area of low pressure that had its origins in the Pacific has made its way across the northern US, impacting the Northern Plains and Upper Midwest with snow. This storm system will phase with a secondary, coastal low pressure system that is currently moving up the coast from the Southeast. As these storms merge, the coastal low will undergo rapid intensification and cyclogenesis, becoming a strong Nor’easter. This storm will be drawing on subtropical moisture, and will encounter an airmass that will be quite cold due to the presence of an Arctic high pressure system prior to the storm’s passage. These ingredients will set the stage for a classic major blizzard for the Northeast late in the winter season, only days from spring.
As always, uncertainty remains about the exact location of the heaviest snow bands with this storm. Areas that are impacted by these bands can easily rack up several more inches than surrounding areas that are spared. The storm is expected to track west of the 40°N/70°W benchmark. However, during the last model runs, the storm track has trended north and west, increasing the chances for the city itself to see the heaviest snow, in addition to areas north and west. If this track shifts west some more, warmer air off the ocean wrapping into the core of the storm from the south could induce mixed precipitation with rain cutting down on totals in the city and Long Island. If the track shifts east, heavier snow would fall over points east of the city.
We’re in for a wild ride over the course of the next 24 hours as our weather goes from possibly record-breaking warmth to what is expected to be the most significant winter storm so far this season. Significant snow accumulations over 6″ and possibly as much as a foot are expected across the region, resulting in a winter storm warning for all of the NYC metro region.
Timing
Judging by the amount of sun we’re getting, temperatures will likely hit record-breaking levels in the low-60s in the city today. They will drop steadily to around 50ºF by the evening commute as a cold front pushes through and Arctic air flows in from the north. Overnight, temperatures will continue falling rapidly to around freezing. Precipitation is expected to begin around 3-4AM Thursday here in the city and continue through the early afternoon. Unfortunately, the timing of the heaviest precipitation does look to bring significant impacts to the morning commute.
North American High Resolution simulated radar 1km resolution, tomorrow at 8AM.
Impacts
Rain/snow mix to start, but by the morning rush, expecting all snow through the region. Heavy snow at times possibly reaching 1-2″/hr. Some thundersnow could occur. Hazardous travel conditions during the morning rush as plows will have trouble keeping roads clear with traffic and the moderate to heavy snow. Gusty winds could produce near-blizzard conditions with low visibility.
Snowfall Totals
Here are some graphics for snowfall totals from our local National Weather Service Forecast office. The general forecast calls for 6″-12″ in the city. The exact extent of totals will depend, as is generally the case with this type of storm, on where the heaviest snow bands set up and for how long they sit over an any given area.
Probabilities for 4″+ and 6″+ of snow respectively
Discussion
An shortwave that’s made its way rapidly across the country from the Pacific will move along the cold front that is pushing through today. As it does so, it will spawn a secondary low off the Mid-Atlantic that will strengthen rapidly as it moves over open water. At the same time, plenty of cold air will wrap around the deepening coastal low with high pressure to the west. This will put in place all the ingredients for a classic coastal winter storm for this area. The only thing keeping this storm from being a major blizzard with snowfall totals exceeding 2 feet is the fairly quick pace that it’s expected to move at.
This coastal storm will drive the expected heavy snows tomorrow. Its track is expected to take it just outside the 40ºN 70ºW benchmark, a spot that from a climatological perspective has translated to heavy snow storms for this region.
A major nor’easter will be bringing a high impact blizzard throughout the NYC region tonight through Tuesday midday. Beginning this evening, snowfall will increase in coverage from south to north. Periods of heavy snow are expected with snowfall rates of 2-4″ per hour, with thundersnow occurring in the heaviest bands of snow. Extended periods of high winds, with sustained winds at least 35mph and gusts over 40mph (even up to 60mph) will lead to blowing and drifting snow, blizzard conditions, and near-zero visibility. Widespread snowfall totals of between 18″-24″ possible throughout the area, with locally higher amounts.
Snowfall Totals
Since yesterday afternoon, forecast models have backed off a bit on the overall total accumulations. At this point yesterday, the quantitative precipitation forecast (liquid water equivalent total) was as high as 2.7-2.8″ and broadly over 2.5″ across much of the area. As seen below, those liquid water equivalent numbers have gone down by about half an inch.
Liquid water equivalent forecast totals
This decrease in overall precipitable water has led to a corresponding downgrading of the overall snowfall totals. Using a 12:1 snow to water ratio, a drop in precipitable water by half an inch translates to a decrease in snow totals by 6″. Indeed, the National Weather Service has decreased the likely totals from 27″+ for many places to closer to 20-22″.
Snowfall accumulation total forecastHighest probabilities for snowfall totals in excess of 18″ during the 48 hour period ending 7AM Wednesday now rests over Southern New England, with the bullseye setting up right over Boston and immediate suburbs. Here in NYC, we are in the range of 30%-50% probability of receiving over 18″ – notice how abruptly the probability goes up as you go further north and east.
Timing
Light snow has already begun falling over the area, however the heaviest snow will not be occurring until after 8PM tonight. The most intense period of this storm is expected overnight tonight, as a deformation banding feature forms and begins moving slowly inland. Based on the simulated radar loop below from the NAM (North American Model), the peak intensity of snowfall looks like it will occur between 1AM-7AM overnight into Tuesday. Snow appears to taper off over NYC by 1PM tomorrow.
It does appear that a secondary set of banding snow will linger over eastern areas of the metro region throughout the afternoon Tuesday until as late as 4PM tomorrow.
By the way, part of the reason the main area of highest snowfall totals is now shifting to Southern New England and Boston is because it is anticipated that these areas will see moderate to heavy snow for much longer than we will here.
NAM model simulated radar output for this storm
Impacts
Snow, heavy at times, beginning in earnest this evening especially after 8PM. Some thundersnow possible, with the most intense snow occurring overnight. Strong sustained winds up to 35mph with gusts over 40mph and as high as 60mph will lead to blizzard conditions with blowing and drifting snow cutting visibilities down to near zero.
Caveats
Forecasters have been pointing out that there continues to be some slight disagreements between different models even though this storm is imminent. Snowfall total forecasts for storms like this one are notoriously difficult to predict with a high degree of accuracy prior to the event itself. This is due to the fact that the exact placement, movement, and intensity of the deformation banding feature on the northwest flank of the low pressure center is hard to foresee until the storm is ongoing. With snowfall rates as high as 2-4″ per hour within this banding feature, a difference of a couple hours under it could translate to 4-8″ difference in overall accumulation in any one location. Same thing with location, as one location that misses the most intense portion of the banding feature could easily miss out on 6″+ in total accumulation. Furthermore, a slight change in the thermal profiles within this type of storm could alter the snow to water ratio to be higher, and of course, a change from 12:1 to 15:1 would result in a dramatic difference in totals.
Yesterday’s Nor’easter will seem downright quaint by the time Tuesday morning rolls around. Just a couple of days ago, forecasters were not even clear if we’d get any precipitation Monday going into Tuesday. Now, words like “historic” are being used to describe what will undoubtedly be the biggest snowstorm of the season so far. When all is said and done, we could be looking at widespread snow totals on Tuesday of 18″ to as much as two feet of snow. During the peak of this much stronger Nor’easter, high winds and blowing snow could lead to an extended period of blizzard conditions near the coast.
The Setup
Forecast models that up to just 2 days ago were displaying significant differences as to how this system would transpire are now in close agreement on a classic setup for a strong Nor’easter, and a powerful, high-impact blizzard for the Northeast.
A relatively weak clipper-type low will be moving across the Midwest during the day today. By Monday evening, a secondary low will form from the remnants of this first system. This second low will rapidly intensify as it tracks on or just west of the 40ºN 70ºW benchmark early Tuesday morning.
NAM model output for the next couple of days
As the low bombs out (dropping more 30mb in less than a day), its forward progress will be slowed by a high pressure to the north. This high pressure over Quebec is a key difference between the setup of the storm on Saturday and this coming Nor’easter. In contrast to Saturday’s storm, this high pressure will allow a relatively deep layer of cold air to take hold prior to the arrival of this storm. As the low pressure continues moving northeast, the pressure gradient between the rapidly intensifying low and this high pressure will allow for strong winds to affect the area from first from the east, then northeast and finally north.
This combination of a slow moving, strong low pressure with ample cold air and moisture available will translate to widespread snowfall totals of over a foot, and close to 2 feet, primarily for the Hudson Valley and points east. This will primarily be due to the influence of a mesoscale deformation banding feature is expected to form north of the storm center, then slowly wrap around the storm as it moves northeast. Because the forward motion of the storm will be so slow, the banding feature (which could contain snowfall rates of 2-4″ per hour) could be sitting nearly stationary over large portions of the region for a prolonged period of time – thus leading to what could be record breaking totals.
With the wind expected to pick up during this event, there is a blizzard watch in effect for coastal areas of the region, where wind sustained winds (25-35mph) could lead to near zero visibilities while heavy snow falls.
Snowfall Totals
As you can see from below, almost the entire region is expected to pick up more than 12″, with eastern areas possibly picking up near 2 feet!
Looking at probabilities of snowfall totals below, you can see that there’s now at least a 70-80% chance a good portion of the NYC region receiving more than 8″ of snow.
This storm will also have ample moisture to draw off of, with the liquid water equivalent of between 1.5″ to over 2″ across a good part of the region. Using the standard 10-1 ratio of snow to liquid water, this would translate to between 15-20″.
Quantitative precipitation total forecasts from the Weather Prediction Center
Timing
Snow will begin Monday, with increasing intensity through the day. Winds from the northeast will also pick up during the day Monday with high temperatures only in the mid-upper 20s. Anywhere between 1-3″ of snow could fall across NYC.
The heaviest snow will be taking place overnight Monday into Tuesday morning, where parts of the area could pick up another 9-13″. Again, the heaviest snow will be occurring within the mesoscale banding feature, where intense snowfall rates of 2-4″ an hour for a prolonged period of time could even be accompanied by thundersnow. Winds will probably peak during this overnight period.
Snow will continue to fall during the day Tuesday, with another 4-8″ of snow possible. High temperatures will again only be in the upper 20s.
Rest of the Week
Wednesday – snow finally ends Tuesday night with conditions clearing by Wednesday, but high temperatures again struggling to reach the upper 20s.
Thursday – a slightly warmer day with high temperatures in the low 30s.
Friday – there’s a chance at some more precipitation (but much lighter) from a weak low pressure system moving through Friday.
