Main weather headline to start the week will be a potent and slow-moving coastal storm bringing a variety of hazards to the region later today through tomorrow morning. This storm is the same one responsible for this weekend’s deadly tornado outbreak down south. Conditions improve dramatically towards mid-week.
Rest of today – a flood watch, coastal flood advisories, and high wind warning are in effect mostly through tomorrow morning. Cloudy with high temperatures steady around 40°F. Winds continue to increase throughout the day as a strengthening coastal low approaches and the pressure gradient between it and a high pressure center over Quebec tightens. A low-level jet will enhance winds. Sustained east and northeast winds of 30-40mph with gusts between 50-60mph will become commonplace late today and overnight. The strongest winds will occur closest to the coast.
Along with the strong winds, periods of heavy rain will bring the potential for 1-3″ of precipitation, which could lead to minor to moderate urban and small stream flooding. Timing of the onset of rain will be around 3pm this afternoon.
The persistent and strong northeast winds off the water will contribute to minor to moderate coastal flooding. This will be exacerbated during a couple of high tide cycles.
High resolution rapid refresh model simulated radar output for 3PM this afternoonThe storm approaching spans the better portion of the entire East Coast
Tuesday – rain and wind abate during the day, tapering off by the afternoon. High temperatures about the same as today in the low-40s.
Wednesday – as the coastal storm continues to pull away, temperatures rebound and mostly sunny skies return. High temperatures anticipated around 50ºF.
Thursday – another nice day with high temperatures in the upper-40s and mostly sunny skies.
Overnight, forecast models shifted the track of the ongoing Nor’easter further west. This has implications for snowfall totals across the region.
Snowfall Totals
These have been bumped up for the city, which is now expected to receive 2-5″. The potential exists for more. Winter storm warnings now extend as far west as Nassau County, with points further east receiving as much as 7-12″.
As always with Nor’easters, even as they are ongoing, considerable uncertainty remains a factor. With these storms, one or more banding features will develop and circulate around the center of the storm as it progresses northeast. The number, extent, intensity, and western limit of advancement of these banding features ultimately determines what areas get the most snow. Within these bands, snowfall rates could easily reach 1-2″/hour. West of the western limit of the progression of these bands, snowfall totals will drop precipitously, such that a distance of 10 miles could mean the difference between 2″ and 6″+.
Timing
You can already see the radar signatures of two bands of moderate to heavy snow spawned by this storm. One of these bands is currently pushing its way west through Long Island, while another progresses towards shore. Within these bands, travel conditions will rapidly deteriorate while accumulations rack up.
Looking ahead to this afternoon, it would appear that the heaviest snow will fall in the city around 2PM, or the early afternoon.
The big weather news for the first full weekend of the new year is the deep Arctic chill that will be gripping the area. We should narrowly miss the core what would have been the first substantial Nor’easter of the season Saturday. The chill lasts through the beginning of next week when temperatures rebound back to above normal levels.
Rest of today – cold, with a mix of clouds and sun and a high temperature in the mid-30s. Wind chills in the low-20s.
Saturday – an uncertain scenario unfolds with the Nor’easter mentioned above. The one thing that is certain is that temperatures will be plenty cold to support all snow with highs only in the upper-20s. Two of the main forecast models continue to show a sizable spread in terms of how far east this storm tracks. This will ultimately determine whether portions west of Eastern Long Island see anything more than than a couple inches of snow. The cutoff between heavier snow and a light coating looks to be quite sharp also.
Sunday – overnight lows this weekend will be chilly, only in the upper-teens. Sunday, the wind picks up as the pressure gradient between the Nor’easter and high pressure building to the west increases. High temperatures will again only range in the upper-20s.
Monday – sunny, but still cold with a high temperature right around freezing.
Drought Update
Recent storms have brought beneficial rain and snow to the state and has helped alleviate some of the worst drought, while also staving off the redevelopment of drought in some areas. The cold temperatures have also been helpful in reducing evaporation from the soil. There’s almost no extreme drought left in the state, though most of Downstate remains in an area of severe drought.
Meteorologically, March is a month of highly changeable weather that can swing from one extreme to another. Thus far this month, we’ve seen snow, and record warm temperatures near 80ºF. This week is no different, and it ends with the possibility for a significant coastal storm that could bring accumulating snow to the region to ring in the official start of spring!
Rest of today – warm, with partly sunny skies and high temperatures in the mid-60s. An unstable atmosphere looks primed to spawn a few scattered thunderstorms. Atmospheric dynamics are supportive of strong wind gusts and possibly small hail with any storms that form this afternoon. Some of these storms could approach severe limits. Based on the latest High Resolution Rapid Refresh model output, there look to be two batches of storms, one impacting the region around 2PM, then again around 5:30PM. At the time of this post, two storm cells were moving slowly east over southern Bergen County and the western Bronx respectively.
Friday – temperatures cool off into the low-mid 50s tomorrow, with a slight chance again for some afternoon showers, though nothing quite as significant as today.
Saturday – an area of polar high pressure will move over southeastern Canada, setting the stage for the winter storm Sunday. Saturday, however, will be a pleasant, sunny day, but temperatures will be below average in the low-mid 40s.
Sunday – all eyes turn to a developing coastal storm/Nor’easter. Forecast models are having a rough time handling this storm, with wide variances noted among some of the models from day to day. Given the uncertainty at this time, only a couple days before the expected onset of the storm, it is difficult to guess at the snowfall accumulations from this storm. One thing that is well understood at this point is that temperature profiles will support a primarily snow event, with some rain mixing in at the coast. High temperatures Sunday will struggle to hit 40ºF. Snow should begin in the morning, mixing with rain in the afternoon Sunday afternoon before transitioning again to all snow overnight. A slight variation in the forecast storm track either west or east could result in dramatically different snowfall totals – more updates to come.
Monday – temperatures rebound back into the mid-40s under partly sunny skies following the passage of this late season snow storm.
You’d be forgiven if you didn’t believe that a record-setting Nor’easter blizzard happened less than a week ago. A week of much above average temperatures and warm weather has quickly melted more than half of the snowpack that was left after the blizzard dropped 26.8″ (.1″ short of the all time record) in Central Park, breaking the single day storm total snowfall record with a new high of 26.6″. Except, of course, those huge snow mounds that are trapping your parked car. Warm weather, with high temperatures near or above 50ºF this weekend means that even more of this snow will melt away. Whatever’s left will likely be completely washed away mid-week next week when we’re expected to hit temperatures near 60ºF with thunderstorms possible.
Rest of today – mostly cloudy with a high near 40ºF. A passing rain/snow shower caused by a weak passing disturbance in the upper atmosphere is possible this afternoon around 1PM.
Saturday – brief clearing caused by an area of high pressure overnight will give way again to increasing clouds with high temperatures around 40ºF again.
Sunday – the high pressure moves quickly off to our east Sunday, allowing for clockwise return flow from the southwest to bring in warmer temperatures in the upper 40s under partly sunny skies.
Monday – warm temperatures continue with highs topping out around 50ºF and partly sunny skies.
Cooldown Coming
Don’t get too used to the warm temperatures because after mid-week next week, cold air returns to the Eastern United States for a period.
Blizzard Brings Drought Relief
One of the best parts about this blizzard was that it brought along some much needed precipitation precisely to areas of the region that most needed it. As you’ll see below, since the blizzard past the area of New York State experiencing moderate drought has decreased from 6.80% to 2.04%, largely because areas of moderate drought in the NYC region and Long Island have gotten slammed with huge amounts of snow that will be replenishing the local watersheds as it melts.
All eyes turn towards this weekend’s Nor’easter which will bring us the most snow we’ve seen since last winter. Confidence is growing that NYC and points south could receive over a foot of snow by Sunday. In addition, forecasters anticipate that this storm will bring sustained winds of 30mph to coastal areas with gusts as high as 40-60mph leading to whiteout blizzard conditions. However, it is important to not, even at this point, 48 hours from the start of this event, that a good deal of uncertainty remains about these forecast snow totals.
Rest of today – mostly clear with high temperatures reaching into the mid-30s but a northwest wind in the 15mph range making it feel colder.
Friday – slightly cooler with highs in the low-mid 30s, clouds I increasing through the day as the headline storm for the weekend approaches.
Saturday – snow should begin falling from southwest to northeast overnight Friday and continue throughout the day Saturday. Sustained northeast winds 25mph-30mph could lead to drifting and blowing snow, making for hazardous teavel conditions. Some potential exists that enough warmer air wraps into the storm off the Atlantic that some areas see a changeover to a rain/sleet/snow mix in the afternoon before transitioning back to all snow Saturday night. Total daytime accumulations are currently forecast between 3-7″. Overnight accumulations could be in the 4-8″ range.
Minimum snowfall for this Nor’easterMost likely snowfall totalsMaximum snowfall possible with this storm
Sunday – some lingering snow showers are possible Sunday morning but conditions should improve rapidly as cloud cover decreases with the storm exiting to our east. High temperatures are expected to be in the mid-30s.
Monday – warmer with high temperatures in the mid-30s and sunny skies.
Complicating Factors for Forecasting the Nor’easter
Model divergence – European models favor a solution that has the storm moving quicker and further south than US based models. This scenario would result in minimal snow for NYC, hence why the minimum snow forecast is only 2″.
Unpredictable snow bands – as we are all too aware from last year’s fiasco of subway shutdowns in anticipation for a blizzard that didn’t materialize, when it comes to Nor’easter type storms, where, when, and for how long deformation banding features (heavy bands of snow) set up will make or break a snowfall total forecast in either direction. However, these types of mesoscale banding features are not easy to predict with confidence before they actually start forming. Should parts of our region fall under one of these banding features where snow could be falling at rates of 1″+ per hour, you could easily see total snowfall forecasts be shattered.
Intrusion of warm air – if enough warm air works its way into this storm off the warm waters of the Atlantic (where above normal temperatures thus far this winter have kept the sea surface temperatures abnormally warm), then some areas could see a rain/sleet mix for periods of time. Forecasters are overall confident the window for this mixing is small enough that overall totals won’t be dented too much, though.
The closer this storm center tracks to the 40ºN 70ºW benchmark, the better the chances become for our are to get a lot of snow. Climatologically, Nor’easters that track closest to this benchmark have been the biggest snowmakers for the NYC region.
Weather to start this week will be rather uneventful, predominantly featuring windy, cold days, but little in the way of precipitation. We did get our first dusting of snow so far this winter in the city last night, and the potential for significantly more exists with a possible Nor’easter coming this weekend. As always, even though we’re within a week of this event, our local forecast office is only forecasting with 30% confidence due to the large changes in impact that even small fluctuations in storm track and intensity could bring.
Rest of today – we’ve already hit high temperatures for the day around 30ºF. A tight pressure gradient is causing breezy west winds near 20mph translating to wind chill values in the 10-15ºF range.
Tuesday – basically a repeat of today, but with slightly stronger winds. High temperatures will be in the upper-20s to around 30ºF with west winds in the 20-25mph leading to wind chills in the single digits to low teens under mostly sunny skies.
Wednesday – warmer, with high temperatures closer to normal in the mid-30s, calmer winds and sunny skies. There could be some flurries Wednesday night with a passing clipper system, but no accumulation is expected in the city.
Thursday – mostly sunny again with high temperatures in the mid-30s.
Possible Nor’easter This Friday – Saturday
Looking ahead towards the end of the week, there is a possibility for the first significant snowfall event in the NYC region thus far this winter. Forecasters are keeping close tabs on the possible formation of a classic Nor’easter towards the end of this week. It is important to stress that even at this point in time, there’s still considerable uncertainty about how this scenario will unfold. A deviation in the track of this coastal low too far north would result in a mainly rain event along the coast, while a deviation too far south would mean significantly less precipitation. If this scenario plays out under optimal conditions, our region would be in the northwest quadrant of this low, an area that favors the development of heavy snow. Even then, as was the case a couple winters ago, slight changes to the track and position of the heaviest snow bands could mean the difference between 5″ of snow or over a foot. Stay tuned for updates.
As many of you woke up this morning, you were probably wondering, what happened here? This storm seemed like a dud. True, the snowfall totals in and around NYC were lower than initially forecast, but portions of the area did get slammed with over 20″ of snow. To put it simply – as I had laid out in the caveats from the last post, slight changes in track of this storm dramatically altered the placement of mesoscale banding features, hence leading to a sharp cutoff in snowfall totals from east to west.
Snowfall Totals
Looking at this snowfall totals map, you can easily make out the line that demarcates where the heaviest snow bands stopped their westward march. We got what appears to be around 6-8″ in the city, but just east of us in Nassau the totals jump to 12″ and then just east of that in Suffolk we see 20″+ totals.
Snowfall total map
On a larger scale, you can see the areas that got the highest snowfall totals, corresponding to where the heaviest bands of snow were able to pass over.
Forecasters are saying that the storm tracked further east than they expected by about 50-75 miles, which literally would have meant the difference from us having 6-8″ snowfall totals here in the city to easily 12-18″+. Now before we all go blaming them for a dud forecast (that some are already saying wasted taxpayer money), there are a couple things to consider:
Forecasters utilize a suite of different computer models to come up with these forecasts, in this case they favored the NAM (North American Mesoscale) and ECMWF (European Center for Medium Range Weather Forecasts) over the GFS (Global Forecast System), UKMET (United Kingdom Meteorology), and Canadian models. There were specific reasons for doing so, one of which is based on forecasters’ experience with these types of systems and which models have historically done a better job with them. ECMWF often does a very good job of modeling strong cyclonic systems like this (and is often favored in forecasting tropical cyclones). In this case, the NAM and ECMWF had the storm moving just far west enough to put us on the cusp of those high snowfall totals.
Mesoscale (medium scale) banding features are notoriously difficult to forecast in these types of storms. The exact position, orientation, and movement of these banding features is often not known until the storm is already ongoing. This is due to a number of complex atmospheric interactions that are responsible for these features forming. To take another example, the Storm Prediction Center can forecast that severe thunderstorms are likely over a certain area 2-3 days out. However, it is exceedingly difficult even the day of to know which towns will get hit by individual storm cells/tornadoes, etc. Despite advances in supercomputing power, forecast skill and accuracy, and understanding of meteorology, these mesoscale events remain challenging to get right even for the most experienced forecaster. So while the general public can say, “I told you so”, I’d challenge any one of them to forecast the next Nor’easter, and the one after that, and so on, and get them right with more skill than a straight up guess.
Anyway, since we all got the day off (the political response to this storm is a whole other debate beyond the scope of this blog), forget about the forecast being a dud and go out to take advantage of a day off!
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.
