After that brief “warmup” during the weekend, we’re once again mired in Arctic cold air. This cold trend continues with a reinforcing shot of cold air as a cold front sweeps through Wednesday. Behind that, high pressure builds in over the area for the end of the week and into the weekend, ensuring another prolonged stretch of chilly, much below normal temperatures.
Wednesday – ahead of what will a dry cold front passing through, high temperatures may be able to climb to just about the freezing mark under mostly sunny skies.
Thursday – once the cold front moves offshore, an area of low pressure will strengthen, but remain well offshore of the area. However, precipitation may still make its way over the region, especially the far eastern areas. There’ll be a chance for snow flurries further west in the city. Temperatures will be back in the mid-20s again in the wake of that cold front.
Friday – clearing skies will be accompanied by stagnant cold temperatures with highs again in the mid-20s.
Saturday – as you’ll se below, a strong 1040mb area of high pressure will be parked over the Ohio Valley will be responsible for the sunny, but cold temperatures through at least Saturday night. Highs Saturday may approach 30ºF. Normal highs for this time of the year are closer to 40ºF.Looking Ahead
Climate Prediction Center’s 8-14 day temperature outlook for March 4th to March 10th, with our region in an area expected to experience below normal temperatures.
The beginning of next week looks to feature a fairly active pattern, with two storm systems passing through, one on Monday, and another on Wednesday. With the current track of the second storm, it looks like we are going to be on the south side of the low pressure center. This would allow for warmer air to wrap into the area. We could top 40ºF again, but the tradeoff will be a slushy, wet day maybe with some mixed precipitation to start. Once this second storm passes through, we return to cold temperatures once again.
Sunday night’s lows were the coldest of the year thus far, indicative of the coldest airmass to hit the area in recent memory. Again, according to climatology, the last time New York City itself hit a low of zero was in January 1994. Unfortunately, the cold snap does not show any signs of abating during the week, although the first half of the week will see daytime high temperatures in the mid-upper 20s as opposed to the teens. We’ll finish the week off back into the teens before a warmup to above freezing with an approaching storm system this weekend. Behind that – you guessed it, another round of arctic air and abnormally cold temperatures.
Rest of today – cold and overcast, with high temperatures not even getting to 20 in the city. Snow should begin falling overnight, with generally light accumulations by daybreak.
Tuesday – slightly warmer with high temperatures in the mid 20s, but also with a chance for snow as a storm system now dumping snow across a vast swath of the South passes well to the south of us. We could still end up picking up 2-5″ of snow in the city, with higher amounts along the south facing shores of Long Island and minimal accumulation north of I-84.
Snowfall total forecast for Tuesday
Wednesday – a weak cold front will pass through Wednesday, and may give us a small chance for light snow, otherwise, expecting cloudy skies with high temperatures in the mid-upper 20s.
Thursday – behind that cold front, we get our next shot of Arctic air, with overnight lows into Thursday struggling to hit 10 in the city, and zero and below in outlying inland areas. Daytime highs will only be in the mid-teens despite ample sun. Thursday night, we might get another shot at low temperatures hitting zero in the city, with lows below zero across most inland locations.
Friday – basically a repeat of Thursday, sunny but with brutally cold temperatures in the mid-teens.
Over the weekend – watching for the development of a storm system that could bring some wintry mix/freezing rain to the area, but finally give us a break from below freezing temperatures.
More Cold on Tap to End February
After the weekend storm, we get yet another reinforcing blast of Arctic air to end the month of February. Below, you’ll see the Climate Prediction Center‘s 8-14 day outlook spanning February 23 – March 1. We’re in a region with a greater than 60% probability of experiencing below average temperatures for this period.
Climate Prediction Center 8-14 day outlook for Feb 23 – Mar 1
The main headline for the upcoming weekend and into next week will be the very cold airmass that will be spreading over the region, bringing with it what will likely be the coldest temperatures we’ve seen thus far this year. The coldest period over this stretch will be overnight Sunday into Monday, when low temperatures in the city could touch zero. If that does happen, it would be the first time the city has hit zero or below since January of 1994, according to National Weather Service records!
Friday – there will be a noticeable difference in daytime temperatures versus today. High temperatures are going to struggle to even hit the upper teens in the city, once the cold front responsible for the off and on flurries today passes through tonight. Overnight lows will again be in the low teens in the city, and colder in outlying suburbs.
Saturday – another clipper-type system will move quickly through the area on Saturday, setting off a period of snow showers that could end up dropping 1-2″ across the region. High temperatures will warm up slightly – if you can call a high near 30 a warm up! Overnight, winds will begin to pick up, with wind chills between -5ºF to -15ºF.
Sunday – a stiff northwest wind will pick up. The clipper system that passes Saturday will rapidly intensify as it moves over the Atlantic. This will set up an increasingly tight pressure gradient with a high pressure center over the Great Lakes. This setup will swing the door wide open for Arctic air to blast into the region. High temperatures Sunday will be in the mid-teens in the city, and overnight lows may be as cold as zero or just below zero. Regardless, the sustained northwest winds will yield wind chill values between -15ºF to -25ºF.
Monday, President’s Day – sunny skies, but that Arctic airmass will still be very much in control, with temperatures struggling to hit 20.
Tuesday – a return to temperatures near freezing again with an approaching low pressure system that will deliver our next chance at precipitation late Tuesday into Wednesday.
Another messy start to the work week is in store for us tonight and into Monday night as we endure a long duration, though relatively light intensity winter storm. Luckily for us, the storm track means we’ll avoid the worst impacts of heavy snow (New England will get the worst of it again). There’s some concern for icing again, although the impact should be slightly less serious than last Monday. The rest of the week will be precipitation free, with the exception of some snow showers possible Thursday. Following these snow showers, another shot of brutally cold Arctic air is expected by week’s end, such that highs will only be in the low 20s and even upper teens.
Monday – as you can see from below, the snowfall totals for the southern portion of the NYC area are on the very low end, only 1-2″ expected in NYC and in Long Island. The higher snowfall totals will be north of I-84 and into Connecticut, with the far northern suburbs getting a chance at over 6″. Bear in mind, the snow is expected over an extended period starting tonight through Monday night.
Storm total snow forecast
Ice is a bigger concern for the immediate coastal areas that will see less snow. High temperatures during the day Monday be below freezing, so freezing rain is expected and could deposit between 0.15″-0.25″ of ice when all is said and done. The majority of this is expected to fall Monday morning before temperatures cool off at the coast and precipitation switches back to all snow.
Storm total ice forecast
Tuesday – high temperatures should be right around freezing with clouds diminishing through the day as the storm system from Monday pulls to the east.
Wednesday – a sunny day expected with highs again near freezing.
Thursday – we get our next chance at snow, on the light side, with a passing low pressure system forming over the Great Lakes and moving east towards us high temperatures will be again around freezing.
Friday – a sunny, but frigid day with highs expected to only be in the upper teens and low 20s. As you can see from the chart above, to the west of the low affecting our area on Thursday, there is an area of high pressure which will usher in that reinforcing blast of Arctic air.
The low overall snowfall totals for NYC yesterday wasn’t so much a problem as the significant icing that resulted from an extended period of freezing rain. Ironically, a week the city government took criticism for shutting down the transit system for blockbuster blizzard that did not come to pass here, it was 1/4″ coating of ice that wreaked havoc on the entire transit system (the hours long complete suspension of the 7 train was an extreme example of this). We do get a couple more shots at snow, once tomorrow night into Thursday, and then again during the weekend, but at this time neither event looks to be nearly as high impact as what we’ve experienced the last two weeks.
Wednesday – will be comparatively mild in the context of the rest of the week and the weather we’ve had recently. High temperatures may actually even hit 40 (slightly above normal). However, as a cold front approaches from the west, we’ll have an increasing chance for snow showers, which maybe mixed with rain at the coast during the earlier part of the evening.
Thursday – chance for snow showers continues along the vicinity of the frontal boundary as it passes over us. Following the passage of that cold front, temperatures take a serious drop as northwest winds allow for Arctic air to make a comeback into the area. Lows overnight Thursday could be as low as the single digits for the city and below zero for outlying suburbs. Coupled with a northwest wind of 15-20mph, this would produce dangerously cold wind chill values.
Generally low snowfall totals expected across the region from this event
Friday – high pressure builds in briefly for Friday, giving us the only guaranteed dry day through the forecast period. It will still be cold with highs only in the low 20s.
Saturday – an arctic front will be approaching during the day Saturday, and ahead of the front, we’ll actually about normal temperatures in the upper 30s due to southwest flow. Clouds build in and the chance for snow showers builds during the later part of the day into the overnight.
Sunday – the arctic front mentioned above moves over us but then it looks like it will stall in our vicinity for an extended period from Sunday into Monday. High temperatures will cool to around freezing in the wake of that frontal passage.
At this time, it’s too early to know exactly how much snow we would pick up. It does appear that the precipitation with this system will be generally on the lighter side, except as the low pressure center depicted over southern Illinois in the graphic below approaches the coast. Once it arrives just west of the coast, it could draw in some moisture off the ocean as the counterclockwise cyclonic flow around the eastern periphery of the low induces an extended period of onshore flow (like a sea breeze, except in this case, the air over the water is actually warmer than it is over the snowpack on the land). If this onshore flow is robust enough, it could warm coastal areas up enough to get some rain out of the storm.
Stationary arctic frontYou can see the distinct separation between warm and cold airmasses demarcated by the stationary front depicted in the image above – the front separates the areas with the blue dotted lines from the areas of the warm dotted lines.
We got a bit of a (cold) respite during the weekend from any precipitation, but all that is about to change in a big way tonight and into tomorrow. A complex storm system that is set to bring snow across a wide swath of the Midwest will be approaching the area tonight and into tomorrow. Various factors make this storm even harder to forecast than the Nor’easter last week, including a still uncertain storm track and a very tight temperature gradient leading to the potential for a mixed bag of all precipitation types in the NYC region.
Impacts
This storm is set to make Monday a downright nasty day to be out. Snow is forecast to begin falling tonight, with areas to the north of the city expected to pick up the most snow through this storm. During the AM rush, temperatures are expected to rise just enough in the lower atmosphere to allow for the possibility of sleet, ice pellets, and a period of freezing rain along the coast near the city, with rain possible further east in Long Island. Then, to close out the day, temperatures will drop rapidly below freezing, such that any slush or melted snow or wet surfaces could flash freeze. Because the temperature gradient is so tightly packed, it will again literally be a matter of miles between a spot that picks up mostly snow and perhaps 8″+, and another location that picks up almost no snow, but gets a significant coating of ice.
Ice accumulation forecast – anything over 0.10″ can cause serious problems.Snowfall total forecast – note the similarity with the last storm as to how dramatically snow totals range across a very small geographic area.
Below are some probabilistic forecast graphics that will give you a good sense of the degree of uncertainty within this storm forecast. First, with respect to snowfall totals over the next 48 hours.
Probabilities of greater than 2″ of snowProbabilities of snow accumulation greater than 4″Probabilities of greater than 8″ of snow
Here’s the same time window, but with probabilities for ice accumulation.
Probability of ice accumulation greater than .10″Probability of greater than .25″ of ice accumulation
In the snowfall probability maps, you can see just how tightly packed the different bands of probability for snowfall are. A matter of 50 miles means the difference between being in an area of 40%-50% probability of receiving more than 4″ of snow, and an area with a greater than 80% chance of receiving the same total.
Timing
Snow will begin to fall later this evening and pick up in intensity overnight. Depending on the area you’re living in, you could see between 3″-8″ overnight, with the highest totals most likely north of the city, and the lowest totals along the coast and in eastern Long Island. Around the morning rush, areas along the coast and eastern Long Island should begin to see a transition from snow to freezing rain, or some type of wintry mix of ice pellets and sleet. Some parts along the coast may even see a changeover from rain/snow to plain rain. In the afternoon, temperatures will drop quickly below freezing, allowing for flash freezing of slush and other wet surfaces. Winds will begin from the east initially before turning northeast and then north through the day.
Why the Uncertainty?
The reason behind the complexity of this storm with respect to precipitation types, uncertainty of total snowfall amounts, rests with storm’s track and the dynamics in the lower atmosphere accompanying this storm. This storm, unlike a Nor’easter, has its genesis over the Central Plains. However, as it approaches the coast, it will still be able to pick up a good amount of moisture off the ocean and from points south.
Recalling that air around a low pressure center in the northern hemisphere in a flows in a counterclockwise motion, you can better understand what is going on here. The low pressure center is forecast to pass just to our south. To the north of the storm center, colder air will dominate, since the cyclonic flow would be pulling air from north to south. Meanwhile, on the south side of the storm center, warmer air is being wrapped into the storm from the south and east. This onshore flow bringing relatively warmer air in close proximity to colder (sub-freezing) air is the reason why there is such a dramatic range in forecast snowfall totals across the area, and also the reason why there is a possibility for a range of different precipitation types.
Above is a forecast map that shows the forecast position and track of the storm. The colored points represent the individual forecast ensemble members (different forecast models with slightly different inputs) predictions for the storm. Notice that there is still a nontrivial spread between these ensemble members. You may also observe that they seem to cluster to the north of the official forecast track (the black line). Indeed, forecasters have been making slight northward adjustments in response to this trend. Should this bear out, and the low pressure center does move a bit further north, we would end up with less snow, more chance for mixed precipitation and even rain. On the opposite end, if the storm track deviates south, we would get more snow, and less chance for mixed precipitation. A very tricky forecast indeed!
On the heels of the nor’easter earlier this week, we get another chance at snow tomorrow night into Friday, albeit of a much lighter intensity. Things get downright frigid after that with low temperatures Friday night in the single digits in the city, and wind chills below zero! The cold locks in over the weekend before we get another chance at precipitation to start off next week, continuing what has been an active weather pattern.
Thursday – clouds increase from west to east, with high temperatures hovering just above freezing. Precipitation begins overnight, and may include some rain/snow mix at the coast (all snow inland), but with minimal accumulations.
We get clipped by a clipper system Thursday night into Friday, with both NAM and GFS models pointing to us being on the periphery of the heavier precipitation.
Friday – light flurries continue into the morning Friday before ending, skies clear quickly while temperatures begin nosediving from a high in the mid-30s during the morning hours to the upper teens by sunset. Winds also pick up from the north and northwest as the departing clipper system from above deepens and the pressure gradient increases between it and a high pressure center over the Midwest. The combination of the cold temperatures and winds will likely induce wind chills below zero, so bundle up before you go out there Friday night.
Saturday – the deep freeze continues, with high temperatures only in the low 20s Saturday despite plenty of sunshine.
Sunday – another day of decent conditions, with clouds increase, but still cold with highs in the upper 20s. Sunday night into Monday, we get another shot at precipitation, although it’s a bit too early to nail down the specifics of this upcoming storm (whether it’ll be rain/snow, rain, or just snow, and how much).
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.
Looking Ahead
