The rainy day yesterday yields a weekend of largely unbroken sunshine and above average warmth. Strong high pressure will dominate our sensible weather bringing stable, dry conditions. Temperatures will be in the mid-50s generally and this mild trend continues into next week. In fact, this mild weather could carry on for the balance of the month. No major chances for rain to speak of in the upcoming days into mid-week next week.
Rest of today – windy with sunny skies and highs in the low-40s. Overnight lows in the low-30s.
Weather Prediction Center surface forecast for 8AM Saturday. Strong high pressure will be nearly directly overhead.
Saturday – sunny with high temperatures in the mid-50s. Overnight lows again in the upper-30s.
Sunday – very similar to Saturday, sunny with highs in the mid-50s. Overnight lows in the upper-40s.
Climate Prediction Center temperature outlook for March 24-28, showing high probabilities of above normal warmth for the Northeast.
Climate Prediction Center temperature outlook for March 26-Apr 1, continuing to show probabilities for above average warmth in this part of the country.
Monday– another great day with high temperatures in the mid-50s and perhaps a few more clouds. Overnight lows in the mid-40s.
We have a cool start to most of the weekend with gradual warming trend taking place as high temperatures move up through the upper-30s into the low-40s. High pressure will be dominating sensible weather with lots of sun and calm conditions. This high remains in control until late next week, when we have our next chance at rain. The center of the high will gradually shift east during this time, inducing warm, southerly/southwesterly return flow next week, continuing the warm up to the point that temperatures could reach near 60ºF by mid-week.
Rest of today – windy with sunny skies and highs in the mid-30s. Overnight lows in the upper-20s.
Weather Prediction Center surface forecast for 7PM Saturday. High pressure is set to build to our west and move in.
Saturday – partly sunny with high temperatures reaching the upper-30s. Overnight lows again in the upper-20s.
Sunday – very similar to Saturday but with sunnier skies and high temperatures in the upper-30s and overnight lows in the upper-20s.
GFS model 850 mb temperature, height and winds for 10PM next Thursday. This shows a remarkable warming trend underway at this level of the atmosphere, which serves as a good proxy for surface temperatures.
Monday– warmer with high temperatures in the low-mid 40s under sunny skies. Overnight lows in the low-30s.
Another accumulating snow event is possible during the day Sunday this weekend, with accumulations somewhere in the 2-4″ range currently most likely. If this storm tracks a bit closer to shore, we could see totals more in the 4-6″ range. The timing of this storm is much faster than the previous one, with onset of snow early in the day Sunday, lasting potentially through the early afternoon hours. As a weaker system, without as strong a high pressure system downstream, winds should also not be as robust as with the Monday storm.
Weather Prediction Center 48 hour 50th percentile snowfall accumulations for the NYC metro region ending 1AM Wednesday
Weather Prediction Center 48 hour 90th percentile(median) snowfall accumulations for the NYC metro region ending 1AM Wednesday
GEFS ensemble plumes for total snow accumulation at KLGA. The mean here is about 4″ with a significant number of ensemble members showing lower amounts.
SREF ensemble plumes for total snow accumulation at KLGA. The mean is about 2″, with similarly large numbers of ensemble members showing lower amounts.
Forecast Details
At the Surface
Low pressure developing over the Southern Plains will emerge offshore of the Carolinas later tonight. This surface low will strengthen modestly as it tracks quickly northeast. Current thinking is that the storm track takes it outside of the classic 40ºN/70ºW benchmark that leads to maximized snowfall for nor’easter type systems in this area.
ECMWF “Euro” model 1000-500 mb pressure, thickness, and surface precipitation/type at 1PM Sunday.
GFS model 1000-500 mb pressure, thickness, and surface precipitation/type at 1PM Sunday.
NAM model 1000-500 mb pressure, thickness, and surface precipitation/type 1PM Sunday.
Weather Prediction Center storm track forecast.
850 mb Level
At this level of the atmosphere, it’s apparent that this storm is much less of a headline maker than Monday’s snowstorm. It’s evident from various models that while there should be enough moisture to sustain precipitation, the winds at this level are not forecast to be anywhere near as strong as on Monday. The lack of a truly robust low-level jet will make for an overall slightly drier scenario.
ECMWF “Euro” model 850 mb winds and relative humidity at 1PM Sunday.
GFS model 850 mb winds and relative humidity at 1PM Sunday.
NAM model 850 mb winds and relative humidity at 1PM Sunday.
500 mb Level
Unlike the last storm, the 500 mb level flow for this upcoming storm is more progressive. This will lead to the storm moving faster through the area. One notable factor contributing to the potential for a decent storm this time is that there will be a negatively tilted trough at this level, indicative of a maturing and deepening low. This feature will serve to enhance divergence at this level and induce surface lift in response.
300 mb Level
As was the case with Monday’s storm, a curved jet streak should set up just north and east of this storm’s surface low. The entrance region of this jet streak should allow stronger divergence and enhanced lift as a result.
A significant snowstorm in store for NYC Monday into early Tuesday morning. Current trends point to 8-12″ likely for most of the city. There is uncertainty with possible mixing late Monday that could cut into this over Long Island, and if the mixing line pushes further northwest, which The European model portrays, this could lower totals in the city to more of the 6-10″ range. It is worth noting that the 850 mb set up suggests the possibility for much bigger totals closer to 18″ if the colder scenarios play out. The timing of this storm is such that the most intense snowfall should occur during the day. A narrow, intense deformation band could remain nearly stationary over some parts of the region during the daytime hours Monday. Strong northeasterly winds will accompany this storm despite relatively modest pressure falls, due to the presence of a 1034 mb high pressure center over eastern Canada creating a tight pressure gradient.
Weather Prediction Center 48 hour 10th percentile snowfall accumulations for the NYC metro region ending 1AM Wednesday
Weather Prediction Center 48 hour 90th percentile snowfall accumulations for the NYC metro region ending 1AM Wednesday
Weather Prediction Center 48 hour 50th percentile(median) snowfall accumulations for the NYC metro region ending 1AM Wednesday
Forecast Details
At the Surface
A low pressure center that tracked through the Midwest this weekend will transfer its energy as it hits the Appalachians to a secondary low offshore of Virginia tonight. The low will then slowly track to the northeast as it deepens somewhat. This isn’t a particularly strong low, and it will elongate, translating eastwards overnight into Tuesday morning (see the last image in the gallery below). The North American models (GFS, NAM) suggest a colder scenario that would see higher snow totals (2nd, 3rd imges below), while the European model (1st image) shows potential for mixing Monday evening. Strong northeasterly winds will accompany the storm.
The presence of very cold air this weekend should help lead to better chances for big totals, however, the cold air will be retreating ahead of this storm, and cold air damming will be modest.
ECMWF “Euro” model 1000-500 mb pressure, thickness, and surface precipitation/type at 7PM Monday.
GFS model 1000-500 mb pressure, thickness, and surface precipitation/type at 7PM Monday.
NAM model 1000-500 mb pressure, thickness, and surface precipitation/type at 7PM Monday.
Weather Prediction Center storm track forecast.
850 mb Level
At this level, a strong easterly low-level jet will bring plenty of moisture into the cold conveyor belt of the storm. The advancement of the warm nose of the low will be key to where the greatest potential for deformation banding and the heaviest snowfall rates set up during the day Monday. The GFS and NAM models (2nd, 3rd images below) depict this warm nose staying just offshore. This would favor the best potential for a mesoscale band setting up right over NYC and slightly north as these bands are typically situated just on the cold side warm nose of a low.
500 mb Level
Part of the reason the surface low of this storm will progress so slowly, bounce around, and elongate is due to the presence of a closed 500 mb low accompanying it. This isn’t really a “classic” set up for a big nor’easter blizzard here, however, the closed low does help keep cold air aloft and help enhance lift via increasing the lapse rate between the surface and this level.
300 mb Level
A curved jet streak should set up just north and east of the developing low during the day Monday. The entrance region of this jet streak should allow stronger divergence and enhanced lift for this low.
An arctic chill with bitterly cold winds kicks off the weekend as strong high pressure moves in. Overnight lows in the teens and high temperatures in the 20s will range 10-15ºF below normal for this time of year. This cold air could set the stage for a nor’easter bringing significant snowfall to the region, with totals > 6″ possible Monday into Tuesday. As usual, track details on this storm will be pivotal, and are not clear at this time.
Rest of today – mostly clear, cold, and windy with high temperatures in the low-20s. A strong arctic high and a departing low will create a tight pressure gradient that ushers in stiff northwesterly winds 20-25 mph. Wind chills will hover around 0ºF. Overnight temperatures drop into the mid-teens with wind chills likewise dropping below zero.
Weather Prediction Center surface forecast for 7AM Saturday. A strong area of high pressure is parked over much of the Eastern US.
Saturday – winds abate with high pressure moving more directly overhead. Sunny, but still cold with high temperatures around 30ºF. Overnight lows will be in the upper-teens under increasing cloud cover.
Sunday – mostly cloudy as the next storm system starts to work in. High temperatures around 30ºF. Overnight lows in the upper-20s with the possibility of snow developing overnight into Monday morning.
GFS model total snowfall accumulation as of 7AM Tuesday
ECMWF model total snowfall accumulation as of 7AM Tuesday
UKMET model total snowfall accumulation as of 7AM Tuesday
Monday– stiff northeasterly winds developing along with snow. High temperatures in the low-30s. The storm possibly bringing us significant snow came ashore over the west coast yesterday and will be transiting the country the next couple days. It is eventually forecast to spawn a coastal low, bringing a nor’easter into our region. Even though cold air will precede this storm, offshore waters are still mild, in the low 40s-50s, and with the storm likely to bring southerly/northeasterly flow at the outset, we could see enough warming to mix to rain at the coast. Storm track and strength will be vital to the eventual snowfall totals. Models seem to signal a very tight banding feature bringing heavy snow – you’ve heard this before but these bands are notoriously difficult to pinpoint even a day ahead of the event. If the optimal scenario plays out, we could see a storm with similar or possibly bigger totals than the one in December. Overnight lows Monday shouldn’t budge much, in the low-30s, with some warm advection associated with portions of the storm.
A strong nor’easter/coastal low will impact NYC tonight into Saturday. Conditions will deteriorate with the worst weather overnight into tomorrow morning. Gusty winds, soaking rains will accompany this storm. Temperatures will also drop as the storm moves off northeast and winds turn to the north and northwest, however, cold air wrapping around the low will not arrive in time to set the stage for accumulating snow here. Storm clears out by later Saturday. Afterwards, calm, seasonably cool temperatures (low-40s) are in store for next week.
Rest of today – temperatures topping out in the upper-40s with warm air advection/warm front moving up ahead of the main storm. Cloudy, with chances for rain increasing through the day, mostly on the lighter side. Overnight lows largely holding steady in the mid-40s again due to the influence of the incoming warm front. Rain expected to increase in intensity overnight going into Saturday morning.
ECMWF hi-res model surface precipitation/precipitation type valid 7AM Saturday
ECMWF hi-res model surface precipitation/precipitation type valid 1PM Saturday
GFS model surface precipitation/precipitation type valid 7AM Saturday
GFS model surface precipitation/precipitation type valid 1PM Saturday
Saturday – models are in pretty good agreement (see above images from GFS and ECMWF models depicting evolution of this storm during the day Saturday) that this coastal storm will evolve quickly and intensify as it tracks offshore southeast of the region. This will result in periods of rain throughout the first half of Saturday, along with increasingly strong winds as the pressure gradient tightens around the deepening low. As the low tracks northeast, winds will be turning from the south to the north and northwest. This will bring in much cooler air, although not cold enough to support accumulating snow at the coast. As a result, temperatures will be dropping during the day Saturday into the low-40s. Precipitation should end rather quickly in the afternoon. Overnight lows will be in the low-30s wit winds easing.
Weather Prediction Center’s forecast storm track based on recent ensemble model runs.
Sunday – sunny with high temperatures in the low-40s. Overnight lows around 30ºF.
Monday– similar day to Sunday with sunny weather and high temperatures in the low-40s. Overnight lows again around 30ºF.
It’ll be a cloudy start to the week with possible thunderstorms later today. Rain chances continue Tuesday with a surface low in our vicinity. Once this low moves off, our weather calms Wednesday. High pressure builds in Thursday and should bring us mostly sunny skies. High temperatures start off slightly below normal in low-50s with clouds and rain, and will warm into normal ranges in the mid-50s later on.
Rest of today – energy from an upper level low will support development of a surface low around its base. Surface troughs from this low may touch off some isolated showers and thunderstorms later this afternoon with the aid of a cold pool aloft (increasing lapse rates and increasing instability). Best chances for this activity will be north of the city. High temperatures in the mid-50s with clouds and rain. Overnight lows in the low-40s.
GOES East Geo Color satellite image. You can see the large area of cloudiness associated with the upper level low
High resolution rapid refresh simulated radar showing the possibility for some convective activity associated with a cold pool later this afternoon around 5PM
Tuesday – this surface low will help move a backdoor cold front through, bringing cool, damp, northeasterly flow to the area. With this air mass, we’re only expecting high temperatures in the upper-40s. Rain chances continue with the low in our vicinity. Overnight lows in the upper-30s.
Wednesday – the low affecting our weather to open the week finally moves off. We’ll get a dry day with diminishing clouds and high temperatures around 50°F. Overnight lows around 40°F.
Thursday– high pressure builds and brings us a mostly sunny day. High temperatures rebound into the mid-50s in response. Overnight lows in the mid-40s.
We have an active weather pattern with two storms moving through NYC this first full week of spring. A nor’easter will pass offshore today, bringing mixed precipitation early then cold rain later. We get a lull Tuesday with temperatures rebounding into the mid-50s, before a second low hits Wednesday. This will bring another round of cold rain with temps back in the mid-40s. Temperatures rebound again Thursday after this second storm.
Rest of today – some light mixed precipitation has already moved through the region this morning. A second round of more consistent, moderate precipitation should hit around lunch. High temperatures only in the mid-40s. Overnight lows around 40°F.
High resolution rapid refresh simulated radar for 1PM Monday
Weather Prediction Center surface forecast for 8PM Monday
Tuesday – the nor’easter pulls away to the northeast and we get a brief period of calm with weak high pressure building in. Partly sunny skies expected with highs in the upper-50s. Overnight lows in the low-40s with rain chances picking up towards Wednesday morning.
Wednesday – a second storm system moves up from the south. This will bring us another round of cold rain, with highs back in the mid-40s. Overnight lows around 40°F.
GFS model 500 mb height and relative vorticity valid 2PM Wednesday. A shortwave trough is evident over the Northeast, providing upper-level divergence for the second storm to hit this week.
Thursday– similar to Tuesday with things drying out. Partly sunny skies with high temperatures in the mid-50s. Overnight lows in the mid-40s.
A long duration Nor’easter slowly moves its way eastwards. Conditions improve during the second half of the weekend. A brief warmup to above average temperatures takes place. This doesn’t last, with another cold front passing through to start next week. Tomorrow, keep an eye out on the skies for a possible glimpse at the aurora borealis, typically not visible at these latitudes.
Rest of today – chance for rain shower diminishing as the center of a slow moving Nor’easter continues to progress northeast. High temperatures reaching around 50ºF. Winds will increase on the backside of this departing low overnight. Winds will shift towards the northwest as well, bringing in colder air and overnight lows in the mid-30s.
GOES East satellite loop of the storm system affecting the NortheastOcean Prediction Center surface analysis for the Atlantic Basin. A strong blocking high is inhibiting the forward progress of the Nor’easter impacting our area. This is leading to a long duration coastal flooding and wind event.
Saturday – decreasing clouds as the low above continues progressing northeast slowly. Winds will increase as this low continues to deepen and the pressure gradient builds between it and and area of high pressure further west. Steady winds in the 20-25 mph range with gusts as high as 40 mph are forecast. High temperatures will be a bit below normal as a result in the upper-40s. Overnight lows will be cold, in the mid-30s with clear skies.
Weather Prediction Center surface forecast for 8AM Sunday, still showing a tight pressure gradient between a high over the Ohio Valley and the departing Nor’easter
Sunday – temperatures rebound into the mid-50s as an area of high pressure builds and slides off to our southeast, and winds turn towards the southwest bringing in warmer air. Sunny skies – this will be the best day of the weekend.
Monday – another cold front approaches from the west and brings a possibility for rain. Temperatures ahead of this front should reach into the low-50s. Behind this, we’ll get another shot of cold air, with temperatures dropping overnight into the low-30s.
Northern Lights Possibly Visible from NYC
On Tuesday, The Space Weather Prediction Center (it exists!) detected a large Coronal Mass Ejection (CME) associated with a potent solar flare. As a result, they have issued a moderate geomagnetic storm watch for Saturday, March 23. Of note, the belt where the charged particles from this CME would impact the Earth’s upper atmosphere and result in an aurora quite a bit further south than where the northern lights are typically visible. In fact, they may even be visible from NYC, although it may be hard to see them due to light pollution.
A winter storm warning is in effect for NYC and the surrounding metropolitan region. This isn’t exactly how we’d all want to start March off! This storm is anticipated to bring some travel impacts to the area, however, for reasons discussed below, this won’t be a blockbuster snowmaker. Watch out for a slog of a morning commute tomorrow. This snow may also stick for a while – a frigid continental polar air mass from Canada will sweep in behind this storm bringing temperatures generally 10-15°F below normal for this time of year. High temperatures in the mid-30s should limit melting.
Headlines
Snowfall totals: I’m forecasting 4-6″ in parts of eastern Queens, southeastern Brooklyn, and lower totals further east into Long Island. Higher totals of 6-8″ are more likely to occur in Manhattan, the Bronx, and points further inland, particularly interior regions of Connecticut. Below are probabilistic forecast maps of various amounts of snow (>= 2″, >= 6″, and >= 8″).
Timing: Precipitation starting in earnest around 8PM. Starting out as a mix of rain/snow near the coast, but transitioning over to all snow later in the evening. The heaviest snow will happen overnight. Because of the fast-moving nature of this storm, precipitation is expected to end rather quickly between 4-6AM Monday morning in the city.
Uncertainties: There is still potential for a wobble in the storm track, further east and south would result in higher snow totals near the coast. Further west and closer to the coast would mean more mixing/rain at the coast and lower snow totals. There will be a rather sharp gradient of increasing snowfall totals spreading across the region (as seen in the previous probabilistic snowfall total forecasts). Mesoscale heavy snow bands will be difficult to pinpoint ahead of time. Some areas could see several inches more than neighboring areas just a few miles south and east.
Synoptic Set Up (The Big Picture)
A storm that’s currently unleashing severe storms with tornadoes across the Deep South now will slide up along the Mid-Atlantic and Northeastern coast of the US. As this storm progresses, it will move close to the 40°N/70°W benchmark, a spot that’s climatologically correlated to heavy snow events along the heavily populated I-95 corridor during the winter. This storm will continue to strengthen as it moves offshore. Snow is expected to develop ahead of the advancing warm front associated with this storm as its precipitation shield advances. Heavier snow is forecast to develop later on as strong isentropic lift associated with the warm front occurs, creating the potential for frontogenesis and some mesoscale bands of very heavy snow. The storm is expected to move quickly along the Northeast coast, such that the duration of precipitation in any one spot is expected to be less than 12 hours.
At the 500 mb level, a shortwave trough will provide positive vorticity and some additional lift/divergence, allowing the storm to continue strengthening. Finally, at the 300 mb level, the surface low will be close to the entrance region of a curved 300 mb jet streak. This will provide yet more divergence and lift, if only for a brief period.
Weather Prediction Center’s surface forecast for 1AM Monday morning
GFS model 500 mb vorticity and height for 1AM Monday
GFS 300 mb height, wind forecast for 1AM Monday, note the brighter red, orange, and white streak over the Northeast, indicating a jet streak.
Evolution of the Storm Track
Over the course of the last three days, forecast models have come into better agreement with this storm tracking close to the 40°N/70°W benchmark (circled in red in the images below). Note the increasingly tight clustering of storm center locations around the benchmark in progressive storm track forecasts from the Weather Prediction Center.
WPC storm track forecast issued 7AM Saturday, the brown spots indicate forecast storm center locations around the benchmark
WPC storm track forecast issued 7AM Sunday, the green spots indicate forecast storm center locations around the benchmark
The tightening clustering of these forecast storm center locations lends greater confidence to the idea that the storm will track very close to the benchmark.
Ensemble Snowfall Totals
The two primary model ensembles (GEFS and SREF) have been edging ever so slightly upwards in their forecast mean snowfall totals, while the model spread has decreased over the weekend
Latest GEFS ensemble plumes for snowfall totals at KLGA
Latest SREF ensemble plumes for snowfall totals at KLGA
These means/spreads were part of what informed my own forecast snowfall totals at the top of this post.
Factors Supporting Heavy Snow
Storm track over or very near the benchmark
Strong isentropic lift and possible frontogenesis (see images below). Strong lift is a critical ingredient for generating heavy precipitation
Possibility of mesoscale bands as a result of this lift, generating heavy snowfall rates
Temperatures probably supporting frozen precipitation through the atmosphere
GFS forecast for 850 mb frontogenesis
NAM 12km forecast for 850 mb frontogenesis and temperature advection (red shades indicate warm advection)
NAM forecast sounding for 1AM Monday
GFS sounding for 1AM Monday
Factors Suggesting Lower Snow Totals
Possibility still remains for storm track to shift further inland, introducing more warm air off the ocean, more rain than snow at the coast
Warm advection associated with the storm’s warm front possibly also affecting snow development. Note how close the overlapping temperature and dew point profiles in the forecast soundings above are to the freezing mark, the dashed blue line the middle of the image that is angled to the right at 45°. Evaporational cooling should help somewhat in staving off warming but if temperatures warm more than forecast, we could see more mixing
Mesoscale bands of heavy snow may not push far enough onshore
Surface temperatures ahead of the storm in the upper-30s near the coast, urban heat island effect could retard snow accumulation
Fast moving nature of the storm, total precipitation window only 12 hours
Small window for the best moisture support at the 850 mb level. No real evidence to suggest a low-level jet carrying a ton of moisture into the region.
NAM model forecast of 850 mb relative humidity and winds. There’s not too big of an area of completely saturated air at this level, and winds are not strong at this level either.
