Summer-like warmth has given way to more seasonable temperatures for this time of the year. The return to normal temperatures will be accompanied by the possibility of rain. Later in the week, temperatures will climb back up again as we are forecast to be back in the warm sector of another approaching storm. This storm should bring some rain Friday and overnight into Saturday, resulting in what should be a decent weekend
Rest of today – mostly cloudy, temperatures in the upper-50s to around 60ºF. Increasing chance for showers later this evening, around 6PM when a line of showers accompanying a cold front is expected to hit the area. Overnight lows behind this front will be much cooler than last night, in the mid-40s.
High resolution rapid refresh simulated 1-km radar for 6PM tonight
Wednesday – should be a nice day with mostly sunny skies and temperatures in the upper-50s. Overnight lows will be cool, around 40ºF.
Thursday – cool start to the day results in high temperatures around the mid-50s with mostly sunny skies and increasing clouds. Overnight lows climbing into the upper-40s.
Weather Prediction Center surface forecast for 8AM Friday. Note that we’ll be in the warm sector of this storm for a good part of the day.
Friday – warmer, with high temperatures in the mid-50s. Chances for rain increasing later in the day with a cold front forecast to be approaching from the west. Overnight lows in the low-50s.
During my time taking classes as part of Penn State University’s Undergraduate Certificate in Weather Forecasting, we were taught that understanding the climatology of the location you are interested in is an important prerequisite for making accurate forecasts. This post continues on this theme, adding a climatology for April.
City Name / Station ID: New York, NY (LaGuardia Airport – KLGA)
Local Geography and Topography
Station Elevation: 10 feet above sea level.
Station Location: LaGuardia Airport (KLGA) is situated on the north shore of Queens along the East River, approximately 6 miles east-northeast of Midtown Manhattan.
KLGA’s location within the broader NYC area, as seen in a Google Maps terrain view
Important Topographical Features: New York City is located in the extreme southeastern corner of New York State, bordering suburban New Jersey and Connecticut. These suburban regions combined with those in Long Island comprise the Greater New York City Metropolitan Area, which is the most populous urban agglomeration in the United States and one of the populous urbanized areas in the world with an estimated population of 18 million. New York City itself sprawls across the coastal plain around the Hudson River estuary. The terminal moraine formed by glaciers of the last Ice Age result in a ridge of higher terrain that cuts a swath from southwest to northeast across the boroughs from northern Staten Island, northern Brooklyn, southwestern through central and northeastern Queens. Otherwise, the city itself is low lying. This ridge varies in height between 200-400 feet, rising sharply from south to north, but tapering more gently north. North and west of the city (about 30-50 miles away), lie significant elevations of the Catskills (north), Poconos (west), Taconics that are part of the broader Appalachian Mountain Range. The elevations of the lower foothills can range from 1000-1500 feet. Some of the elevations in the Poconos and Catskills, west and north of KLGA respectively, peak between 2000-3000 feet. The open expanse of the Atlantic Ocean lies south of KLGA and New York City. Long Island Sound also lies east-northeast. The vast urbanized area of the NYC metropolitan region has significant effects on local microclimates via differential heating (urban heat island effect). KLGA is in a low-lying area sensitive to UHI effects and marine influences.
On winter mornings, ocean temperatures which are warm relative to the land reinforce the effect of the city heat island and low temperatures are often 10-20 degrees lower in the inland suburbs than in the central city. The relatively warm water temperatures also delay the advent of winter snows. Conversely, the lag in warming of water temperatures keeps spring temperatures relatively cool. One year-round measure of the ocean influence is the small average daily variation in temperature.
National Weather Service – NYC Office
Wind Patterns
Below is a wind rose – you can read more about how to interpret this chart here.
Frequency (percentage) of the single most common wind direction: Due northwest occuring about 13% of the time.
Directions that are most and least common: Most common wind directions following due northwest are due south (10%), west-northwest (9%), and due northeast (8.75%). Least common wind directions are east-southeast (1.25%), due east (2.5%), and due southeast (2.75%).
Direction(s) most likely to produce the fastest winds: Winds from the northwest, west-northwest, and to some extent the northeast and east-northeast tend to produce the fastest winds.
Direction(s) least likely to produce the fastest winds: Winds from the east-southeast, due east, and south-southwest are least likely to produce the fastest winds.
Impacts of wind direction on local weather: Like March northwesterly winds during April are likely tied to the passage of cold fronts and coastal storms. Cold air advection from these winds will still be quite robust during the beginning of the month especially, as record lows for this month suggest. Winds from the northeast are still tied to backdoor cold fronts arriving from the Canadian Maritimes, bringing a moist, cool maritime polar air mass, or the advance of coastal Nor’easter type storms. During April, sea surface temperatures around NYC become markedly cooler than the air temperature as average highs continue climbing in response to more direct sun angle on longer spring days. On days approaching record warmth, in an overall environment of otherwise light winds, you could even see some sea breezes start forming along the coasts.
Maximum observed two-minute wind speed for the month: 48 knots (55 mph).
Temperature and Precipitation Averages/Records
Temperature units are in Fahrenheit and precipitation is in inches.
Worth Noting
April is the first month in the spring when record high temperatures exceed 90ºF. Record lows still routinely dip into the 20s during this month, reflecting the variability that spring can bring. The most recent record low was set in 2021, at 29ºF for 4/2. April also has the second highest single day precipitation record with 6.69″ falling on 4/15.
High pressure gives way to a be coastal storm that will sideswipe the area. Following this, we’ll see a brief warm up, but temperatures will cool off towards the end of the week. We have rain chances overnight into tomorrow and Friday night.
Rest of today – high temperatures around 50°F. Increasing clouds ahead of a coastal approaching from the south. Overnight, chance of rain with low temperatures around 40°F.
Weather Prediction Center surface forecast for 8AM Wednesday, depicting a coastal storm passing us to the southeast.
Wednesday – winds increasing to 15-20 mph in the afternoon. High temperatures warming into the low-60s be with clouds dissipating and winds shifting to the southwest. Overnight lows drop back into the low-40s behind the passage of a dry cold front. Winds will shift to a colder northwesterly direction.
Thursday – cooler with partly sunny skies and high temperatures in the mid-50s. Low temperatures colder in the upper-30s.
Friday – another low approaches from the southwest. High temperatures below average in the mid-40s, rain chances increase later in the day with the low pressure drawing closer. Rain chances continue into the overnight hours with lows in the low-40s.
We will have a warm though not too sunny start to the weekend. A solid chance for rain hits Sunday with the passage of a cold front. After that, temperatures will drop to below normal levels again. Looking ahead into next week, there should be a dry start to the week but a coastal storm may impact the area mid-week. There’s some outside chances for snow with this storm.
Rest of today – cloudy, with some chance of light rain though most rain should remain over interior. With southwesterly flow, despite clouds we should still reach into the upper-50s to 60°F. A cold front approaching from the west is forecast to stall out and acquire semi-stationary characteristics. Thanks to the continued influence of high pressure off to our east, we should stay mostly dry today. Overnight lows should be warm, near 50ºF.
Saturday – the warmth continues, with high temperatures forecast to reach well into the upper-60s though clouds will still linger around with the stationary front to our west. Overnight lows will be similar to tonight around 50ºF.
Weather Prediction Center surface forecast for 8AM Sunday
Sunday – the stalled frontal boundary finally picks up forward momentum and pushes through the area as a cold front. Ahead of it, temperatures will still be mild in the mid-50s. A line of showers is expected with this front during the day. Overnight lows behind this cold front will be considerably colder, in the low-30s.
Monday – dry, sunny weather, but with a chilly start to the day, temperatures are expected to only be in the upper-40s to near 50ºF, slightly below normal. Overnight lows are expected in the mid-30s.
This week’s weather features the prominent impact of a slow moving, strong area of high pressure over the region. That translates to calm, generally sunny conditions with a warm up towards the end of the week as the high slides east and we end up in a milder southwesterly flow on its western edge.
Rest of today – sunny but with cool northerly winds, we will remain below average with highs in the upper-40s and overnight lows in the low-30s
Wednesday – once again we have a cooling influence this time with northeast onshore winds that will keep temperatures below normal in the mid-40s with sunny conditions. Overnight lows again in the low-30s.
Weather Prediction Center surface forecast for 8PM Wednesday
Thursday – as the high pressure moves east of us, we see a shift in winds to the south. This should result in high temperatures right around average in the mid-50s. Should be comfortable spring weather for the Yankees home opener with a light wind blowing from right to left field. This is a welcome contrast from last year, when snow postponed the home opener! Overnight lows will be milder also in the mid-40s
Friday – the warm up continues with high temperatures kicking above normal in the low-60s. It appears the limiting factor for temperatures will be increasing clouds ahead of a cold front. Overnight lows in the upper-40s
Much above average warmth last Friday resulted in a spectacular light show from passing thunderstorms. In the wake of this, temperatures have dropped into a below average range, considerably cooler than this weekend. There will be a warm up later in the week though, along with some rain chances.
Rest of today – mostly sunny with high pressure in control. High temperatures in the mid-40s, overnight lows dropping into the mid-30s.
Tuesday – not too much of a difference between these two days. High pressure remains in control. High temperatures maybe a little warmer in the upper-40s, overnight lows again in the mid-30s.
Weather Prediction Center surface forecast for 8AM Wednesday
Wednesday – as high pressure shifts eastward, we should see a shift in winds to the west, allowing temperatures to warm into the low-50s. Overnight lows around 40°F.
Thursday – chance for showers with a frontal boundary moving through. High temperatures in the low-50s with mostly cloudy skies. Lows in the low-40s.
This weekend will see a warm start but then a cool down into the below normal range going into next week. A rumble of thunder and showers will precede this cool down. Weather looks pleasant for St. Patrick’s Day festivities and the NYC Half Marathon this weekend.
Rest of today – mostly cloudy with some breaks of sun after a warm front passes over shortly and we sit in the warm sector of the same storm that tore through the central US earlier this week. As the trailing cold front pulls through this evening, it could provide enough lift for some additional showers and possibly a couple thunderstorms. High temperatures will be above average in the low-60s, mid-60s if some sun breaks through while we’re in the warm sector. Overnight lows behind the cold front should be in the low-40s.
Weather Prediction Center surface forecast for 8PM Friday
Saturday – bright, sunny day with high pressure building behind the cold front. Temperatures cooler, around 50°F. Overnight lows much cooler in the low-30s.
Sunday – cold start to the NYC Half Marathon in the low-30s but high temperatures will end up in the mid-40s with lots of sun. Overnight lows again around the freezing mark
Monday – increasing clouds with a possibility for some precipitation but chances are too low now to call. Highs in the mid-40s and overnight lows back down in the low-30s again.
After a chilly start to March, things will take a turn towards much more seasonable weather this week. Still, temperatures will be slightly below average on several days. Precipitation chances don’t pop up until Friday when an approaching cold front should bring a warm up and then rain.
Rest of today – sunny, with a high near 50°F. Overnight lows around freezing.
Tuesday – a weak cold front passes through in the morning, but there will not be enough moisture for precipitation. High temperatures will be cooler than today, in the mid-40s with mostly sunny skies. Overnight lows will be cooler around 30°F.
Wednesday – sunny skies and a high temperature again in the mid-40s. Clouds will be on the increase overnight as a warm front approaches from the southwest. Overnight lows will be a touch warmer in the upper-30s.
Weather Prediction Center surface forecast for 8PM EDT Wednesday
Thursday – warmer but mostly cloudy with high temperatures in the mid-50s. Overnight lows expected to be in the mid-40s with the chance of rain increasing.
As we spring forward this Sunday, our weather pattern finally takes a step forwards towards spring as well. Rain will accompany this warmup, then we start next week with temperatures close to average for this time of year.
Rest of today – Increasing clouds as an area of low pressure moves offshore well to our south. High temperatures in the upper-30s. A 500 mb (upper level) shortwave trough passing through overnight could provide enough lift for some scattered flurries. Lows dipping to around freezing.
Saturday – High temperatures in the mid-40s with lots of sun as high pressure temporarily exerts its influence. Overnight lows in the mid-30s. Rain starts overnight going into Sunday as a storm system draws near.
Weather Prediction surface forecast for 8AM Sunday
Sunday – rain during the morning with improving conditions later. Overcast to start with cloud cover decreasing as the storm departs to the east. High temperatures around 50°F. Overnight lows in around 40°F
Monday – sunny and seasonable with highs in the upper-40s. Overnight lows cooler than Sunday in the mid-30s.
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.
