The slow-moving storm system that brought us heavy rain overnight last Friday into Saturday continues to linger off the coast of the Northeast, finally exiting by tomorrow. Rain chances will exist today, but give way to better conditions tomorrow. More rain is possible overnight into Wednesday, before drier weather works its way in on Thursday.
Rest of today – cloudy, with an increasing chance for showers in the afternoon and evening hours. High temperatures in the mid-60s. Overnight lows in the mid-50s.
High resolution rapid refresh model simulated radar for 4:45 PM today
Tuesday – with this low finally exiting, we should see a sunny day with temperatures warming into the low-70s. The sunny weather doesn’t last, as clouds increase overnight and rain is possible. Lows in the mid-50s.
Wednesday – conditions should improve after the morning hours, when the cold front that produces the rain chances overnight into Wednesday moves offshore. High temperatures should rebound nicely into the upper-60s. Overnight lows will be cooler in the low-50s behind this cold front.
Weather Prediction Center surface forecast for 8AM Wednesday
Thursday – high pressure should take over and result in a sunny day with high temperatures in the low-60s. Overnight lows going into Friday in the low-50s.
It’s been four months (!!) since I’ve done one of these detailed forecasts. I’m a bit out of practice but trying to get back into the groove. Lucky for me, I picked a day to forecast that has a decent bust potential for precipitation. I’ll discuss that below.
Friday is going to start off decently enough. It should end up being the warmest day of the week. However, it’s also going to be the start of a protracted period of unsettled weather that will affect the weekend. A flash flood watch is in effect late overnight Friday going into Saturday for this reason.
My Forecast High: 70°F | Low: 58°F | Max sustained winds: 30 mph | Total precipitation: 0.10″ – verification for temperatures and precipitation will come from METAR data for the period between 2AM Friday and 2AM Saturday (06Z Friday to 06Z Saturday) at LGA. Wind speed verification will draw on the daily climate summary from the National Weather Service.
Verification High: 76°F | Low: 56°F | Max sustained winds: 24 mph | Total precipitation: 0.16″ – I did decently forecasting the low, and the total precipitation. Hedging way down on precipitation totals towards the NAM solution on a slower moving storm was a good idea. On the low temperature, I think a 2°F margin is acceptable here. Being off by 6°F on the high temperature here constitutes a forecast bust that I’ll put a post-mortem together for – as it turns out the bust happened here and not with precipitation. Winds were also not as strong as anticipated. I should have hedged a bit down too with less intense precipitation anticipated.
Weather Prediction Center surface forecast for 8PM Friday
Synoptic Set Up We begin the period in the warm sector of a low with a center forecast to sit over southwestern Quebec. A secondary surface low is forecast to form over the OH valley and strengthens as it briefly moves northeast. This low is then forecast to stall out and retrograde northwest as it matures and occludes. This will lead to a protracted period of precipitation, with the primary focus being along a cold front moving through Sat morning. This may result in the best chance for heavy rain being outside the forecast period.
At the 850 mb level, a strong low-level jet will provide efficient moisture transport. At 500 mb we’ll be downstream of a longwave trough, with an embedded closed low that becomes cutoff (this mid-level cutoff low will be tied to why the secondary surface low retrogrades). The best vorticity and divergence (lift) associated with this upper low seems to move through after forecast period according to NAM forecast model. GFS has a bit earlier timing, and hence brings precipitation in earlier Friday. Finally, at the 300 mb, there’s not much evidence of enhanced divergence and lift at this level since, we’ll be east of any favorable entrance/exit regions of a 300 mb jet streak.
NAM forecast model’s depiction of the 500 mb layer at 11PM Friday. The cut off low referenced above is circled in green. The shades of yellow-purple indicate increasingly strong vorticity, which is linked to divergence and enhanced lift.
High Temperatures GFS and NAM MOS are in pretty close agreement here. It should be warmer than average, since we’ll be in the breezy warm sector of a low as mentioned above. Limitations on warmth will be evaporational cooling due to precipitation, but this doesn’t appear to be a factor until late in the forecast period, past normal times for peak temperatures. The other factor is thick cloud cover. However, temperatures will largely be driven by warm advection tomorrow and not necessarily solar heating. EKDMOS suggests a temperature over 70ºF. In deference to this ensemble model, I’ve sided with the warmer GFS and EKDMOS (as well as National Blend of Models) and call for a high temperature of 70ºF.
GFS MOS output
NAM MOS output
Low Temperatures NAM and GFS MOS are again in close agreement. With warm advection happening during the course of the overnight hours (strong winds at large angles to isotherms, southerly flow), have no reason to disagree that temperatures could actually go up early then back down a touch before rising again with daybreak, and I’m going with an overnight “low” of 58ºF that is well above average for this time of year.
NAM showing temperature contours and wind direction/speed for 2AM Friday. Note the direction of the wind barbs (pointing from south) is crossing at large angles of relatively closely packed isotherms. This is a set up favorable for warm advection (transport of warm air).
Max Sustained Winds NAM is lower on winds than GFS, but the ensemble EKDMOS skews towards faster GFS solution. This makes sense with heavy rain possible and downward momentum transfer. Winds are forecast to back from south-southwest to south-southeast during the period. These directions don’t typically produce the strongest winds climatologically. However, a strong 45-60 knot low-level jet aloft mixing down with precipitation could easily top 20 knots, especially if elevated convection and thunderstorms materialize. I’m going with the EKDMOS 50th percentile range and going with 25 knots.
The NAM forecast sounding at 5PM tomorrow shows considerably drier low-mid levels.
In contrast, the GFS forecast sounding shows a deep saturated layer indicative of ongoing precipitation by 5PM tomorrow.
Total Precipitation There’s a large spread between NAM and GFS on forecast totals (more than 0.50″) because the GFS is coming in with precipitation starting much earlier in the forecast period than the NAM. The local forecast office seems to buy more into the NAM solution due to its consistency with slower onset of heaviest precipitation. There is some indication as well of MUCAPE present in SREF plumes, could result in some elevated convection that would boost precipitation totals. Any faster timing and/or burst of elevated convection could cause heavier rain to fall earlier, resulting in a forecast bust.
Counting against that, I don’t see any strong signal for frontogenesis at the 850 mb level enhancing lift. SREF doesn’t show too much in the way of strong lift either. Still, the fact that SREF ensemble shows much heavier precipitation totals are not far off to the west during this forecast period makes me a bit nervous.
Lastly, moisture isn’t a total lock, and there’s some evidence of drier air offshore and pockets of dry air moving through from the west at times. NAM is notably drier than GFS at both outset of the forecast and throughout the forecast period, as seen in the comparison forecast soundings above. Training of storm cells possible with steering currents set up parallel to the forecast orientation of the cold front.
The same storm system that impacted the Deep South this weekend with severe weather, including several tornadoes that caused fatalities, swept through the area overnight. Some severe wind gusts were reported, and area transit networks experienced some delays due to storm-related damage. As this storm departs east, it will continue deepening, resulting in strong winds the remainder of today. Another storm system is forecast to move in to the region Thursday and going into the weekend. Temperatures during the week are expected to be mostly around normal for this time of year.
Rest of today – windy, with decreasing cloud cover. Steady west winds between 20-30 mph later in the day. This will help bring colder air into the area, with highs already peaking this morning in the low-60s then dropping back to the mid-50s by this afternoon. Overnight lows in the low-40s with partly cloudy skies.
Tuesday – sunny day, with winds calming and seasonable high temperatures in the low-60s. Overnight lows in the mid-40s and mostly cloudy.
Weather Prediction Center surface forecast for 8AM Wednesday
Wednesday – increasing clouds as a backdoor cold front works its way through. High temperatures in the low-60s. Overnight, mostly cloudy with lows in the mid-40s.
Thursday – chance of rain as a low tracks slowly from the Plains to the Great Lakes. East of this low, a slow moving warm front could touch off showers during the day and overnight Thursday. High temperatures around 60°F, overnight lows quite mild due to the influence of the approaching warm front and warm advection, in the low-50s.
Two distinct storms will affect weather in the area this weekend going into next week. The first is the remnant of the once mighty “bomb” cyclone that brought an abrupt return of winter conditions to the northern Plains states and Upper Midwest. The second will be a storm developing over Texas that could be a severe weather threat down South. Neither should result in a washout as the bulk of precipitation associated with these storms is timed to fall later in the day or overnight. Temperatures will be largely above normal during this period.
Rest of today – cloudy with chance of drizzle early. High temperatures around 60°F. Overnight lows in the mid-50s. Winds are forecast to turn to the south ahead of an anticipated cold front and in the wake of a warm front passing. Rain should accompany this frontal passage overnight.
Weather Prediction Center surface forecast for 2AM Saturday
Saturday – warm day in store with highs reaching into the low-70s despite mostly cloudy skies as the cold front passing overnight is forecast to stall and become stationary during the day. Overnight lows in the mid-50s again.
Sunday – shower chances increase as the next storm approaches. Temperatures will be cooler with highs in the low-60s due to clouds and rain. A second, more vigorous cold front is forecast to pass overnight into Monday. Rain, heavy at times, possibly with thunderstorms as overnight lows fall into the mid-50s.
GFS model output for 8PM Sunday
Monday – rain associated with this second storm should clear out around lunchtime. Cloudy day forecast now, but could see more breaks in the clouds and warmer temperatures in the upper-60s.
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.
A cool start to the weekend should give way to a nice couple of days before another storm moves in to start next week. During this period, high temperatures will start well below normal, then rise above average before finally settling around average. Looking ahead, another storm system appears to impact the area late next week, bringing a colder weekend next week in its wake.
Rest of today – cool, cloudy with high temperatures only in the mid-40s. Increasing rain chances towards the evening and overnight hours. Rain should taper off overnight then we should see overnight lows stabilize in the low-40s as warm advection takes hold.
Saturday – clouds diminishing as the low responsible for the rain moves over the Atlantic to our south. High temperatures in the mid-60s, maybe a touch warmer if we see clouds break earlier than forecast. Overnight lows milder in the upper-40s.
Weather Prediction surface forecast for 8AM Sunday
Sunday – high pressure stays in control and gives us a pleasant, mild day with high temperatures in the low-60s. The high pressure and nice weather doesn’t stick around long though, with another storm system approaching during the overnight hours going into Monday. Overnight lows should hold around 50ºF as rain starts to fall.
Monday – despite clouds and rain sticking around, temperatures will surge to about 70°F with a warm front forecast to pass through.
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
