As with last week, high pressure will play a big role in sensible weather this week. Rain chances are going to be limited to later this week when a frontal system moves across the area. Temperatures will be warm to start in the upper-80s then cool off later in the week back into the mid-80s.
Rest of today – early showers move through then we’ll see gradual clearing. Temperatures in the low-80s. Overnight lows in the low-70s.
Weather Prediction Center surface forecast for 8PM Tuesday
Tuesday – much warmer with temperatures in the upper-80s, and lots of sun with high pressure building and taking over. Overnight lows in the low-70s.
Wednesday – continued warmth with highs again in the upper-80s and mostly sunny skies. Overnight lows in the low-70s.
GFS model output for 1000-500 mb thickness, surface pressure, and precipitation valid for Thursday 8PM
Thursday – clouds increasing late with high temperatures in the mid-80s. Chance for showers and thunderstorms late and going into the overnight hours. Overnight lows in the low-70s.
It looks like we’re going to get lucky for Independence Day this year in NYC. While many areas of the Eastern US may see a chance for rain, the Northeast should remain under the influence of strong enough high pressure that we stay dry. That means good news for all the outdoor activities folks have planned coming up! This will be my first detailed forecast that draws on the recently released GFS FV3 forecast model upgrade, so it will be interesting to see how this upgrade performs.
My Forecast High: 88°F | Low: 74°F | Max sustained winds: 15 mph | Total precipitation: 0.00″ – verification will come from METAR data for the period between 2AM Thursday and 2AM Friday (06Z Thursday to 06Z Friday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report
Verification High: 93°F | Low: 71°F | Max sustained winds: 16 mph | Total precipitation: 0.00″ – Spot on with the wind forecast for yesterday. It was a good call to bump that forecast up with possible sea breeze enhancement in the mix. Unfortunately, these winds didn’t do enough to cool temperatures off during the day, and I was off by 5°F for the high temperature. Skies turned out to be pretty much sunny the whole day and while statistical forecast models should factor in urban heat island effects, it would have been prudent to still have forecast at least 90°F in light of this. Also, given the 850 mb relative humidity profile, I should have probably sided with a less cloudy outlook that would have favored warmer high temperatures. Of note, the new GFS model had issues initially with a cold bias that should have been corrected. In this case, it was warm on the low, but too cool on the high. This is worth noting even though these two points of data aren’t necessarily indicative of a trend.
Weather Prediction Center surface forecast for 8PM Thursday
Synoptic Set Up A stationary front currently along the northern tier of Illinois, Indiana, Ohio, Pennsylvania and western New York will attempt to push northwards tomorrow as a warm front. However, with a 500 mb ridge aloft and an area of surface high pressure over the Northeast and translating over the Gulf of Maine, this frontal boundary is forecast to become stationary, holding just southwest of the NYC metro area. Moisture above the surface looks modest, and without any impulses of low pressure at the surface or troughs aloft, there doesn’t appear to be any support for precipitation.
NAM 500 mb heights and vorticity valid for 8PM Thursday. Note the presence of a ridge over the Northeast (upside-down U pattern of the black height lines)
High Temperatures GFS, NAM, and NBM agree that July 4th a warm day. All three statistical models come in at between 88-89ºF for high temperatures. EKDMOS (ensemble MOS) 50th percentile matches is very close, at 87-88ºF. The only hitch to warm temperatures is that NAM shows the possibility for low clouds and wind directions are forecast to veer from east-northeast to southeast. Cloud cover could eat into temperatures rising too much, and winds coming from the directions indicated would bring a cooling influence of marine air with sea surface temperatures still in the low-60s at this point in the season. With these factors in mind, but also keeping in mind the effects of the urban heat island, I’ll side with a middle of the road forecast of 88ºF.
Low Temperatures NAM and GFS MOS both show the chance that the low temperature during this forecast period may actually fall overnight going into Friday. Either way, both are very close showing lows ranging 73-75ºF. EKDMOS 50th percentile shows 74-75ºF for the low. Increasing cloud cover should stall any serious radiational cooling, and there’s little indication of any temperature advection either way with weak winds. I’m again going with the mean here and siding with a forecast of 74ºF for the low.
Max Sustained Winds NAM, GFS, and NBM average out to 8 knots for the max sustained wind tomorrow. EKDMOS is more aggressive with winds in the 50th percentile about 13-15 knots. While forecast soundings don’t show too much evidence to support a forecast above 10 knots since the entire wind profile looks remarkably calm for tomorrow, this same tendency to weak synoptic winds could allow for a fairly robust sea breeze to develop, and this could be the what allows sustained winds to top 10 knots. I’ll go with the low-end of the EKDMOS and call for 13 knots (15 mph).
GFS forecast sounding for 8PM Thursday. Indications of high clouds are shown, but low levels remain dry. Wind profile in this forecast looks weak with no winds above 20 knots forecast anywhere in the atmospheric column.
Total Precipitation High pressure is forecast to be in control, with a 500 mb ridge in place. There aren’t any frontal boundaries moving through to create lift and even if there were, there simply isn’t enough moisture to support precipitation. Both the forecast sounding above and 850 mb forecast for relative humidity and winds below show moisture values that are insufficient to bring about any precipitation.
NAM forecast for 850 mb winds and relative humidity at 8PM Thursday
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 July.
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 south (13.5%).
Directions that are most and least common: Most common wind directions include due southwest (9.5%), due northeast (9.25%), and due northwest (8.5%). Least common wind directions are east-southeast (1%), due east (2%), and due southeast (2.5%).
Direction(s) most likely to produce the fastest winds: Winds of 16.5-21.4 knots are most frequently found coming from due northwest, and due south.
Direction(s) least likely to produce the fastest winds: As is the case with several other months, the least common wind directions of due east, east-southeast, and due southeast also rarely seen winds in excess of 16.4 knots.
Impacts of wind direction on local weather: July winds are remarkably similar to June. Southerly and southwesterly winds are a bit more common in July than in June, and northwesterly winds a little less so. This pattern of winds continues to suggest the influence of mid-latitude lows tracking inland north of the area, bringing more southerly warm sector flow. As with June, persistent, subtropical high pressures continue to be a factor at times in July over the western North Atlantic. The clockwise flow around these high pressure centers would result in more southerly and southwesterly winds, which can lead to the onset and maintenance of heat waves. Southerly winds (along with easterly and some northeasterly winds) would bring cooler, and more stable marine air, sometimes in the form of sea breezes. Sea breezes can become commonplace during this month whenever there’s light synoptic winds. At this point in the year, the average max temperatures well exceed the threshold of 5-7°F warmer than sea surface temperatures (which are slowly climbing through the mid-60s) required for sea breezes.
Maximum observed two-minute wind speed for the month: 46 (53 mph)
Temperature and Precipitation Averages/Records
Temperature units are in Fahrenheit and precipitation is in inches.
Worth Noting
July is the month when average temperatures peak at 86ºF. However, sweltering heat is possible well beyond this point, and record highs in this month are frequently in the upper-90s. Meanwhile, record highest low temperatures can easily be in the upper-70s and low-80s – making for very uncomfortable nights. July is also on average the wettest month of the year, which makes sense given the possibility for thunderstorms and a connection to tropical moisture.
Weather this week will mostly be governed by the presence of high pressure, with the exception of a cold front sweeping through Tuesday night into Wednesday that could bring some showers and thunderstorms. Temperatures will remain warm in the upper-80s and low-90s during this time. July 4th festivities look to be safe from any rain at this time.
Rest of today – sunny skies with high temperatures in the mid-80s. Overnight lows in the low-70s.
Weather Prediction Center surface forecast for 8PM Tuesday
Tuesday – mostly sunny with high temperatures in the upper-80s, close to 90°F. Chance of showers and thunderstorms later in the day as a cold front approaches from the north. Overnight lows in the low-70s.
Wednesday – high pressure starts building again with mostly sunny skies expected. High temperatures in the upper-80s with overnight lows in the low-70s.
Climate Prediction Center forecast for temperature trends between Jul 6-10, showing possibility for above average warmth to continue into the weekend.
Thursday (Independence Day) – another day of slightly above average warmth with high temperatures forecast in the upper-80s. Increasing clouds due to the approach of a weakening warm front from the southwest. Overnight lows in the low-70s, rain should hold off for fireworks viewing.
Earlier showers and thunderstorms today presage the passage of a warm front over the area. Behind this, high pressure begins to build tomorrow and persists through the end of the week. Temperatures during this stretch are likely to consistently reach into the upper-80s and low-90s in the city. As if on cue, the first full week of summer this year may also see a possible heat wave.
Rest of today – clouds gradually diminishing towards the evening. A few scattered showers still possible with a cold front forecast to move through later. High temperatures in the low-80s with cloud cover in place. Overnight lows will be mild in the low-70s.
Weather Prediction Center surface forecast for 8AM Wednesday
Wednesday – relatively warm start to the day allows temperatures to climb into the low-90s in the city with the urban heat island effect. Mostly sunny skies with high pressure now in control. Overnight lows in the low-70s.
Thursday – high temperatures again into the low-90s with lots of sun. Luckily, the position of this particular high pressure doesn’t translate to the influx of a humid airmass, so the overall feel of these temperatures won’t be as muggy. Overnight lows in the low-70s.
GFS 850 mb temperature anomalies for 2PM Thursday. Warmer than normal 850 mb temperatures can be a good indicator of hot surface temperatures.
Friday – yet another day of 90°F+ temperatures possible, which would mean an official heatwave. Still mostly sunny with high pressure remaining in control over sensible weather. Overnight lows continuing to be mild, in the mid-70s. Great beach weather!
Lingering showers and cloudiness should clear the area later today. Summer officially starts today and a welcome pattern change will coincide with this, giving us excellent weather this weekend. A break from the rain with lots of sunshine is in store. Upper level ridging should block any inclement weather from hitting until a weak storm system passing late Monday into Tuesday.
Rest of today – skies gradually clearing by late afternoon. High temperatures moderated by cloud cover, rising to the upper-70s. Overnight lows in the low-60s. Air mass will be drying out behind a cold front passing today.
Weather Prediction Center surface forecast for 8AM Saturday
Saturday – sunny with highs in the low-80s. High pressure building over Ontario and Canada should keep things nice and calm. Overnight lows in the mid-60s.
Sunday – another sunny day with highs in the low-80s. Overnight lows in the mid-60s.
GFS model output of 500 mb heights and vertical vorticity valid for 8PM Monday
Monday – mostly sunny with increasing clouds late and high temperatures in the low-80s. Overnight lows in the upper-60s with chances for rain.
A cold front that pushed through overnight leaves us with some cool, crisp air to start the weekend. The first half of the weekend will be characterized by plenty of sun before a slow moving frontal system approaches later in the weekend. This will bring back chances for showers and thunderstorms going into next week when it appears an active weather pattern could take root.
Rest of today – mostly sunny with high temperatures in the mid-70s. A post-frontal trough may touch off a few isolated storms later in the afternoon. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8AM Saturday, showing high pressure off the coast of NC
Saturday – mostly sunny with highs in the low-80s. High pressure takes hold off the Southeast US coast, with clockwise return flow bringing some warmer air this way. Overnight lows in the low-60s.
Sunday – with a frontal boundary approaching from the northwest, clouds increase and chances for showers and thunderstorms do also. High temperatures should still be mild in the low-80s. As the Overnight lows in the mid-60s with rain chances continuing.
NAM output of 1000-500 mb thickness, surface pressure and precipitation for 8PM Sunday.
Monday – the frontal boundary that approaches from the northwest weakens and stalls out. This is partly due to flow at the upper levels flattening out/becoming somewhat parallel to the front’s orientation, and partly due to the high pressure that by this time will become anchored over Bermuda. Multiple waves of low pressure are forecast to move along this stalled front bringing another day that holds chances for showers and thunderstorms. Prolonged southwest/westerly flow ahead of the cold front which really slows down should allow temperatures to reach the mid-80s despite more cloud cover and precipitation. Overnight lows in the upper-60s with yet more rain possible.
After a rainy start to the week, high pressure takes over during the mid-week period. Another storm system moves in Thursday. Behind this next bout of rain, a dry and mostly sunny weekend should await us.
Rest of today – skies clearing as a cold front pushing. Winds picking up with some subsidence (sinking air, since air mass behind the cold front is cooler and drier). High temperatures reaching into the upper-70s with this subsidence and some downsloping from the northwest. Overnight lows in the mid-60s.
Weather Prediction Center surface forecast for 8AM Wednesday
Wednesday – high pressure remains firmly rooted over the area. High temperatures in the mid-70s with mostly sunny skies. Overnight lows in the low-60s.
Thursday – a developing low closer to the coast and another one further inland over the Great Lakes will bring showers and thunderstorms to the area. First, like Monday, a warm front will lift through earlier in the day, then a cold front is expected to follow later on. High temperatures in the low-70s due to rain and cloud cover. Overnight lows in the upper-50s.
NAM model for 1000-500 mb thickness and surface reflectivity at 8AM Thursday, showing a distinct area of rain associated to a low emerging off the coast of the Delmarva Peninsula
Friday – with a cool start, temperatures top out in the mid-70s. Mostly sunny in the wake of the cold front Thursday. Overnight lows in the low-60s.
High pressure will build over southwestern Quebec this weekend, and this will be the predominant influence on sensible weather in the area. This should result in the first rain-free weekend in quite a while, so get out and enjoy it if you can. By the beginning of next week, rain comes back into the picture. Temperatures through the period will be at or slightly above average in the upper-70s.
Rest of today – filtered sun through a deck of higher clouds appears to be on the order of the day with a cold front stalling out and becoming stationary to our south. No rain though! High temperatures around 80°F. Overnight lows in the mid-60s.
Weather Prediction Center surface forecast for 8AM Saturday. That big area of high pressure over Quebec will be bringing us some sunny skies for a change.
Saturday – this will be the best day of the weekend with sunny skies as high be pressure builds north and high temperatures staying in the low-80s. Overnight lows again in the mid-60s.
Sunday – still a good day for being outside with more clouds expected and becoming mostly cloudy late. High temperatures in the upper-70s with overnight lows in the low-60s.
NAM output for 2PM Monday, by this time, it appears that a cold front bringing showers along with it will be nearing the area.
Monday – the next storm system comes through with a cold front forecast to pass Monday into Tuesday. Rain chances look to be sometime in the afternoon at this point. High temperature in the mid-70s with mostly cloudy skies and overnight lows in the low-60s.
This week starts off right around average for this time of year, with pleasant, sunny conditions. High pressure remains in control for a good part of the week and temperatures start creeping up as the high pressure continues moving east and offshore. Clockwise flow around this exiting high pressure from the southwest and west will help warm temperatures up before the next chance for rain comes in Wednesday and Thursday.
Rest of today – clear skies with high temperatures in the low-70s. Overnight lows in the mid-50s.
Weather Prediction Center surface forecast for 8AM Tuesday
Tuesday – high pressure still in control, temperatures again in the low-70s with plenty of sun. Overnight lows warming up into the low-60s.
Wednesday – the high pressure center will be southeast of us and a warm front will push through. This should allow temperatures to reach into the low-80s with partly sunny skies. We could see an afternoon shower or thunderstorm as a result of increased instability. Overnight, a prefrontal trough and cold front is forecast to push through and lead to more chances for showers and thunderstorms with low temperatures in the mid-60s.
Pivotal Weather rendering of GFS model output for 1000-500 mb thickness and precipitation, 2AM Thursday
Thursday – partly sunny skies again with continuing chances for shower and thunderstorms later in the day. High temperatures in the low-80s. Overnight lows in the mid-60s.
