High pressure and fair weather will get punctuated with the passage of a cold front scheduled to push through overnight into Sunday. This front could touch off a few thunderstorms. Temperatures during this time will be slightly above average in the upper-70s. A cooler airmass should finally move in Monday with more easterly onshore flow.
Rest of today – sunny with high temperatures in the upper-70s. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8PM Saturday
Saturday – warmer, with high temperatures around 80°F and sunny skies. Overnight lows in the upper-60s. Scattered thunderstorms are possible overnight as a cold front pushes through
Sunday – sunny again with high temperatures in the upper-70s. Despite the cold front, we should see some warmth from downsloping northerly winds and subsidence in the wake of the frontal boundary causing compressional warming. Overnight lows in the low-60s.
NAM model output for 2PM Monday, mean sea level pressure and 10 m above ground level winds. Note the easterly flow in NYC imparted by the high pressure to our east-northeast
Monday – another sunny day with cooler high temperatures in the low-70s, overnight lows in the low-60s.
A warm start to fall yesterday gives way to cooler, drier weather that will actually feel like fall. Much as was the case last week, high pressure will be in control over the area. This should lead to generally fair weather. However, there is some chance for rain Thursday as a cold front pushes through.
Rest of today – mostly sunny with high temperatures in the upper-70s. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8AM Wednesday
Wednesday – high temperatures again mild in the upper-70s with warming influence of downsloping northwest winds. Overnight lows in the mid-60s.
Thursday – increasing clouds with high temperatures in the low-80s and overnight lows in the upper-50s. A chance of showers later in the day as a cold front approaches.
GFS model output for 2 meter above ground level temperature and 10 meter above ground level winds at 8PM Friday
Friday – high temperatures in the mid-70s with sunny skies and overnight lows in the low-60s behind the cold front.
The story of the weekend will be a continued stretch of fair weather with high pressure remaining in control. The positioning and movement of the high pressure center will result in a gradual warming pattern as winds turn to the south with high temperatures returning to summer-like levels in the low-mid 80s by the end of the weekend. A cold front scheduled to move through beginning next week will bring cooler weather back but warmer temperatures could make another return later next week, despite the autumnal equinox taking place Monday and fall formally starting.
Rest of today – sunny with high temperatures around 80°F. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8PM Saturday
Saturday – warmer, with high temperatures in the low-80s and sunny skies. Overnight lows in the mid-60s.
Sunday – sunny with high temperatures in the mid-80s. Overnight lows in the upper-60s.
Monday – another sunny day with high temperatures in the mid-80s, overnight lows in the mid-60s.
Climate Prediction Center short-range outlook for temperatures the second half of next week.
A weak frontal boundary passes through today. Behind this, high pressure will build and extend into the weekend. This persistent high pressure will result in mostly sunny conditions. Below normal temperatures in the low-70s will accompany northeasterly flow but a warming trend is forecast for the weekend as the center of high pressure shifts to the east.
Rest of today – mostly cloudy with a cold front pushing south then stalling out. Chances for light rain linger through the day. High temperatures in the upper-70s. Overnight lows in the low-60s.
High resolution rapid refresh simulated radar for 5PM today, showing some scattered light showers
Tuesday – high temperatures cool off into the low-70s behind the front. Winds turn to the northeast as high pressure builds over central Quebec. Overnight lows around 60°F but could dip into the upper-50s.
Wednesday – mostly sunny with high temperatures in the low-70s and overnight lows in the upper-50s.
GFS model output for surface pressure and winds valid at 2PM Thursday. The area of high pressure over the Northeast will serve to keep our weather fair, while pushing Hurricane Humberto safely out to sea.
Thursday – high temperatures remain in the low-70s, overnight lows in the upper-50s. It will definitely feel like autumn has arrived a few days early!
Easterly onshore winds will keep things cool to start the weekend. Strong high pressure slowly gives way to a frontal system late tomorrow, bringing a chance for rain. Behind this system, high pressure should build in again and persist, giving us some nice weather Sunday into next week.
Rest of today – mostly sunny with strong high pressure north of the area. Cool with highs in the low-70s under the influence of easterly onshore winds. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8AM Saturday
Saturday – clouds build ahead of an advancing warm front and the day should end up being mostly cloudy. High temperatures a bit warmer in the mid-70s with winds shifting to the south ahead of the warm front. Rain chances increase towards the evening and overnight hours, with lows in the upper-60s.
Sunday – a trailing cold front will pass through and conditions should improve with rain ending early and gradual clearing. Highs in the low-80s, with some assist from downsloping winds from the west and northwest. Overnight lows in the nid-60s.
GFS model output for 2 meter above ground level temperature and 10 meter above ground winds at 2PM Sunday
Monday – high temperatures in the low-80s with mostly sunny skies as high pressure continues to build. Overnight lows in the mid-60s.
Temperatures are on an upward trend towards midweek. A cold front moving in from the north brings the chance for rain and thunderstorms tomorrow into Thursday. Behind the cold front, a brief cool down to below normal temperatures occurs before temperatures go back to above normal in the low-mid 80s over the weekend.
Rest of today – early clouds should give way to some partial clearing by the afternoon, high temperatures in the upper-70s. Overnight lows in the upper-60s.
GFS model output for 2 meter above ground level temperatures and 10 meter above ground winds at 11AM Wednesday. Noticeably warmer temperatures will accompany the shift to southwesterly winds.
Wednesday – high temperatures in the upper-80s, with a chance for scattered showers and thunderstorms later in the day as a prefrontal trough associated with a cold front approaches. Overnight lows in the low-70s with continued chances for showers. Overall, a much warmer and more humid feeling, summer-like day with southerly winds and the presence of a high pressure center south of the area.
Thursday – clearing skies with highs in the low-80s. Cooler and drier behind the passing cold front. Overnight lows in the low-60s.
GFS model output for surface pressure and 10 meter above ground level winds on 2AM Friday. Winds by this time are forecast to have shifted to the northeast and east. Onshore flow will keep temperatures cool on Friday.
Friday – high temperatures remain in the mid-70s, overnight lows in the mid-60s as high pressure builds in briefly to the north. This will bring a cooler, northeasterly onshore wind to the area.
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 September.
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 northeast (9.5%).
Directions that are most and least common: Most common wind directions include due south (9%), due southwest (8.5%), and northwest (8%). Least common wind directions are east-southeast (1.5%), due southeast (2.5%), and due east (3.5%).
Direction(s) most likely to produce the fastest winds: Winds of 16.5-21.4 knots are most frequently found coming from due northeast, and due northeast. North-northwest, east-northeast, and due south directions can also see less frequent winds over 21.4 knots.
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: September’s wind profile sees a shift away from the general pattern of the summer months preceding it (June, July, August) during which southerly winds are predominant, and during which due south is the single most common wind direction. April is the last calendar month when due south isn’t the single most common wind direction, so it takes quite a bit of time in order for winds to shift off this summer pattern.
The most common wind directions in September are almost evenly split between northeasterly and northwesterly and southerly and southwesterly winds in percentage terms of frequency. Northwesterly winds are notably more frequent, and faster northeasterly and northwesterly winds start to appear in September as opposed to the summer months. Northwesterly winds in general will bring cooler, drier Canadian air into the region following cold fronts. Northeasterly winds, on the other hand, are related to backdoor cold fronts sweeping from the Canadian Maritimes, the onshore flow ahead of an advancing warm front, or a passing coastal storm.
The continued downward trend in southerly winds is likely a reflection of the diminishing influence of sea breezes as average land temperatures cool while average sea surface temperatures are still close to their peak (though also cooling). The narrowing gap between these two will tend to reduce the potential for sea breeze circulations to set up. However, these sea breezes can still exert an influence on local temperature and can still provide boundaries for convection. Southwesterly winds are also similarly capable of bringing in oppressive heat, as seen in the temperature section below.
Maximum observed two-minute wind speed for the month: 44 knots (51 mph)
Temperature and Precipitation Averages/Records
Temperature units are in Fahrenheit and precipitation is in inches.
Worth noting: September can still offer up oppressive heat, especially in the first half of the month. The monthly all-time record high of 102°F is also the second highest record temperature recorded for the year at KLGA (August has the hottest record high: 104°F). September’s monthly precipitation record of 4.63″ in one day is also has the 3rd highest single-day precipitation record after April and August. While it can get quite hot in September, it’s also possible for temperatures to get cold too, with the record low for the month in the low-40s! Average high temperatures dip back below 80°F and average lows drop below 60°F again in September after the summer months, marking a definite fall feel.
Labor Day weekend is shaping up to be a good one overall in terms of sensible weather. A dry cold front passage today sets the stage for high pressure to take control over the remainder of the weekend. The only wrinkle is a warm front forecast to pass Monday that could bring some rain. Looking ahead into next week, a warm up should precede another cold front mid-week. The big weather story this weekend will be much further south of us, as Hurricane Dorian takes aim at Florida as a dangerous Category 4 storm.
Rest of today – sunny with high temperatures in the mid-upper 80s. Overnight lows in the upper-60s.
Saturday – high pressure starts to build from the west, which will result in a cooler weather with northerly winds. High temperatures topping out in the low-80s with lots of sun and overnight lows in the mid-60s.
Sunday – high pressure will progress east, giving us another pleasant day with lots of sun and comfortable temperatures in the low-80s. Overnight lows warm up in the upper-60s with a warm front approaching from the southwest.
Monday (Labor Day) – chance for rain during the day as a warm front, then a weakening cold front approach. High temperatures in the low-80s with mostly cloudy skies. Overnight lows around 70ºF.
Hurricane Dorian Heading Towards Florida
Over the course of the last few days, Hurricane Dorian made a pass over the Northern Lesser Antilles, hitting the Virgin Islands, and Martinique, but sparing Puerto Rico. This was a blessing for an island still recovering from the devastation of Hurricane Maria. However, because Dorian avoided the disruptive influence of high terrain in Puerto Rico, it entered the open waters of the Western Atlantic north of the island ready for continued intensification. Unfortunately, various forecast models have been consistently depicting Dorian making landfall somewhere in Florida early next week as a dangerous Category 4 hurricane packing max sustained winds of 140 mph.
Latest GOES visible satellite imagery of Hurricane Dorian
Overnight going into today, Dorian’s been steadily strengthening and is now showing a markedly more symmetrical structure than before, along with an eye developing in visible satellite imagery. This suggests that the southerly shear and dry air that was afflicting the storm yesterday has abated somewhat. At this point, there is nothing really stopping Dorian from continuing to strengthen to a major hurricane.
National Hurricane Center official forecast for Dorian as of 11AM Friday
Forecasters continue to have high confidence that Dorian will make a turn towards a more westerly direction as high pressure builds over Bermuda and keeps building to the west. This will block Dorian from taking a northerly route away from Florida. Worryingly, forecast models have trended towards a slower and more southerly track overnight, then a turn north after landfall. On this current track, a large part of Florida would be affected by the storm for a considerable amount of time, increasing the risk of damaging storm surge and inland flooding from prolonged heavy rain.
After a week of hot, humid weather and several bouts of strong to severe thunderstorms, we will finally get a break from both the heat and the rain just in time to enjoy the weekend. Behind a cold front that’s slowly pushing south, high pressure will build in and usher in a Canadian polar airmass that will bring a noticeable change to high temperatures – 10ºF cooler in most cases. Rain chances return late in the weekend period.
Rest of today – showers associated with a wave of low pressure moving along the cold front that passed last night should end by noon. Mostly cloudy with gradual clearing. High temperatures in the upper-70s and overnight lows in the mid-60s.
NAM (North American Model) forecast for 2 meter above ground level temperature Saturday at 2PM
Saturday – mostly sunny, high temperatures in the upper-70s, noticeably drier feel with dew points much lower than the past few days with Canadian high pressure taking over. Overnight lows in the mid-60s.
Sunday – below average temperatures continue with high temperatures in the mid-70s. By this time, the high pressure center will have shifted to the northeast and will thus enable cooler, more moist onshore flow to influence the weather. We should see more clouds and could even see some scattered rain showers. Overnight lows in the low-60s.
Weather Prediction Center surface forecast for 8AM Sunday
Monday – high temperatures in the upper-70s with partly sunny or mostly cloudy skies. An area of low pressure (which could become a tropical depression this weekend) off of Florida will track along the East Coast and should at the very least bring cloudier weather. Overnight lows in the mid-60s.
A stationary front stalled out southeast of the city over the Mid-Atlantic will be the primary agent responsible for an extended period of humid, cloudy, and unstable weather over the weekend. As was the case last weekend, temperatures will be on an upward trend from the low-80s into the low-90s by the start of next week.
Rest of today – mostly cloudy with isolated showers and thunderstorms particularly closer to higher terrain north and west of the city. High temperatures in the low-80s. Overnight lows in the low-70s.
Weather Prediction Center surface forecast for 8AM Saturday
Saturday – more clouds than sun with the stationary front just south of the area. Continued onshore easterly flow behind north of this stationary front will keep things cooler and humid. High temperatures in the low-80s. Chance for showers and thunderstorms to develop again in the afternoon hours with an unstable airmass (due to the high moisture content caused by the onshore flow) as heating increases. Overnight lows in the low-70s.
Sunday – temperatures begin to warm up into the upper-80s as winds shift towards the south. The stationary front attempts to move north as a warm front but high pressure is forecast to develop west of us and block this northwards advance. Scattered showers and thunderstorms are again possible in the afternoon hours. Overnight lows in the mid-70s.
GFS model 2 meter above ground level temperature, 10 meter above ground level wind forecast for 2PM Monday
Monday – with winds shifting to towards the southwest, much warmer air will advect into the region. High temperatures expected to top out in the low-90s with overnight lows in the upper-70s. Mostly sunny skies forecast with the high pressure building.
