Thanksgiving week starts off with warmer than average temperatures largely in the mid-50s ahead of an approaching storm that should impact the area Wednesday. Behind this storm, temperatures are forecast to drop back into the 40s. Thanksgiving Day will be dry, however, the low responsible for the mid-week storm will deepen as it exits the region, resulting in winds possibly strong enough to ground the Macy’s Thanksgiving Day Parade balloons.
Rest of today – partly sunny with high temperatures in the low-50s. Overnight lows heading down into the low-40s with mostly clear skies overnight.
GFS model 500 mb height anomalies, showing positive anomalies over much of the Northeast on Tuesday
Tuesday – southwesterly flow ahead of an approaching cold front/storm system should allow temperatures to warm into the mid-50s. Overnight lows in the mid-40s.
Wednesday – cloudy with high temperatures in the mid-50s. Chance of showers during the day and into the early overnight hours. Decreasing clouds overnight, with lows in the mid-40s and increasing winds.
GFS model output for 1000-500 mb heights, surface pressure, and precipitation
Thursday – mostly sunny with high temperatures around 50°F, winds should be quite breezy with a tight pressure gradient forming around the deepening and exiting low pressure center. Overnight lows in the mid-30s.
Thursday will probably end up being the best day of the week. High pressure will be in control from most of the period allowing for a sunny day with seasonable temperatures. Winds may be stiff overnight as well as late Thursday night into Friday. Rain associated with a low pressure system moving in will hold off until Friday.
My Forecast High: 50°F | Low: 38°F | Max sustained winds: 20 mph | Total precipitation: 0.00″ – verification will come from METAR data for the period between 1AM Thursday and 1AM Friday (06Z Thursday to 06Z Friday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.
Verification High: 53°F | Low: 39°F | Max sustained winds: 14 mph | Total precipitation: 0.00″ – high temperatures ended up being a bit warmer than expected, more towards the EKDMOS 90th percentile range. I think this had to do with the fact that overnight lows were warmer (did a good job edging up on that), and because northwesterly winds backing to the west introduced an element of downsloping. Compressional warming from this was not offset by any other temperature advection, and allowed for temperatures to hit exactly the average high for this time of year. The other aspect I missed on was max wind speed. Here, looking at surface analyses from yesterday compared to the forecast models, there was a larger distance between the center of high pressure and the departing coastal low, leading to a weaker than expected pressure gradient early. The fastest winds ended up being clocked from the southwest as a result, ahead of the approaching cold front.
Weather Prediction Surface forecast for 7AM Thursday
Synoptic Set Up The forecast period starts with a north-south elongated high pressure over much of the Eastern US, centered over the Ohio Valley. The coastal low that impacted the area Monday is still forecast to linger southeast of Nova Scotia. A decent pressure gradient will be in place at the beginning of the forecast period as a result (high pressure measuring ~1025 mb, low ~998 mb). An approaching low pressure center will travel northeast from the Midwest across the Great Lakes into Southwestern Quebec during the forecast period. The low will continue intensifying and will erode the northern part of the high pressure center. Precipitation associated with this low won’t reach NYC until Friday, though. The primary influence of this low for the forecast period will be in shifting winds from the northwest to the southwest.
Above the surface, at 850 mb winds are forecast to start off northerly, between 20-25 knots. Wind speeds ease as they continue backing from north to west, then pick up in intensity to 30 knots from the southwest. Dry air, though moistening, will prevail at the 850 mb level throughout the forecast period. At 500 mb, slight ridging takes place during the day, then increased vorticity starts to pivot through ahead of the primary shortwave axis associated with the maturing surface low over the Great Lakes. Finally, at 300 mb we’ll start in the entrance region of a jet streak, then followed by a period of calm before the exit region of another jet streak approaches from the west.
GFS 2-meter (surface temperatures) in contours, and 10-meter wind barbs, valid 1AM Thursday. This shows a decent environment for cold air advection with winds at almost perpendicular angles to the temperature contours, pointing from colder to warmer temperatures. However, wind speeds are modest so the strength of an CAA would not be strong.
By 1AM Friday, GFS 850 mb height, moisture, and winds show depict winds shifting to the southwest, but the air above the surface will still be quite dry.
High Temperatures Statistical models (GFS, NAM, NBM) are good agreement, within a degree or two of 50°F. EKDMOS at 12Z similarly showed a tight band around 50°F, though this widened a bit at 18Z. 50°F is just a touch below climatological norms. I’m not seeing too many surprises here. Moisture is lacking for clouds to form until late in the period after the sun goes down. As winds shift to the southwest later in the day, they will largely parallel local isotherms so there won’t be appreciable warm air advection to look at either. I think 50°F is a good bet here.
Low Temperatures Stiff winds from the northwest will offset relatively clear conditions in terms of radiational cooling. Cold air advection (CAA) is looking modest. While the wind direction is looking to cut at almost perpendicularly across temperature contours from cold to warmer temperatures, wind speeds aren’t going to be sustained at strong speeds for too long. I think 38°F is reasonable because statistical guidance is only a degree cooler or so, with EKDMOS showing this temperature at about the 50th percentile.
GFS MOS forecast
NAM MOS forecast
Max Sustained Winds 850 mb winds have two peaks and so do surface winds in EKDMOS: one early, then one late in the forecast period. I tend to concur the fastest winds will come early in the forecast period, since northwest winds are climatologically favored to produce fast high speeds. However, I also don’t see evidence to support mixing of strong winds aloft down to the surface. One wrinkle is if the pressure gradient ends up being tighter between the lows and the high pressure, as that would drive stronger than anticipated winds. 20 mph is above statistical guidance, but not that much higher.
NAM forecast sounding for KLGA valid 7PM Thursday. Distinct moistening of the mid and upper levels is evident with the dew points (green line) nearly overlapping the environmental temperature (red line). Lower levels are still markedly drier.
Total Precipitation This is the easiest part of the forecast as strong high pressure and dry air throughout most of the atmospheric column for most of the day makes it nearly impossible for precipitation to materialize.
Spells of rain will bookend what should otherwise be a pleasant week of mostly dry weather. Temperatures will trend slightly below normal for this time of year, however, we will avoid any dramatic swings in temperature. Record cold will not be on the table either. All in all, it should shape up to be a fairly typical mid-November week.
Rest of today – windy, mostly cloudy, with chances for scattered rain showers as a slow moving coastal low continues spinning off of the coast of New England. High temperatures should only hit the mid-40s with the cooling influence of clouds and persistently northeasterly flow. Chances for rain continue overnight with lows dropping into the upper-30s.
Weather Prediction Center surface forecast for 7PM Monday
Tuesday – rain chances should finally end as the coastal low affecting us finally pulls away to the northeast. Clouds should break up leading to a decent day with high temperatures in the low-50s. Overnight lows should be around 40°F.
Wednesday – partly sunny with highs around 50°F. Overnight lows in the mid-30s.
GFS 500 mb height, relative vorticity for 1PM Friday. We can see a distinct shortwave trough approaching from the west. Enhanced vorticity around the base of this trough should help touch of some precipitation at the surface as a cold front sweeps through.
Thursday – best day of the week with high pressure briefly building in. High temperatures again around 50°F, with overnight lows in the mid-40s.
Record setting cold is on the way mid-week. Overnight lows in the mid-20s and daytime highs hovering around freezing Wednesday will make this week feel more like January than mid-November. Luckily, this bitter cold snap will be short-lived, with temperatures rebounding back into the 50s by the end of the week.
Rest of today – temperatures will be falling through the 40s during the day. Precipitation should end as an Arctic front pushes through. Temperatures will continue dropping into the 30s throughout the evening and bottoming out in the mid-20s. Precipitation should end before it gets cold enough to produce snow. Winds will become stiff with the parent low strengthening and a tight pressure gradient forming between that and an incoming high pressure center.
Weather Prediction Center surface forecast for 7AM Wednesday
Wednesday – sunny with record low high temperatures in the low-30s as a frigid Arctic air mass takes hold. Overnight lows continue to be cold, in the upper-20s.
Thursday – temperatures start to rebound into the upper-40s as a warm front approaches and we enter the warm sector of the next storm. Return flow around the western edge of the high pressure exiting east will also assist in helping move some warmer air in. Overnight lows in the mid-30s.
GFS model 500 mb temperature, height and wind at 1AM Wednesday, note the closed 500 mb low and the strong troughing over much of the Northeastern US
By 7PM Friday, the 500 mb trough is forecast to have flattened out considerably, allowing for temperatures at this level and at the surface to rebound
Friday – the warm-up continues, with temperatures reaching back into seasonable levels in the low-50s. A moisture starved cold front passes through late bringing overnight lows back down to the low-30s
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 November.
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 (12%).
Directions that are most and least common: Other most common wind directions include west-northwest (10%), due west (8.5%), and due southwest (8.25%). Least common wind directions are east-southeast (1.5%), due southeast (1.75%), and south-southeast (2.75%).
Direction(s) most likely to produce the fastest winds: Winds in excess of 21.4 knots (~25 mph) are most frequently found coming from due northwest. West-northwest, north-northwest, due northeast, 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: November wind patterns are a marked shift from the prior two months. Winds coming from the northwestern quadrant become prominent. Meanwhile, winds from the south and southwest decline in frequency.
In general, northwesterly winds bring cooler, drier Canadian air into the region following cold fronts. Northwesterly winds will tend to warm slightly because of compressional warming as they downslope coming off the higher terrain of the Catskills, and Poconos outside of the city. This can sometimes lead to warmer temperatures than would normally be expected for this wind direction. Northeasterly winds, on the other hand, are often related to backdoor cold fronts sweeping from the Canadian Maritimes, the onshore flow ahead of an advancing warm front, or a passing coastal storm to the south.
The pattern of winds in November suggests the prevalence of classic frontal systems moving through, where warmer southwesterly winds precede the passage of a cold front, behind which strong, gusty westerly and northwesterly winds pick up. Northeasterly winds are, as pointed out above, a sign of passing coastal storms.
Maximum observed two-minute wind speed for the month: 41 knots (47 mph).
Temperature and Precipitation Averages/Records
Temperature units are in Fahrenheit and precipitation is in inches.
Worth noting: Average high temperatures in November start falling into the 50s, while lows fall into the upper-30s. November is the first fall month in which no record high temperature exceed the 90°F.
The week after we set our clocks back for the fall will see a shift to the coldest temperatures we’ve yet seen this season. High temperatures will trend from normal levels to slightly below normal (upper-50s to low-50s) before plummeting into the 40s following the passage of a low pressure center and cold front. The chilly air following this system will begin a longer term trend of below average temperatures going into the middle of the month at least.
Rest of today – mostly cloudy with a chance of showers as a cold front passes through later in the day. High temperatures on the mild side in the low-60s as we’ll be in the warm sector of the parent low bringing the cold front through. Overnight lows in the low-40s.
Weather Prediction center surface forecast for 7AM Wednesday
Wednesday – sunny with cooler high temperatures in the low-50s. High pressure depicted above will keep things nice and dry. Overnight lows in the low-40s.
Thursday – starting off mostly sunny with high temperatures in the mid-50s. A storm system will approach later in the day and bring the chance for rain at first, with rain and snow mixing possible overnight as lows drop into the mid-30s.
Climate Prediction Center temperature anomaly forecast for November 10-14
An anomalously low area of 500 mb heights will produce cold temperatures at the surface
Friday – the real cold sets in with high temperatures only in the low-40s. Rain/snow should taper off early giving way to sunny conditions, with winds picking up due to the low bringing this weather strengthening as it continues moving off to the northeast. Overnight lows are shaping up to be below freezing, near 30°F with winds forecast to die down and skies clearing allowing for some good radiational cooling.
Sunny and seasonable weather with highs in the mid-60s will be punctuated by the passage of a strong frontal system mid-week. The timing of this frontal passage should bring the bulk of the rain through overnight Tuesday, such that Wednesday ends up still being a nice day. Looking ahead, a second cold front is forecast to move through late in the weekend but is not expected to bring significant rain at this time. Temperatures throughout this forecast period and beyond are looking to be at or above normal in the low-60s/
Rest of today – mostly sunny, with highs in the mid-60s. Overnight lows in the low-50s.
Weather Prediction Center surface forecast for 8PM tonight. We will be wedged between the storm that brought steady rain yesterday to the east and an approaching frontal system with a parent low over the Upper Midwest.
Tuesday – increasing clouds with high temperatures in the low-60s. Rain chances increasing especially later in the day. Bulk of the rain accompanying the cold front should arrive overnight. Overnight lows in the mid-50s.
Wednesday – rain should clear the area. Temperatures expected to rebound back into the mid-60s under sunny skies with some downsloping westerly flow behind the front. Overnight lows in the upper-40s with a cooler, drier airmass working in.
Climate Prediction Center temperature outlook for Oct 26-30. We will be in an area with about equal chances of above or below normal temperatures up to 33% for warmer than normal temperatures.
Thursday – another really nice day with high temperatures in the mid-60s and mostly sunny skies. Overnight lows around 50°F.
The week starts off with warm temperatures for this time of year, followed by entry of a cooler airmass. A storm system is forecast to bring rain mid-week. Temperatures will cool even more behind this storm with high temperatures dropping to slightly below normal levels in the low-60s by the end of the week.
Rest of today – mostly sunny, with highs in the low-70s. Overnight lows in the low-50s.
Weather Prediction Center surface forecast for 8PM Tuesday
Tuesday – a dry cold front passes over the region later today, leading to cooler high temperatures in the low-60s for Tuesday on the back of colder northwest winds behind the front. It should be a sunny day. Overnight lows in the low-50s.
Wednesday – a low pressure system over the Great Lakes will track east towards the area. Mostly cloudy skies will prevail with highs warming into the mid-60s due to a shift in winds to the south and southeast. Rain should start to overspread the area later in the afternoon and continue overnight. Overnight lows in the low-50s and even cooler possibly in the upper-40s. A secondary coastal low forming off the Carolina coast will become the primary low as energy transfers from the inland storm.
GFS model output for 1000-500 mb thickness and precipitation valid 2PM Wednesday
GFS model output of the same metrics for 2AM Thursday
Thursday – rain should clear out before the start of the day but winds will be breezy from the northwest. This will bring in cooler air again with high temperatures in the upper-50s and partly sunny skies. Overnight lows around 50°F.
A distinct fall feel this week with grey skies the norm and spotty rain chances for many of the days. A coastal storm brewing off the Southeast coast is forecast to track north and then northeast. National Hurricane Center is tracking this system as it has some potential to acquire subtropical characteristics. This will be a slow moving storm that will bring a long period of northeasterly winds to the area.
Rest of today – mostly cloudy, with highs in the upper-60s. Overnight lows in the upper-50s.
Weather Prediction Center surface forecast for 8PM Wednesday
The developing coastal storm depicted above.
Showers and thunderstorms over the western Atlantic between the southeastern coast of the United States and Bermuda are associated with a broad, non-tropical area of low pressure. This system is forecast to move northward or northeastward and could acquire some subtropical characteristics off the east coast of the United States by the end of the week.
Wednesday – although the storm referenced is forecast to remain well offshore, outer rain bands from it could bring showers to the area along with persistent northeast winds. These wind are anticipated to be on the strong side, steadily in the mid-teens with gusts in the 25 mph range. Mostly cloudy with highs around 60°F. Overnight lows in the low-50s.
Thursday – rain chances continue as the storm develops and becomes a closed low. Mostly cloudy with highs in the low-60s. Winds will become blustery from the northeast around 15 mph with higher gusts. This will be due to the increasing pressure gradient between the deepening low and high pressure over eastern Quebec. Overnight lows in the low-50s.
GFS model output of 850 mb winds and relative humidity. The coastal storm continues to spin off the Northeast coast, although its center remains well offshore (just above the pivotalweather logo in this frame).
Friday – rain still lingers though the storm starts to finally make some eastward progress as a trough approaches from the west. High temperature remain in the low-60s with mostly cloudy skies. Overnight lows in the upper-50s as warmer southerly flow starts to work into the region.
This Saturday will likely start off with the coldest overnight low temperatures so far this season for NYC. Strong high pressure will be moving in from the west overnight and during the day, the center of this high pressure will be passing almost directly overhead. As a result, we should see a sunny day with diminishing winds, though high temperatures will be much below normal (69°F) with the day starting off pretty chilly. Quite a contrast between this past Wednesday when we set a new daily record high across the city with temperatures peaking at 92-93°F! Autumn is certainly in the air.
My Forecast High: 61°F | Low: 48°F | Max sustained winds: 14 mph | Total precipitation: 0.00″ – verification will come from METAR data for the period between 2AM Saturday and 2AM Sunday (06Z Saturday to 06Z Sunday) at LGA (LaGuardia Airport), and the KLGA Daily Climate Report.
Verification High: 60°F | Low: 46°F | Max sustained winds: 20 mph | Total precipitation: 0.00″ – Temperature forecast turned out to be pretty good, especially high temperatures. Off by 2°F on low temperatures, which ended up 1°F colder than statistical guidance. I believe this was due to slightly stronger cold air advection than expected leading into the forecast period. Off by 6 mph for max sustained winds, which qualifies as a minor bust. The highest wind speed direction was northeast. Judging by METAR data, winds were coming form this direction sometime between 7-8AM Saturday. I think it’s possible that the pressure gradient was tighter than forecast the day before, which would have resulted in the potential for faster winds like these.
Weather Prediction Center surface forecast for 2PM Saturday
Synoptic Set Up A strong area of high pressure is forecast to be the dominant feature at the surface for much of the Northeast, Mid-Atlantic, and Ohio Valley during the forecast period. The center of this high pressure will be moving east during this time and will be nearly overhead for the hours of peak solar heating tomorrow. This high pressure will be accompanied by a dry airmass throughout nearly the entire atmospheric column. Reference the images below, which show NAM model output of relative humidity and winds at 300 mb, 500 mb, and 850 mb respectively. The brown hues shown indicate very dry conditions.
High Temperatures GFS, NAM, and NBM are in good agreement that tomorrow will be a much below average day in terms of high temperatures. These forecast sources depict high temperatures ranging from 58-62°F, which is 7-11ºF below normal for this time of year. They also show winds that are veering from northerly to east-southeast, which makes sense given the forecast position and track of the high pressure center. Although northeasterly and easterly are onshore wind directions, the near surface layer of the atmosphere is forecast to start off so dry that it would take quite a while for moisture off the ocean to make an impact and produce clouds that could eat into high temperatures. Furthermore, sea surface temperatures at this time are actually ranging in the upper-60s, so onshore flow should actually serve to bring warmer air in. EKDMOS 50th percentile for high temperatures is about 60°F. NAM is a touch cooler at 58°F while GFS and NBM call for 62°F. NAM seems to suggest slightly more cloudiness than GFS. I’m going with a high of 61°F, which I think is a reasonable balance that incorporates the data points above.
Low Temperatures Just as is the case with high temperatures, statistical guidance similarly shows that low temperatures could be as much as 8°F below normal for this time of year. These temperatures are more typical of the end of October. This is a result of decent cold air advection leading into the beginning of the forecast period. Clear and dry conditions should carry though the overnight hours. However, winds should be strong enough so as to limit radiational cooling. EKDMOS has 47°F as the 10th percentile, and 50°F as 50th percentile so going with 48°F seems plausible when considering that statistical guidance is nearly unanimous calling for 47°F as the low.
NAM MOS forecast, initialized at 8AM Friday
GFS MOS forecast, initialized at 2PM Friday
Max Sustained Winds Climatologically, winds during October can be quite strong from the northeast, but easterly to southeasterly winds are typically the weakest. Since the center of the high pressure should be moving overhead during the forecast period, the pressure gradient should be decreasing, leading to diminishing winds. Statistical guidance looks on point calling for peak winds at the beginning of forecast period. Even with a well-mixed layer forecast to form during the afternoon tomorrow, winds aloft will be weak, so wind speeds should be subdued. NBM came in with max wind speeds well below the other statistical guidance at only 6 knots. EKDMOS 50th percentile is about 10 knots, thus a forecast of 12 knots here should be OK.
GFS model forecast sounding for 2PM Saturday
Total Precipitation This is the easiest part of the forecast as strong high pressure and very dry air throughout most of the atmospheric column makes it nearly impossible for precipitation to materialize.
