Steven Copertino

Dry and Seasonable Pattern Holding On, Substantial Changes Looking More Likely Next Week!

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Good Evening! 

Today was the warmest in a series of mild days across the entire Northeast. Dry air in the mid levels of the atmosphere was quite abundant this afternoon, and this dry air helped to mix the warmer mid level temperatures down to the surface with stout northwesterly/westerly flow. Mostly sunny skies and light winds helped much of the region see highs rise into the well-above normal values this afternoon, with many stations across the Northeast breaking the 60 degree mark. In fact, some stations across portions of Long Island and southern New Jersey saw readings in the middle 60’s, which is a good 10-15 degrees above normal for this time of year! As the day progressed, we had a weak cold front with extremely limited moisture push through the Northeast. This front was weak enough that surface temperature did not/have not immediately responded as the main cold air pool is located well behind the surface front. High pressure is gradually building into the Northeast this evening, with the onset of cooler temperatures finally reaching northern portions of New York and New England where temperatures have since fell off into the low to middle 30’s.

The rest of this evening should be quiet, with winds shifting to more northerly/northwesterly. As this happens, conditions will be rather good for efficient radiational cooling to take place across much of the Northeast. This should allow for lows to drop into the middle to lower 30’s across much of the area, with middle to upper 20’s possible further north and west.

This evenings Real Time Mesoanalysis showing surface temperatures and surface observations across the Northeast. Temperatures are gradually becoming cooler from north to south across the region as a cooler airmass works in (Courtesy of Simuawips)

This evenings Real Time Mesoanalysis showing surface temperatures and surface observations across the Northeast. Temperatures are gradually becoming cooler from north to south across the region as a cooler airmass works in (Courtesy of Simuawips)

Thursday and the Weekend

Thursday should start off a good deal cooler than Wednesday did, but as the area of high pressure currently located over Canada quickly moves offshore, we should see offshore flow overspread much of the Northeast, leading to increased temperatures and available moisture. As this high quickly rockets east, a shortwave trough will also be quickly heading east, embedded in the fast west to east zonal flow over the country. This disturbance should be located over the Great Lakes region by tomorrow afternoon, with a cold front extending southward. Unlike the past few fronts, this one may be able to tap into some moisture lingering over the Gulf of Mexico, which should allow the front to be a bit more active with showers likely along the front. As we head into tomorrow afternoon, southwesterly flow should be rather stout at the surface as well as the mid levels, ushering warmer mid level temperatures as well. With the increased low level moisture from the offshore flow, there may be more clouds than sun across portions of the Northeast, but we still expect temperatures to still reach into the upper 40’s to lower 50’s. This should be right around normal for this time of year, but some locations to the south of the NYC area may see readings into the middle 50’s.

By tomorrow evening, the cold front should begin to move through the Northeast with light to occasionally moderate rain likely. The rain along this front should be limited due to the overall dry mid to upper level conditions and quick movement of the upper level system. With clear conditions behind the front expect temperatures to generally fall into the lower to middle 30’s across much of the area, with colder readings to the north and west.

This evenings RPM model showing the progression of the weak cold front moving over the Northeast tomorrow evening. Only light rain accumulations are expected (Courtesy of WSI)

This evenings RPM model showing the progression of the weak cold front moving over the Northeast tomorrow evening. Only light rain accumulations are expected (Courtesy of WSI)

Another high pressure will build into the Northeast by Friday morning, bringing in renewed northwesterly flow and slightly cooler temperatures in the mid levels. The vast majority of the day should be dry, but a couple of spotty showers may be possible around Long Island and Connecticut as some residual energy behind the aforementioned cold front moves over the area. Highs will likely stay around normal for this time of year, with readings in the middle to upper 40’s-with a couple of locations reaching 50 possible. Friday night looks to be a calm and clear evening with radiational cooling likely, so we expect lows to drop down into the upper 20’s and lower 30’s across the immediate NYC metro area. Areas farther north and west could see lows drop into the middle 20’s if conditions allow strong enough cooling to take place.

Saturday and Sunday look rather quiet and seasonable, with highs likely staying in the upper 40’s to lower 50’s range. The only real chance of precipitation may come on Sunday night when a sloppy mid level piece of energy moves quickly eastward from Canada. This system looks to be rather moisture-starved, so it does not appear to be of major concern at this time.

This afternoons ECMWF model showing above normal temperatures persisting across much of the country this weekend as a mid level ridge builds in.

This afternoons ECMWF model showing above normal temperatures persisting across much of the country this weekend as a mid level ridge builds in.

Substantial Changes Likely Next Week! 

We have been watching the pattern for the upcoming week very closely for the past seven days or so, and it seems like with every successive model run, things continue to look more and more interesting for a major pattern change to take place in this time period. By the middle of next week, we should begin to see the development of a major ridge over the west coast of the United States, which should extend deep into Canada. This ridge is whats referred to as a “PNA ridge”, and when coupled with the right ingredients, can lead to a very cold and potentially stormy pattern across the United States. As this ridge gets stronger as time goes on next week, it will begin to send Arctic air from the far northern regions of Canada and even Russia into a building trough which will likely be located over the central part of the country.

This afternoons ECMWF model showing a very impressive area of mid level ridging going up over the west coast and deep into Canada. This pattern is highly supportive of colder weather in the east.

This afternoons ECMWF model showing a very impressive area of mid level ridging going up over the west coast and deep into Canada. This pattern is highly supportive of colder weather in the east.

Another key ingredient of this pattern change will be increased high pressure/ridging over Greenland (a negative NAO), which will help to slow down the trough in the central/eastern US. This is very important as it will allow the Arctic air to pour in and build as it moves east. Model guidance has been very consistent on these ingredients taking shape, and have even been strengthening them to a degree as we get closer in time which is extremely important for this pattern to actually come to fruition. With the ridging in the west and in the east, the pattern becomes “blocked up”, meaning that systems have a chance to slow down and amplify, which is the exact opposite of the pattern we are currently in! This means that there will be an increasing storm threat for the eastern half of the country starting late next week and into the middle portion of December. At this point in time, it seems that below-normal temperatures are very likely in the 8-14 day period across the central and eastern parts of the country, and possibly extending deep into the month. In summary, it appears that starting next week we will see major changes taking place across the hemisphere that could gradually push us into a classic winter pattern for the month of December! We’ll have more on this pattern as new details arise!

University of Wisconsin CIPS analogs based on the GEFS showing extremely high probabilities for below normal temperatures starting as soon as next week!

University of Wisconsin CIPS analogs based on the GEFS showing extremely high probabilities for below normal temperatures starting as soon as next week!

For more information and posts like this one, make sure you sign up for Premium Forecasts — where multiple detailed articles, videos, and interactives are posted each day. Also, come interact with our staff and many other weather enthusiasts at 33andrain.com!

Have a great night!

Steve Copertino 

Doug Simonian

Extremely Amplified Pattern Will Set the Stage for Arctic Cold

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Good evening! The changes to the pattern have been discussed for a while, but now that the model data has finally caught on, things are starting to truly get interesting and we can entertain possibilities.

An initially very zonal pattern will quickly become very amplified thanks to changes with a train of waves in the Pacific and a traffic jam of waves building in the Atlantic. Eventually this forces an amplified ridge in the Pacific to build towards the Arctic and dislodge plenty of cold into the Eastern half of the US, as the corresponding deep trough will have nowhere to go thanks to the aforementioned traffic in the Atlantic.

The video below has all of the details on the coming cold, its severity, and potential duration. It also discusses potential winter storm threats that may arise in the pattern.

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John Homenuk

Confidence increasing in development of cold, active pattern in Eastern US

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Good morning and happy Wednesday, everyone! Anomalous warmth has currently spread across a large majority of the United States, well forecast in is breadth and timing, but impressive nonetheless. Since the beginning of the week, much of the Midwestern United States has been blanketed by temperatures several degrees above normal averages for this time of year. The mid and upper level ridge in the atmosphere that is responsible for this warmth will continue its trek eastward over the next few days, allowing warmer temperatures to gradually move towards the Eastern United States.

As we speak, thousands of miles away, in the North Pacific Ocean, a major change to the hemispheric weather pattern is underway. This fundamental change will mark the end of the anomalous warmth across the aforementioned regions, working in tandem with several other global circulations to support the development of an anomalously cold pattern. In fact, by the middle of next week, temperatures will fall well below average across a large portion of the Mississippi River Valley and East Coast. This will obviously have a large impact on the markets, and Gas Weighted Heating Degree Days are expected to quickly jump above the 10 and 30 year averages. Lets break down why this is happening and how we can expect things to evolve.

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Steven Copertino

Mild and Dry Conditions Settle In, Signs of Change?

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Good Evening! 

Today was a nice start to the work week as an area of high pressure moved over the East, which prompted an increase in temperatures and calmer conditions over the entire Northeast. Much of the day was characterized by a mix of sun and clouds as a cool mid level airmass from Canada moved south on the heels of a weak cold front. This cold front is relatively weak and does not have any substantial moisture associated with it, thus any showers or flurries were extremely isolated in nature and did not last long. Otherwise, most of the New York metro area saw highs in the upper 40’s to lower 50’s, with lower to middle 40’s further north and west. These temperatures are just around normal for this time of year, with only a couple stations going slightly above normal.

The rest of the evening should remain quiet and cool as the high pressure remains firmly planted in place over the Tennessee valley. With the recent cold front passage, dewpoints have lowered and winds have also dropped a bit. This will set the stage for some stout radiational cooling to take place across the Northeast despite some warmer air in the mid levels trying to creep in overnight.  Lows should be able to drop into the middle 30’s for the immediate New York City area, with upper 20’s and lower 30’s likely for the suburbs. Locations well to the north and west may see more efficient radiational cooling this evening, and could even drop into the upper teens and lower 20’s.

Real Time Mesoanalysis Temperatures for the Northeast this evening showing an impressive gradient over the area. Notice readings in the middle teens over northern New England , with 50's closer to the coast! (Courtesy of Simuawips.com)

Real Time Mesoanalysis Temperatures for the Northeast this evening showing an impressive gradient over the area. Notice readings in the middle teens over northern New England , with 50’s closer to the coast! (Courtesy of Simuawips.com)

Tuesday Into Thursday 

Tuesday will likely start of with clear skies and cool conditions area-wide, as the area of high pressure located to our south begins to move over and east of the region by the morning commute. The center of the high pressure will likely be situated just off the coast through the morning and into the afternoon hours, and this should introduce more southwesterly winds in the mid levels of the atmosphere. These southwesterly winds should be capable of ushering a warmer airmass over the region, but the degree of this warmth should be muted somewhat by return flow from the Atlantic. This should keep highs in the area mild, but not too warm. Expect temperatures to get into the lower to middle 50’s during the afternoon hours tomorrow, with some locations having a shot at middle to upper 50’s near the coast. Calm conditions should last throughout the day, with warm air advection increasing once again by the time we head into the overnight hours. With the high pressure located offshore and warmer mid level temperatures working their way in, expect lows to be warmer tomorrow night with readings likely in the upper 30’s to lower 40’s, with some locations north and west staying in the 30’s.

Wednesday looks to be a full-on above normal day as the strong southwesterly flow begins to surge northwards during the day. Mid level dry air will be present tomorrow afternoon, and this will help warmer mid level temperatures to reach the surface and cause highs to rise into the middle to upper 50 across much of the New York Metro area, with some locations closer to the coast possibly getting to the 60 degree mark by the afternoon hours. As the day goes on, another weak cold front looks to push through the area. This front should be another moisture starved front, so any showers will be isolated and weak in nature.

By Thursday, we see the pattern across the United States become rather progressive and zonal in nature, meaning that the jet stream will be flat and west to east oriented. This will allow the high pressure behind the cold front to quickly move offshore, providing more return flow from the south once again. This time there should be more Gulf moisture involved with this flow, and this should only increase as another disturbance works its way east across the country. The system should be located in southern Canada by Thursday evening, with a cold front extending down into Pennsylvania. Light to moderate showers will likely extend along this front as it moves through the Northeast, with only minor rain accumulations expected.

The rain should quickly head offshore by the early morning hours of Friday, with improving conditions thereafter.

This afternoons ECMWF ensembles showing the rather flat nature to the pattern over the US, leading to rather calm and mild conditions.

This afternoons ECMWF ensembles showing the rather flat nature to the pattern over the US, leading to rather calm and mild conditions.

Major Long Range Questions

Some of you have likely heard the buzz on social media that this boring weather pattern is likely to change and snap into a colder and potentially stormy one. While any potential pattern changes are a long ways out, we do have to mention that there is a growing consensus among the more reliable long range computer models that pattern across the Globe will shift to one that is much more supportive of at least a brief period of below normal temperatures across much of the country. This period looks to start during the second week of December and could possibly continue into the rest of the month depending on how other larger factors behave. At this time, we think that the models do have a relatively good grasp on the pattern at hand, and other outside factors like the MJO, and Stratosphere support the ideas being put forth by these models. We will continue to monitor this potential change as it moves up in time and will provide updates on any developments when they come up!

This afternoons ECMWF ensembles showing a major change to a much colder pattern with the potential for some winter weather threat to take shape by the middle of the month.

This afternoons ECMWF ensembles showing a major change to a much colder pattern with the potential for some winter weather threat to take shape by the middle of the month.

For more information and posts like this one, make sure you sign up for Premium Forecasts — where multiple detailed articles, videos, and interactives are posted each day. Also, come interact with our staff and many other weather enthusiasts at 33andrain.com!

Have a great night!

Steve Copertino