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Warmer Conditions Arrive Tuesday, How Does Thanksgiving Day Look?

Good Evening! 

Today was another cold and breezy day across much of the Northeast, as the strong low pressure area that affected our region earlier this weekend continues to move off to the east and over the martime regions of Canada. The interaction between this low pressure system and a high pressure system to our south has created a steep pressure gradient which has been the source for these gusty conditions over the past day or so. Strong northwesterly flow in the mid levels of the atmosphere has also contributed to colder air aloft blowing over the Great Lakes, which has produced some lake effect snow showers that have mainly been focused across far northern New York state and Pennsylvania. However, some of these “lake-effect” snow showers moved over portions of the New York metro area, producing some of the first flakes of the year for most locations. While surface temperatures over the area were not at or below freezing, cold mid level temperatures allowed precipitation to remain mostly frozen, with ice pellets also being recorded in northern New Jersey. While these snow showers did catch some people by surprise, they weren’t anything more than “mood flakes”, or just some light flurries that do not stick to any surfaces-allowing travel to proceed as usual.

The rest of our Monday was rather chilly, with a mix of clouds and sun keeping our temperatures limited to the lower to middle 40’s across much of the area. Winds have really begun to weaken over the entire northeast as the pressure gradient between the two surface systems really diminishes with time as the systems grow further apart. As we head into tonight, the area of high pressure located over eastern Carolina will remain in control of our weather, bringing lighter winds out of the southwest and clearer skies. Lows tonight will likely have a range to them, with the far northwestern locations likely dropping below freezing and into the upper 20s, while locations near New York City willy likely get down into the lower to middle 30’s.

RTMA Analysis of the current temepratures over the Northeast, with surface observations finally showing a change from the gusty NW winds we have been seeing for the past day or so (Credit: Simuawips)

RTMA Analysis of the current temperatures over the Northeast, with surface observations finally showing a change from the gusty NW winds we have been seeing for the past day or so (Credit: Simuawips)

Tuesday morning will likely start off rather cool, but mostly sunny as the area of high pressure that we’ve been following moves offshore and into the western Atlantic by the morning commute. This will mean that as the day goes on, warmer mid level air from the southwest will move into the Northeast, allowing temperatures to moderate quite a bit when compared to today. Additionally, a vigorous area of mid level energy will be diving down from Canada by the afternoon hours of tomorrow, which will be accompanied by a moisture-starved area of low pressure at the surface. As this system heads east with time, it will increase the strength of the southwesterly flow, leading to an increase in winds across much of the Mid Atlantic and Northeast by the late afternoon hours. The relatively clear and conditions and warmer mid level temperatures from the south will allow highs to climb into the lower to middle 50’s tomorrow, with the warmest readings likely just inland from the coast.

As we progress into Tuesday evening, we should see moisture being to develop in the southern states as another messy batch of disorganized mid level energy moves in behind the first system in the Great Lakes. As this takes place, a cold front associated with the system in the Great Lakes region will continue to move east and into the Northeast by the end of the day. This front will remain relatively dry as it moves over the Northeast due to the system to the south and west of it stealing most of the moisture deep in the Gulf of Mexico.

Things may become a little more interesting during the very early morning hours on Wednesday when the upper level jet streak from the Great Lakes system begins to interact with the energy over the south and moisture begins to flow more northerly. The question with this time period is just how much will the precip expand and move west as the new low develops to the south? Today’s model guidance diverges a bit on the extent of the precipitation shield on Wednesday, but as of right now it looks like the immediate coasts of NJ and LI could see some steadier rain, with showers possible further North and West. Since these two systems will remain mostly independent from one another, this is very unlikely to be a big deal, but even slightly more interaction with these systems and a healthier upper level jet streak could promote the development of precipitation further inland, and this will have to be monitored. Otherwise, highs on Wednesday will likely remain in the lower to middle 50’s despite the incoming cold front. The front should clear the area by late Wednesday afternoon, with any residual shower activity quickly leaving the scene as well. Wednesday evening should be a cold one, with lows likely dropping into the middle to upper 20, with warmer readings near the coast.

18z NAM 500mb loop showing the initial energy with Wednesdays cold front quickly moving east while more energy drops down into the Gulf of Mexico and becomes "stuck"

18z NAM 500mb loop showing the initial energy with Wednesdays cold front quickly moving east while more energy drops down into the Gulf of Mexico and becomes “stuck”

Thanksgiving Day and Beyond

A colder airmass from Canada will be in place over the Northeast behind Wednesdays cold front, which should cause the day to start off rather cold in the upper 20’s and lower 30’s. Left over dry air in the wake of the cold front should allow mostly sunny conditions to take over on Thanksgiving day. A colder airmass, clear skies, and calm winds should only allow temperatures to rise into the upper 30’s and lower 40’s across much of the New York metro area, with warmer readings located over portions of Long Island. From a historical standpoint, this Thanksgiving should be a rather cold one, as highs will likely come in 10-15 degrees below-normal! Conditions during the remainder of the day should be quite pleasant as a weak area of high pressure moves in from the west. This area of high pressure will cause winds to shift back to a more southeasterly component by the evening, which will signal the arrival of another warmer mid level airmass. Lows during the evening hours should drop into the middle to upper 20’s, with some warmer temperatures likely across locations closer to the coast.

Calm and cool conditions are expected through Saturday afternoon, before another strong area of low pressure over southern Canada drags a cold front through the region early on Sunday. As of right now, this cold front also looks to be moisture-starved, but the big deal with this system will be the temperatures, not the precipitation. With a large area of high pressure over the western Unites States, this cold front will have the potential to dump some impressive cold over the east, which could drop the area down into the lower 30’s and upper 20’s for highs. Though its just under a week out right now, this cold shot does look to be on the quick-hitting side, as the upper level trough associated with the cold air will quickly move out by the middle of next week.

This afternoons ECMWF model showing the potential for a potent, but quick-hitting cold shot by the end of next weekend.

This afternoons ECMWF model showing the potential for a potent, but quick-hitting cold shot by the end of next weekend.

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 

epsblockcropped

Why might forecast models be diverging with the long range pattern?

Good morning! The past several days have been quite active in the meteorological community.We began last week on the tail end of a pattern featuring stagnant warmth, with ridging in the Eastern United States and cold air bottled up in Western Canada and the Pacific Northwest. A well advertised change has occurred since that time, however, with cold air surging southeastward into the Great Lakes and Northeast States.

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Winter Forecast 2017-2018

Seasonal forecasting is quite the challenge, but one we always look forward to. It seems every year we learn something new about the atmosphere. It is critical to have a fundamental understanding of how the atmosphere works, and the implications that changes from its base state can have on the weather pattern.

Instead of focusing on individual numerical indexes and their verbatim values, we are going to try to paint a picture of the atmosphere and what it will be doing over the next few months based on these phenomena:

  1. ENSO (El Nino Southern Oscillation) and tropical forcing
  2. High latitude behavior and blocking
  3. Analog years based on global pattern evolution

Read more

simuawips (90)

Record Cold Quickly Departs, Potentially Stormy Pattern Setting Up In the Long Range?

Good Afternoon! 

The Arctic front that we have been talking about for around a week now has finally cleared the entire Northeast, leaving well-below normal temperatures in its wake. Earlier this morning, the front blasted through the region with some rain and snow showers, some of which were heavy up towards the central locations of upstate New York. These showers were quickly undercut by much more dry and dense Arctic air from Canada and promptly dissipated. Todays high temperatures were actually set in the early morning hours just ahead of then cold front, with most locations peaking in the lower to middle 40’s. After the front blasted through, temperatures promptly dropped a good ten to fifteen degrees across the entire area, with temperatures in the upper 20’s to lower 30’s being reported from most stations. Temperatures just behind the front change quite a bit with height, which has allowed stronger low level winds to mix down to the surface and cause conditions to become quite blustery, with gusts in the 25-35 mph range this afternoon. This has allowed for wind chills in the metro area to fall into the lower 20’s and teens. As mentioned earlier. the Arctic air has brought in a significantly drier airmass, so any shower activity into this evening will be confined to locations near the Great lakes, where the temperature differential will support the growth of some gusty snow squalls.

The area are of low pressure that brought the Arctic front through the area begins to occlude and weaken while pulling east, the pressure gradient between the Arctic high and the low pressure will decrease significantly, leading to winds steadily decreasing by sunset. As the winds calm and high pressure takes over, we should have near-ideal conditions for steep radiational cooling to take place across the entire Northeast. This will mean that lows will quickly drop off into the teens and even single digits for locations off to the north and west. These temperatures will likely break record lows for many stations across the Northeast, with some readings likely being 15-30 degrees below-normal for this time of year! Any locations that have not yet had their first freeze this Fall will certainly experience a hard freeze this evening, with any vulnerable plants quickly succumbing to the below-freezing temperatures.

RTMA temperatures showing the near-record cold readings across the area in conjunction with the gusty winds behind the Arctic front

RTMA temperatures showing the near-record cold readings across the area in conjunction with the gusty winds behind the Arctic front

Saturday morning should start off quite cold and clear with the area of high pressure developing right over the Northeast. Winds will likely be much calmer than they are this afternoon, so we may start off a little more pleasant than originally thought. Mid level temperatures will begin to increase a bit, but still be cold enough that much of the Northeast experiences somewhat below normal temperatures tomorrow with highs likely staying in the middle to upper 30’s, with some locations hitting the 40-degree mark. The day as a whole should be relatively calm as a more west-east oriented jet stream sets up aloft, which should shift winds to the east/northeast as the day goes on. Later in the evening, the area of high pressure should be located just offshore of the Mid Atlantic coast, which will be the area more of an onshore flow. This could cause some low level moisture to work into coastal sections of NJ, CT, and NY, but the very low dewpoints in place may keep much of this marine airmass at bay. Regardless, expect another cold night with lows likely dropping back down into the lower 30’s and upper 20’s farther north and west, where radiational cooling will be prevalent. As a side note, the somewhat increased moisture and calm winds may allow for patchy frost to develop, especially across the interior.

High pressure will likely still remain just offshore by Sunday morning, with clear skies and cool temperatures likely. As we head into the afternoon hours of Sunday, a weak disturbance will be caught in the very quick west to east oriented jet stream that we talked about. Without any kind of blocking to slow this system down and let it organize, it will likely remain sheared out and weak as it nears the area later in the day on Sunday and Sunday night. This disturbance will likely cause a slight increase in temperatures during the day Sunday, with hgihs likely hitting the lower to middle 40’s. An increase in clouds is also expected as the day goes on Sunday afternoon, with some light showers possible across the southern locations of the Northeast and Mid Atlantic states.

This afternoons ECMWF model showing the very quick west to east positioned jet stream. This pattern has no blocking to slow down any mid level disturbances to allow them to organize and strengthen.

This afternoons ECMWF model showing the very quick west to east positioned jet stream. This pattern has no blocking to slow down any mid level disturbances to allow them to organize and strengthen.

As we head into the beginning of next week, the west to east jet stream will likely stick around,  allowing for a large area of mid level ridging to develop across the Central part of the United States and into southern Canada. This should bring temperatures up a bit, with highs likely rebounding back into the upper 40’s and 50’s through Wednesday or so. This area of riding and quick mid to upper level flow will also prevent any major rain events in the medium range, so expect at least the first half of next week to remain calm and dry.

Long Range

As we get deeper into next week, we may see a pattern shift towards more blocking near Greenland, which would not only slow down the flow across the country, but also allow for below-normal temperatures to start to creep back into the country. The models and their ensembles have been keying in on this type of blocking pattern to set up for about a week now, and things may kick off as early as next weekend. In addition to the blocking near Greendland, some higher heights over the North Pole may also help to drain cold air southward by next weekend and beyond, which could allow for cooler temperatures and even a few wintry precipitation events to exist near the Thanksgiving time period over the Northeast. While this has been advertised for a while on a variety of the models, this is still over a week out and things could very quickly change due to the chaotic nature of the jet stream over the  Pacific. Regardless, we expect an increased chance for below average temperatures and above-normal precipitation over the east starting the end of next week and heading into Thanksgiving. This is a developing pattern, so make sure to check back for further updates!

Long Range ECMWF Ensembles centered on next weekend illustrating an active pattern with potential cold air intrusion.

Long Range ECMWF Ensembles centered on next weekend illustrating an active pattern with potential cold air intrusion.

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