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Arctic Cold
Steven Copertino

Potential midweek storm & major Arctic outbreak expected

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Calm Conditions Persist Through the Weekend

High pressure will continue to build to the east during the early morning hours of Saturday, causing any remaining gusty/breezy conditions to subside significantly. Partly cloudy skies and cooler temperatures are expected to prevail into the afternoon hours, with highs likely getting back into the lower to middle 30’s for the entire forecast area. By Saturday evening, a large upper level low situated over portions of southern Canada is expected to begin to move to the south. This will set up a more southwesterly flow over the area into the overnight hours. While the mid level airmass source region will be different than this evening’s, clearing skies and relatively dry conditions throughout much of the lower to middle levels of the atmosphere should allow for robust radiational cooling to take place. This will still cause lows to drop into the upper teens to lower 20’s Saturday night-which will once again be below normal across the area.

By Sunday morning the large and impressive upper level system just to the north of the Great Lakes will continue to shift to the south and east, spawning a surface low pressure system well to the north of our area. While direct impacts in the form of precipitation are unlikely from this low pressure area, it will help to increase low to mid level clouds over much of the Northeast. Additionally, this surface low to our northwest will also increase southerly winds over the area, leading to slightly warmer highs during the day. Temperatures should be able to reach back into the lower to middle 40’s across much of the NYC area, with upper 30’s likely across the interior-which will be on the order of 5-10 degrees above normal. Finally, a cold front associated with the area of low pressure to our north will move through during the evening and overnight hours of Sunday. At this time it appears that the cold front will likely be significantly lacking in moisture, making this frontal passage a dry one. The front will also usher in colder middle to lower level temperatures once again, bringing lows back down into the lower to middle 20’s.

Surface Temperatures

This evenings NAM model showing the progression of warmer surface temperatures into Sunday, followed by another cold front Sunday night (COD Weather)

Potentially Messy Storm System and Major Arctic Blast Set to Impact the East Next Week

As we highlighted back in our last update, another northern stream shortwave trough will be heading into the Northern Plains by Monday morning that bears watching.

This system will be pushed well to the south by Monday evening as a deep upper level system that is directly associated with the tropospheric polar vortex makes its way into Southern Canada. As this deep and highly-anomalous system continues it’s push into Southern Canada on Tuesday, precipitation will likely break out over portions of the Southeast and extending up into the Ohio Valley along a frontal boundary. As this boundary approaches the Northeast by Tuesday night, large scale upper level divergence will be on the increase over much of the East Coast. This would support the development of a quickly intensifying low pressure system near or over the Northeast late Tuesday and into early Wednesday morning-but this is where the reliable model guidance begins to diverge.

This afternoon’s European model showed a substantial amount of energy swinging through the Mid-Atlantic states, causing the development of a rapidly intensifying surface low that moves inland over portions New England by Wednesday morning. Such a solution would bring some light rain/snow during the onset, with a quick flip to more significant mixed precipitation as the low pressure rapidly strengthen and drags in much colder air from the northwest. The rest of this afternoons guidance does indeed show a low pressure system forming along the frontal boundary, but disagree on the exact location and magnitude of deepening of this potential system. Needless to say, these factors will play a major role in determining the overall outcome of this system.

At this time, even a compromise of these solutions (weaker vs. stronger) would bring the potential for some impactful weather to the area Tuesday/Wednesday AM. We will need to closely monitor this system over the next few days as new data comes in. 

EPS MSLP Low Locations

12z European Ensembles showing a significant amount of members developing a strong secondary area of low pressure over the Northeast on Wednesday AM (WxBell)

Regardless of what the Tuesday/Wednesday system does, virtually all available model guidance and their respective ensembles agree that the westernmost lobe of the tropospheric polar vortex will swing into the Northern Plains and Great Lakes by Wednesday night. This will cause a very impressive Arctic airmass to blast its way into the northern tier of the country-with potentially record breaking temperatures for the Great Lakes region. As this Arctic airmass heads into the Northeast, early indications are that it may begin to moderate just enough that portions of the Northeast are spared from record cold. However, the potential will certainly be there for an extremely cold end to next week with high temperatures struggling to break out of the single digits, in addition to dangerous wind chills well-below zero.

Surface Diagram

Diagram showing an Arctic high pressure system moving into the Central US during the middle of next week, dumping extremely cold temperatures into the CONUS (White colors denote areas that are below 0F)

We’ll continue to update you on this Arctic outbreak as well as the potential storm system for mid-week! 

Have a great weekend!

-Steven Copertino

3km NAM Storm
Steven Copertino

Multi-faceted winter storm to impact the region this weekend

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Highlights: After light snow today, a more notable winter storm approaches for the weekend, with arctic air moving in behind it and a colder and active weather pattern to follow. 

Good Evening!

Today has been a rather gloomy and cold January day across much of the Northeast as the weak system that dropped some light snow across portions of the metro area this morning continues to quickly head offshore. As discussed in previous updates, this system was likely to only produce a trace to one inch of snow over the area, and that is exactly what has been reported as of this afternoon.

As the snow departed late this morning, mainly cloudy conditions remained overhead with mid level flow increasing out of the southwest. These southwesterly winds have allowed for a slightly more marginal airmass to overspread the area today. Coupled with the persistent cloudy conditions, this caused highs today to rise into the middle to upper 30’s across much of the forecast area-with 40’s reported closer to the coast. Cloudy and slightly above-normal temperatures will continue into the evening hours before a mid level disturbance passes well to our north. This system will be accompanied by a cold front that should help to clear out some of the remaining clouds tonight and usher in colder temperatures from our northwest.

Lows will likely drop back down into the lower to middle 20’s for the majority of the area this evening, which will be right around normal for this time of year.

3km NAM Simuawips

This evenings high resolution NAM model showing lows backing down into the 20’s and lower 30’s for the NYC area

Complex and Impactful Winter Storm This Weekend

While tomorrow (Saturday) will likely start off quite calm and clear, the winter storm we have been talking about for nearly ten days now will be quickly approaching from the west. By 8 am, the storm will be centered over the Tennessee valley, with moderate to heavy snow expanding into much of the Ohio Valley. While the main shortwave trough associated with this system will not be able to completely interact or phase with the larger system over Canada, it does appear that there will be just enough of an interaction to keep the bulk of the heavy snow well off to the north and west of the immediate NYC area.

As we head into Saturday afternoon, the surface low over the Tennessee valley will be picking up steam and intensifying. As it does so, a large area of warm/moist air will begin to stream northward over much of the Southeastern states. All of this warm and moist air just above the surface will collide with a strong Arctic high pressure system over southern Canada and cause a moderate to heavy band of snow to develop over portions of New York and Pennsylvania. Light snow will likely begin to move into portions of Eastern New Jersey by 3-4 pm, with the snow quickly picking up in intensity over time. This band will continue to head east by 4-5 pm, likely overspreading the entire metro area by that time. All of the warm/moist air moving into the Northeast and colliding with colder air to the north will cause an enhanced area of lift within this band of snow, which could push snowfall rates into the 1-2″ per hour range–especially over portions of EPA, SNY, and NW NJ.

This area of moderate to occasionally heavy snow will likely continue into the evening hours of Saturday. It is at this time that precipitation types will start to become an issue. Due to the SW to NE orientation of this system thanks to the modest interaction with the system located over Canada, warmer air in the lower levels of the atmosphere will begin to overspread much of Southern and Central New Jersey, and eventually into the immediate NYC area. While the overall track of this system and the actual degree of interaction with the aforementioned Canadian system will determine the timing of this changeover, much of the metro area will likely see a change to a mix of sleet, freezing rain, and plain rain by 11 pm to 1 am. Locations off to the north and west of the immediate NYC area could potentially hold onto pure snow few a few more hours, causing a steep snowfall gradient to develop over our area.

Warm/moist air will continue to push further north into the forecast area overnight on Saturday and into the early morning hours of Sunday. Locations around the immediate New York City area have a good chance to flip to all rain at this time, with locations to the north and west potentially changing over to a dangerous mix of sleet and freeing rain. In fact, the freezing rain threat will be quite high over this area, with up to a tenth to a quarter of an inch of freezing rain possibly falling by Sunday morning. 

The combination of moderate to heavy snow and freezing rain will likely cause very significant travel disruptions north and west of the city on Sunday morning.

Total Snow Forecast

Our latest total snowfall accumulation map for Saturday and into Sunday morning. The hatched area denotes the potential for significant freezing rain and sleet accumulations.

Dangerous Flash Freeze Possible Sunday and into Monday

Precipitation will likely still be ongoing by 8 am Sunday morning, with rain mostly expected for the vast majority of the forecast area as the surface low pressure system will likely be over Southern New Jersey at this time. Despite the change to plain rain, much colder air will be quickly approaching the area as the surface low begins to pull to our east during the afternoon hours on Sunday. Temperatures will quickly fall well-below freezing and into the lower to middle 20’s from west to east, likely causing any standing water to refreeze. Any residual precipitation over the area will need to monitored, as a flip to snow would be possible.

Regardless, true Arctic air will work blast through the entire forecast area by Sunday night, with lows dropping down into the single-digits! Winds will also be quite strong behind this system, with gusts up to 35 mph possible. If significant ice accumulations do occur over portions of the area, then there could be an enhanced threat of power outages Sunday night.

The colder than normal weather pattern is very likely to remain in place into next week, as a piece of the polar vortex fractures and settles in to the north of the region. This will keep cold and potentially active weather in the forecast as we move toward the back half of the week, and especially into next weekend.

We will Continue to provide updates on this storm over the next day or so. Please stay tuned to our social media accounts for up to the minute information!

Thanks for reading!

-Steven Copertino/John Homenuk

Steven Copertino

Another Round of Records May Fall, Any Chance of Warmer Weather Soon?

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Good Afternoon! 

We hope everyone out there has been bundled-up over the past couple of days as we continue to endure a record-breaking temperatures across much of the Northeast. Today was a little warmer than yesterday, but warmer in this sense is still relative. Temperatures were stuck in the upper teens to middle twenties across the entire New York Metro area, with some middle to lower teens further north and west of the city. The same stout northwesterly flow in the mid levels of the atmosphere are still prevalent across the entire northern tier of the country, which continues to pump dry, Continental polar air into the country. Mainly dry conditions can be expected for the rest of the afternoon and into the evening hours before a weak shortwave trough begins to move into the Ohio Valley later tonight. This system looks to be too weak and too far west to really bring any precipitation into the region, but we should see an increase in mid to upper level clouds during the overnight hours. These clouds will work to dampen the maximum amount of radiational cooling we can achieve, but lows tonight will still be downright frigid once again. Middle to lower teens are expected tonight for the immediate NYC area, with single digits likely just to the north and west.

This afternoon high resolution visible satellite imagery, regional radar mosaic, and surface observations showing yet another bitterly cold day across the entire Northeast.

This afternoon high resolution visible satellite imagery, regional radar mosaic, and surface observations showing yet another bitterly cold day across the entire Northeast.

Light Snow Possibly Saturday

The weak shortwave trough that we mentioned earlier will continue to move east overnight and into the early morning hours on Saturday, likely bringing some very light snow to portions of the Mid Atlantic states. This system will be seriously moisture-starved, but any snow that falls will be high-ratio snow. This means that even if you see around .1″ of liquid, you could still manage to see about 1.5″ of fluffy snow. Scattered light snow should begin to overspread portions of eastern PA and NJ by the early morning hours tomorrow, with more concentrated bands possible over MD/DE. Light snow should then move over the rest of the area by the late morning and afternoon hours as a secondary low begins to develop just off of the Mid Atlantic coast. Once this secondary low begins to mature, snow should be ending over much of NJ and points west, with trace to maybe an inch of snow possible. Our secondary low should have more of an impact further east over portions of Long Islands and Connecticut where it should act to rejuvenate snow over those areas and possibly add a boost to the intensity. Slightly higher accumulations may be possible in these areas, with 2-4″ possible before the low quickly races off to the east and precip shuts down by 8-10pm. Note: Due to the extensive dry air ahead of this system, we could see prolonged periods of virga over the area leading to the possibility of little to no snow at all in some places. 

The rest of the night looks to be very cold, with scattered snow showers possible over much of the Northeast as another shot of Polar air moves into the region overnight. Lows will drop down into the middle to lower teens around the city, with single-digits likely to the north and west.

This afternoons RPM model showing a light area of snow overspreading the region on Saturday morning

This afternoons RPM model showing a light area of snow overspreading the region on Saturday morning

Sunday will compete to be the coldest day of the year on the last day of the year as Polar high pressure builds into the Northeast during the morning hours. Highs during the day will be bitterly cold, with readings likely in the middle teens to right around 20. Strong northwesterly flow should keep enough dry air in the column to keep any clouds at a minimum. Dry and cold weather can be expected to last into the evening hours, just in time for New Years Eve. This should be one of the colder New Years Eve’s in recent memory, with the potential for quite a few records to fall across the Northeast. NYC may come very close to breaking a record low minimum temperature of around 9F.  Readings across the entire area will be exceedingly cold, around the low teens to single digits area, with wind chills a good 5-10 degrees colder. We would seriously advise against being out for a prolonged period of time in this kind of cold, but if you are planning on it, make sure to wear multiple layers of clothing and cover up any exposed skin. Bare skin will be very susceptible to frost-bite during the evening hours!

National Weather Service forecasted lows on New Years Eve, with the circles representing possible records being tied or broken!

National Weather Service forecasted lows on New Years Eve, with the circles representing possible records being tied or broken!

New Years Day & Beyond! 

We look to start off 2018 with another frigid and potential record-breaking day as very strong northerly flow dumps the remaining Polar air right into the Northeast. Most locations near the City will likely not be able to reach the 20’s, with middle to upper teens likely as highs during the day. Locations even further to the north and west will also struggle to see highs come out of the single-digits, making Monday an excellent day to just stay inside and enjoy a nice warm beverage!

Will things improve and warm up later next week? The short answer is absolutely not. We could see temperatures briefly come back into the upper 20’s, but most of the Northeast may be stuck below-freezing for at least the next 10 days or so! To further complicate things, a coastal storm may past to the east of the region on Wednesday, which would bring down another extremely cold airmass from deep in Canada. At this time, this system appears to have a low chance of impacting the East, but we will be monitoring this system very closely since some of yesterdays guidance did show the potential for a rather high-impact storm if all the pieces come together at just the right time and place (thread the needle type of system)

This afternoons ECMWF model showing a reload of the cold weather with a shot of true Arctic air next week.

This afternoons ECMWF model showing a reload of the cold weather with a shot of true Arctic air next week.

Have a great weekend and we’ll see you in 2018!

Steve Copertino

John Homenuk

The importance of the EPO and upcoming cold risks

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For some time now, we have discussed the likelihood that colder than normal air would be a common theme in the Northern and Eastern United States during the month of December. Like most things, it was not expected to be constant, but it was expected to be prevalent, and especially when compared to the past few December’s which featured nearly coast-to-coast anomalous warmth in the United States.

After a warm start, colder than normal air invaded the Great Lakes, Ohio Valley and Northeast during December’s second week. Winter weather threats have followed, with many areas recording multiple snowfalls. While this airmass hasn’t broken records, it has been just as anomalous as advertised, and has had an obvious impact on markets and businesses. After a brief period of moderation, forecast models are beginning to signal the return of arctic air into the USA – and this time it may be more anomalous than before.

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