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Steven Copertino

Strong Fall Storm Likely To Impact the Northeast This Weekend

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Good Afternoon! 

Today was another in a series of cooler and more fall-like days after the passage of a strong cold front earlier in the week that has worked to keep temperatures rather seasonable and the humidity low. Most of the area is currently under the influence of a large area of high pressure currently situated off of the North Carolina coast, which extends northeast into the Atlantic. This area of high pressure has been providing much of the Northeast with light winds out of the south/southeast this afternoon, which has allowed for slightly warmer mid level temperatures to work their way northward. These ever-so-slightly warmer mid level temperatures in conjunction with relatively clear skies have allowed highs to only reach into the low to middle 60’s across the Northeast. The rest of the day should remain quite clear and clam, with only a few high cirrus clouds likely during the day due to strong sinking air associated with the high pressure to our south. This evening should also be quite pleasant in terms of sensible weather as low dewpoints, clear skies, and light winds dominate the area. These conditions will also allow for radiational cooling to take place once again this evening, but not quite as expansive/severe as last night due to slightly warmer temperatures located a few thousand feet above the surface. Lows tonight will likely range in the upper 30’s to middle 40’s across the area, with the lowest temperatures located to the north and west of the immediate city.

Tomorrow (Saturday), we should see a pretty clear and pleasant start to the day, but southerly flow will increase in earnest ahead of a strong cold front which will be located over the Ohio Valley. As the southerly flow increases, we can expect mid level clouds to develop by the afternoon hours, but with even warmer mid level temperatures, highs will likely warm up into the upper 60’s to lower 70’s tomorrow despite the cloudier conditions. As we head deeper into the afternoon and early evening hours, the strong cold front will likely be located over western/central Pennsylvania with moderate to heavy rain over that region. Closer to the metro area, we can expect overcast to take over before dark, with a chance at a few showers over the region. Humidity will be on a rapid increase Saturday evening, and the strong frontal system begins to funnel deep tropical moisture to the north, associated with a tropical system down near Florida.  The increase in cloud cover and the additional moisture will lead to temperatures remaining relatively mild for this time of year, with lows in the middle to upper 50’s.

This afternoons high resolution visible satellite imagery, regional radar mosaic, and surface observations showing a relatively calm day to end the work week

This afternoons high resolution visible satellite imagery, regional radar mosaic, and surface observations showing a relatively calm day to end the work week

Sundays System 

Conditions should begin to deteriorate quite quickly across much of the Northeast on Sunday as the upper level system currently located over the Great Lakes region begins to intensify. As this system intensifies Sunday morning, the rain associated with the original cold front will begin to increase in intensity as well as coverage. Simultaneously,  the remnants of a tropical system will be drawn northward into the coast of the Carolinas. As these two features gradually merge over the Mid Atlantic states, a very potent upper level jet streak located tens of thousands of feet above the ground will also intensify with wind speeds of around 190 mph. This intense jet streak will provide excellent upper level divergence and surface convergence for the developing low pressure near the Mid Atlantic states, which should cause the system to intensify quite quickly as we head into the afternoon hours of Sunday.

By Sunday evening, the energy in the base of the upper level trough will begin to swing eastward and take on a more negative orientation, which will further promote the development and expansion of precipitation over the Mid Atlantic and Northeast states. This afternoons model guidance has shifted westward and a bit stronger with the overall system, indicating that the low pressure area will be located in the vicinity of Atlantic City, NJ by 8pm Sunday. This scenario would lead to very heavy rainfall rates over the entire Northeast, with strong, gusty winds from the east also increasing through the evening. This afternoons European ensembles, which is a blend of 51 models with different initial conditions shows that the low will then take a track to the NNW into New Jersey, and then Pennsylvania by late Sunday night and into the early morning hours of Monday. The storm would likely be intensifying while still heading inland, with the European model showing pressures in the low 970’s-which is common for an Atlantic hurricane. Widespread heavy rainfall and strong winds will likely continue as the low heads inland over portions over southern New York state and finally begins to weaken into the day on Monday.

This afternoons European model showing a very strong storm tracking inland over NJ/PA Sunday evening with very heavy rains and damaging winds

This afternoons European model showing a very strong storm tracking inland over NJ/PA Sunday evening with very heavy rains and damaging winds

Impacts

As of this afternoon, it appears that this low pressure system has the potential to bring rainfall in excess of 2-4″ across much of the New York metro area, with locally higher amounts possible over Long Island. With a system like this, usually the heaviest rains will be on the western side of the low pressure track, while the strongest winds will be on the eastern side. With that said, much of New Jersey, New York, Connecticut, and the rest of SNE could see strong wind gusts in the 40-60 mph range. This could be conservative in some locations, where some of the high resolution models have winds nearing hurricane force (around 75 mph+) over portions of Long Island. However, the exact magnitude and extent of the winds will likely be under question until tomorrow afternoon when we get into the prime range for our model guidance and the tropical system down south is better resolved. Regardless, these kinds of winds could easily down small tree limbs, and potentially down a couple trees due to saturated grounds. In addition, the heavy rains will likely cause some small-stream flooding and ponding of water in roadways, but a marginal drought over the region should be able to soak up enough of the storms rain so that widespread flooding is not likely.

Preparedness– Due to the possibilities of strong winds and the time of year, it is recommenced that any Halloween decorations are either taken down, or secured so that do not blow around and cause damage to property. Also, make sure that you do not have any weak, or lose branches near utility lines that may cause lose of power. Make sure to stay up to date with your local NWS office for any potential warnings and updates on the forecast over the next 36 hours. There are still some questions regarding the overall evolution of this system, so make sure to check back to get the latest on this system!

Total rain accumulation from the Weather Prediction Center

Total rain accumulation from the Weather Prediction Center

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Have a great and safe weekend!

Steve Copertino

John Homenuk

Strong storm expected in the Northeast this weekend

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Amidst an anomalous pattern, which features a large ridge in the Western United States and a changeable Pacific Ocean wave progression, sensible weather changes have been observed across the Continental United States. Nowhere is this more apparent this morning than Minnesota, where snow is on the ground across much of the Central and Northern parts of the State after a very warm October. Nationally, though, the anomalous warmth has gone on a hiatus as well, as the Western USA ridge acts to promote cooler air surging southward.

These anomalous patterns on either of our coasts can often preclude multiple storm threats, including the potential for larger ones, and this pattern will be no different. After a handful of storm systems in the Central US and Great Lakes will come a larger, more significant storm threat later this weekend in the Northeast States. A deep trough is expected to dig into the Mississippi River Valley this weekend, interacting with energy over the Southeastern United States.

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Steven Copertino

Rare July Nor’Easter Possible This Weekend With Heavy Rains and Wind

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Good Evening! 

Today was yet another in a series of days with below average high temperatures and low humidity. The difference with today, was the fact that we were able to mix out some early morning clouds and have a mostly sunny day across the vast majority of the area, as well as the Northeast. The area of high pressure that contributed to some pleasant and cooler weather yesterday moved directly over the NYC metro area this afternoon, and this further helped to conditions quite pleasant, with light winds generally from the south. With low humidity, clear skies, and a fresh high pressure system over the area, we saw highs limited to the mid to upper 70’s, with a few locations off to the west and north over Pennsylvania and northern New England reaching into the lower 80’s this afternoon. Overall these temperatures were around 5-10 degree below the norm for this time of year, and quite the contrast to the miserable heat and humidity we had over the entire Northeast just a week ago.

As the area of high pressure that was in control for most of the day continues to head eastward, it will begin to kick up more of a southerly flow in its wake later this evening. As it does so, this will lead to increased low level moisture building over the region as well as mid level temperatures increasing ever so slightly. The gradual increase in low level moisture should allow for the development of cloudier conditions for the rest of the evening, which should allow for overnight lows to not be quite as low as they were the past few nights, with temperatures getting down into the lower to middle 60’s across much of the area.

This afternoon/evenings latest high resolution visible satellite imagery, regional radar mosaic, and surface observations, showing relatively pleasant conditions with some high clouds beginning to move in as the high pressure to our east gradually fades (Courtesy of Simuawips.com)

(Click To Animate) This afternoon/evenings latest high resolution visible satellite imagery, regional radar mosaic, and surface observations, showing relatively pleasant conditions with some high clouds beginning to move in as the high pressure to our east gradually fades (Courtesy of Simuawips.com)

Thursday into Thursday Evening

Thursday should start off with mostly broken clouds, with some overcast further inland as the area of high pressure really begins to back off to the east and begins to introduce a brand new moist airmass into the Mid Atlantic and Northeast regions during the late morning and afternoon hours. Additionally, south-southwest flow will also begin to increase markedly ahead of a mid level shortwave that will be located over the Great Lakes region as well as the Ohio Valley. As this south-southwest flow begins to increase, mid level temperatures will begin to increase once again, which should support a round of warmer temperatures by the mid afternoon hours. Despite the possibility of some cloud cover, highs should be able to get into the low to middle 80’s-which will be right around normal for the area during late July. It should be noted that some influence from afternoon sea breeze activity could work to cut highs along coastal sections tomorrow by five or so degrees. In addition to the increasing temperatures, the dreaded dewpoints will once again be on the rise tomorrow afternoon-with values ranging in the mid 60 to lower 70 range, making for a muggy afternoon tomorrow, reminiscent of the days last week.

With all of this increasing moisture in the low levels of the atmosphere, we will likely also see instability begin to increase tomorrow afternoon and into the evening hours. Though not as impressive as it looked a few days ago, tomorrows setup should still yield a marginal risk for severe thunderstorms across the Northeastern states as a weak mid level system will gradually work its way east and potentially spark some showers and thunderstorms during the late afternoon and evening hours. The main limiting factors for any widespread/impressive thunderstorm development will be relatively meager mid level lapse rates, as well as any impressive shear to help keep potential updrafts organized and coherent. However, more favorable parameters may come together over portions of Pennsylvania and New York, so those with interests in those locations may have a better shot at seeing strong to severe thunderstorms capable of damaging winds and possibly a brief tornado. Otherwise, any storms that form near the NYC metro area will likely be capable of producing gusty winds, heavy rainfall, and frequent lightning before they gradually fade to the east by sunset. Expect another humid evening with lows ranging in the middle to upper 60’s once again.

This evenings latest RPM model showing the general evolution of Thursday weather, with some showers and thunderstorms possible. Widespread severe thunderstorm development is not anticipated (courtesy of WSI)

This evenings latest RPM model showing the general evolution of Thursday weather, with some showers and thunderstorms possible. Widespread severe thunderstorm development is not anticipated (courtesy of WSI)

This Weekends Potentially Impactful Nor’Easter 

Back on Monday we highlighted the possibility that the Northeast would have to deal with an area of heavy rain moving in from the west during the evening on Friday and into the early morning hours of Saturday, however since that time there have been some marked changes with regards to the duration, timing, and overall severity of this potential system. While the overall main players remain the same, with the initial monsoon energy moving up and around the periphery of the large heat ridge located in the Plains, as well as a small, but potent shortwave diving out of Canada-how these two interact remains to be far from settled at this time.

This afternoons model guidance suggests that as the initial monsoon energy heads into the Ohio valley, the potent Canadian shortwave trough will begin to interact with this energy and begin to phase together to some degree. This setup is something we’d typically be talking about in the Winter months, but the overall outcome may wind up being quite similar-just with warmer temperatures this time around. As these mid level systems interact and potentially phase, this will cause a surface low to develop over the Mid Atlantic states during the afternoon hours on Friday. As this surface low begins to become more established, it will have a very warm and moist feed of tropical air pumping into it from the south. Additionally, it looks quite likely that there will be a favorable upper level jet configuration overhead of this system, which should promote a healthy amount of upper level divergence and convergence at the surface levels. In short, when all of these factors come together in just the right manner, its a rather strong signal that very heavy rain will be likely for portions of the Mid-Atlantic.

So what could go wrong? Though this system will have some potentially favorable synoptic support, there are some serious questions that still remain with this system that make this a very difficult forecast. First off, the trough diving down from Canada is whats known as “positively tilted” in nature, meaning that the majority of its energy is located in the bottom left quadrant of the trough, which often allows the system to be progressive in nature. It also does not help that we have been stuck in a rather progressive west to east pattern for the past week or so, with no upstream blocking to help slow things down. This pretty much eliminates the chances of a large, wrapped up system along the coast unless something drastically changes. Next off, the initial monsoon energy out ahead of the Canadian system will be moving quite quickly to the east, and as the Canadian system drops south, it may wind up shearing out the energy ahead. This would create a much weaker and disjointed system that would likely have the heaviest rain offshore.

Taking all of this into account and carefully looking at this afternoons model guidance, I have decided to go with a blend of the ECMWF/NAM/ECMWF-ENS/UKMET at this time. This would lean towards a more progressive solution for this system, bringing the surface low from the Mid Atlantic coast, to well southeast of New England. This track would likely still bring moderate to heavy rain to the NYC area, but areas south of NYC would likely feel the brunt of this system (PA/MD/SNJ). At this time, it seems likely that the heaviest batch of rainfall should be able to drop 1-2″, with some higher amounts possible along the coasts of NJ and LI. This system is forecast to exit the region by Saturday afternoon, with some showers and gusty winds lingering around thereafter.

We will be carefully monitoring this system over the next few days and providing updates as needed!

This afternoons ECMWF model showing a rather impressive Nor'Easter for this time of year affecting the Mid Atlantic and portions of the Northeast with heavy rain and gusty winds (Courtesy of Accuweather Pro)

This afternoons ECMWF model showing a rather impressive Nor’Easter for this time of year affecting the Mid Atlantic and portions of the Northeast with heavy rain and gusty winds (Courtesy of Accuweather Pro)

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 day!

Steve Copertino

Miguel Pierre

3/30 All Zones AM Update: Significant Storm with Heavy Rainfall Likely on Friday

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Happy Thursday! High pressure will support another beautiful day for the region with more sunshine and dry condtions. Some high clouds will arrive by the afternoon hours, ahead of the next storm system approaching from the west. High temperatures today will be a little cooler than on Wednesday– in the lower to middle 50s. But with the center of high pressure near the region, winds will be much calmer this afternoon.

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