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Cooler Conditions Hanging On, Changes Coming This Week

Good Evening! 

The storm that bombarded portions of the Northeast over the past day is quickly moving out over eastern Canada, but the storm certainly left its mark. Most of the Northeast saw heavy rainfall totals in the range of about 2-5″, but the main event from this system were the winds that roared in overnight last night. As the low pressure area rapidly deepened and moved ashore over NJ and eventually progressed into New York state, it carried a large an impressive area of high winds just above the surface over portions of Long Island, Connecticut, Rhode Island, Massachusetts, Vermont, and Maine. As the storm began to fill in with warmer air and weaken, these winds just above the surface were able to rapidly crash down to the ground and cause an impressive amount of tree damage. Hundreds of thousands of folks are still without power in many of the states above, with over 400,000 customers without power in Maine alone. While these winds were rather impressive, the main story west of the immediate area of low pressure were the torrential rains that fell. Deep tropical moisture streamed northward into the Mid Atlantic and Northeast states, and when this moisture was met with the strong dynamics aloft, heavy rain became focused over New Jersey and portions of New York for several hours. Some locations were able to rack up rain totals in the 4-5″ range when all was said and done, with some minor street and river flooding noted. As we stated last week, the reason that these rains were not a bigger story was because an existing minimal drought muted out the overall impacts.

Sunday nights radar near the peak of the coastal storm that brought heavy rains and high winds over the region

As day broke today, a strong westerly jet associated with the backside of the low pressure system was working its way over the Northeast. Due to more mixing of dry air in the atmosphere, this low level jet was able to bring gusts down to the surface in the range of 30-40 mph, which brought some additional tree damage to the region. It also made for a cooler and more classic fall day as cooler Canadian air was briefly tapped. With partly sunny skies and cooler temperatures aloft, highs were able to make it into the middle 50’s across much of the region, but cooler conditions to the north and west kept highs down in the low to upper 40’s-with some stations in New York state even reporting snow showers! As the massive low pressure system continues to pull away this evening, wind have shifted from northwest to southwest as high pressure begins to build in from the south. As the winds shift, the gusty 20-30 mph conditions will begin to die down as the pressure gradient from the two opposing systems weakens with time. Given the clear skies and low humidity, conditions will be marginally supportive for radiational cooling to occur tonight which should knock temperatures down into the upper 30’s and lower 40’s across the area.

High resolution visible satellite imagery and surface observations over the northeast showing cooling and windy conditions

High resolution visible satellite imagery and surface observations over the northeast showing cooling and windy conditions

Tuesday and Beyond

The area of high pressure just south of the area will continue to build north throughout the day tomorrow, which will allow for dry conditions and generally clear skies. Highs will likely be limited to the middle to upper 50’s  during the day tomorrow despite winds coming from southwest winds at the surface, but cooler Canadian air continues to work in at the lower levels of the atmosphere. Winds will also likely die down completely by tomorrow afternoon, so as we work our way into the evening hours, we should see ideal conditions for radiational cooling to take place over the entire area. Low level temperatures will likely be below freezing already, so expect lows to drop into mid to upper 30’s, with some of the more interior locations possibly even dropping below-freezing and into the upper 20’s. With little to no winds, frost will be increasingly likely the farther away from the coast you move.

By Wednesday some changes will be in the works as a large area of low pressure begins to move towards the Great Lakes region. As this low heads northeast, it will bring a surge of warmer air along a warm front over the area, which should work to bring highs back into the upper 60’s and lower 70’s once again. Given the breadth of this system, we will likely be in between the cold front and warm front until Friday, when the cold front will finally pass, bringing a marginal chance of showers during the afternoon hours. Highs will likely remain in the upper 60’s to lower 70’s through this period, before the cold front knocks temperatures back down to more seasonable levels.

By this weekend temperatures should once again cool down with northwesterly flow returning from Canada, but we may have to watch for a threat of showers once again later in the weekend as a potential wave of low pressure rides north along a stalled cold front over the area. There is still considerable uncertainty with this solution and we’ll have more details by Wednesday as the model guidance converges on a more clear solution.

Snapshot from the 12z ECMWF model showing slightly above normal temperatures during next weekend with the return of higher heights in the east

Snapshot from the 12z ECMWF model showing slightly above normal temperatures during next weekend with the return of higher heights in the east

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Have a great night!

Steve Copertino

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EPO ridging a sign of changing pattern across USA

A pattern in fluctuation has led to several changes in sensible weather conditions across the Continental USA over the past few weeks. Stagnant warmth gave way to several shots of cold air, first affecting the Northern Plains and eventually leaking southward into the Tennessee and Ohio River Valleys. The change in wavelengths and  increased amplitude led to the development of a few significant storm systems; namely one which brought snow to the Upper Midwest, and another which delivered damaging winds and torrential rain to the Northeast.

The hemispheric pattern is set to change again  as we approach the middle part of this week, with appreciable changes already occurring in the Pacific Ocean. As we discuss quite often, what occurs in the Pacific Ocean from the Bering Sea towards the Gulf of Alaska (more affectionately known as the North Pacific) can often have major implications on the weather in the USA. There are other factors to consider, always, but we can often look there for clues, and the coming weeks will be no different.

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(Tropical Tidbits)

Significant storm system to impact Northeast states

A well discussed storm system is in the process of developing this Saturday evening and overnight, as a large and anomalous trough digs into the Mississippi River Valley. Meanwhile, Tropical Storm Phillippe continues to move swiftly through the Caribbean, shifting northeastward and eventually on track to interact with the aforementioned trough. While the two disturbances will not completely “phase”, they will interact – and the result will be the development of a powerful storm system by late Sunday.

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Strong Fall Storm Likely To Impact the Northeast This Weekend

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

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 and safe weekend!

Steve Copertino