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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

Steven Copertino

Public Analysis: Unsettled Conditions Persist, Another Cool Shot Looming?

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Good Evening! 

After a very dreary past two days, mostly due in part to a stalled front to our south and persistent cool winds coming off of the Atlantic, today was finally a nice change with highs finally climbing to just below seasonable levels! More seasonable conditions should persist through the end of this week and into the beginning of the weekend, but this should be rather short-lived as a complex disturbance from Canada dives down our way and brings a chance at some increasing clouds and showers once again by late Sunday into early Monday. Beyond that, there are hints that below normal temperatures and more rain threats will likely persist into at least the first half of June, as high-latitude blocking near Greenland and Central Canada take shape once again!

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After seeing overcast and mostly cloudy skies with some patches of drizzle embedded in some spots this morning, a cold front moving past the region ushered in a drier Canadian air-mass. This dry air in the mid levels of the atmosphere worked to significantly weaken the cloud deck across much of the area, which allowed most areas to start to see breaks in the clouds. As the afternoon progressed on, these breaks became more numerous, and most locations broke out with full-blown sunny skies. These sunny skies, light winds from the south, and warmer temperatures aloft allow for highs today to make quite the rebound, with most areas seeing temperatures rise into the mid-upper 70’s, with low 60’s to lower 70’s across some coastal locations. These cooler readings were felt primarily along the south-facing shores of Long Island and Connecticut, but even these locations managed to see clearing take place at one point or another during the day.

With this clearing taking place this afternoon, in addition to some more moist air being lifted over north and west portions of the area, we have also seen the return of summer-time thunderstorms developing ahead of yet another cold front. The environment over the area this afternoon has been characterized by rather marginal instability and some decently strong wind shear. There is also a piece of energy swinging through portions of Pennsylvania that will act as a trigger to set off any potential storms later this afternoon and into this evening.

The best chance for any organized severe thunderstorm activity will likely be north and west of the city, but it would not be impossible to see some residual activity work its way down into the New York City metro area, as some short-range models are hinting at. The main risks with these storms will likely be some gusty winds around 50 mph, small hail, and frequent lightning. The Storm Prediction Center in Norman Oklahoma has placed locations north of the city in a Severe Thunderstorm Watch until 9pm this evening. As night falls, any residual storms should begin to rapidly weaken, and any storms that happen to approach the coast will also begin to rapidly weaken due to a much more stable airmass in place over those locations.

This afternoons latest regional radar mosaic, surface observations, visible satellite imagery, and watch/warning information. Note the yellow boxes and lines, which delineates Severe Thunderstorm Warnings (solid) and Watches (lines)

This afternoons latest regional radar mosaic, surface observations, visible satellite imagery, and watch/warning information. Note the yellow boxes and lines, which delineates Severe Thunderstorm Warnings (solid) and Watches (lines)

Thursday and Friday 

The cold front that is responsible for these showers and thunderstorms will begin to overspread the region very early tomorrow morning, around 5-8am. More dry air will likely be reinforced over the area as an area of high pressure also works its way towards the Northeast, thus giving way to mostly sunny conditions. These dry and relatively calm conditions tomorrow will allow highs to once again reach into the mid to upper 70’s, with some inland locations likely reaching into the 80’s by late-afternoon. Though things look rather tranquil, there is a very slight chance that some showers or thunderstorms could pop-up during the afternoon hours as another piece of energy embedded in a large upper-level low over our area rotates through. Any shower activity would likely be very limited in coverage and quite short-lived.

Much of the same is expected on Friday, with highs likely staying in the same range as Thursday, but the shower threat may be slightly increased as there will be some more available moisture and lift to trigger possible thunderstorm/thundershower development across the area. However, another cold front looks to push through the area later in the evening, so this shower threat does not look like it will have much potential to linger around at all, as a dry and stable air-mass will likely establish itself and remove any lingering activity.

This afternoons European model showing a closed upper level low sitting over the region on Friday, with associated pulses of energy rounding the base of the trough, which may provide a chance at some afternoon thunderstorms (Valid Friday 2pm)

This afternoons European model showing a closed upper level low sitting over the region on Friday, with associated pulses of energy rounding the base of the trough, which may provide a chance at some afternoon thunderstorms (Valid Friday 2pm)

This Weekend and Beyond

More unsettled weather is likely later this weekend and into early next week as a frontal boundary will be draped to the south of the region with an upper level jet streak placed in a favorable spot to provide divergence in the upper levels, which looks to support at least multiple waves of low pressure developing along the boundary and affecting the area with the potential for more moderate to heavy rain. This afternoons model guidance is quite bullish with the development of a rather large area of low pressure that then begins to transfer to the coast with time. This would provide the area with quite a bit of heavy rain, but other computer models diverge with the handling of this system, but it does seem like we may have to watch the period of early next week for our next heavy rain threat.

Unfortunately, it seems like any prolonged period of summer-like warmth will be denied once again due to high-latitude blocking over Greenland and Central Canada providing yet another cool shot for the eastern half of the country starting next week. The long range ensemble models have been holding onto this period of below-normal temperatures and increased precipitation for what looks to be the first half of June. While the details are very far from final right now, the overall atmospheric pattern that we are in, combined with what has happened the past few weeks would support such an event.

We will continue to update you on the next possible heavy rain threat next week in addition to the potential cool shot looming next week!

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Have a great evening!

Steve Copertino

 

Steven Copertino

Public Analysis: Heavy Rains Likely Friday, Below Normal Temperatures Next Week

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Good afternoon! 

After the strong cold front that came through on Monday evening that brought some showers and thunderstorms to the area, we are finally back into a rather nice period of weather which started with yesterday’s mostly sunny skies and highs in the upper 60’s to lower 70’s. After another cold front moved through the region early this morning and brought a reinforcing shot of cooler air as well as drier conditions. These conditions should last though the day tomorrow, but a rather large storm system is once again gathering strength to the south and looks to impact our area on Friday with heavy rains and some gusty winds.

Today Into This Evening

As mentioned, we had a cold front push through the area early this morning which brought in yet another cold shot from deep into Canada, in addition to clearer and drier conditions. As of 2pm this afternoon, temperatures around the area were steady in the upper 50’s to lower 60’s across the entire area. As weak residual energy associated with the old cold front exits the region, spotty clouds and maybe a very light shower may be possible (especially over portions of Connecticut). However, as this residual energy continues on quickly to the east, high pressure from the west currently over Great Lakes region will move towards our area this evening and into tomorrow morning. As this high moves east, clouds should gradually dissipate and be replaced by mostly clear conditions as we head into the late afternoon and evening hours.

It is worth noting that there will still be a rather impressive pressure gradient still over our area the rest of this afternoon due to the interaction between the advancing high pressure to our west and the retreating low pressure off of the Canadian maritimes. This will support some gusty winds until sundown of around 15-25 mph, which may also make it feel a little cooler than it actually is, despite temperatures being right around normal for this time of year.

As we head into this evening, the combination of clearing skies, cool mid level temperatures in the atmosphere, and subsiding winds will lead to perfect conditions for a rather cool night for the entire area as radiational cooling takes place.  Most of the immediate New York city area, should remain in the mid to upper 40’s, but as you head away from the coast, low temperatures will have the potential to dip into upper 30’s and low 40’s. Locations near the Pine Barrens may have a shot at seeing their coldest lows in a while as temperatures have the potential to fall into the middle 30’s. These lows will be around 5-8 degrees below normal, so it will definitely feel like we’re leaping back a few weeks during the early morning hours tomorrow.

 

Latest regional radar mosaic, surface temperatures, and visible satellite imagery as of 2pm this afternoon showing clearing conditions from west to east (Courtesy of GREarth)

Latest regional radar mosaic, surface temperatures, and visible satellite imagery as of 2pm this afternoon showing clearing conditions from west to east (Courtesy of GREarth)

Thursday Into Friday Evening

Tomorrow morning should start off rather sunny, but relatively chilly with temperatures likely staying in the 40’s for the morning commute. As the high pressure continues onwards to the east, it will change the wind flow from light northwesterly winds to southeasterly winds from off of the cool Atlantic. As we progress through the day, the chilly start and increasing cloud cover out ahead of the large storm system will effectively work to cap our highest potential temperatures tomorrow afternoon into the upper 50’s and low 60’s for most locations. With the addition of southeasterly winds, coastal locations will likely see highs a few degrees lower in the middle to upper 50’s, with the added possibility of some overcast as moisture begins to increase in the low levels of the atmosphere. As we get into tomorrow evening, clouds should continue to increase to the point that overcast will overspread the entire area before sunset. With weak winds  coming off of the ocean, increasingly cloudy conditions, and a warmer layer of air working its way north, lows tomorrow will likely stay in the upper 40’s to low 50’s across the entire area.

The main show for this period will be located to our southeast Thursday evening and into the early morning hours on Friday. The aforementioned negative NAO (North Atlantic Oscillation) that we talked about last week has indeed transpired, which will help to trap an energetic piece of energy currently located over the central portion of the country. As this piece of energy gets “trapped” but the blocking high pressure over Greenland, it will begin to phase, or combine energy with another system diving down from Canada. Once these two pieces of energy come together fully by tomorrow morning, the result will be a very large and impressive storm system. As this storm continues to intensify over the Tennessee valley, the storm will likely begin to take in a massive amount of water vapor from the south and southeast, and begin to transport that water vapor north towards our area. This is quite similar to what is often referred to as an “atmospheric river”, or a long fetch of moisture originating from a deep tropical airmass, which will have the potential to produce heavy rainfall. In this case, the source regions for the warm, tropical air mass will be the Gulf of Mexico and the southwestern Atlantic, both of which have above-normal sea surface temperatures for this time of year.

This afternoons European model showing the very impressive moisture feed pouring into the Mid-Atlantic coast during the day on Friday with associated strong mid-level winds (Valid 2pm Friday)

This afternoons European model showing the very impressive moisture feed pouring into the Mid-Atlantic coast during the day on Friday with associated strong mid-level winds (Valid 2pm Friday)

In addition to the very impressive moisture feed from the south, the cyclone will have strong low level winds in the lowest few thousand feet of the atmosphere that will help to not only bring in more moist air, but also provide a mechanism for rising air in the atmosphere, which could generate isolated very heavy rainfall and training of storms. If we do see the low level jet strengthen like this afternoons model runs show, then there will be a potential for some localized flooding, mainly on roads with poor drainage as the rainfall rates quickly overwhelm the drainage systems.

With a great number of details being highlighted this far out, there are some uncertainties regarding this system that will ultimately determine how much rain the region sees. For example, if we see the low level jet become more delayed in future model runs, then the potential for the heaviest rainfall will shift east to portions of southern New England. Additionally, the models have been trending more towards a quick hit of around 6 hours for the heaviest rainfall during the day on Friday. There is the potential that the models are sniffing out  the potential for more convection to develop and affect the region, which may produce very heavy rains for some locations, but not nearly as much around that convection, or storms. At this time, we do feel that there is a reasonable amount of confidence in around 1-2″ of rainfall during the day on Friday, with some gusty winds of around 25-35 mph in the heaviest downpours. Local amounts of up to 3″ may be possible in areas that see training of the heaviest rain. Stay tuned for further updates on this storm over the next 48 hours, and make sure to check in with your local NWS for information on any watches or warnings that may be posted!

This afternoons high-resolution 3km NAM showing very heavy training showers and isolated thunderstorms over the NYC metro area by 12pm Friday afternoon

This afternoons high-resolution 3km NAM showing very heavy training showers and isolated thunderstorms over the NYC metro area by 12pm Friday afternoon

Saturday and Beyond

With the aforementioned negative to remain in place for the foreseeable future, unsettled weather is expected to continue through Saturday and into Sunday as the storm system becomes trapped and will potentially deliver some cloudier weather once again with the potential for showers on both days. Into next week, high pressure diving down from Canada may briefly stabilize things while simultaneously providing below-normal temperatures for the vast majority of next week. Make sure to stay tuned for further updates on this potentially significant system!

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For more information and posts like this one, make sure you sign up for Zone 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 evening!

Steve Copertino

John Homenuk

Coldest air of the season arrives Monday Night

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With news of an impending rain storm and warmup on Monday, hope may be rising for increasingly pleasant weather during the next week. That hope will come crashing down as quickly as Monday Night, along with temperatures throughout the forecast area. An arctic blast, straight out of Canada, will rush into the area on Tuesday behind Monday’s storm system, bringing the coldest air of the season into the area.

Forecast models have been consistent in hinting at this potential for 7 days or more, but are just now beginning to focus in on the intensity of the cold air. Anomalous and impressive, the cold air will surge in from Central Canada. First into the Ohio Valley, and then into the Northeast — straight to the coast

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