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Steven Copertino

Public Analysis: Heavy Rain Exits, Calm Weather Sets In

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Good Evening! 

After a relatively calm few days, the area of low pressure that developed along the leftover stalled frontal boundary this morning sparked numerous showers and isolated thunderstorms that tracked over eastern Pennsylvania, New Jersey, New York, and portions of Connecticut. Deep tropical moisture ahead on the order of about 2.3″ of PWATs allowed for the overall complex to contain very intense rain rates, upwards of two inches per hours in some locations! To make matters worse, these storms were chugging along with a weak low level flow, so areas of heavy rain were rather slow and this allowed for some spots to experience flash flooding in areas of poor drainage. As the dynamics began to really ramp up as the low pressure intensified, some gusty winds began to be reported with a few embedded storms that tracked through northern New Jersey and into Long Island. There were some reports of small tree limbs being taken down with localized power outages, but due to the time of day, lack of greater instability, and weak mid level winds, these gusts luckily weren’t anything too serious.

As the low moved off the coast and began to intensify some more, the area of rain associated with the low began to accelerate, and this is what likely saved the area from seeing much higher rainfall totals that would have caused more widespread flooding. The rain gradually tapered off as the low pulled away and some more dry low level air worked its way in behind the system, which finally allowed for conditions to calm down. The cloudy, tropical air-mass gave way to mostly sunny skies, which allowed temperatures to rise into the upper 70’s and lower 80’s across the entire area, with light westerly winds. With daytime heating taking place, instability was able to build back to limited values, which promoted the development of some more showers and thunderstorms to our North and West this evening. These showers will gradually slide east/east southeast and likely diminish in intensity as the sun fades, and with it-the fuel they need to survive. The main threat with these storms will be some additional, brief heavy rain, but these storms will be moving at a decent pace, so the overall flood threat is low. Some patchy fog should develop this evening and into tomorrow morning as an inversion in the atmosphere traps the leftover humid airmass. With the inversion in place, lows should be quite mild with most of the area seeing temperatures in the mid 60’s to lower 70’s.

This afternoon/evenings latest regional radar mosaic, surface weather plots, and high resolution visible satellite imagery of the Northeast. showing the remnants of this mornings system exiting to the east.

Saturday looks to start off rather clear despite some areas of patchy fog, which should quickly burn off as the morning progresses. This should allow skies to become mostly sunny, with some spotty clouds as we head into late afternoon. To our north and west, a large mid level trough will be progressing east with a disorganized piece of energy. As the energy from this trough nears the area by the afternoon hours, the leftover tropical airmass and sunshine will allow instability to build to modest levels, with some decent wind shear allowing for the potential of muti-cell thunderstorms to develop over the area. With the upper level jet streak and greatest energy for storm development located to our north over New England, the main focus for storms looks to be over that region, but we expect scattered development at the most, with the main threat being gusty winds, small hail, and heavy rains.

Otherwise, the afternoon will likely be a hot and humid one as temperatures likely reach into the upper 80’s and even to lower 90’s across the region. The area should gradually dry out during the late afternoon hours and early evening hours as the cold front to our west begins to push through. As the front moves through tomorrow evening, the humidity should drop a bit as more stout westerly winds develop, so it should be quite pleasant with lows dropping down into the upper 50’s and lower 60’s.

Sunday will likely be a good deal quieter than the previous day as the cold front moves well to our east and the dry air to the west really begins to work its way into the area. A surface high to the south will begin to build, which will likely allow for mostly sunny skies and low dew points. The overall drier atmosphere will work to negate any threat for afternoon thunderstorms over the entire area. High temperature s on Sunday should be near-normal, with highs likely reaching into the lower 80’s across the entire area. Sunday evening should also continue the theme of being rather calm, with clear conditions and light winds expected, lows should be able to drop into the upper 50’s area-wide.

This evenings Rapid Precision Model showing the development of some afternoon thunderstorms tomorrow, followed by clearing conditions in time for the evening hours (Courtesy of WSI)

Extended Range

A strong heat ridge is expected over Western/Central parts of United States this weekend and into early next week. This will support a more longwave trough over much of the Great Lakes and Northeast with temperatures closer to normal overall. There are some timing differences on model guidance currently with individual disturbances embedded within the longwave trough could still produce some isolated-scattered convection over the region. But much of the time, just warm and dry  with some sunshine each day, as high pressure gradually builds in from the Ohio Valley.

Later in the week, we may have another infusion of deep tropical moisture into the area, with increasing temperatures. Whether or not we see another period of heavy rain will be highly dependent on if we have a trigger mechanism to set off any showers and thunderstorms. At this time, the chance for anything outside of afternoon thunderstorms seems low, and a general increase in both temperatures and humidity seems likely at the very least. We will continue to monitor this period in case anything does try to take shape.

This afternoons ECMWF model showing near-zonal flow across the country, with the main weather features located in the central regions of Canada. (Courtesy of Accuweather Pro)

This afternoons ECMWF model showing near-zonal flow across the country, with the main weather features located in the central regions of Canada. (Courtesy of Accuweather Pro)

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Have a great evening!

Steve Copertino

Steven Copertino

Public Analysis: Increasing Heavy Rain Threat Thursday, Seasonable Conditions Likely This Weekend

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Good Evening! 

We hope you had an excellent holiday weekend over the past few days and managed to dodge any showers and thunderstorms that popped up during Monday and Tuesday!

After some relatively hot and humid days on Monday and Tuesday, today was quite the improvement as a weak area of high pressure off of the Northeast coast moved offshore this morning and ushered in winds from the ocean, which were able to drop dewpoints by quite a bit across the area. A frontal boundary rode northward through the area earlier this morning and into the afternoon hours, which increased clouds briefly, but with the easterly winds coming off the Atlantic, the atmosphere was able to stay relatively stable and prevented the development of showers. The cooler marine airmass and relatively sunny skies allowed temperatures to climb into the upper 70’s and middle 80’s across the region this afternoon, which is just slightly below normal for this time of year.

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Steven Copertino

Public Analysis: Stormy Start to the Holiday Weekend, Possible Break for the Fourth of July?

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Good Evening! 

As was mentioned all the way back on Monday, today has featured quite an extensive development of showers and thunderstorms over much of the Northeast. These storms were fueled mainly by the built up heat and humidity which created modest levels of instability to build during the afternoon hours today. Additionally, the storms were aided by strong vertical wind shear in the atmosphere, which helped some storms to produce damaging wind gusts, and even some rotation which prompted at least three tornado warnings. Radar images also indicate that there is a rather high amount of moisture in these showers and thunderstorms, which can be attributed to the impressive resurgence of tropical moisture over the area that occurred yesterday when the high pressure that was over our area on Tuesday began to back away to our east, causing winds to surge from the south. As opposed to most days this year that featured decent convective development, these storms were generated by a strong mid level short wave at around 700mb, in contrast to the traditional cold front.

While the vast majority of any actual severe weather was confined to areas well north and west of our area, some locations in southern New York and portions of Connecticut did see some wind damage, frequent lightning, and very heavy rainfall. As the evening rolls on and the sun gradually fades away, the heat and instability that we had will begin to drop off quite significantly, and any remaining strong storms will weaken below severe limits, while heading generally eastward. Some storms in southern Connecticut may still be capable of producing damaging winds as they feed off residual instability and favorable parameter space that had not been touched by previous cells.

The rest of the evening should feature improving conditions, with partly cloudy skies likely for most of the area. Due to the lack of a coherent frontal system, the humid airmass that spawned these storms will linger around and make for another muggy night, with lows likely staying in the lower 70’s and into the middle 60’s.

Animated loop of the evenings latest regional radar mosaic, regional surface observations, and high resolution visible satellite imagery (Courtesy of College of DuPage)

Saturday should start off quite nice, with a mix of sunshine and scattered clouds to start off the day. Although, with warm mid level temperatures, winds from the south, and a humid airmass in place, the conditions will be ripe for temperatures to quickly rise into the upper 80’s and even pass the 90 degree mark in locations like NE NJ and SNY. As we go through the late morning and early afternoon hours, a shortwave trough and associated cold front will be working its way east towards the area. This will set the stage once again for instability to begin to pool up ahead of the frontal system, which will act as a forcing mechanism for thunderstorm development later into the afternoon. Like today’s threat, the best wind shear and parameters are likely to stay to the North and West of the immediate New York City area, but more isolated strong storms will be possible towards the area as the day progresses on. The main threats tomorrow appear to be gusty winds, frequent lightning, and very heavy rainfall. Due to this risk, the Storm Prediction Center in Norman, Oklahoma has placed locations to our north and west in a Slight Risk for severe thunderstorms.

Showers and storms may continue to longer through the late afternoon and evenings hours as the lift associated with the cold front will trigger additional shower and possible thunderstorm development if there is any left over instability to work with. The main threat from these storms later in the day appear to be confined to gusty winds and heavy rain. Lows tomorrow evening will remain quite warm, with upper 60’s and lower 70’s likely.

This evenings latest Rapid Precision Model, showing scattered showers and thunderstorms developing mainly to the north and west of the city tomorrow afternoon/evening (Courtesy to WSI)

This evenings latest Rapid Precision Model, showing scattered showers and thunderstorms developing mainly to the north and west of the city tomorrow afternoon/evening (Courtesy to WSI)

Sunday should feature a less humid start to the day as the cold front moves through during the early morning hours and mixes out the tropical airmass that has been lingering over the past few days. As dry air behind the front moves on in, mostly sunny conditions are likely to hold up for the rest of the day on Sunday. With mostly sunny skies and a much less humid airmass over the region, high temperatures will gradually build up towards the upper 80’s-with some locations possibly reaching that 90 degree mark once again!

Monday will likely features much of the same conditions as Sunday, with low humidity, clear skies, and an overall low threat for afternoon storms. Highs should also be quite similar, with temperatures likely peaking around the middle to upper 80’s. Overall, both days will be very pleasant and a great lead up to Independence Day.

Tuesday (Fourth of July) – the day that everyone has been wondering about for over a week now actually looks to have quite an excellent setup in place during the day! A stationary front-the remnants of the cold front that passed on Sunday-will be located to our south, which will leave a large area of high pressure in control for the day, providing light winds, low humidity, and clear skies! Highs should continue their warm, but not outrageously hot trend, with temperatures likely reaching the middle 80’s over much of the area! In summary, it should be an excellent outdoors day, with near perfect conditions for firework-viewing, with only high cirrus clouds likely during the day!

We hope everyone has an excellent Holiday Weekend!

A quick summary of the conditions for the Fourth of July-orange colors denote areas of higher than normal pressure

A quick summary of the conditions for the Fourth of July-orange colors denote areas of higher than normal pressure

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 evening!

Steve Copertino

Steven Copertino

Public Analysis: Above Normal Temperatures and Thunderstorm Threats Return for the Holiday Weekend

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Good Evening! 

Today was yet another beautiful day across the Northeast due to a weak area of high pressure to our south bringing in low humidity, mild temperatures, and light southerly winds for the entire region. Highs today were generally limited to the low to upper 70’s across our area due to cooler temperatures aloft associated with a deep area of mid level toughing located just to our north. As we get deeper into the evening hours across the area, high altitude cirrus clouds should begin to move in from the west, signaling the beginning of another pattern change. With clear skies, low dewpoints, and light winds from the west, conditions will be near-perfect for radiational cooling to take place, so expect low tonight to fall into the middle 50’s to low 60’s across the area, with some locations well-removed from the coast possibly sinking into the low 50’s during the early morning hours.

This afternoon/evenings latest high-resolution visible satellite imagery, surface observations, and regional radar mosaic, showing relatively calm and mild conditions for your Wednesday evening.

Thursday is looking more like a rather large step in the direction of above-average temperatures for the entire region as mid level ridging to our south and east begins to build northward over our area, especially during the afternoon hours. The same high pressure that provided the area with extremely comfortable weather over the past few days will begin to turn on us by directing winds from the south and southeast. This will lead to much higher dewpoints overtaking the tri-state area, which will lead to a muggier feel for tomorrow. In addition to the increasing humidity, rising heights will also allow mid level temperatures to rise significantly. The combination of warm mid level temperatures, a muggier airmass, and southerly winds will lead to high temperatures likely reaching all the way into the middle to upper 80’s tomorrow with some potions of Notheastern New Jersey and southern New York state likely seeing temps pass that 90-degree mark.

In lieu of all this warmer weather, a pretty tight pressure gradient will set up shop over the area as the aforementioned high pressure system begins to move off of the Mid-Atlantic Coast and an area of low pressure in the Great Lakes Region continues to gradually move north and east. This will likely increase winds to around 15-25 miles per hour, with gusts likely reaching into the 30-40 mph range during the day. Some isolated wind gusts will be capable of taking small twigs off of trees and blowing around lawn furniture. Additionally, this strong southerly flow may be able to limit just how warm south-facing shores of Long Island and Connecticut can get tomorrow if the winds kick in during the early afternoon hours as opposed to later in the day.

Later tomorrow evening, increasing mid level moisture as well as the enhanced southerly flow should create some increased cloudiness, with any chance at some showers limited to the far northern regions due to a total lack of forcing for any kind of thunderstorm development. Tomorrow evening will be quite warmer than Wednesday evening as temperatures are only likely into the middle to upper 60’s, with some 70 degree low temperatures possible in the more insulated locations.

This evenings North American Model showing relatively high wind gusts tomorrow afternoon and into the evening hours due to an increasing pressure gradient overhead. Please refer to the NWS for any potential Wind Advisory's tomorrow

This evenings North American Model showing relatively high wind gusts tomorrow afternoon and into the evening hours due to an increasing pressure gradient overhead. Please refer to the NWS for any potential Wind Advisory’s tomorrow

Friday looks to be yet another warm and borderline hot day as mid level ridging continues to build over the area. With the high pressure firmly off of the Mid Atlantic coast by this time, winds from the south should continue to usher in very warm and moist air in the lower levels of the atmosphere that will push a frontal system well to our north. With this frontal system located to our north, any potential pieces of energy that will be capable of triggering any shower and thunderstorms will also remain north of our area during the day. Regardless, Friday will likely be another increasingly muggy and warm day with mostly sunny skies leading to highs in the upper 80’s, and possibly even 90 once again for portions of New Jersey and southern New York. Friday evening looks to be a warm, but bearable one as humidity decreases ever so slightly, but temperatures will likely remain in the low to middle 70’s for lows.

As of now, it appears that the more unstable day appears to be on Saturday as a frontal system associated with some energy from an approaching mid level trough over the Great Lakes region heads eastward. Saturday will also likely feature rich tropical moisture, increasing instability, and some improved wind fields that will be necessary for thunderstorm development towards the afternoon hours. While the thunderstorm threat will definitely need to be revisited on Friday, there does seem to be support from the NAM, GFS, and ECMWF for this scenario. Anyway, Saturday will likely feature mostly sunny condition’s, with increasing clouds towards the afternoon hours once again. Highs will likely be able to eclipse Fridays highs, with 80’s and lower 90’s looking possible.

Sunday also looks to be rather unsettled with increasing cloudiness and an enhanced threat of showers and thunderstorms as yet another lobe of energy rounds the base of the trough located in southern Canada. This lobe of energy will send off some energy through the Ohio Valley, which will act as a trigger and potential development zone for precipitation during most of the day. Due to the enhanced clouds, Sunday will likely be only slightly cooler than the previous two days, with highs likely reaching into the mid 80’s.

This afternoons European model showing yet another possible Canadian disturbance dropping southward and potentially increasing the threat for showers and thunderstorms for the later half of the holiday weekend (Courtesy of AccuweatherPro)

This afternoons European model showing yet another possible Canadian disturbance dropping southward and potentially increasing the threat for showers and thunderstorms for the later half of the holiday weekend (Courtesy of AccuweatherPro)

Drier conditions appear possible for Monday as a subtle mid level ridge builds in behind the weekend system, but this afternoons model guidance has been hinting at the potential for another system to work its way in and potentially provide another chance for some showers and thunderstorms on the 4th of July. We will have a full update on the Holiday Weekend and beyond on Friday afternoon!

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 evening!

Steve Copertino