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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: Brief Calm This Weekend, Multiple Rain Chances Next Week

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Good Evening and Happy Friday! 

Today has been yet another pleasant and rather seasonable day, and the good news is these conditions look to last well into this weekend. The bad news is that we do appear to be headed into yet another unsettled and dreary period staring late Sunday, and into the work week next week. Additionally, the negative phase of the North Atlantic Oscillation that we have been covering for over a week now looks to bring about another unseasonably cool airmass for the majority of next week. However, in the extended range we may begin to see a switch back to seasonable temperatures and more stable conditions.

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Recap and This Evening

Earlier today we saw mostly sunny skies and light winds from the north and west due to an area of high pressure moving through the Ohio Valley and western portions of the Mi-Atlantic states. Just to the east of the high pressure system, a large upper level low was situated over northern New England and portions of Canada, which was helping to usher in cool and dry air in the mid-levels of the atmosphere. As the day progressed and the surface levels of the atmosphere began to warm up, this caused a similar scenario that we have seen a few times in the past few weeks where the warmer air near the surface quickly rises into the cooler levels of the atmosphere and begins to form clouds.

With very marginal upper level support, some converging moisture boundaries over the area, and an area of energy rounding the base of the upper level low, we actually began to see some congested cumulus and ragged cumulonimbus form over portions of New York, New Jersey, and Connecticut. Due to the dry air being entrained in from Canada, these showers and storms were generally pretty tame in nature and did not have muhc lasting power, but due to the cold mid to upper levels, some pea-sized hail and gusty winds were reported mainly to the north of New York City.

Moving on, with rather abundant sunshine, light gusty winds, and a relatively dry airmass, highs today were able to climb into the mid to upper 70’s once again, with the exception of coastal New Jersey and portions of Long Island. As we move into the evening hours, the breezier conditions left over from a frontal passage will gradually subside. Additionally, skies should begin to clear out quite significantly as dry air and diurnal heating begins to wane over the area. These conditions will be quite favorable for radiational cooling to take place this evening, so expect overnight lows to drop quite a bit with temperature ranging from the low to mid 50’s across much of the area, with 40’s possible in locations north and west of the city.

This evenings latest visible satellite imagery, regional radar mosaic, station plots, and watch/warning information. Note the rather tranquil conditions after a few brief showers and storms earlier this afternoon (Courtesy of College of DuPage)

This evenings latest visible satellite imagery, regional radar mosaic, station plots, and watch/warning information. Note the rather tranquil conditions after a few brief showers and storms earlier this afternoon (Courtesy of College of DuPage)

Saturday Into Sunday 

As we head into tomorrow morning, another disturbance from Canada will begin to work its way down south, and towards our area. This upper level system may have enough energy associated with it to produce some overcast and showers, but this system will be rather progressive in nature and will likely move out by late morning due to its close proximity to the aforementioned high pressure system exiting to out east. Any rainfall accumulations should be quite light in nature, with more dry air reinforcing itself over our region directly from Canada once again. Gusty winds from the north and northwest behind the tiny, but relatively strong area of energy may become quite widespread over the region tomorrow. As skies clear out and the dry air works its magic, we should see highs climb back into the middle to upper 70’s once again, with the off-chance that some locations may reach the 80 degree mark if the initial disturbance is quicker than currently forecast. Clear to partly cloudy skies are likely Saturday evening, with temperatures falling back into the upper 50’s to around 60 near New York City, and urban areas reaching down into the lower to middle 50’s over much of region.

Sunday looks to start off with mainly clear conditions as marginally dry air from the north and west continue to feed into the region. Clouds will likely begin to increase throughout the day as moisture advances ahead of the third in a series of strong mid level disturbances. As the day marches on, the threat for showers will increase, especially through the late afternoon and evening hours as the mid level disturbance begins to strengthen just to the west of our area. As this mid level system begins to strengthen during the evening hours of Sunday, an area of low pressure will likely form over the Great Lakes region, and this low pressure will be capable of advecting an impressive amount of water vapor over our area, which may set the stage for potentially heavy rains Monday morning.

High resolution North American Model showing a very large area of moisture gathering just to the south of a developing low pressure system in the Great Lakes, which is usually a very strong indicator for moderate to heavy rains (Red and pink areas delineate very moist air-mass)

High resolution North American Model showing a very large area of moisture gathering just to the south of a developing low pressure system in the Great Lakes, which is usually a very strong indicator for moderate to heavy rains (Red and pink areas delineate very moist air-mass)

Monday and Beyond 

With all this moisture gathering to the south of the area on Sunday and into Monday morning, a strong mid to upper level disturbance strengthening over our area, and a favorable upper level jet streak to the north, the writing is on the wall for a wet and dreary day on Monday, with periods of moderate to heavy rainfall quite likely. The main question in this forecast appears to be just how far north the area of low pressure in the Great Lakes moves as it pushes up against an area of confluence located over Canada. Where this confluence sets up will also likely dictate how much, and where the heaviest rains fall on Monday.

There is a small chance that the confluence-or blocking could be positioned further south than currently forecast, and this would allow for a possible scenario where another surface low redevelops off of the Mid Atlantic coast and enhances the rain potential. Confidence in this scenario is low at this point, but we will provide updates on the storm as we draw closer.

Some unsettled weather with scattered showers and possibly some thunderstorms could continue into Tuesday and Wednesday with the upper-level low still lingering over the Northeast. Temperatures will likely run near or below normal depending on amount of clouds and rainfall each day.

This afternoons European model showing the system that will likely produce a heavy rain threat on Monday still lingering over the Northeast on late Tuesday evening. This system could produce more rain later in the week depending on how long it meanders around

This afternoons European model showing the system that will likely produce a heavy rain threat on Monday still lingering over the Northeast on late Tuesday evening. This system could produce more rain later in the week depending on how long it meanders around

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Have a great weekend!

Steve Copertino

Steven Copertino

Public Analysis: Calm and Cool Weekend, Turning Unsettled Next Week

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Good afternoon and Happy Friday! 

Today has been yest another hot and relatively muggy day in a strong of abnormally warm, summer-like heat. This heats time is very limited as a cold front is set to move through the region, leaving much cooler and stable conditions for the upcoming weekend. As discussed over the past week or so, high-latitude blocking over Greenland and Atlantic Canada will set the stage for a large upper level trough to set up over the eastern two-thirds of the country. This trough will likely bring a few shots at some heavy precipitation, potentially lasting through much of the work week as we draw closer to the Holiday Weekend!

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Today and This Evening

This afternoon we saw temperatures shoot back up into the upper 80’s and lows 90’s across the entire region, with some stations like La Guardia Airport and Caldwell, New Jersey seeing highs shoot into the mid 90’s (95F)! Despite the clear skies and slight breeze today has also felt relatively muggy as dew-points rose into the lower to mid 60’s. This muggy air-mass has also allowed instability to build over much of the Mid-Atlantic and Northeast states, and combined with some modest wind-shear, has allowed some very isolated showers and thunderstorms to develop across portions of New Jersey and Southeastern Pennsylvania. Due to the fact that the best instability and wind-shear are disjointed from each other, the prospects of widespread, organized thunderstorms is quite low. However, very isolated showers and thunderstorms will be possible, especially over southern New Jersey and Southeastern Pennsylvania. The main threat from these showers and storms will be gusty winds of around 40-50 mph, however small hail and frequent lightning may be possible with some of the stronger storms.

As we head into this evening, a cold front located over southern New England and central New York state will continue to sag south and overspread the region late tonight and into very early tomorrow morning. The flow behind the front will begin to change from very warm southerly winds, to much cooler northerly winds from Canada. These will bring lows down into the 50’s for much of the area, which will be quite the departure from what we have seen over the past few days.

Latest visible satellite imagery, station observations, and regional radar mosaic over the area, showing yet another warm and muggy afternoon. (Courtesy of College of Dupage)

Latest visible satellite imagery, station observations, and regional radar mosaic over the area, showing yet another warm and muggy afternoon. (Courtesy of College of DuPage)

This Weekend

As we start up the weekend tomorrow morning, we should see some relatively cloudy skies behind the cold front as an area of mid-level moisture works in over cool easterly winds coming off of the Atlantic which should produce areas of overcast and scattered clouds throughout most of the day. Temperatures should be relatively cool with highs in the upper 60’s to lower 70’s, which will be 20-25 degrees cooler than the past three days for much of the area. In addition to these cooler conditions, the Canadian/Maritime airmass will limit any chance for measurable precipitation throughout the day. As we head into tomorrow evening, an area of high pressure will be moving to our north and will work to reinforce the maritime airmass over our area. This will allow temperatures to drop into the upper 40’s and lower 50’s across much of the area, with partly cloudy conditions remaining.

We should see more clouds on Sunday as the continued maritime airmass and weak mid-level moisture hold over the area. Temperatures should be in the upper 60 to lower 70 range once again, but these highs should be quite variable as any areas that see prolonged peaks of sun may raise above the lower 70’s, while areas closer to the coast that may see prolonged cloudiness and southeasterly winds could wind up staying in the middle 60’s. Moisture will begin to increase later Sunday as the area of high pressure begins to shift off of the New England coast and as an area of low pressure moves through the Great Lakes region. This area of low pressure will drive a warm front through the Mid-Atlantic region, just south of our area. As time progresses, cloudiness will be on the rise and will likely become overcast towards the end of the evening as winds shift from easterly, to southerly once again. This afternoons model guidance was not in agreement on the exact timing, but the aforementioned cold front will likely not be able to progress east enough to produce widespread showers by Sunday evening. Overnight lows should remain quite moderate, with temperatures likely staying in the low 60’s to upper 50’s for most of the area.

This afternoons European model showing moisture beginning to build to the south of the region as a cold front associated with an area of low pressure in the Great Lakes begins to trudge eastward (Courtesy of AccuweatherPro)

This afternoons European model showing moisture beginning to build to the south of the region as a cold front associated with an area of low pressure in the Great Lakes begins to trudge eastward (Courtesy of AccuweatherPro)

Next Week

This afternoons model guidance did differ on the exact timing and placement of the cold front by Monday morning, but indications are that it should be located over eastern Pennsylvania by the morning commute. With moisture surging up to the east of the front, substantial cloudiness is likely to be present over the region, but depending on just where the warm front is located, some isolated peaks of sun will be possible. High temperatures on Monday will be very dependent on where the warm front is located as this will dictate where partial sunshine will be possible. By late morning, the actual cold front will likely move through the region and will likely have the potential to bring some showers and thunderstorms over the region. A strong southerly jet will continue to feed moisture north over the area for six hours or so and there will be the potential for some heavy rainfall with training storms. Although it doesn’t seem overwhelmingly likely, there may be the potential for some localized flooding, so make sure to stay tuned for further updates!

Tuesday will likely be a calm and cooler day as another storm begins to gather to our south with more possible moderate to heavy rainfall for the area on Wednesday. This will continue to be the theme for the week as a large upper level trough will be cemented over the central and eastern states due to another period of prolonged high latitude blocking that will allow multiple systems to slow down and congeal together to our south. While it is possible that this trough produces multiple rain threats over the next week, there is also the potential that we return to another period of below-normal temperatures coming down from Canada. Though it’s around ten days out as of today, there are some indications that this period of cooler and unsettled weather may last into the Memorial Day weekend. Stay tuned for the numerous upcoming rain threat as well as details on the upcoming Holiday Weekend!

This afternoons European model showing a very large and very anomalous upper level trough parked over the Ohio Valley and Eastern US that has the potential to bring multiple shots at heavy rain and below-normal temperatures (Courtesy of Accuweather Pro)

This afternoons European model showing a very large and very anomalous upper level trough parked over the Ohio Valley and Eastern US that has the potential to bring multiple shots at heavy rain and below-normal temperatures (Courtesy of Accuweather Pro)

or 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 weekend!

Steve Copertino

Doug Simonian

Gradually improving, slightly warmer weather

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The same mid-level cutoff low that helped bring the heavy rain and strong winds on Tuesday, as well as multiple days of snow showers since, is still meandering in the vicinity of the Northeast US today. This has helped to keep an island of cold in an otherwise sea of warmth across much of the US, as well as instability and moisture to produce wrap-around snow showers.

Impressive lapse rates have remained over the region over the past few days, allowing for the continuation of snow showers and squalls. They’ll be much more isolated on Friday, however, as the upper level low finally begins to pull away. As it does so, it will remove our area from the pocket of stronger instability. So, we expect highs in the upper 30’s to near 40 on Friday with a much lower chance of snow showers — in fact, cloudy to partly cloudy skies should be the general rule.

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