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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: Seasonable Temperatures Return, Turning Unsettled Once Again

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Good Evening! 

Though high temperatures this afternoon were not quite as oppressive and did not reach the 90 degree mark to continue to the heat wave, it was still a few degrees above normal across the majority of the region which helped to keep that summer feel around for another day. The theme of much-above normal temperatures is likely to be over for at least the medium range as Thursday and Friday will feature an appreciable drop in high temperatures-with some locations possibly struggling to get out of the upper 60’s on Friday! This weekend looks to have some rebounding of temperatures on Saturday and Sunday, but these will be highly dependent on the degree of unsettled weather that each day will likely feature. Finally, the start to the workweek on Monday be a wet, and possibly stormy one as a frontal system works through the area during the day.

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This Evening Into Thursday 

Some scattered showers moved through the immediate New York Metro area early this morning, producing locally moderate to heavy patches of rain. As storms last night died off in Northwestern New Jersey, they left a pool of residual moisture and instability that waited until the sun rose for showers to once again take off.

These showers gradually progressed to the south and west, leaving generally sunny skies over the entire region. Clearing skies and winds from the east due to an area of high pressure over New England led to a warm, but not overly warm day today. Highs generally ranged in the low to mid 80’s, with coastal locations seeing highs a few degrees lower. Some patches of ragged cumulus clouds attempted to pop up during the late afternoon hours, but these were not long for this world as the stable air associated with the maritime airmass quickly knocked these back down before they could develop further. Mostly clear skies, light winds, and decreasing dewpoints should last through sunset and into the evening hours tonight, allowing temperatures to drop down into the upper 50’s to lower 60’s for lows tonight.

This afternoons latest available high resolution true-color visible satellite imagery, regional radar mosaic, and surface temperatures, showing a rather tranquil and warm late-afternoon (GOES-16 imagery Preliminary and Non-Operational)

This afternoons latest available high resolution true-color visible satellite imagery, regional radar mosaic, and surface temperatures, showing a rather tranquil and warm late-afternoon (GOES-16 imagery Preliminary and Non-Operational)

As we start the day tomorrow, conditions should be mostly sunny with more concentrated clouds and showers possible over far northwestern New Jersey and Northern Pennsylvania. One thing that will be almost immediately noticeable during the late morning and early afternoon hours tomorrow, will the much lower levels of humidity. The easterly winds being ushered in by an area of high pressure over New England will provide yet another push of stable/maritime air-which should not only limit tomorrows temperatures, but also provide a chance of increasing clouds throughout the day tomorrow as the cool maritime air near the surface runs into increased levels of moisture in the middle layers of the atmosphere. With the maritime airmass in control and the threat of increased cloudiness, high temperatures tomorrow will likely be a good deal lower than they were over the past few day. Highs should range in the middle to upper 70’s-with some locations that see prolonged sun possibly getting into the 80 degree territory.

Shower will likely be confined to the far northwestern locations of New Jersey and possibly portions of southern New York, as they will be under less influence from the maritime airamss. Clouds will continue to increase through the evening hours, becoming overcast by late evening. As the area of high pressure over New England begins to retreat east, a frontal boundary over the Delmarva will shift low level winds from the east/east-southeast and usher in some more robust low level moisture. Showers may begin to form along the coast during the evening hours, but these will likely be scattered in nature.

This afternoons GFS model showing the eastward progression of the high pressure system leading to a frontal boundary over the Delmarva peninsula increasing low level easterly/southeasterly winds. At the very least, increased clouds are expected Thursday evening (Courtesy Tomer Burg UAlbany)

This afternoons GFS model showing the eastward progression of the high pressure system leading to a frontal boundary over the Delmarva peninsula increasing low level easterly/southeasterly winds. At the very least, increased clouds are expected Thursday evening (Courtesy Tomer Burg UAlbany)

Friday Into Saturday 

Friday looks to start off rather unsettled and cloudy for most of the area as low level moisture from the south and east continues to increase through the morning hours. As moisture continues to increase, an area of energy associated with a large, but slow-moving upper level low over Canada will begin to move towards the area during the afternoon hours. Though there will be ample moisture in place, and a “trigger” in place to set off any potential showers and thunderstorms, the onshore flow from the Atlantic may act to push the best areas of lift inland over portions of Northwestern New Jersey-possibly even into New York state. The model diverge significantly on where the best moisture convergence/showers will be during the day on Friday, but at this time it appears likely that the best threat for steadier rains will be located just inland over portions of Northeast Pennsylvania, Northwestern New Jersey, and Southern New York. This will likely have to be looked at again tomorrow, as though there is a frontal boundary in place, we have seen the model guidance severely underestimate just how much a maritime airmass can advance, which in turn will determine the location of the best threat of rain.

Any showers that do develop during the day on Friday should move east/northeast during the late afternoon and into the evening hours, gradually diminishing as time progresses. Highs on Friday will be highly dependent on how much cloud cover takes hold, and whether or not sustained precipitation develops, but highs should range in the low to middle 70’s, with some locations not being able to make it out of the 60’s!

Saturday will likely be another unsettled day, as the frontal boundary that was located to our south on Friday, lifts up and over the region as a warm front during the day. This will lead to increase in temperatures, but with ample moisture and weak lift, some showers in the morning and possibly even a thunderstorm will be quite possible during the afternoon hours. Highs will likely make a slight rebound back into the upper 70’s to lower 80’s across much of the region.

This afternoons European model showing a large upper level trough moving in from the Pacific Northwest , strengthening over the Great Lakes region and providing multiple chances of rain on both Sunday and Monday

This afternoons European model showing a large upper level trough moving in from the Pacific Northwest , strengthening over the Great Lakes region and providing multiple chances of rain on both Sunday and Monday

Fathers Day and Beyond 

During the day on Sunday, a large upper level trough our to west will be heading east/northeast in the Great Lakes region while strengthening. This strengthening area of low pressure will spawn a large cold front that will likely be located far to our west during Sunday. Ahead of this front should exist some more instability over the region, but with the main trigger-the cold front located far to our west, it may be rather hard to get actual showers and thunderstorms to pop during the day. Assuming the front does take its time in getting to the region, skies should generally be sunny during the day, which should allow for highs to reach into the low to middle 80’s.

As the front and the best forcing begins to make its way into the region during the day on Monday, instability and moisture should be more than sufficient for shower and thunderstorm development across the area, with some storms possibly being strong to severe in nature. The overall level of severity will rely strongly on the timing of this front, as strong surface heating and destabilization would lead to stronger storms. At this time, it appears that the main threat with any showers and thunderstorms will be gusty winds and heavy rainfall, but this threat will have to be monitored over the next few days.

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

 

Steven Copertino

Public Analysis: Relatively Cool and Unsettled Memorial Day Weekend Likely

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Good Evening and Happy Friday! 

The area of low pressure that was previously located over the Ohio Valley during the day Thursday that brought moderate to heavy rainfall over much of the area, died off as was forecast back on Monday, while a more powerful and impressive area of low pressure began to develop off of the New Jersey coastline late last evening due to strong upper level energy rounding the base of a large trough located over the Mid-Atlantic coast. This secondary area of low pressure brought more steady rain overnight, especially for locations north and east of New York City. As this system began to wrap up and move along the coast, it brought some lingering showers this morning and through portions of the afternoon, many of which were light to moderate in nature.

These residual showers were mainly fueled by the very cool upper level temperatures high up in the atmosphere, combined with clearing skies which lead to surface heating. As some locations began to see prolonged periods of sun and as their temperatures rose, that warmer air near the surface began to quickly rise into the cooler upper levels, which caused that warm to quickly condensate, and form cumulus clouds, with some isolated showers. As the low pressure off of the New England coast began to move away late this afternoon, it began to draw in more dry air from Canada which helped to mitigate any widespread shower development. These Northwesterly winds also ushered in a new Canadian air-mass that allowed temperatures to rise into the low to mid 70’s across much of the region, which made it feel quite pleasant compared to the past few days.

As we progress into the evening hours, the vertical temperature gradient will begin to level off, and when combined with drier air in the mid levels of the atmosphere, this should make for rapidly diminishing clouds. Light Northwesterly flow, a new dry air-mass from Canada, and clear skies will be quite favorable for any leftover surface heat to rapidly radiate back into the atmosphere, which is what is often referred to as “radiational cooling”. This should allow temperatures to quickly dip into the 50’s for urban and coastal sections, with 40’s possible for locations removed from the coast.

Latest regional radar mosaic, surface temperatures, offshore winds, showing a rather pleasant evening with showers located mainly to the north of the area

Latest regional radar mosaic, surface temperatures, offshore winds, showing a rather pleasant evening with showers located mainly to the north of the area

Saturday Into Sunday 

As we head into the Memorial Day Weekend tomorrow, a very weak area of high pressure associated with some increasing upper-level heights will be moving over the region during the early morning hours. This should promote a rather sunny start to the day with some wispy, high clouds likely. Then as we progress into the late morning and early afternoon hours, clouds will likely begin to increase as a weak disturbance from the remnants of a thunderstorm complex over the Ohio Valley will be working its way towards the region.

Moisture and instability will be lacking quite significantly due to the renewed dry Canadian air-mass, so only isolated-scattered showers will be possible with this system as it moves through during the late afternoon hours. Regardless, highs will likely be able to climb into the low 70’s once again, but if the disturbance coming in from the Ohio Valley happens to be stronger, it will have more clouds and showers accompanying it, which may limit tomorrows highs to the upper 60’s. Tomorrow evening will likely be another cool and clear evening as another weak area of higher heights builds over the region, allowing for more radiational cooling, which will support lows dropping back into the 50’s for locations closer to the coast and New York City, with 40’s once again possible for locations away from the coast.

Sunday looks to start off the day with a mixture of sun and clouds and the weak area of ridging that approaches our area begins to strengthen and bring in more dry air into the mid-levels of the atmosphere. With this area of ridging overhead, winds will likely be coming from the relatively cool Atlantic, which should really work in tandem with the increased cloud cover to cap off high temperatures in the mid to upper 60’s for coastal locations, which may be under the influence of thicker cloud cover and a more stiff easterly wind. Inland locations may be able to see a good deal of sun mixing with clouds, therefor highs in the lower to mid 70’s appear likely at this time. Then as we move into the evening hours, clouds should begin to increase as the entire region begins to feel the full effects of the maritime air-mass working its way westward from the coast. The increased cloud-cover will likely limit lows into the mid to upper 50’s for Sunday evening.

The high-resolution Rapid Precision Model showing increasing clouds and the potential for some showers during the afternoon on Saturday. The timing will be crucial in determining how warm the high temperatures area (Valid 12:30pm Saturday)

The high-resolution Rapid Precision Model showing increasing clouds and the potential for some showers during the afternoon on Saturday. The timing will be crucial in determining how warm the high temperatures area (Valid 12:30pm Saturday)

Memorial Day Monday

As we talked about earlier in the week, the Memorial Day Monday forecast looks to be highly dependent on an upper level trough diving south through Canada late in the day Sunday. This upper level trough will cause the ridging that provided the region with mainly dry conditions to eventually break down by the morning hours on Monday. In response, a surface low will begin to track from Missouri and into the Great Lakes region late in the evening Sunday. This afternoons latest model guidance shows that as this low pressure moves into the Great Lakes, a warm front will begin to lift into the area by the very early morning hours on Memorial Day, which should begin to increase cloudiness quite substantially and bring the threat for some showers and possibly even a thunderstorm. Moisture will also be increasing as the front begins to push northwards, so some of these showers and isolated thunderstorms may contain locally heavy downpours, but no organized severe weather is expected due to poor timing, lack of strong instability, and disjointed dynamics.

As we get deeper into the day, the forecast becomes quite a bit more uncertain with regards to how much farther north the warm front will move, if at all. As we have seen numerous times this year that these fronts can be very fickle and tough to nail down outside of twenty-four hours due to the fact that these fronts can bring very warm temperatures and sun to the south of the boundary, and cool and cloudy conditions to the north of the warm front, with the gradient sometimes being quite sharp.

This afternoons individual GFS ensemble members showing a very wide range of possibilities regarding the positioning of key frontal boundaries

This afternoons individual GFS ensemble members showing a very wide range of possibilities regarding the positioning of key frontal boundaries

However, at this time we are leaning towards the warm front making its way over the region quicker than the models have it doing so, and the antecedent cold front from the low in the Great Lakes also moving through quicker, leaving the area with warmer temperatures in the upper 60’s to mid 70’s and some clearing of the cloud cover will also possible during the afternoon. This forecast will likely need to be tweaked as we approach Monday, especially regarding any precipitation potential, so make sure to check back for more details!

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 holiday weekend!

Steve Copertino

Steven Copertino

1/27 PM Zone Update: Gusty, return to seasonable conditions this weekend

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Today has been yet another cooler departure from the previous few days as much of the region is currently experiencing mostly cloudy conditions with some disorganized snow showers moving through the eastern areas of Pennsylvania and southern New York. These disorganized squalls have made some progress into central and southern New Jersey, but ultimately will have a limited impacts for the New York metro this afternoon and evening. Downslope flow and drier air work to keep these squalls on the lighter side and confined mainly to the north and western regions. However it is important to note that some of these bands could work their way down later this afternoon and produce reduced visibility as well as slippery roads for some folks in the area, so it is important to remain alert during the afternoon commute.

Otherwise, the main focus for the rest of today will be the gusty winds of around 20-30 mph affecting most of our area which can be attributed to a large low pressure system over eastern Canada. The locally higher areas of winds can be seen in the latest visible satellite imagery as ripples in the overall cloud pattern. As temperatures once again drop down this afternoon to the upper 30’s, we should begin to see the winds diminish and gradually die off once we head into the evening hours. Any remaining squalls and the mostly cloudy conditions should also depart this evening as temperatures fall into the middle to low 30’s for most of the area, with upper 20’s possible in the outlying regions.

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