Steven Copertino

Public Analysis: Heavy Rains Possible Tonight, Another Storm Likely Friday

/by

Good Afternoon! 

A strong cold front that was a part of a very large storm system that affected the Central US this past weekend will be moving through parts of the Mid-Atlantic states this afternoon and into this evening. This cold front will bring the potential for strong thunderstorms capable of producing heavy rain, gusty winds, and some small hail. Cooler weather is expected behind this front Tuesday through Thursday, but we may have to worry about a stronger storm system gathering to our south late Thursday. Depending on the track that this system takes Friday, a wide range of impacts are possible with gusty winds, heavy rains, and some thunderstorms possible.

Monday Into This Evening 

After some thick cloud cover and spotty shower activity earlier this morning and into the early parts of the afternoon, some breaks in the clouds have been common across southern and central portions of the area. With clouds clearing out more significantly over portions of southeastern Pennsylvania and southern New Jersey, temperatures have been able to climb into the mid 70’s to lower 80’s across that region. While more significant clearing has taken place over northeastern NJ, and western Long Island, cool and much more stable air is being introduced from the Atlantic which has prevented similar warming. This will limit the highs today from the low to upper 60’s (with a few 70 degree readings possible), with the higher temperatures to the south and cooler readings being confined to southern New York, Long Island, and Connecticut.

As the strong cold front works its way through Pennsylvania, instability and wind shear to our west may be just strong enough to support some isolated showers and thunderstorms. This threat will mainly be focused to the north and west of New York City as the cool and stable marine layer that is currently over the majority of the area will quickly weaken any storms that approach the area later this evening. Additionally, the overall timing of the storms not arriving until after the peak heating of the day will also limit the overall potential for any severe thunderstorms in the immediate NYC area.

However, given marginal conditions still in place and strengthening low level winds arriving after dark, any shower or storms that do approach the area will have the potential for some gusty winds and heavy downpours. With a good deal of moisture trapped in the atmosphere, some localized street flooding and ponding on roadways may be possible with any of the heavier storms or storms repeatedly tracking over the same area. The latest outlook from the Storm Prediction Center in Norman, Oklahoma has placed the majority of our area in a “marginal risk” for severe thunderstorms, mainly for locations to the west of NYC.

Latest regional radar composite, surface winds, visible satellite imagery, surface temperatures, and SPC watch information. Note the Tornado Watches out to the west in red (Courtesy of GREarth)

Latest regional radar composite, surface winds, visible satellite imagery, surface temperatures, and SPC watch information. Note the Tornado Watches out to the west in red (Courtesy of GREarth)

Tuesday Through Thursday 

Much calmer and cooler weather looks to be on tap starting tomorrow morning after the passage of the cold front. With cool winds out of the northwest tomorrow morning, the day should start off in the upper 50’s to low 60’s with some broken clouds leftover across the area. Much drier air also should be able to work its way into the area behind the front tomorrow, which should allow most clouds to give way to clear skies by the afternoon. With clearing skies and dry air, temperatures should be able to rise into the 60’s and possibly low 70’s further south. Later in the evening, another cold front will pass through the region giving another shot of cooler air to the area, so expect temperatures to fall into the 40’s tomorrow evening, with 50’s possible near the coast.

After the second cold front moves through on Wednesday, a much cooler airmass in the mid levels of the atmosphere in addition to stronger northwesterly winds will make for an overall cool Spring day on Wednesday. High temperatures should range in the low to mid 60’s during the day, which will be somewhat below average for this time of year, but it will feel somewhat cooler when combined with the gusty winds from the northwest.

Much of the same will be expected for Thursday as an area of high pressure moves to the north of the area and then off of the Mid-Atlantic coast ahead of a gathering storm system in the southern US. Highs will range in the 60’s for the most part across the entire area on Thursday, but as the day continues on, clouds will begin to increase from southwest to northeast. Later in the evening temperatures should be capped off in the low 50’s due to increasing moisture ahead of the upcoming storm system

Afternoon European model showing below-normal temperatures across the area on Wednesday behind a second shot of cooler air (Courtesy of Accuweather Pro)

Afternoon European model showing below-normal temperatures across the area on Wednesday behind a second shot of cooler air (Courtesy of Accuweather Pro)

Friday and Beyond 

A large and very energetic closed-off low pressure system will be over the Tennessee valley very early Friday morning. This strong upper level energy will cause the development of a powerful surface low pressure system along the Appalachian mountains that will be capable of drawing copious amounts of moisture from the Gulf of Mexico northwards and into our area. This afternoons model guidance is in very good agreement that a potentially significant amount of rain could set up during the day Friday and into the early morning hours of Saturday as a strong low level jetstream continuously brings deep, tropical moisture to the north.

While there is some uncertainty in the exact timing and evolution of this storm system, there is a reasonable chance that there could be the potential for flooding rains, with totals of around 1-3″ and strong, gusty winds affecting the area. We will be monitoring the latest trends over the next four days to pinpoint the exact timing and severity of this system as we head deeper into the week.

Low pressure will be into Quebec by Saturday. A cooler, a Canadian airmass will come in behind it for the for this upcoming weekend. Temperatures will may several degrees below normal, especially by Sunday. An upper-level low linger over the Northeast may enhance enough instability for some isolated or widely-scattered showers. But mostly dry conditions with a mix of clouds and sunshine is anticipated, at this time.

Afternoon Canadian model showing the potential for very heavy rainfall during the day on Friday across the area. Trends will need to be monitored for any changes over the next few days

Afternoon Canadian model showing the potential for very heavy rainfall during the day on Friday across the area. Trends will need to be monitored for any changes 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: Cool and Damp Friday, Coastal Cut-Off Next Week?

/by

Good afternoon and Happy Friday!

Today has been another unsettled and damp day as rather thick cloud cover and some associated showers have worked their way through the region late last night and into the morning. This was due largely in part from a retreating back door cold front, or a cold front that sinks from northeast to southeast due to more dense air being able to overcome the more shallow and weak warm layer to the south. Offshore winds and thick cloud cover should remain over the remainder of the afternoon, and there does exist the potential for some patchy areas of drizzle or even a shower or two. Any steadier showers will likely be limited to areas along the coasts of New Jersey and Long Island, as the marine influence will be greatest along those areas.

With this aforementioned cloud cover and the back door cold front established well to our south and west, temperatures in North and Central New Jersey, as well as points to the north will struggle to reach out of the mid 50’s this afternoon. Further south into southern portions of New Jersey as well as southeast Pennsylvania, we may see temperatures reach into the low to middle 60’s, but this is highly dependent on whether or not if the warm sector in central Pennsylvania is able to advance during the late afternoon hours.

Some more steady showers and possibly even a thunderstorm or two may be possible for portions of southeast Pennsylvania as well as southern New Jersey later into this evening, but as of right now, it is looking like any shower /thunderstorm development will be isolated in nature. Weak instability, moderate wind shear, and some clearing skies over central Pennsylvania has lead to an area where we may see these potential showers and storms develop and potentially progress east during the afternoon hours. This area will be monitored for any potential development, so make sure to check in here for the latest and on our twitter page @nymetrowx for up to the minute updates! Due to the risk of some weak/isolated severe thunderstorms, the Storm Prediction Center in Norman Oklahoma has place portions of our area in a Marginal Risk for large hail and potentially damaging wind gusts. Heavy rain and cloud to ground lightning will also be possible with any stronger storms, so make sure to be aware of any approaching storms later on.

Latest surface temperatures, regional radar mosaic, and visible satellite imagery across the Northeast showing the very stark temperature gradient in place this afternoon (Courtesy of GREarth)

Latest surface temperatures, regional radar mosaic, and visible satellite imagery across the Northeast showing the very stark temperature gradient in place this afternoon (Courtesy of GREarth)

As we move on through the day and into the evening, a cold front will begin to push through the region later this evening. However, there is a chance that some moisture will be trapped in the lower levels of the atmosphere later on tonight, which could cause some low clouds and areas of patchy fog to remain late tonight and early tomorrow morning, especially closer to coast. Cloud cover will significantly dampen any chance of radiational cooling tonight, which should  keep temperatures from dropping out of upper 40s to lower 50s overnight over much of the region. Some interior valleys could be a little cooler in the lower to middle 40s, which is a good 8-14 degrees below normal for this time of year.

Saturday Into Sunday 

As the cold front continues to push through the southern Mid Atlantic region tomorrow morning, broken clouds and even some overcast will be possible as some residual moisture continues to stick around in the lowest levels of the atmosphere. The short-term models disagree on whether or not the cloudiness will burn off or not through the afternoon hours, but we do expect some peeks of sunshine tomorrow with a relatively cool air mass settling in tomorrow. With some limited cloud cover, light winds, and cooler mid level temperatures expected tomorrow, temperatures should be able to only rise into the low to middle 50’s across most of the New York metro area, with the possibility of interior locations possible seeing highs limited to the upper 50’s due to cool northwesterly winds from Canada. These winds will also usher in some more dry air into the mix, so expect any residual clouds to gradually fade iater into the day.

Sunday will be the beginning of another unstable period as a low pressure system in the mid levels of the atmosphere “cuts off” from the main flow and begins to meander towards the southeast coast of the United States. This low pressure will have a very nice feed of moisture from the Gulf of Mexico, so it’s overall precipitation field should be quite large in nature, as well as have the potential to drop a moderate to heavy amount of rain wherever it does track. This afternoons guidance really has not converged on any particular solutions, with some models bringing the low from the Outer Banks of North Carolina, to just offshore of the southern coast of Long Island, while other models have the system meandering off the Mid Atlantic coast with little, if any direct impacts through Sunday and Monday.

As of right now, we expect that this system will not be able to gain enough latitude once it reaches the southeast coast to impact our area with any significant rains or winds at this time. High pressure centered in Canada will likely keep this system offshore throughout this period, but this system will need to be monitored, as a small deviation in overall setup could chance the forecast quite a bit.

12z GFS model showing the large cutoff low pressure system stalling out and remaining off of the Mid-Atlantic coast throughout the weekend and into early next week.

Extended Range  

Stronger ridging should begin to develop over our area on Monday and into Tuesday, and this will begin to force the remnants of the cutoff low to the south and east early next week. This should allow any significant impacts like heavy rain and winds to remain well-offshore before the system gradually weakens and heads out to sea. More unsettled weather will likely take shape once again as a very active Pacific jet stream begins to set up off of the west coast of the United States.

This very active jet stream will have the potential to place a deep trough in the central portions of the country, which would in turn bring a large ridge of high pressure into the southeastern region of the country. This combination would be capable of bringing temperatures well-above normal next week for the Northeast, along with the risk for multiple rounds of severe storms in the Plains states and on east, possibly beginning on Wednesday. Regardless of the exact details, it does look like we are possibly heading into a very active and warm pattern once again, so make sure to stay tuned over the next few days for more updates!

——————

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 weekend!

Steve Copertino

Miguel Pierre

Significant Severe Weather Threat for the Deep South Sunday

/by

For several weeks now, we have been discussing the likelihood of an active pattern developing throughout the United States — in particular, the potential for severe weather. That pattern has finally arrived over the past several days, and another in a series of potential severe weather events is expected to unfold on Sunday across the South Central United States in parts of Texas and Louisiana on Sunday.

The potential for severe weather, while in a higher-end space than an “average” event, features considerable uncertainties even at this short range forecast juncture. We detail the intricacies of the setup and how we expect things to evolve on Sunday below.

Read more

Steven Copertino

Public Analysis: Strong to Severe Thunderstorms This Afternoon

/by

Severe Weather Video Update (Doug Simonian)

An active afternoon and evening is possible as a large area of low pressure moves through the Great Lakes region and into Canada today. The progression of this low pressure system to our northwest has allowed for warm/moist air to surge in from the south and provide a marginally unstable airmass for the southern half of the region as of 1pm. This unstable airmass will be aided by very strong wind shear, which is essentially the difference in wind direction as you get higher in altitude within the atmosphere. Even though most of the area did have heavier showers and even some isolated rumbles of thunder this morning, clearing has begun to take place. This is allowing for the sun to peek through some leftover high clouds and this will work to warm up the moist ground, which promotes evaporation. This evaporation ahead of the line of storms will allow for more instability to build, which will be key for the strength of any potential thunderstorms later on. As of right now it does appear that the greatest amount of clearing is currently taking place along the central and southern zones of NJ and PA, and as a result these areas are under a Severe Thunderstorm Watch mainly for damaging winds in excess of 60 mph ( Storm Prediction Center in Oklahoma)

Current visible satellite imagery showing clearing begining to take place in PA and parts of NJ (Simuawips.com)

Current visible satellite imagery showing clearing beginning to take place in PA and parts of NJ (Simuawips.com)

The area of storms expected to impact the region is currently located back in Pennsylvania with multiple severe thunderstorm warnings active. In addition, we have begun to notice some increase in intensity over the past hour as this line passes over locations that experienced areas of scattered sunshine earlier. This line will be sustained by the very strong upper level winds and an increased instability feed from the south and we expect this line to begin to impact the region around 4pm. As mentioned the exact intensity of these storms will be highly dependent on how these storms interact with the environment, but we expect the southern zones (SE PA, SNJ, and into portions of Central NJ) to receive the strongest impacts with the potential for damaging wind gusts, lightning, heavy rains, and possibly some small hail in the strongest storms. Further north, the lack of instability will limit the potential impacts to some strong winds and occasional lightning as well as some heavy rain that will reduce visibility.

Current look at the radar along with active Severe Thunderstorm Watches and Warnings across the area (Courtesy of Simuawips)

Current look at the radar along with active Severe Thunderstorm Watches and Warnings across the area (Courtesy of Simuawips)

Gradually, the threat for severe weather will shift southeast through these zones during the afternoon and early to mid evening hours. The main complex of storms will move offshore, shifting through Southeast NJ (Atlantic City and Cape May) during the early to middle evening, and then offshore. Cooler and more stable air will move into the area behind the storm complex.

impactmap_mar1

 

Make sure to stay updated over the next few hours with these potentially dangerous storms!

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.

 

Have a great day!

Steve Copertino