Steven Copertino

Public Analysis: Heavy Rains Exit Today, Unsettled and Cooler Next Week

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Good afternoon and Happy Friday!

The large area of low pressure that we have been talking about for over a week now is finally making is way through the Northeast, and is certainly making its presence known. As of 2pm, most of the region has seen anywhere from 1-3.5″ of rain over the past 6 hours or so. All of this heavy rain in such a short period of time has lead to street flooding to be quite common in areas with poor drainage that also saw some of the heavier 2.5-3.5″ amounts. Flash flood warnings are currently out for portions of central NJ, Northeast NJ, Long Island, and southern Connecticut. While street flooding will be possible across portions of northeast New Jersey, Long Island, and Connecticut due to training of very heavy pockets of rain, more significant creek, river flooding is not expected at this time-though a few isolated cases may be possible as totals may approach 4″ in some isolated locations later this afternoon.

Please pay close attention to you local National Weather Service office for any information on Flash Flood Warnings or statements over the next few hours. Additionally, exercise caution when driving through heavy downpours and if you do encounter flooding of roadways-DO NOT attempt to cross that area of water no matter how deep you think it may be. We have seen upwards of 10 reports already of people trapped in vehicles, which required rescuing! Turn around and don’t drown!

As we work our way through the rest of the afternoon, dry air will begin to work its way in from the southwest and will work to effectively shut down the heavy rains. Mostly cloudy conditions are expected the rest of the afternoon as the rain tapers off from west to east by around 3-4pm. Temperatures may be able to rebound slightly into the low to mid 60’s across the area as a warm front begins to work its way up from the south just behind the bulk of the rains. As this warm front continues to move north through this evening, some more shower will be possible over the region, but heavy rainfall with these showers appears unlikely as the atmosphere will contain significantly less water vapor than it did this afternoon. Temperatures this evening will remain quite warm as the area will be within the warm sector of the low pressure area moving through Pennsylvania.

Latest regional radar mosaic, surface temperatures, visible satellite imagery , and NWS Flood Warnings (in green) showing the heavy rains finally pushing out of the area (Courtesy of GREarth)

Latest regional radar mosaic, surface temperatures, visible satellite imagery , and NWS Flood Warnings (in green) showing the heavy rains finally pushing out of the area (Courtesy of GREarth)

Saturday and Sunday 

The unsettled pattern will continue through the evening hours and into tomorrow as the negative NAO block helps the storm’s remnants stall out and decay over our area for at least the rest of the weekend. Tomorrow should start off relatively warm underneath partly cloudy skies and light southerly winds as the warm front continues to move north of our area. Depending on how much clearing we see tomorrow, some areas could reach highs into the middle to upper 60’s by late afternoon, while the rest of the region sees highs generally in the low to mid 60’s. Some residual energy associated with a cold front will likely move through the area late tomorrow afternoon or early evening, and bring the potential for some more showers and even an isolated thunderstorm depending on whether or not the area sees enough clearing earlier in the day to support some buildup of instability.

Cool and drier air will funnel in behind the cold front early Sunday morning, so any remaining showers and thunderstorms will likely taper off from west to east once again. As we get to daybreak on Sunday, another cold front will be working its way east, so expect some broken clouds to start off the day, but cloudiness should gradually increase as a the cold-core of the upper level low that will have stalled over the region begins to sink to the south and towards our area. This pocket of colder upper level temperatures will harbor a more unstable environment, so some showers will be possible during the afternoon. With the cooler air being reinforced by two cold front on Sunday and cloudier weather likely, highs should remain in the upper 50’s to lower 60’s during the day.

This afternoons high resolution NAM model, showing unstable conditions underneath with rain/snow showers possible for locations to the North and West (Valid 8pm Sunday)

This afternoons high resolution NAM model, showing unstable conditions underneath with rain/snow showers possible for locations to the North and West (Valid 8pm Sunday)

Extended Range

The latest computer model guidance consisting of the American model, the Canadian model, and the European model, all show the negative NAO continuing into next week and even strengthen the block while bringing it back further west. This will keep a large upper-level low trapped over the Northeast, which will ensure that cooler weather stays locked in place. This large upper level low locked in over the region will also be capable of swinging multiple disturbances around the base of the low, and possibly back into our area.

For the most part, each day early next week should be relatively similar, with early morning sunshine giving way to cloudier conditions with the threat of some showers by later afternoon and evening. Given the cooler temperatures in the upper levels of the atmosphere, some ice pellets or event wet snowflakes may be possible for locations to the north and west. Otherwise, each day is mainly looking at highs in the mid 50’s to lower 60’s for highs, with lows ranging from the low 40’s to 30’s possible for inland locations.

No real significant precipitation events are expected in the medium range, however we are beginning to watch the period around Mother’s Day for a potential coastal system. The time to really watch for larger storms or heavier precipitation events in this type of pattern is typically when the NAO block begins to weaken and move away. At this time, we don’t really see the possibility of this happening until around late May. Stay tuned for further updates on the unusually cool pattern over the foreseeable future!

This afternoons European model showing below-normal temperatures over the next week for the Northeast US, courtesy of a large upper-level low parked over the region (Image Credit: Ryan Maue)

This afternoons European model showing below-normal temperatures over the next week for the Northeast US, courtesy of a large upper-level low parked over the region (Image Credit: Ryan Maue)

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

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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Have a great evening!

Steve Copertino

Steven Copertino

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

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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: Warm End To the Week, Unusual Spring Pattern Setting Up

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Good afternoon!

After the dreary and cool weather we’ve been stuck in for the past few days due to the large and sluggish cut-off low pressure system earlier this week, conditions have finally improved rather markedly this afternoon. With clear skies, light westerly/southwesterly winds, and warm mid-level temperatures have allowed highs to reach into the upper 70’s and lower 80’s across the entire area. Some locations along the coast of Long Island and Connecticut have experienced a little more offshore flow this afternoon, therefor temperatures are stuck in the lower 70’s as of 2pm.

As we near the late afternoon hours and early evening, winds may turn more to the southeast ahead of a weak mid-level disturbance approaching our area. With winds out of the southeast, more moisture from off of the Atlantic may be able to work its way into the lower levels of the atmosphere and produce some overcast, especially for coastal sections of NJ and Long Island. After sunset, some locations closer to the coast may also have to deal with patchy fog as that moisture right off of the coast gets brought inland.

Later this evening and into very early tomorrow morning, we may have to watch out for the potential for some possible heavy rain as strong thunderstorms develop later this afternoon over portions of the Ohio Valley. These storms may wind up tracking through our area later on this evening and into tomorrow morning. These residual showers and possible thunderstorms would be fueled by the leftover instability provided by the southerly winds and approaching mid-level disturbance over Pennsylvania. The latest hi-resolution guidance has this activity reaching the area by 4-6 am, but if these storms do manage to maintain themselves, there could pose a threat for locally heavy downpours, gusty winds, and  some thunder. There are still uncertainties regarding these storms as they have not developed yet, but one concern is that they could slip to the south of the NYC area and cause little if any impact . Otherwise, tonight should be relatively warm as clouds work to trap the remaining heat in the low levels of the atmosphere, leading to lows in the upper 50’s and low 60’s.

Current conditions featuring the latest surface temperatures, visible satellite imagery, and regional radar mosaic, showing a very nice end to the work week.

Current conditions featuring the latest surface temperatures, visible satellite imagery, and regional radar mosaic, showing a very nice end to the work week.

Saturday and Sunday

As we move into tomorrow morning, some leftover showers and clouds may linger into the early afternoon hours, especially as a backdoor cold front works its way from north to south. While not as “intense” as the previous backdoor fronts that we have had over the past few weeks, this front will bring a mix of clouds and sun and gusty winds of around 25-35 mph during the afternoon hours. High temperatures tomorrow afternoon will be somewhat tricky to forecast depending on how far south the front can sag to the south, but highs should generally be in the upper 70’s and low 80’s across the entire area. It is worth mentioning that some locations in Southern New Jersey and portions of Southeast Pennsylvania could possibly see highs in the mid-upper 80’s with enough sun.

It is worth mentioning that there is some potential for some isolated showers and thunderstorms late tomorrow afternoon and evening as the backdoor front sags south through Pennsylvania and New Jersey. Instability will be quite high to the south of this front, and wind shear will also be quite supportive of some strong or possibly very isolated severe thunderstorms which may produce some isolated large hail, locally heavy rainfall, and damaging winds. However, due to the lack of a “trigger” to set these storms off, and the fact that the cold front could be well south of the immediate NYC metro area by the time the other ingredients are in place, we do not anticipate widespread significant severe weather tomorrow afternoon. Otherwise, Tomorrow evening will definitely be much cooler than Friday, as the cold front leaves behind cooler winds from the north west, with lows in the lower 50’s to upper 40’s further inland.

On Sunday a much cooler airmass will be over the region as maritime floods the entire area due to winds coming in from the Atlantic ocean. While starting off relatively cool in the morning, a mix of sun and clouds and calmer winds from a high pressure system to the north east will allow temperatures to get into the low to middle 60’s across the area, which is around 8-10 degrees below normal for this time of year!

Later in the evening, we may see the stalled out front over portions of the Mid-Atlantic begin to return northwards with some warmer air and clouds, but at this time the timing and placement of this feature is somewhat uncertain. Overall, we expect cloudiness and possibly some showers to take over during the evening on Sunday.

This afternoons 12km North American model showing a rather significant amount of instability to the south of the NYC metro on Saturday afternoon (Valid 4pm Saturday)

This afternoons 12km North American model showing a rather significant amount of instability to the south of the NYC metro on Saturday afternoon (Valid 4pm Saturday)

Monday and Early Tuesday 

As mentioned, there are some very significant uncertainties as to how far north the front will advance once again on Monday, as this will be crucial in determining how the day plays out. If the front happens to reach far enough north of our region by the afternoon hours, we could see a very warm and pleasant day on Monday with highs in the upper 70’s and low 80’s once again. However, even if this warmer solution is realized on Monday, a very large system is expected to be gathering in the Great Lakes region Monday evening.

As this system continue to move north and east through the Great Lakes region very late Monday and into Tuesday, it should drag a rather strong cold front through our area. This cold front will have access to deep tropical moisture, extending all the way from the Gulf of Mexico, so there is a real threat for heavy rain and potential thunderstorms associated with this cold front as it progresses through our area.  At this time, it appears that the showers and thunderstorms will be passing through during the evening hours, so the overall severity of the associated thunderstorms should be quite limited.

Extended Range

A cooler airmass is expected to trail the front later in the day on Tuesday and into Wednesday, but the main story will be the ensuing pattern that will be taking shape. We have talked about the North Atlantic Oscillation many times in the past, and especially during the winter months since it is such a large factor in helping to get large coastal storms to drop copious amounts of precipitation over our area when it heads towards its negative phase. In an interesting series of events, it now seems that a very large and powerful ridge will be setting up over Greenland during the middle of next week. If this actually does materialize, and most of the computer model guidance does support it, then we could be entering a rather cool and stormy pattern for at least the next 7-10 days across the Northeast.

Interestingly enough, the models have even been beginning to show a series of potential coastal storms in the long range taking tracks quite similar to storm tracks that we would see during the Winter months! We will continue to monitor this very interesting pattern over the next few days and provide updates and more details become available!

GFS and ECMWF ensembles both agreeing on an extended period of a negative NAO, which could promote cool and stormy weather in the east

GFS and ECMWF ensembles both agreeing on an extended period of a negative NAO, which could promote cool and stormy weather in the east

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