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500mb height anomalies 1/9
Steven Copertino

Light Mix Tonight, Unsettled Pattern Remains In Place

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Good evening! 

Well it may be a new year, but we are certainly stuck in the same old pattern that we have been entrenched in since the beginning of December. A decaying high pressure system to our north is currently moving off the coast of New England, which has allowed for a more mild and moist airmass to overspread the Mid-Atlantic and much of the Northeast. Clouds have been on the increase for virtually the entire day, and the combination of increasing clouds and mid-level flow switching over to the southwest has allowed for temperatures to rise into the upper 30’s to lower 40’s this afternoon. While still generally “cool”, these temperatures are anywhere from 5-10 degrees above normal for early January.

Cloudiness will continue to increase throughout the rest of this evening and into the overnight hours as a weak shortwave trough approaches the Northeast from the Great Lakes. Temperatures will be falling tonight, but the increasing cloudiness will put a cap on just how low they can fall tonight. Precipitation from the weak area of low pressure approaching the New York City metro will likely begin as a light snow/rain mix by 11pm-1am, but should quickly turn to all rain for the vast majority of the area. Locations that have the best chance at staying mostly (light) snow through the overnight hours will be elevated locations that are off to the north and west of the immediate New York City area.

Regardless, this system will be moving very quickly to the east this evening/overnight, which will severely limit how much moisture from the south is able to interact with it. Even those who manage to stay 100% frozen tonight will only see a half-inch of snow at best–most of which will be erased as precip quickly shuts off from west to east before dawn.

This evenings high-resolution NAM model showing the evolution of the quick-hitting system this evening/overnight

Yet Another Rainstorm Likely on Saturday 

As mentioned, the area of low pressure impacting our area through the overnight hours and into the early morning hours of Thursday will be quickly moving off the coast by the AM commute. As this system departs, any remaining precipitation over the Northeast will come to an end by the early afternoon hours. Partly cloudy skies with breezy conditions will be prevalent tomorrow afternoon, with temperatures remaining in the middle to upper 40’s. Our next system will remain off to the south long enough to allow for calm conditions to persist through the evening and overnight hours tomorrow night. Clear skies and gradually subsiding winds will allow for radiational cooling to set up, which will cause temperatures to drop into the middle to upper 20’s across the entire forecast area.

Conditions will remain calm and clear into Friday as surface high pressure quickly moves to our south during the day. This will cause dry and mild weather for the majority of the day, with temperatures once again staying in or around the middle 40’s. The weak surface high pressure will then quickly exit off the coast by Friday afternoon, which should set the stage for a cut-off upper level low to gradually move into the Mid-Atlantic states on Friday evening. Cloudiness will slowly increase from north to south Friday night, with showers developing over portions of Southern New Jersey by 8-10pm. This slow-moving system will not have any cold air to work with as precipitation moves to the north, so this entire storm will be another wet and mild system.

As the upper-level low continues to edge in over the Mid-Atlantic during the early morning hours on Saturday, surface low pressure will begin to intensify off to our south. This will result in another impressive low-level jet overspreading the NYC metro area, with more steady rain developing by the late morning/afternoon hours on Saturday. The surface low should then take on a more easterly course during the day, likely moving off the NJ coast during the afternoon hours. Steady rainfall will continue into the evening, before gradually tapering off from west to east Saturday night. Though the exact amounts and timing will still need to be tweaked over the coming days, this looks to be another dreary and inconvenient weekend storm opposed to anything truly impactful-outside the potential for some coastal flooding.

ECMWF 500mb vort

This afternoons ECMWF model showing a compact closed low over the Mid-Atlantic on Saturday morning

Unsettled Conditions Last Through Next Week

An active northern stream jet will allow for another disorganized shortwave to move through the Northern Plains states on Monday and into the Great Lakes by Monday night. While there may be some blocking over Greenland at this time to allow the system to slow down a bit and organize before impacting our area, there is still no real cold air source anywhere outside of New England and Southern Canada. This afternoons model runs have been rather consistent in showing the possibility of some front-end mixed precipitation for our area overnight Monday, before a changeover to rain Tuesday morning as the surface low tracks over the Lower Hudson Valley.

At this time the overall potential for impactful winter weather looks to be low for the NYC area, with an increasing chance once you get into New England. It is important to note that this system is still five to six days out and there are many details that need to be ironed out. We will continue to update you over the next couple of days on this potential system!

ECMWF model

PM European model showing the potential for some wintry weather over portions of the Northeast Monday night/Tuesday

Have a great night! 

Steve Copertino

Steven Copertino

Dreary and complex weekend ahead

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Good evening!

After the very light rain/snow mix yesterday, we’re now firmly entrenched within a much more mild and moist airmass thanks to the large upper-level system over the Southeastern US that we have been talking about since last week. This system has been quite challenging to nail down over the past few days, as key features that will determine the overall impacts from this system are constantly changing.

So what exactly has changed?

Well, the first major change that we’ve seen is that the system as a whole is quite a bit more disorganized than what the models originally projected, and this has led to the precipitation over the Southeast to also become quite disorganized and lackluster in nature. Another major change that we’ve seen is that a shortwave trough currently over eastern Canada has trended stronger and further south over the past couple of days, which is keeping the overall storm much further south than previously expected. Now if this sounds familiar to you, this is generally the same thing that happened with last weekends snowstorm that stayed well to the south of the Northeast but still managed to significantly impact portions of the Mid-Atlantic and Southeastern states.

With these two significant changes in mind, this means that the strong low-level jet that was supposed to overspread the Northeast will now be less impressive and much more suppressed to our south this evening and throughout the day on Saturday.

With the main mechanism for heavy rain potential now located our south, this evening and the majority of Saturday should really only be capable of light to locally moderate rain showers for much of the New York Metro area, with more steady rain likely over southern portions of New Jersey. Regardless, with warm air advection from the south increasing overnight and cloudy conditions remaining in place during the entire day on Saturday, we should see highs in the middle to upper 40’s over the entire area, with lower 50’s possible closer to the coast, making for quite the dreary day.

These temperatures will be running anywhere from 5-10 degrees above-average for this time of year, which is quite the change considering we were 10-15 degrees below-average earlier this week.

Dreary conditions likely this

This afternoons high resolution NAM model showing the vast majority of the heavy rain staying to the south of the NYC area Fri/Sat

Unsettled conditions remain through Sunday night

As we head into the evening and overnight hours on Saturday, we should begin to see the upper-level low slowly begin to move into portions of the southern Mid-Atlantic states. As this systems pushes to our south late Saturday night and during the early morning hours of Sunday, the positioning of the upper-level system will allow for stronger areas of lift to develop from north to south, which should finally result in a batch of moderate to heavy rainfall pushing through the Mid-Atlantic and Northeastern states.

The complex part of this forecast really begins on Sunday afternoon when another shortwave trough will be quickly moving over southern Canada. Recent model trends have shown that this Canadian shortwave trough will have the potential to interact with the upper level low located to our south, which could help to spawn an area of low pressure off the New Jersey coast. While southerly flow and very marginal surface temperatures should keep precipitation limited to a dreary and cool rain throughout our area, we could see some colder temperatures begin to bleed in over the Northeast later Sunday afternoon. This will have some very important implications for locations well to the north and west of the New York city area as we head into the evening hours on Sunday when the surface low pressure system begins to strengthen off the New Jersey coast. With the colder air bleeding in from the north and the upper-level low to the south of Long Island providing sufficient lift for continued precipitation over PA/NY/NJ, there is the possibility that we could see rain gradually change to a wet snow/rain mix for locations over NE PA, SNY, and elevated portions of NW NJ. Again, temperature profiles are very mild and the best chance for a light mix of precipitation will come from “dynamic cooling” within heavier areas of precip to the NW of the city.

NYC Weekly Planner

~Updated NYC Weekly Planner ~

Clear and cooler start to the work week 

As the shortwave trough moving through Canada gradually digs into the Northeast overnight on Sunday and into Monday morning, we should see the mild and dreary conditions gradually fade from northwest to southeast. A much cooler mid-level airmass will be moving into the area during the afternoon hours on Monday, which should also eliminate most of the residual clouds from this weekends storm system in addition to bringing high temps across the area back into the middle to lower 40’s. Relatively clear and calm conditions should persists through the middle of the week as an upper-level ridge and associated area of high pressure gradually builds in over the East. Highs will likely be limited to the upper 30’s to middle 40’s Tuesday to Thursday before our next potential storm system begins to build to our west. Unfortunately, it appears that we could be looking at yet another dreary weekend next weekend over much of the East as an area of low pressure develops well to our west, dragging mild/moist conditions  along the coast.

ECMWF 700mb RH and Winds

This afternoons ECMWF model showing much of the same late next week as another area of low pressure brings the potential for rain in the East

We’ll have updates on Sunday’s  wintry mix potential likely during the day tomorrow, so stay tuned for updates!

Have a great weekend! 

Steven Copertino

Steven Copertino

Light wintry mix possible tomorrow, dreary weekend ahead

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Good afternoon!

The cool and quiet conditions that have been with us for the past week or so continue over the Northeast this afternoon, with the only real changes being that cloudiness has increased in earnest and highs today are only slightly warmer than the previous couple of days. Despite temperatures running a few degrees above what they have been, we’re still seeing highs across the New York metro area in the upper 30’s to lower 40’s, with lower to middle 40’s over portions of Southern New Jersey. Conditions should stay rather cloudy this evening and overnight as a shortwave trough over portions of the Great Lakes continues to head to the east, dragging up warmer mid-level air from the south. Temperatures this evening should remain cool, but not nearly as cold as the past few nights thanks to the increased low/mid-level clouds limiting any potential for radiational cooling. Expect lows to generally stay in the upper 20’s to lower 30’s for most of the New York City area-with middle to upper 20’s well to the NW and middle to upper 30’s over portions of SNJ.

7-day Weekly Planner

Weekly Planner for the next 7-days

Light wintry mix possible tomorrow morning/afternoon

During our previous update we introduced the possibility of a period of light snow/rain moving through the Northeast on Thursday, and since that time we have seen models become a bit more bullish on this event. The same shortwave moving through the Great Lakes this afternoon/evening will be over portions of PA/NY by early tomorrow morning, with light snow likely breaking out over Central Pennsylvania.

Though this shortwave is rather dry, it will be given small boost of moisture from relatively warm and moist air advecting into the Northeast. This should allow the small area of snow to sustain itself during its journey through Pennsylvania tomorrow morning, possibly reaching New Jersey by 7-9am. Once we get to around 10-11am, we should see precipitation expand into New York City and portions of Long Island. Given the limited dynamics/moisture available with this system in addition to very marginal surface temperatures, this system will not be an areawide snow producer. As of right now, it looks like locations mainly to the north of Trenton, New Jersey to NYC should begin as snow, but the same warm air advection that will be causing the precipitation will also help to gradually change precip over to light rain or a wintry mix from south to north.

Locations to the north and west of the immediate New York City area should have the best shot at staying mainly light snow for most of the morning/early afternoon, in addition to locations with greater elevations. While snow will likely be in the air tomorrow, the vast majority of the area should see issues with the snow sticking, outside of colder surfaces given the very marginal airmass. Additionally, snow growth a few thousand feet above the surface will be far less than ideal, meaning that snowflakes could be very small and malformed. This only further complicates any accumulation talk, but at this time a general coating to two inches is expected from Pennsylvania and into portions of NNJ/SNY (with the potential for locally higher amounts for elevated locations).

The timing of the precipitation ending will be highly dependent on when the shortwave outruns the best WAA (warm air advection), but this looks to be during the late afternoon hours. Any remaining precip during the late afternoon hours should change to a light wintry mix for the remainder of the area. All in all, this should not be a highly impactful system, but it could cause some slick road conditions, so please use caution when traveling tomorrow.

3km NAM simulated radar

Loop of this afternoons NAM model showing the light snow/mix event for tomorrow morning and afternoon. Note how most locations around New York City end as rain.

Weekend storm likely to deliver wet and dreary conditions through Sunday

Back on Monday we mentioned the potential for heavy rain from an approaching upper level low over portions of the Southeast, however since that time the reliable computer models have trended weaker/more disjointed with this system as a whole. The result of a weaker system for the Northeast means that the strong low level jet that was forecast to occur over the East coast is now much less likely which severely limits the heavy rain/wind threat.

While we will likely see moderate to possibly locally heavy rain move into the area by Friday night and into Saturday morning, the risk for widespread heavy rain and potential flooding is now much lower. As the upper level low exits the coast on Sunday there will be the chance for some additional rainfall, especially along the coast. Interestingly enough, some models develop a coastal storm late Sunday and into Monday that could potentially extend the wet/unstable period a bit longer, but this remains quite uncertain at this time. We will continue to monitor the progress of this system as more details become clear in subsequent updates.

12z ECMWF PWATS

This afternoons ECMWF model showing a weaker/disjointed low level jet over portions of the East Coast early Saturday morning

We will have further updates on tomorrow light mix event and this weekends rain event by tomorrow! 

Have a great evening! 

Steve Copertino

Steven Copertino

Winter Storm Likely Wednesday for Portions of the Northeast

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Good evening! 

Today has been a rather cold and blustery day across the entire Northeast as a cold front quickly blasted across from west to east early this morning. This cold front ushered in a fresh blast of cold air from Canada, causing temperatures to drop a few degrees this morning before peak daytime heating. As the cold front moved offshore, dry air filtered into the region which allowed for mostly sunny conditions to persist throughout the rest of the day. Despite the clear skies, the cold mid level temperatures only allowed for temperatures to rise into the lower to middle 30’s for the immediate NYC metro area. Highs were a bit lower to the north and west with temperatures staying in the middle to upper 20’s-which is only slightly below normal for this time of the year. The main story today was actually the winds that arrived immediately after the frontal passage, which gusted at around 30-35 mph at times. These winds really helped to make conditions feel quite a bit colder than they actually were, with wind chills in the middle to lower teens. Additionally, any residual standing water left over from melting snow quickly froze this morning, leading to some very slippery conditions across the entire Mid Atlantic and Northeast.

Conditions will remain quite clear, with winds gradually abating by around midnight. A weak area of high pressure will work over the Mid Atlantic this evening and provide rather favorable conditions for radiational cooling to take place tonight. Highs should drop down into the middle to lower 20’s for most of the NYC metro area, with locations to the north and west getting down into the middle teens for lows.

This afternoons high resolution satellite imagery and surface observations over the Northeast

This afternoons high resolution satellite imagery and surface observations over the Northeast

Calm Tuesday, Winter Storm Likely Wednesday 

Tuesday: A weak area of mid level energy will be racing across the Ohio Valley and into portions of the Northeast tomorrow morning, which will have to be closely monitored for possibly being able to produce some areas of light snow in the morning. This area of energy, being so weak, will not have a reliable source of moisture and will also be running into dry air. This will cause the threat of snow to be greatest over western locations of the Northeast. Any snow that does fall will very light in nature and should only lead to accumulations of around a trace to an inch. This area of energy will likely move off the coast by the middle afternoon hours, gradually giving way to clearing skies from west to east.  Despite the threat for some isolated snow, the rest of the day should be mainly calm and cool, with highs staying in the low to middle 30’s across the immediate NYC metro area. These calm and conditions will last through the evening hours, with lows ranging in the middle to upper 20’s.

By Wednesday morning, two areas of energy will begin to interact over the central Plains states, leading to a very weak surface low developing over the Tennessean valley. As this low develops Wednesday morning, it will drag up a moderate amount of moisture with it that will likely cover the majority of the eastern US. The area of high pressure that is currently dominating our weather will be retreating to the east by this time, leaving some residual cold air behind over the Northeast. Precipitation will likely expand further to the north and east during the morning commute on Wednesday as an impressive upper level jet streak strengthens overhead. Since the surface high will be displaced to the east, the cold air will only be able to stick around for so long as warmer air begins to rise up from the south. This will likely lead to a quick-hitting period of moderate to heavy snow propagating from south to north , that will gradually change to rain over time as warmer air moves north. The further north and west you get from New York City, the better chance you have at more wintry precipitation. At this time, points south and east stand to get maybe a coating to an inch before the changeover to rain, but locations over NW New Jersey and SE New York have the best chance to see at least a couple of inches before a mix and eventual change to rain sets in.

It is important to note that the hi-res models have been waffling quite a bit over the past day or so, and this is mainly due to the handling of the extent of the low level cold air. If the cold air sticks around longer, there will be a greater threat of snow lasting longer in addition to more substantial frozen precipitation accumulations. These types of events usually do tend to be colder than forecast, which is why we feel that those traveling Wednesday morning keep an eye on the weather and stay tuned for further updates, as travel may be at least moderately impacted across the region.

Precipitation will gradually end from southwest to northeast as the low quickly heads off to sea during the evening hours on Wednesday.

This evenings NAM model showing the evolution of the winter storm over the Northeast on Wednesday

This evenings NAM model showing the evolution of the winter storm over the Northeast on Wednesday

Another Storm Possible Next Weekend

The computer models continue to depict another area of low pressure developing over the Tennessee valley Saturday and into Sunday as yet another area of high pressure exits to our east. This system will likely be quite large and disorganized in nature as the upper level pattern remains quite unfavorable for a strong surface cyclone. Additionally, there does not look to be a reliable source of cold air over the east, therefore any chance at significant snowfall through the weekend remains low at this time. There is still a lot of time for this to change over the next couple of days so make sure to check back for updates as they become available!

This afternoons GFS model showing the potential for another system to impact the east this weekend

This afternoons GFS model showing the potential for another system to impact the east this weekend

Have a great night!

 

Steve Copertino