Steven Copertino

Significant Snowstorm Likely on Wednesday for Portions of the Northeast!

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Good evening! 

After a very significant Nor’Easter that impacted the Northeast this past weekend, it looks like we’ll have a shot at yet another system! However, we may have to deal with much more snow over the PHL-NYC corridor this time around.

Gradually making our way to the main system, today has been a rather calm, but cold day across the entire east coast as the area remains in a northerly flow coming in from Atlantic Canada. This is partly due in part to the large area of low pressure that impacted the east this past weekend with heavy rains, hurricane-force winds, and over 40″ of snow in some locations. After the moved off the coast, it was blocked from moving North and into the North Atlantic due to record-high blocking near Greenland. Regardless, this massive system has still had a large impact on our weather for the past three to four days now, but that will soon come to an end. Mid level ridging will increase just enough for a strong area of high pressure to attempt to build in over the Northeast this evening, allowing for calm and cold conditions to persist throughout the evening hours. Very dry mid to upper levels of the atmosphere in-between disturbances will ensure that clouds are kept at a minimum, and with clear skies and relatively light winds, we should see rather favorable conditions for radiational cooling to take place. This should allow lows this evening to drop into the middle to upper 20’s, with some locations off to the north and west  seeing readings drop down into the lower 20’s.

This evenings latest surface observations, surface winds, regional radar mosaic, and water vapor imagery

This evenings latest surface observations, surface winds, regional radar mosaic, and water vapor imagery

Significant Snowstorm Likely for Portions of the Northeast Wednesday 

Tuesday morning will likely start off quite clear and cold as residual high pressure attempts to creep in ahead of our next system. Dry mid to upper levels of the atmosphere are expected to continue throughout most of the day, so expect sunny to partly cloudy skies for the vast majority of the day tomorrow.  Winds will gradually become light and variable throughout the late afternoon hours as we await the arrival of the next system. With a cool mid level airmass in place, moderately sunny skies, and light winds, expect highs to only rise into the lower to middle 40’s tomorrow afternoon-with some locations further to the north and west likely staying in the upper 30’s.

Further west, we will be watching a large, and closed off piece of mid level energy that will be over Plains by tomorrow afternoon. This system has been producing heavy snow in the northern Plains, and some scattered strong thunderstorms in the south, but this will begin to change tomorrow afternoon as the surface low pressure begins to occlude and decay. As the surface low heads west and decays, a vigorous piece of energy over southern Canada will be forced south and into the Great Lakes region by tomorrow afternoon. This interaction will cause the nature of the trough in the eastern third of the country to become more negatively tilted, which is very important for the development of a secondary surface cyclone along the east coast. By tomorrow evening, we should see widespread showers extend from NY state and down into the Gulf of Mexico associated with the stalled out, and decaying front. As the night goes on, we should see a weak area of low pressure likely develop over, or just off the Mid Atlantic coast, which will be our main focus on Wednesday.

 

This evenings NAM model showing the mid level evolution leading up to our potentially significant snowstorm on Wednesday

This evenings NAM model showing the mid level evolution leading up to our potentially significant snowstorm on Wednesday

Our mid level systems should be completely phased together by 8am Wednesday morning as the trough over the east goes fully negative. This will allow the weak area of low pressure near the Mid Atlantic to begin a period of rapid intensification thanks to an expanding upper level jet streak and an impressive amount of positive vorticity advection moving just off the Delmarva peninsula to promote heavy precip development. This systems precipitation shield should begin to rapidly expand once it begins to mature, with locations in Maryland, Southeast PA, Delaware, and southern New Jersey all receiving the first moderate to heavy bands of snow around 8-11am. These bands will gradually pivot and continue moving north/northeast as the day goes on, with some of the most intense banding likely holding off until the afternoon hours of Wednesday.

As the mid levels system matures, there are strong indications it should begin to close off at around 500mb. The quicker that this process occurs, the more the surface low will be able to tuck into the coast with intense banding spreading deeper into NJ/PA. As of this afternoon, the models keep the 500mb low from closing off until the mid-afternoon hours on Wednesday as the system is just off the NJ coast. As soon as this feature is able to close-off, we should see very strong vertical motion begin to develop over portions of NJ/NY, which is a strong signal for very heavy snow bands capable of producing snowfall rates in excess of 1-3″ per hours with pockets of thundersnow possible. While the intensity of the snow will be quite heavy, it is worth noting that this system is quite small in nature and moving quickly. This presents some problems for this forecast, as any subsequent deviations with the surface low can mean the axis of heaviest snowfall totals can change quite quickly/significantly. Additionally, this system could potentially bring in some warmer air on the backside of the low pressure, meaning places like coastal Long Island and Connecticut could see a changeover, or complete flip to rain during the afternoon hours on Wednesday. This would require a large reduction in overall snowfall totals, but for this forecast we have decided to leave it as is due to uncertainty.

Overall, we expect the heaviest snowfall to occur from SW to NE over SE PA, Central/Northern NJ, Southern NY, and possibly into portions of Connecticut. While this system will be moving quite quickly, the heaviest snows look to happen during the afternoon/early evening hours, with the evening commute possibly being heavily impacted. Snowfall rates may be too intense in some locations for road crews to keep up with, so please begin to come up with alternate plans if you will be traveling during the day on Wednesday. Otherwise, snow will begin to taper off during the early evening hours from south to north, with conditions clearing out by the overnight hours of Thursday. Accumulations should generally top off in the 9-12″ range, however there are some indications that locally higher amounts of up to 12-18″ could be possibly in the most intense banding. We will have another update tomorrow morning to address any changes that occurred overnight.

This evenings forecast storm total snowfall for Wednesday storm

This evenings forecast storm total snowfall for Wednesday storm

Have a great evening!

Steven Copertino

Doug Simonian

VIDEO Analysis: Potential Heavy Snow on Wednesday

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The very active pattern for early March will continue, as we are tracking yet another potential major storm system that would impact the area on Wednesday. The large -NAO blocking pattern will continue, which will force multiple potent, dynamic disturbances to our south, and with the airmass a bit colder this time around compared to the Friday’s storm, snow — potentially heavy — is a much bigger threat for the NYC area.

In our latest video, we discuss Sunday’s 12z ECMWF (Euro), Sunday’s 18z GFS, and Sunday’s 18z NAM. The Euro is the furthest east solution, which would only give significant snow for Long Island and Southern New England, the GFS is the furthest west solution, which would give the immediate I-95 suburbs a significant snowfall, but areas further southeast more rain and subsidence, while the NAM is the snow-lover’s ideal “in between”, which hits the entire NYC Metro region with a heavy snowfall. Not only is the NAM model “in between”, but it is also the most dynamic of the three solutions, maturing its mid-level centers earlier. If this were to occur, the storm would slow down just off the coast, and bring in a heavy band of snow for a long period of time.

This storm is an interesting case, because it could track very close to the coast, which would normally mean a rain event. However, with the circulation very compact and dynamic, more northerly winds would “rush” in towards the center of the storm than is usual, so the banding could be more compact and stronger closer to the coast, and temperatures could also be much colder than what is “typical” for a storm track of this nature.

We also discuss why each model is portraying the scenarios they are, as well as which we believe is most likely to occur in this pattern.

Doug Simonian

VIDEO Analysis: Major Nor’Easter with Myriad of Impacts

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Good morning! Our latest video discussion details the formation and impacts of this major Nor’Easter that will impact the entire Northeast today. Heavy rain will change over to heavy wet snow, leading to significant localized accumulations, but varying precipitation types and temperatures just above freezing will prevent significant accumulations in many locations as well.

Later this morning and this afternoon, there will be multiple bands of heavy wet snow throughout a decent chunk of NJ, NYC, W LI, and the Hudson Valley — and when combined with wind gusts between 50 and 65 mph, blizzard conditions are likely. But areas in between these bands will have lighter precipitation and thus rain, and nailing down these specifics is extremely challenging.

Thus, we want to emphasize the impacts rather than the actual snowfall accumulations. The strong winds combined with heavy precipitation with already quite moist top soil will lead to some tree damage and power outages. Coastal flooding is also likely, as the low-level jet rams into some coastal areas — especially for coastal New England. Surprises are in store as well, as some locations are going to receive a lot more snow than expected, but other locations very close by may not receive much snow at all!

Steven Copertino

Potentially Record-Breaking Warmth and Unsettled Conditions Take Hold Over the East

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Good evening! 

It certainly has been a wild swing of events over the past week or so, with above normal temperatures, a snowstorm, and now the potential for some record breaking warm weather later this week! This will likely be a gradual process, with the first major changes taking place during this afternoon and evening. A very large upper level trough out in the western half of the country is currently digging into southwest, allowing for a very large mid level ridge to build over the east. This large mid level trough has also spawned a weak, but expansive low pressure system over the Plains today, with numerous showers and thunderstorms extending from the deep south, into the Ohio Valley and Northeast. This large low pressure system has sent moisture north into the region which has been collecting along a mid level frontal system. This mid level front has been responsible for areas of steady rain over portions of New England, with more patchy rain to the south over Pennsylvania, New Jersey, New York, and Connecticut. This area of rain should continue to lift north with the frontal system through the overnight hours, leaving spotty drizzle and cloudy conditions behind. Mid level temperatures will be rising quite a bit this evening as high pressure to our south sends a stout southwesterly flow over the East. This will ensure that conditions stay rather cloudy with much above-normal temperatures this evening. In fact, lows may not drop at all for most of the immediate coastal plain, and may actually rise a bit into the middle to upper 40’s. The only real chance for any cooling looks to be well to the north and west of the city, with lows only getting down into the lower 40’s. Due to some locations still having some snow on the ground and increasing surface temperatures, there may be some areas of fog that develop after dark. These areas of fog could be locally dense, so please use caution if you are driving this evening!

This afternoons national radar mosaic, surface temperatures, mid level temperatures, and mid level heights showing a clear southwesterly flow in place already over the East

This afternoons national radar mosaic, surface temperatures, mid level temperatures, and mid level heights showing a clear southwesterly flow in place already over the East

Tuesday Into Wednesday 

Tuesday morning will likely start off rather mild, with patchy fog and mostly cloudy conditions over much of the Northeast. The mid level warm front will be located well to our north over southern Canada by tomorrow morning, so the threat of rain looks rather low for tomorrow-though some patchy drizzle may be possible closer to the coast. Relatively dry air is forecast to punch into the Northeast tomorrow afternoon, which should help to burn away the vast majority of the cloud cover tomorrow afternoon. With mid level temperatures much above normal and sunny conditions in place, highs tomorrow will likely reach well into the 60’s over much of the New York metro area, with a chance at breaking into the 70’s for portions of Northeast New Jersey and locations to the south of New York City. “Cooler” highs in the lower 60’s will be possible off the north and west as well as along coastal locations due to onshore flows bringing in a more maritime airmass. While not as widespread, tomorrow will be the first day the record high temperatures could fall across the interior locations of the Northeast. Clear and mild conditions should last well into the evening and overnight hours, with southwesterly flow continuing to increase mid level temperatures. This should allow lows to be quite warm for this time of year, with many locations seeing readings stay in the lower to middle 50’s-which could potentially set record maximum low temperatures for this time of year.

Wednesday looks to be the warmest day of the week as deep southwesterly flow is maximized over the region, bringing in highly abnormal temperatures across much of the East. The day may start off with some low clouds and fog, but dry mid levels will likely aid in the vast majority of this cloud cover burning off by the early afternoon hours. After that, temperatures will be off to the races across the entire Northeast. Widespread records may fall during the afternoon, as readings soar into the middle to upper 70’s across the Northeast. Lower readings are guaranteed over portions of coastal NJ, CT, and Long Island due to onshore flow that will bring in that maritime airmass once again. Cloud cover will then begin to increase later in the afternoon as a cold front approaches from the west, with scattered showers along it. As this front approaches, shower activity will likely be on the steady decline, so only expect broken showers through the area during the evening and overnight hours. Temperatures should fall during the overnight hours as the front passes through the region, with lows still staying 5-10 degrees above normal.

NWS forecasted highs on Wednesday with the circles representing potential records being broken

NWS forecasted highs on Wednesday with the circles representing potential records being broken

Unsettled and Mild Into the Weekend

The very impressive mid level ridging over the Western Atlantic will remain in place throughout the remainder of the week, keeping conditions rather mild, with chances at light to moderate rain events. The first potential rain event looks to occur on Thursday evening as Gulf moisture streams up and around the mid level ridging and into the Northeast. A very impressive upper level jet streak also looks to be just to the north of the area, so this will likely promote the development of at least light to moderate rain over the Mid Atlantic and Northeast. The chance for rain looks to continue through the overnight hours on Thursday and into Friday, as another upper level system digs into the West. This will create yet another plume of moisture streaming north into East, with moderate rain likely over at least western portions of the Northeast. The models begin to divergence on the last rain threat over the weekend, but this afternoons European model shows a rather expansive area of rain developing over the Ohio Valley and Northeast Saturday night and lasting into Sunday. Despite the run-to-run uncertainty, the overall upper level pattern looks to be one that could support some rather widespread moderate rain over the area, with some potentially heavy showers embedded into the mix due to a favorable/peaking jet structure. Temperatures during this period look to be above-normal, but not as warm as Tuesday or Wednesday, with highs in the 40’s and 50’s. In the longer range, we may have to watch for a potential shift in the overall pattern, but we will dive into this more later in the week.

This afternoons European Ensembles showing a very wet and active pattern in the central and eastern US over the next week

This afternoons European Ensembles showing a very wet and active pattern in the central and eastern US over the next week

Have a great night! 

Steve Copertino