Winter 2017-2018 Archives - New York Metro Weather

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Mild and Unsettled Conditions to End the Workweek, Winter to Make a Comeback?

March 28, 2018/by Steven Copertino

Good evening!

Today has been a rather dreary and cool day across the entire Northeast as sharp trough over the Plains continues to send weak mid level energy east, and into our area. This mid level energy had been responsible for mostly cloudy conditions with some light to moderate showers passing through the Mid Atlantic states most of the day in association with a weak warm front at the surface. Despite the occasional light showers and drizzle, it appears that the best lift for sustained rain will be off to our south and west, so mainly cloudy conditions with a chance at some light showers and drizzle will be commonplace across the majority of the Northeast. Mostly cloudy skies and a rather marginal airmass have allowed temperatures to climb into the lower to middle 50’s across much of the New York Metro area, with some locations closer to the coast and off to the north and west staying in the middle to upper 40’s. Temperatures should remain slightly above-normal through the overnight hours, with lower to middle 40’s likely, due to the thick cloud cover. Some, cooler lows in the middle to upper 30’s are possible for interior locations, though the overall theme of the evening will remain the same.

This afternoons visible satellite imagery, regional radar mosaic, and surface temperatures, showing a rather gloomy day across the Northeast.

Thursday and Friday

Thursday morning should start off rather mild and cloudy, as the same upper level trough over the Central US continues to draw closer to the Northeast. As it does so, mid level lift should begin to increase over the Mid Atlantic and Northeast, providing a better chance at some more showers, likely starting during the late morning hours and into the afternoon. As the day continues on tomorrow, an area of high pressure off the Southeast coast will begin to press up against the incoming trough to our west and provide some impressive warm air convection into portions of the Mid Atlantic and over southern New Jersey. While conditions are likely to remain mostly cloudy throughout the afternoon, the cloud deck may thin just a bit over this region, allowing just enough mixing to bring in some much warmer highs tomorrow afternoon. This warmer mid level airmass from the south will also work into the Northeast, but will be moderated somewhat by thicker cloud cover and mid level moisture. Expect highs to get into the lower to middle 50’s across much of the New York City metro area, with lower to middle 60’s possible across portions of Southern New Jersey and Pennsylvania. We should see the surface low pressure system begin to strengthen a bit over portions of the Ohio Valley tomorrow evening, which will likely drag another warm front through the Northeast.

As of right now, it looks like mid level ridging off the southeast coast will be just strong enough to bump the plume of moisture extending from the Gulf of Mexico and into the Northeast just off to our north and west tomorrow night. Most of the NYC area should remain generally quiet, with the exception of some isolated light to moderate showers passing from southwest to northeast. Lows will be quite mild tomorrow night, with readings in the NYC metro staying in the middle to upper 40’s. Further south, lows will likely remain in the lower to middle 50’s thanks to the increased warm air advection.

This mornings GFS model showing an impressive and exspansive upper level jet streak exteding from the Gulf Coast and into Canada. This upper level jet will have the potential to enhance dynamics and create some potentially heavy downpours on Friday morning.

This mornings GFS model showing an impressive and expansive upper level jet streak extending from the Gulf Coast and into Canada. This upper level jet will have the potential to enhance dynamics and create some potentially heavy downpours on Friday morning.

It appears that the surface cold front will be over Central Pennsylvania by the very early morning hours of Friday, with warm and moist air filtering into the region from the south. Surface low pressure should be over portions of Central New York by 8am, with increasing lift and moisture over the Metro area. In response to this increasing lift and marginally unstable airmass, some of the higher resolution models have been developing an area of heavy showers and thunderstorms over the Mid Atlantic, which eventually could impact the AM commute on Friday. Severe weather Friday morning is highly unlikely unless the timing of this system dramatically changes in the next 48 hours, however, some heavy rainfall, gusty winds, and thunder are all possible if we see the development of convection along/ahead of the cold front Friday morning. The surface cold front should clear the Northeast by the mid to late afternoon hours on Friday, but it appears that the Northeast will likely remain at least partly cloudy for the remainder of the day on Friday. Highs will likely be reached during the morning hours, but temperatures should drop back down into the middle to upper 40’s-with some 50 degree readings likely. The main upper level energy looks to pass over the Northeast on Friday night, so expect some showers to gradually make their way through as this upper level system begins to finally exit the country. Conditions on Friday night should be much colder than the previous two days, with lows likely getting down into the lower to middle 30’s over much of the Metro area. Areas well to the north and west will have the chance to drop below freezing, making for a much below average night across the area.

This afternoons NAM model showing the potential evolution of the storm system off to our west

Winter Weather…in April?!

The short answer to this questions, is yes, its certainly possible. It has happened a few times in the past, with some major snowstorms taking place during the first half of April. Of course we aren’t saying that a major snowstorm is likely during the next two weeks, but if you haven’t checked already, Doug Simonian wrote an excellent article yesterday as to why its looking like we may have to watch this upcoming pattern closely. Jumping right into things, it looks like we’ll have another high-latitude blocking episode take place over portions of Greenland and into central Canada by the middle of next week. However, unlike the previous blocking period in mid-late March, we’ll have much more cooperation from the Pacific side of things, as an area of ridging sets up over the Aleutian islands. We know that a negative NAO helps significantly when it comes to slowing a pattern down and creating the chance for a snowstorm, but why is the Pacific a big deal? Well, in short, a ridge just to the west of Alaska helps to funnel cold air down directly from the Arctic. This is crucial when looking for any kid of Spring snow in the Northeast, as there are many things working against snow during this time of year, and a fresh Arctic airmass would certainly help provide the cold air. We expect the major synoptic players will be present by early next week, but as Doug stated in his post, we usually have to wait until these features are beginning to wane to really get a shot at yet another snowstorm for the East.

While nothing is a lock this far out regarding snow, it does appear that we are heading back into a more wintry pattern next week, starting with much colder than average temperatures for this time of year. We’ll have to see how things progress over the next couple of days, but I would not be surprised at all if we we’re once again talking about a snow threat within the next 7-10 days. We will continue to provide updates on this pattern as more information comes in!

This afternoons ECMWF model showing a very impressive pattern for cold and some potential snow beginning to take shape as early as next week

Have a great night!

Steve Copertino

Update: Significant winter storm expected through Thursday

March 19, 2018/by Steven Copertino

Expected Snowstorm Impact | 7/10 (Significant)

Quick Link: Storm Total Snowfall Forecast

Good morning!

There has been a rather substantial shift over the past 24 hours with regards to the potential waves of wintry weather that could impact portions of the Mid Atlantic and Northeast Tuesday through Wednesday night. Back on Friday, we highlighted the potential outcomes for this system as a whole, with the first option being that the system remains weak and the blocking (confluence) to the north remains too strong. For the entire weekend, the model guidance showed that this was likely going to be the outcome, with the bulk of the precipitation staying south of the Mason Dixon line. However, over the past few days, the model guidance had shifted towards a much more impactful solution, with several of our more reliable models even bringing significant precipitation into the vicinity of the New York City area.

Calm and Cool Weekend Ahead, Watching Mondays Storm Potential

March 9, 2018/by Steven Copertino

Good evening!

Today has been a relatively cool and calm day across the Northeast as the large area of low pressure that produced very heavy snowfall over a good chunk of the Northeast continues to pull away. Despite this surface low pulling away, a large upper level low over Canada continues to shift to the south and east, bringing in some weak mid to upper level energy. This weak energy over the region has produced some isolated snow showers and mostly cloudy conditions this afternoon, with some more impressive snow squalls located over the northern portions of New York and New England. As the day winds down, these snow showers and squalls should gradually die down, but a quick coating to an inch of snow cannot be ruled out over the aforementioned locations. Back towards the New York city area, westerly winds and cloudy conditions continue to persists with some very light snow showers present over southern New York and Northeast PA. Due to the large surface low pressure to our northeast, northwesterly/westerly winds have been prominent over the region. In addition to these surface winds from Canada, we also have a relatively fresh airmass coming in from southern Canada that has allowed for a relativity cool day across the Northeast. Highs were only able to make it into the upper 30’s to lower 40’s, with occasionally gusty winds making conditions feel a bit colder than they actually are. Winds will also gradually die down as the pressure gradient over the region continues to weaken. Low to mid-level clouds over the area should persist as the upper level low over New England continues to meander, so expect lows to range from the middle 20’s to lower 30’s across much of the Northeast tonight.

This afternoons latest surface temperatures, regional radar mosaic, and high resolution visible satellite imagery

Calm and Cool Weekend Shaping Up

The large upper level system over New England will continue to slowly meander to the east tomorrow morning, leading to continued partly cloudy conditions. Mid level energy will continue to rotate around this large system, leading to a slight chance at some scattered shower/flurries during the afternoon hours, but all in all, tomorrow should be a relatively calm and less windy day than today. In addition to the partly cloudy conditions, we will still have an active northwesterly flow coming out of southern Canada, so expect highs tomorrow to range from the middle 30’s to lower 40’s across much of the Northeast tomorrow afternoon. Conditions appear to grow slightly more stable by tomorrow evening as the surface low and upper level low continue to have much less of an influence on our sensible weather. Clouds should generally dissipate tomorrow night, giving way to mostly clear skies. This will set the stage for ripe conditions for radiational cooling to take place over the Northeast, which will lead to a steep drop in temperatures overnight. We should see lows drop into the lower to upper 20’s, with some locations closer to the coast just staying below freezing. This may create some slippery conditions overnight as any melted snow pack will quickly refreeze on most untreated surfaces.

Sunday will likely start off quite calm and cool across the Northeast, there will be bigger and more important things happening off to our west over the Plains. Ridging will be present over the Western US, which will allow for multiple disturbances to drop south from Canada. The first of these disturbances should be located over the central Plains by Sunday morning, with precipitation breaking our over much of the South by the afternoon hours. Conditions back over the Northeast will remain tranquil and cool as a surface high pressure system over the Great Lakes provides rather cool temperatures in the upper 30’s to lower 40’s across much of the Northeast. The tricky part of the forecast begins on Sunday evening as the main disturbance over the Plains begins to move south and east into the Tennessee River Valley region. The models continue to struggle with the evolution of this system, varying their outcomes with just how consolidated the mid level energy can get by Sunday night. The overall evolution of this piece of energy will be crucial for the potential for another coastal system on Monday, which we will discuss in the next section.

This afternoons NAM model showing the very complex evolution of the various pieces involved for the potential coastal system on Monday.

Watching for a Potential Coastal System Monday

As mentioned above, we will have a vigorous piece of energy diving into the Plains Sunday, as ridging in the West amplifies and allows heights to become more north-to-south oriented over the Plains. This piece of energy alone has been poorly modeled over the past couple of days with significant run-to-run variance even on this afternoons runs. However, there is another piece of the puzzle that is arguably just as important, if not more important than the first piece. This “second” piece originates from a large trough over the Gulf of Alaska, and gets “chopped off” from the main trough once the ridging in the west begins to reach its peak amplification. With a large upper level low to the east of the system over Nova Scotia, this piece of energy has nowhere to go, but south. However, the point at which this piece begins to head south into the CONUS is crucial, as it will dictate how organized, and how much interaction (if any) occurs between the first and second pieces of this potential system. If the second piece diving down from Canada is quicker than what the models have at this point in time, more interaction and favorable height fields will exist along the east coast for a potential coastal storm. If the second piece is held up in Canada for too long, OR the first piece of energy is too disorganized, than we will likley see the mjority of the energy slide harmlessly out to sea.

As of right now, the overall chance of a major snowstorm along the east coast is low, but it would not take much to have this system develop closer to the coast and pose a much more significant threat to the east.

Stay tuned for further updates on the latest model data and updates to our thoughts on the systems progression!

A very rough synoptic breakdown of the upper level pattern expected by Sunday. Each feature will play a key role on the overall potential for a storm on Monday

Have a great weekend!

Steve Coeprtino

Significant Snowstorm Likely on Wednesday for Portions of the Northeast!

March 5, 2018/1 Comment/by Steven Copertino

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

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

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

Have a great evening!

Steven Copertino

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