February 2018 Archives - New York Metro Weather

Mild and Calm Conditions Take Hold, Watching a Potential Coastal Storm for Friday

February 26, 2018/by Steven Copertino

Good evening!

After the cool and dreary conditions over the past couple of days, today was a slight improvement for much of the Northeast as a cold front gradually passed through the region, signaling a change to the sensible weather pattern. This front was luckily rather tame in nature, as the energy associated with the front was strung-out and not well-organized. This allowed for only moderate changes to gradually take place during the course of the day, with a rather cloudy and cool start to the day. As the day continued on, we saw high to mid level clouds lessen with time, eventually giving way to some peaks of sun. Winds shifted to the northwest behind the front, with more dry and cool air filtering into the Northeast. Modest cloud cover and a renewed airmass from Canada kept temperatures in check, with highs ranging from the lower to upper 40’s, with some locations reaching the 50 degree mark. Dry air from the north and west should continue to mix out any residual low level moisture over the next 6-12 hours, leading to mostly clear skies this evening. Additionally, an area of high pressure will be building in over the Mid Atlantic and Northeast tonight, so expect any winds to gradually diminish over time. These conditions will be quite favorable for radiational cooling to take place overnight, with temperatures likely dropping quite a bit into the lower to middle 30’s over much of the area. Some locations off to the north and west will likely drop into the middle 20’s this evening, causing any residual moisture on roadways to freeze, so please watch out for slick patches if you’re driving tonight.

This evenings latest high resolution water vapor imagery, surface observations, and surface winds, showing a more calm temporarily setting up.

Tuesday through Thursday

Tuesday will likely start off quite chilly, but clear as the area of high pressure continues to build and move eastward with time tomorrow morning. Conditions will be quite dry throughout the majority of the atmosphere, so skies will likely remain mostly sunny for the majority of the day, with a few upper level cirrus clouds passing through. The fresh Canadian airmass in place in combination with the high pressure will work in tandem to keep conditions cool, but not too cool over the entire Northeast. Highs tomorrow afternoon should remain in the middle to upper 40’s, with some inland locations likely hitting the 50 degree mark again. All in all, tomorrow should be a rather nice day, but will likely still require a light jacket to stay comfortable. Tomorrow night looks to be calm and cool as well, but not quite as cool as tonight. Lows will likely dip down into the middle to upper 30’s for the majority of the Northeast, with some locations possibly just getting below freezing.

Wednesday looks to be one of the more mild days of the week as the area of high pressure that has been dominating the east begins to move off the Mid Atlantic coast. This should create more southerly flow in the mid to low levels of the atmosphere, bringing in slightly warmer highs for the afternoon hours. Moisture looks to also increase with the southerly flow as a shortwave trough digs into the desert southwest, sending some residual energy into the east. This energy out ahead of the main system should allow for some clouds and even a few isolated showers to develop in the late afternoon hours, but not significant rain is expected. Highs will likely be able to rise into the lower to middle 50’s across the vast majority of the Northeast. Cloudy conditions will likely continue throughout the overnight hours, with the threat of a couple of showers lasting into the early morning hours. Cloud cover and southerly winds should keep lows from dipping too much, with readings likely staying in the middle to upper 30’s-with some locations seeing lows in the lower 40’s.

Things begin to get a little more interesting on Thursday, as the system that was in the southwest begins to move into the Plains and interacts with another shortwave coming down from Canada. As these systems interact and attempt to phase, a primary surface low pressure system should form over the Great Lakes region, with a large area of rain expected over much of the Southeast. As this low moves closer to the Northeast, cloudiness will likely increase in addition to the threat of some showers as we head into the late afternoon hours. Later in the evening, this area of low pressure should continue to intensify, as the mid level system becomes much more organized. This process should continue into the overnight hours, as a stationary front likely sets up over the Mid Atlantic, which may become the focus for a secondary low pressure system to form. Temperatures on Thursday will likely remain mild, with highs in the lower to middle 50’s over the entire Northeast.

This evenings NAM model showing the development of a potentially impactful system for the Northeast

Potentially Impactful Coastal System Shaping up for Friday

This afternoons model guidance continues to show the potential for the primary low pressure system that travels over the Ohio Valley to redevelop just off the Mid Atlantic coast early Friday morning, but there are still a large amount of uncertainties with this forecast. Regardless, what we do know is that an area of blocking will be located over Greenland, which will act to slow down the mid level system and allow it to strengthen as it nears the coast. This should lead to the development of a strong low pressure system adjacent to the Mid Atlantic coast during the day on Friday, likely leading to a wide range of impacts. Almost all of the model guidance shows an impressive swath of winds just above the surface with this system due to a tight pressure gradient. Additionally, this system will be capable of tapping moist air from the south, so it will likely have a good amount of moisture to work with, leading to the development of widespread moderate to heavy precipitation. Lastly, winds out over the ocean will likely be directed towards the coast, which will create at least a moderate threat of coastal flooding as we enter a full-moon phase. One of the main things we do not know at this time is exactly when and how much phasing will occur with the two original disturbances over the Ohio Valley. A quicker phase would lead to a stronger coastal low tucked right along the coast, while less/delayed phasing will likely lead to a weaker and more elongated system.

There is also the question of precipitation type, which is something that seems to be highly sensitive at this time. While a stronger system would be able to create enough dynamic cooling for some snow to fall, this solution would also mean that the primary low in the Great Lakes sticks around longer, which creates more warm air for the coastal plain. At this time it does not seem like a widespread significant snowfall is likely from this system, but there could be some locally heavy snow in the higher terrains of the Northeast if conditions line up correctly. We will be keeping a very close eye on this system this week and will continue to provide updates as they become available!

This afternoons European ensemble individual members showing a wide variety of solutions for Friday’s system

Have a great night!

Steve Copertino

Winter storm expected in the Northeast tonight, moderate accumulations likely

February 17, 2018/1 Comment/by John Homenuk

A winter storm will approach the Northeast states this evening, beginning first in the Mid-Atlantic states and gradually approaching from the southwest towards New England. The storm system is developing on the heels of a frontal boundary that crossed the Northeast states on Friday evening and Saturday morning (you may have noticed it’s a bit colder outside) and that frontal zone will serve as a highway for the development of low pressure.

In the atmosphere’s mid levels, the system remains somewhat progressive – in other words, this is not a huge, powerful Nor’Easter. But there is plenty of moisture, aided by a strong low level jet stream, and that will act to enhance precipitation rates as the storm moves by. There are still a few uncertainties remaining with the system:

Quick-Hitting Snowstorm Likely for Portions of the Northeast Saturday Night

February 16, 2018/by Steven Copertino

Good evening!

Today has been yet another in a string of warmer and unsettled days across the Northeast, with light to moderate rainfall training over portions of the Mid Atlantic and Northeast. Today’s rain was part of the same strung-out and progressive upper level energy that was responsible for the heavy rain and flash flooding that occurred over portions of the Ohio Valley and Mid Atlantic states last evening. The heavy rains last evenings moved quickly along a frontal boundary that remained stationary over the same areas, causing showers and even some embedded thunderstorms to train over the same locations. While the vast majority of these showers and thunderstorms very quite weak in nature, there were some stronger storms over the Ohio Valley and Northeast that produced some damaging wind gusts, along with an EF-1 tornado just to the south and east of Pittsburgh. Regardless, today was a rather dreary day across the entire region as the mid level energy over the Ohio Valley quickly moved east and caused numerous showers to break out once again. The showers have since moved offshore as the majority of the mid level energy moves off to our east, leaving behind mostly cloudy conditions. Despite the mostly cloudy and rainy conditions today, temperatures were able to rise to above-normal levels once again across the Northeast. Readings varied from the lower to middle 50’s over the New York metro area, to middle 50’s to lower 60’s across portions of southern New Jersey. These mild conditions should last until the late evening hours as a cold front begins to approach the area from the west, bringing in cooler temperatures overnight along with Northwesterly winds. High pressure will begin to build in over the Northeast tonight, with lows likely falling quite a bit into the middle to upper 20’s over the majority of the area, with lower 20’s expected to the North and West of the city. Calm conditions will likely prevail through the overnight hours as the high pressure expands over the Northeast.

This evenings latest high restitution water vapor satellite imagery along with regional radar mosaic and surface temperatures from across the area. Note the clearer and more dry air over portions of northern PA and NY.

Quick-Hitting Snowstorm Likely Tomorrow Across Portions of the Northeast

Well, with the way this week has went the last thing you would expect is a snowstorm for this weekend, but that is exactly what looks to be shaping up for portions of the Mid Atlantic and Northeast tomorrow night into Sunday morning. A weak a relatively disorganized area of mid level energy will become trapped in the fast-moving west-to-east flow over the CONUS tomorrow morning and begin to race towards the East. As it reaches the Great Lakes region tomorrow afternoon, it will begin to meet up with some energy from the sub-tropical jet over the Southern Plains states, and this will likely cause numerous showers and some localized thunderstorms to develop over portions of the Tennessee valley. At the same time, the area of high pressure that will be over the region this evening will be moving off of the coast, leaving some stale cold air over the region. Winds will begin to shift to the south over the Mid Atlantic and Northeast, bringing in a slightly warmer low level airmass for tomorrows highs, but overall temperatures look to stay in the middle to upper 30’s. As we get deeper into the evening hours tomorrow, we should see the shortwave trough associated with tomorrows potential storm begin to amplify or strengthen a bit as the ridging over the southeast and western Atlantic causes the system to buckle.

This afternoons NAM model showing the potential evolution of tomorrows snowstorm

As the mid level energy begins to strengthen tomorrow evening, we will also see the upper level jet streak associated with this system begin to expand, allowing precipitation to break out farther north into portions of the Mid Atlantic by sunset. Surface low pressure should then begin to develop over the Mid Atlantic coast tomorrow night, with snow quickly expanding from southwest to northeast over the Northeast. This afternoons model guidance still shows a reasonable amount of uncertainty with the strength of this system, which will be crucial to this forecast. Depending on how deep this low gets will determine how much dynamic cooling will take place as the precipitation is falling. A weaker storm will be warmer at the surface with less precip, and therefore less snow. A stronger system will be able to overcome marginal surface temperatures and have increased snowfall rates, yielding higher snow totals. At this time, a healthy compromise of the two seems plausible. Precipitation may start off as a mix of snow and rain over southern portions of the Northeast, but should turn to all snow by 8-10pm or so with the exception of immediate coastal areas. The snow will quickly become moderate to heavy over portions of Pennsylvania, New Jersey and New York, with an enhanced chance at mixing over Long Island due to easterly winds. Moderate to heavy snow should continue through the overnight hours, likely until 3-5am as the system quickly accelerates to the north and east and moves offshore. Totals will likely vary by location and elevation over the region, but right now we expect a general 3-6″ from southeastern PA through northern NJ, and into SNY and CT. Portions of Long Island may see less than shown here due to prolonged periods of mixing. Travel conditions will likely be quite hazardous if you plan on driving tomorrow evening, so please stay up to the date with your local NWS for any watches or warnings in your area!

Our latest storm total snowfall map

We will have updates tomorrow on this system including a new snowfall map!

Have a great weekend!

Steve Copertino

Snowstorm increasingly likely in the Northeast this weekend

February 16, 2018/1 Comment/by John Homenuk

Good morning and Happy Friday! As many of us in the Northeast, and especially the Northern Mid Atlantic, make our way to work without a heavy jacket for the first time in what seems like months, the atmosphere is already undergoing a significant transition. Warm, humid air is entrenched in the region right now and a disturbance passed by overnight leading to heavy rain (and severe thunderstorms in parts of Pennsylvania, where it is believed a tornado touched down in Uniontown last night). A frontal boundary approaches and slides towards the coast later this evening.

Lurking back to the west is another disturbance which will emanate from the Pacific and track across the United States, ending in the Ohio Valley and Northeast states late Saturday into Sunday. The frontal boundary will have sunk southward towards the Mid-Atlantic Coast, allowing cold air to filter back in. And when the disturbance approaches this front, the temperature gradient will promote the development of low pressure. Increasing lift will lead to the expansion of precipitation – likely in the form as snow for many areas.

The low pressure will develop off the coast late Saturday Night with snow spreading northward, from the Washington DC Area towards Philadelphia and then eventually New York City. There are several uncertainties that still remain:

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