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

February 19, 2018/1 Comment/by Steven Copertino

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

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

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

Have a great night!

Steve Copertino

Wintry pattern expected to return by early March

February 18, 2018/by John Homenuk

And you thought the worst was over.

For the past few weeks, we’ve been chatting both on our blog and internally with enterprise clients regarding the development of a Sudden Stratospheric Warming event (SSW). In laymen terms, this occurs when a rapid temperature rise occurs in the Arctic stratosphere. In this situation, the stratospheric polar vortex has split in two, and rapid (nearly record breaking) warming has occurred in the stratosphere, particularly in the Arctic regions of the North Atlantic and across the North Pole.

We wrote last week and a few weeks back about the importance of this event – how stratospheric warming, when coupled properly with the troposphere (where our weather occurs) can have a significant impact on our weather by promoting high latitude ridging and blocking. We are starting to see these exact things come to roost on forecast models – and we’ll explain why we have higher than normal confidence in wintry weather returning to the Eastern United States by the first day of March.

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

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