Posts

Steven Copertino

Public Analysis: Unsettled Weather Along a Series of Frontal Systems

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Good afternoon and Happy Friday!

Earlier this morning we saw some light showers pass over the northern sections of the NYC metro with some localized reports of light sleet/freezing rain mixing in. This precipitation was associated with the passage of a mid-level warm front that passed through the region at around 9am this morning. Colder air near the surface allowed localized areas to see some very limited mixed precipitation, but while the radar this morning may have shown some areas of heavier rain and/or mixing, most of this was not able to reach the surface due to a very dry wedge of air  in the lowest few thousand feet of the atmosphere.

As the lower levels began to warm to above-freezing levels across the entire area, precipitation became predominantly rain, except for elevated locations in Connecticut and Massachusetts. Temperatures have warmed a good 12-15 degrees after the mid-level warm front, in conjunction with southwesterly winds have brought in a much more seasonable airmass for this time of year. Even though we have warmed quite a bit over the past few hours, there is still a pretty stark temperature gradient over the region, with portions of southern New York and Connecticut remaining in the upper 30’s, while the NYC metro area and locations to the south are in the mid 40’s and lower 50’s as of 1pm.

Any remaining light rain should begin to taper off as the front that triggered this precipitation quickly exits off to our north and east. With clouds likely lingering throughout the rest of the afternoon, temperatures shouldn’t be able to rise all that much from where they are right now, so expect highs to be generally in the lower 40’s to mid 50’s, with the higher temperatures being located to the south.

As we head into the evening hours, not much clearing is expected as another frontal system approaches the area with increasing clouds ushered in by a stout southwesterly flow. Due to the amount of warm air being pushed into the area overnight, we may see temperatures increase throughout the evening hours, possibly into the mid-upper 40’s. Some showers are also possible into the early morning hours as moisture advection also begins to steadily increase.

Current view of radar, surface observations, visible satellite imagery, and frontal positions over the Northeast. (Courtesy of Simuawips)

As we move into tomorrow, a complicated gradient will begin to take place as the frontal system that will be responsible for this evenings temperature rises begins to lift to the north and eventually stalls out. Where the frontal system decides to stall out will be crucial in determining just how warm temperatures get tomorrow. The latest computer model guidance is indicating that temperatures should be able to rise into the upper 50’s and the lower 60’s across much of the area by early tomorrow afternoon. As will be the theme over the next few days, locations like SE PA and Central and Southern New Jersey all have a better shot of reaching the mid to upper 60’s tomorrow-with lower 70’s possible in some locations. As mentioned, this will create quite a temperature gradient with areas south of the front seeing Spring-like conditions, and those to the north seeing much cooler temperatures in the 40’s.

The aforementioned frontal system will then have the potential to sink back to the south by the mid-afternoon hours tomorrow as a strong Canadian high pressure system strengthens and introduces a backdoor cold front. This front will continue to sag south as the cold, dense Canadian air brings temperatures back down to the 30’s and 40’s tomorrow evening.

3km NAM valid tomorrow afternoon showing the stalled frontal system over SNY, with cool temperatures to the north and much warmer temperatures to the south of the front

3km NAM valid tomorrow afternoon showing the stalled frontal system over SNY, with cool temperatures to the north and much warmer temperatures to the south of the front

This cold front will then stall out over southern Pennsylvania and Maryland on Sunday morning, so this will allow the colder Canadian air mass to block any warm, maritime tropical air that lies just to our south. Unfortunately, it looks like Sunday will be a more dreary and unsettled day. with the potential for showers and mostly cloudy skies existing throughout the day. After finally getting some above-average temperatures again on the board, we should drop down to at least 10-12 degrees below-normal by Sunday afternoon. So be prepared for tomorrows warmth to be very brief and enjoy it while you can!

This frontal boundary should remain draped over the region on Monday as well as Tuesday, as a few waves of low pressure begin to move along the front. Each one of these waves will bring some chances at some more steady rain threats beginning on Monday morning. Temperatures should remain quite variable as the front lifts north, and then eventually sags back to the south as each impulse of low pressure moves over the area.

12z ECMWF model showing a more stable pattern later next week as a Canadian high pressure system dives to the south (Valid Thursday morning)

12z ECMWF model showing a more stable pattern later next week as a Canadian high pressure system dives to the south (Valid Thursday morning)

Finally, things looks to stabilize later in the week as another Canadian high pressure system is forecast to take over and clear out any pesky leftover frontal systems. This high pressure system should be able to usher in more seasonable, or even slightly below-normal airmass before an active storm track to our south and west takes over by Friday and into Saturday.

We will have more on these upcoming systems and make sure to check in over the next few days for updates as these frontal systems can change quite quickly!

For more information and posts like this one, make sure you sign up for Zone Forecasts — where multiple detailed articles, videos, and interactives are posted each day. Also, come interact with our staff and many other weather enthusiasts at 33andrain.com!

Have a great weekend!

Steve Copertino

John Homenuk

3.23 PM Zones: Unsettled weather on the way this weekend

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A happy Thursday afternoon to you all! The weather has remained calm and cold over the past few days and today was no exception. The calm and cold weather will persist into the evening hours tonight as high pressure remains in general control of the areas weather. Clear skies will dominate the Northeast US to begin the evening and radiational cooling will again occur, leading to temperatures falling well below average tonight.

However, clouds will gradually increase from the west/southwest as a warm front makes its approach towards the region. The warm front is associated with a storm system over the Central United States, making a gradual progression towards the Northeast. Clouds are expected to increase late in the evening towards the early morning hours of Friday. Precipitation, however, should hold off as the atmosphere will remain dry.

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Steven Copertino

Public Analysis: A Tale of Two Seasons This Week

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Astronomical Spring has finally arrived even though meteorological Spring has been here since March 1st. The only difference between the two is that meteorological Spring is based on the division of our calendar into four separate seasons, each having three months in each season. This makes it easier for observations and the ability to compare things like seasonal statistics. Astronomical Spring (or the Vernal equinox) is determined by the 23.5 degree tilt of the Earth’s rotational axis in relation to the Earth’s orbit around the sun.

Regardless, today has been mostly sunny across the entire New York Metro area with a few high clouds noted on the latest visible satellite imagery. Temperatures have been able to rise in the high 40’s and lower 50’s across much of the area, which is right around normal for this time of the year-if not a few degrees below normal. Winds are generally calm across the area, but portions of NJ, NYC, and Long Island are seeing some winds in the 10-15 mph range with higher gusts, which are bringing wind-chills into the low 40’s in some locations, so we’re not feeling the Spring weather just yet. As we move on throughout the rest of the day, predominantly clear skies will be commonplace over the area as we await the arrival of a weak frontal system that it currently situated over the Ohio Valley.

Current visible satellite, surface observations, and regional radar composite for the Northeast US (Courtesy of Simuawips.com)

Current visible satellite, surface observations, and regional radar composite for the Northeast US (Courtesy of Simuawips.com)

This weak frontal system is currently over Indiana, producing some strong showers and thunderstorms which have dropped hail up to 2″ in diameter as they track to the south-east. This area of showers, in conjunction with a very weak mid-level system located southeastern Canada will work towards our area later this evening. While the main area of stronger thunderstorms will die-off quite quickly as they move into a stable airmass, the associated showers and cloudy weather will begin to take over during the overnight hours.

With increasing cloud cover, temperatures will likely struggle to get lower than the mid 30’s to low 40’s for this evening’s low temperatures across the area. This afternoon’s computer model guidance has the bulk of the shower activity from these systems remaining to the south west of the NYC area as a very weak area of low pressure forms along the frontal system that will push through the region tomorrow morning.

After some limited light showers and clouds initially, Tuesday afternoon should clear up quite nicely as winds from the northwest (moving over deep snowpack in NY and PA) usher in drier air. Temperatures should be able to rebound quite quickly tomorrow into the lower to middle 50’s across much of the area by late afternoon, which will be a few degrees above normal.

This above-normal air mass will be very short-lived as a stronger cold front associated with a large area of high pressure centered in Canada will slowly make its way towards the Northeast. By Wednesday morning this cold front will be situated right to the north west of the metro area, with winds from the NW steadily increasing. Once the front passes, temperatures will likely struggle to push out of the 30’s across the entire area, with gusty winds making it feel like its even colder in most locations.

3km NAM model showing the strong cold front and its associated winds and temperatures at 850mb or 5,000 feet in the atmosphere.

3km NAM model showing the strong cold front and its associated winds and temperatures at 850mb or 5,000 feet in the atmosphere.

Temperatures should remain 10-15 degrees below normal until at least Thursday, before a large ridge begins to build over the central part of the country and begins to head east. This ridge could possibly bring temperatures back to normal or even back to above-normal conditions by this weekend. However, we are monitoring the *potential* for some possible wintry precipitation across the northern sections of the area this weekend as a very delicate and complicated pattern takes shape.

The models at least agree on a cutoff low pressure system developing over the US Plains states by Friday afternoon with a large ridge of high pressure situated over the Southeastern states. With another upper-level system in Canada pressing down on the upper level ridge to its south, this setup would create “confluence” to our north, which would essentially limit the storm system in the Plains from cutting through the Great Lakes like these types of systems usually tend to do. Instead, with a large and cold high to the north, the storm would have the potential to stay underneath that high pressure and track more eastward. While it is getting very late in the season, this setup does have the potential to produce a redeveloping low pressure system off the Mid-Atlantic coast as the initial cutoff low transfers its energy.

500mb map from the GFS showing a very complex situation developing for this weekend regarding any chance for wintry precipitation

500mb map from the GFS showing a very complex situation developing for this weekend regarding any chance for wintry precipitation

We will continue to monitor this system throughout this week, so make sure to stay tuned for future updates. However at this time, we do not feel there is a lot of support for significant wintry precipitation this weekend, especially closer to the coast.

For more information and posts like this one, make sure you sign up for Zone Forecasts — where multiple detailed articles, videos, and interactives are posted each day. Also, come interact with our staff and many other weather enthusiasts at 33andrain.com!

Have a great evening!

 

Steve Copertino

Steven Copertino

Public Analysis: Snow Possible Saturday, Quiet Week Ahead

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Today has been a beautiful day in contrast with the previous few days across the entire area as temperatures have climbed into the mid-upper 40’s the afternoon underneath mostly sunny skies. While it does feel more comfortable outside, these temperatures are still below-normal for this time of year. Some gusty winds were noted this afternoon as a large area of high pressure situated to our south and a quick-moving low in Canada create a pressure gradient over the Northeast. As we head into the evening, the winds should subside a bit, but as the aforementioned low pressure in Canada begins to move to the south east, some broken high clouds should begin to take over. This is part of a frontal system associated with the low in Canada that could bring the threat of some light rain or snow to western areas of NJ and eastern Pennsylvania.

While precipitation should remain quite light for those who do happen to experience any rain/snow this evening, no significant accumulations are expected at this time as the frontal system begins to slow its approach towards the New York City metro area until tomorrow. Temperatures will vary quite significantly this evening, with lower 30’s possible around coastal areas and close to the city, but locations that are more inland should see temps drop into the 20’s for an overnight low.

Latest visible satellite imagery with temperatures for the entire area (Credit: GREarth)

Latest visible satellite imagery with temperatures for the entire area-note the white on the image is actually snowcover and not clouds  (Credit: GREarth)

As we move into tomorrow, there is potential for some snow starting very early Saturday morning as the low pressure in Canada begins to move into the Great Lakes region, which will act to push the stationary front towards the area. Clouds should increase in earnest tomorrow morning with an early threat of some light rain or snow, but mainly a mix of rain and snow is expected for New York City, Central New New Jersey, Long Island, as well as locations to the south. Since we are getting further into March, ground temperatures will be an issue-as is the case with tomorrow’s initial batch of precipitation. Since the rain/snow mix will be quite light in nature along with warmer surface temperatures, very little to no accumulations are expected for these aforementioned regions. Since thermal profiles will be more supportive of an all-snow scenario to the North and West, some light accumulations can be expected-especially on grassy surfaces. Even though accumulations should be relatively minor with this first batch of precip, they may create slick driving conditions even if they are in the form of plain rain, so please use caution.

3km NAM simulated radar valid at 9am tomorrow morning showing a very light mix of rain and snow over the area (Credit: Tomas Burg UAlbany)

3km NAM simulated radar valid at 9am tomorrow morning showing a very light mix of rain and snow over the area (Credit: Tomas Burg UAlbany)

The associated upper level energy with system at about 500mb (or 18,000 feet) is very potent with this system. As it dives down from Canada, it will cause the main low pressure system in the Great Lakes to slowly die and subsequently fill-in. As the upper level energy continues east, it will also trigger the development of a secondary-low pressure system that will form off the Mid-Atlantic coast Saturday afternoon or early evening. This is what is called a Miller-B type storm development with a primary transferring all of its energy to the coast so that a secondary low can take over and drop more significant precipitation.  As the low begins to form off the coast, colder air from the North/North East will begin to wrap into the low pressure system from which should help to turn any precipitation over the area into mostly snow by evening. As we talked about, the upper level trough associated with this system is quite impressive and as it moves east, energy will rotate underneath the base of this trough and work to strengthen the low at the surface while it continues to the east.

This advection (or movement) of energy will allow steadier precipitation to break out across the area as the atmosphere becomes much more conducive for snow during the evening. As we have mentioned a few times this winter, “lift” is very important if you want to see heavier snow rates, especially since these areas of heavier snow can also work to cool the local environment (which would help accumulations). As of this afternoon’s computer model runs, we have noticed a trend where the higher resolution models are hinting at the potential for such lift to exist over Long Island, Connecticut, and even portions of Northeast New Jersey. As we get later into the Winter season, it is a bit tougher to get accumulating snow in a marginal setup like this with no fresh cold air supply. So to counter that, you need the snow to fall more quickly than it can melt at the surface. This is achieved through these favorable dynamics mentioned above, and coupled with cooling from the strengthening surface low which should allow snow to accumulate at a more steady pace across the area on most/if not all surfaces through Saturday night.

12km NAM showing very favorable lift (in yellow, orange, and red) for heavier snow on Saturday evening

12km NAM showing very favorable lift (in yellow, orange, and red) for heavier snow on Saturday evening

At this time, with the high uncertainty, we are still maintaining our snowfall total forecast for light accumulations. But will be likely be reevaluating our forecast later this evening, as new model data comes in. Nevertheless, there will still be huge bust potential on either the high or low side, with snowfall totals, if model guidance is poor in handling where the heaviest snow and amount of cooling that will take place. The storm should move far enough offshore to for more clearing by Sunday evening.

Overall, next week is looking relatively seasonable with some cool nights in store as a few frontal systems move through the area with a chance of some light rain. Later in the week, a ridge of high pressure should begin to build over the area, which would allow for more continued quiet weather with potentially warmer weather in the longer range.

For more information and posts like this one, make sure you sign up for Zone Forecasts — where multiple detailed articles, videos, and interactives are posted each day. Also, come interact with our staff and many other weather enthusiasts at 33andrain.com!

 

Have a great evening!

 

Steve Copertino