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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.

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Have a great evening!

 

Steve Copertino

Steven Copertino

3/12 PM All Zones Update: High-Impact Blizzard Likely Tuesday Into Wednesday

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Today has been what some may call the “calm before the storm”, as the day has been characterized by mostly sunny conditions across the entire area with temperatures only in the upper 20’s to low 30’s, which is below normal for this time of year. We have also seen some gusty winds across the area thanks to isobaric packing between an Arctic high pressure system centered over the central Canadian prairies and a deep low pressure system off of the eastern Canadian maritime region. As this low pressure continues to the east, winds should gradually diminish this evening as the high pressure from Canada takes control. Tonight should be an excellent night for steep radiational cooling. Under mostly clear skies and light winds, temperatures will be able to fall into the upper single digits for inland locations and teens for the rest of the region, so another very cold night is expected.

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Steven Copertino

Public Analysis: A Battle of Two Seasons

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After another impressive but brief shot of cold weather this past weekend, another warmup is likely tomorrow and Wednesday along with some showers. Afterwards, the high-latitude blocking that we have been discussing for a few weeks now will provide a few chances for accumulating snowfall and colder weather for the NYC metro area.

This afternoon has been a cool, but pleasant one as a large area of high pressure that is currently centered off of the Mid-Atlantic remains in control of today’s weather. Light southerly winds of around 5-10mph have warmed temperatures into the 40’s across the entire area with some light high clouds noted on visible satellite imagery. Even though the area is a good 5-10 degrees higher than what they were yesterday, temperatures are still a few degrees below normal for this time of year. This will be short-lived as a large and very intense low pressure system intensifies over the Central part of the country and introduces even stronger southerly winds courtesy of a warm front overspreading the area. These southerly winds will usher in much warmer air and increasing cloud cover this evening, so temperatures should be above normal for our low temperatures tonight. Due to the low level moisture increase, some spotty drizzle or showers may be possible by this very late this evening and into the morning tomorrow.

Latest observations, radar, and visible satellite imagery for the Northeast showing relatively quiet conditions. (Courtesy of Simuawips.com)

Latest observations, radar, and visible satellite imagery for the Northeast showing relatively quiet conditions. (Courtesy of Simuawips.com)

As we move through tomorrow morning, mostly cloudy skies should be commonplace for the entire region with some showers present as well during the morning commute hours. The strong warm front that was mentioned will continue to usher in strong low level flow from the south, which will allow temperatures to warm well into the 50’s tomorrow afternoon despite persistent cloud cover and rain. While the cold front from the large area of low pressure in the Plains continues to advance to the east, moisture will also be abundant by later tomorrow afternoon. This moisture will stream ahead of this front and create more widespread showers for the entire area that should last into the early morning hours of Wednesday.

Since the best dynamics with this cold front are off to our north in Canada, heavy rain is not likely a threat at this time. Once the actual cold front clears the area on Wednesday, temperatures should still be able to climb into the 50’s and even 60’s during the afternoon hours as any residual moisture is removed from the area and clear skies begin to take over. Late Wednesday evening and into Thursday is when the colder air arrives as the main upper level energy associated with the low pressure in the Plains passes to our north and allows for cold air to really “bleed” and overspread the metro area. This will be especially true just a few thousand feet above our heads while winds gradually shift from the Northwest.

 

Afternoon NAM showing more cold air bleeding into the region by Thursday afternoon and evening

Afternoon NAM showing more cold air bleeding into the region by Thursday afternoon and evening

As we move later into the week, a change in the large-scale pattern evolution over the Western Hemisphere, aided mostly by the development of significant high-latitude blocking, will support the return of at least some colder weather over the Northeast and Mid-Atlantic regions. Today’s latest model and ensemble guidance suggest several separate waves could bring wintry precipitation into the region this weekend and into next week. There is still much uncertainty with the track and intensity of each of system, especially with the northern stream flow being fast and zonal initially. As we have seen, the trend for disturbances to trend quicker and weaker has been something commonplace this winter, but that was mainly due to a lack of blocking.

The first potential system that we are tracking looks to take place on Thursday evening and into Friday morning. This afternoons model guidance has diverged significantly on the exact outcome, but there seems to be at least some potential for a wave of low pressure to track from the Central US underneath the strong blocking high to our north and a large upper level low in SE Canada. Depending on just how far south this upper level low pushes the wave of low pressure will determine whether or not our area sees measureable precipitation from this event. This afternoons American model showed the wave of low pressure being able to track more to the north thanks to the upper level feature in Canada not pressing down on it as much, and ultimately delivers some light to moderate snow on Friday.

GFS ensembles mean precipitation output for Friday afternoon

GFS ensembles mean precipitation output for Friday afternoon showing light to moderate snow for the area

Another Pacific disturbance comes ashore later this week, and even more questions arise with this potential threat. As the disturbance tracks to the east over the Rocky Mountains, a low pressure will likely form in the Central Plains. This area of low pressure will have an area of high pressure off of the Mid-Atlantic coast that should provide it with a very impressive moisture feed as it begins to strengthen over the Tennessee/Ohio Valley. The aforementioned blocking will provide fresh cold air for this system as it traverses a very sharp temperature gradient, but where this exact gradient establishes itself is the real question as of right now.

If the blocking to our north is too strong, then the gradient and the system will wind up suppressed to our south and the area will see little, if any impacts. If the blocking isn’t as oppressive on the system, then the low pressure will be able to take a more northerly track. If this system is able to track directly to our south, then all of the moisture that is sucked up from the record-warm Gulf will fall over the region and possibly have significant impacts. It i worth noting that this afternoons European model has trended a bit further south with no impacts for our area and very clearly represents what could happen if this system isn’t able to gain enough latitude due to the upper level feature in Canada. 

12z GFS model showing significant precipitation for the Northeast on Saturday evening due to less oppressive blocking able push the system south

12z GFS model showing significant precipitation for the Northeast on Saturday evening due to less oppressive blocking able push the system south

Finally, later next week, more pacific shortwave energy digging may lead to another storm along the East coast. However, the blocking to our north may weaken by this point to allow for track further northwest or system to phase to late with northern stream off the coast. This may result more mixed or lighter precipitation in the region.

***It should be noted that each individual threat discussed here still remains extremely uncertain. As the models begin to catch on to the pattern evolution, we may see more drastic changes with the upper-level features and evolution of individual system.

We believe the chances are pretty high for cold and snow threats with this pattern evolution — but that doesn’t mean anything is guaranteed. Stay tuned for further updates and details as we move closer.

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.

 

Have a great evening!

Steve Copertino

 

Steven Copertino

Public Analysis: Snow Squalls Possible Today, Unsettled Next Week

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As we head into the end of the workweek this afternoon and evening, most of the area is experiencing quite the contrast from what we were looking at this time last week. Some heavier snow showers and temperatures in the teens are possible this afternoon and evening, with a cold weekend likely. Continuing the theme of this winter, a return to more above-normal temperatures is possible as early as Monday.

If we take a look at the visible satellite imagery this afternoon, we can see that there are numerous clouds associated with a very large and potent upper level system that is responsible for the impressive temperature drop we have seen over the past day or so across the area. This upper level system is also responsible for producing widespread snow showers and snow squalls, courtesy of very steep lapse rates (which is the difference of temperature with height). As of 2pm, the majority of these squalls were located over Pennsylvania and even though they do not look too impressive on radar, these squalls have been responsible for numerous car accidents as they are able to reduce visibility down to near-zero in less than a minute.

Current visible satellite imagery along with radar and surface observations showing numerous heavy snow squalls over PA (Courtesy of Simuawips.com)

Current visible satellite imagery along with radar and surface observations showing numerous heavy snow squalls over PA (Courtesy of Simuawips.com)

As the afternoon continues on and the atmosphere nearly maxes out the low level lapse rates as we head toward sunset, these snow squalls should continue east and possibly affect the NYC metro area by 4-6pm and 6-8pm for Long Island and Connecticut. Though these squalls may be slightly weaker by the time they reach the area, they will still be capable of rapidly dropping visibility, rapidly dropping temperatures, making roads very slick, as well as producing some gusty winds which may knock some small branches off of trees. Please exercise extreme caution if caught in these squalls, especially as we get closer to the afternoon commute. Due to the more spread-out nature and quick movement of these squalls, any accumulations should be limited to a trace in all locations.

HRRR model showing snow showers and possible heavier snow squalls working their way into the area this afternoon and evening

Later this evening, clearing skies and a very cold airmass above our heads will easily allow temperatures to drop down into the teens for inland areas and into the 20’s for locations closer to the coast, which is a massive departure from what we have experienced over the past week with lows in the 50’s! We expect the below normal temperatures to continue into tomorrow behind the large upper level system, with highs only being able to reach into the upper 20’s and low 30’s across the area. Due to a somewhat impressive pressure gradient draped over the region, there will be the potential for some gusty winds which will make it feel quite chilly throughout the day tomorrow with windchills in the single digits and teens. The winds should begin to die down towards sunset as clear skies once again dominate the area with another cold night on tap, with lows in the teens and even single digits across the area. Sunday looks to also be slightly below average with temperatures in the 30’s as an area of high pressure begins to take control over the area, which will reduce any winds and make it a much more bearable day. Overall, it should be a much more seasonable weekend, with mostly clear and dry conditions expected both Saturday and Sunday.

NAM model showing a large area of low pressure directly over our area by Sunday afternoon, providing calm and cold conditions

NAM model showing a large area of low pressure directly over our area by Sunday afternoon, providing calm and cold conditions

As we head into  Monday, the large area of high pressure over the Northeast should begin to exit to our east and position itself off of the Mid-Atlantic coast. This will allow above normal temperatures to work their way into the region from the south as a large low pressure area looks to track into the Mid-West, which may provide a chance at some heavier precipitation by Wednesday morning and afternoon as a cold front works its way through the Northeast. Model guidance diverges significantly once we reach the end of the next week, but there does exist the potential for another return to below-normal temperatures if we are able to sustain high-latitude blocking near Greenland. This is all very uncertain right now, so make sure to stay tuned over the next few days for more updates on this evolving weather pattern!

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.

 

Have a great day!

Steve Copertino