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All Zones Free Video Update: Significant snowstorm continues

February 9, 2017/by John Homenuk

A free mesoscale update this morning for those of you who may possibly be looking for additional information on the evolution of the storm system. The low pressure system continues to develop as expected and only minor tweaks were made to our forecast from yesterday! Snow continues throughout the majority of the area for the next few hours while beginning to gradually taper from west to east around noon.

Heavy snow will develop over Long Island and Connecticut with blizzard conditions and rapid snowfall accumulation expected there from late morning into the early afternoon hours. Our latest video discussion below covers the latest developments and analysis of mesoscale features:

Public Analysis: Significant Snowstorm Likely Tomorrow

February 8, 2017/by Steven Copertino

After tracking this potentially significant system over the past couple of days, we have seen some sizeable differences showing up on the computer models regarding potential impacts and accumulations, but this afternoon’s computer model guidance has come into line and it is looking quite likely that the entire New York metro area will be seeing seeing a significant amount of snow during the next 24 hours with a variety of potential impacts.

As was talked about on Monday, we have our two key pieces of energy that have to interact and come together this evening in order for our storm to take shape and really begin to intensify. If we look on the 500mb chart below, which is essentially what’s happening up in the atmosphere at roughly 18,000 feet, we can see our two distinct features highlighted in pink. Our first piece can be seen over Kansas City, Missouri this afternoon which has generated the beginnings of our storm over Arkansas and Tennessee with precipitation starting to break out all the way up into Illinois/Indiana/Ohio. As our second feature begins to dive south from its current position to the north of Bismark, North Dakota and interacts with the piece of energy in Missouri, the low pressure currently in the south will begin to speed up and track into northern Tennessee this evening. More precipitation will begin to blossom to the north of the low pressure area as time goes on. This low should steadily deepen as it tracks through Virginia by the early morning hours and bring the onset of the precipitation to the southern New Jersey by 2-3am. This area of snow and rain should gradually move up from southwest to northeast and since we have temperatures in the 50s-60s this afternoon, the initial precipitation may be in the form of a rain/snow mix due to residual warm air. As the precip starts to come down at a heavier rate, a switch to heavier snow/mix is likely for much of the area.

Public Analysis: Increasing Snow Chances for Thursday

February 6, 2017/by Steven Copertino

A very dynamic work week is taking shape as both near-record high temperatures as well as a threat for accumulating snow seems to be possible by Thursday.

As we head into Wednesday, our attention turns toward two key pieces of energy that could possibly come together and strengthen over the Midwest/Great Lake states to produce an area-wide accumulating snow event Wednesday evening and into the day on Thursday. As of this afternoon, the first piece of energy for this potential storm system was located well offshore the California coastline. This first piece will likely come ashore on Wednesday afternoon and continue to move briskly into the Rocky Mountain region while a second piece of energy begins to dive down from the far northern territories of Canada. Today’s model guidance has shown us a wide range of possible solutions for what happens when/if these two pieces interact on Wednesday, but right now a blend of today’s models would show that these two pieces would begin to come together late Wednesday evening, which would produce the beginnings of our potential storm in the form of a surface low over the Tennessee valley.

18z NAM showing interaction between the northern stream and Pacific energy (Valid 8pm Wednesday)

18z NAM showing interaction between the northern stream and Pacific energy and formation of a surface low (Valid 8pm Wednesday)

This newly-formed surface low would then have the potential to track quickly to the east/northeast during the very early morning hours of Thursday as precipitation starts to break out from southwest to northeast. Guidance shows that possible moderate precip could overspread at least the southern half of the New York metro by the time the morning commute begins on Thursday. As this system continues to head to the northeast and eventually off to the coast, the models have been hinting at the presence of an organized upper-level jet streak that would promote a strong amount of divergence (or ventilation of air) in the atmosphere which would in turn intensify precipitation at the surface as well as work to expand the extent of the precipitation to the north/west during the afternoon on Thursday into most of the area. One aspect of this system to keep an eye on is that a blend of the recent guidance as well as a look at the upper level jet configuration would suggest that as this system intensifies, there exists the potential that bands of snow may set up over the locations where forcing and precipitation are strongest, but these features in determining where the steadiest snow would exist can easily shift over the next few days and will be difficult to nail down. Though the finder details and timing of precipitation are still subject to change, it does look like the threat for at least light to moderate accumulating snowfall is increasing for Thursday.

12z GFS Ensembles Mean showing a blend of various solutions for Thursday potential system (Valid 8am Thursday)

While it’s important to mention the possible impacts for this system, it’s also very important to mention what could, and more than likely will change from what we see right now. As mentioned earlier in this post, we have two key pieces of energy for this potential system that are coming from deep in the Pacific as well as deep in the northern territories of Canada. The first potential problem is that both areas are currently in regions where we have very limited methods of sampling these each feature so that we can hope to have our model guidance get an idea of what they may do in the future. As of this evening, it looks like the Pacific energy will be onshore and available for sampling sometime tomorrow evening, and the northern stream should be available around that same time. Once we can get more accurate sampling of these features, we should begin to see the guidance converge on a solution. Our second potential problem is that the Pacific energy is embedded within a very quick flow, and once it comes onshore, the energy may continue along at a quick pace and miss the essential interaction with the northern stream energy, resulting in a much weaker and drier system than is currently shown. Another issue that we saw happen just last week in quite a similar fashion was that the Pacific energy that came ashore was much weaker than what was forecast by the models, and this would lead to a solution where a weaker and more suppressed system would be likely. With these features still quite literally up in the air, make sure to check back over the next few days as this storm could trend in either direction for our area. Posts like this one are available multiple times each day to Personal and Commercial clients, including Zone Forecast subscribers. Contact us today for more info!

Have a great evening!

Public Analysis: Light snow Tuesday, Possible Weekend Storm Threat

January 30, 2017/by Steven Copertino

Yet another northern stream system will be dropping down from Canada this evening and progressing very quickly off to the east on Tuesday. This quick-moving disturbance will have a high likelihood of bringing a measurable snow threat for the northern areas of the NY metro by early-mid afternoon tomorrow. Steady snow should begin just after the bulk of the morning commute on Tuesday. With the upper-level jet streak in a favorable position overhead, as well as sufficient low-level moisture advection (the movement of moisture in the lower levels of the atmosphere) taking place, a band of light to moderate snow should become fairly widespread over the northern half of New Jersey, Long Island, Southeast New York, and most of Connecticut. While the upper-level system associated with this snow is rather impressive, this system is much like the others that have come before and will remain solely connected to the northern stream and a deep continental polar air mass. While providing sufficient cold for snow, this will limit the overall potential moisture from this system.

4km NAM showing Composite Reflectivity, 700 mb Relative Humidity & Vectors, and 500mb Heights and Vorticity valid 15z Tuesday (Courtesy of Simuawips.com)

Today’s model guidance has been consistent in showing that the low pressure system will then reform off of the New Jersey coast and just to the south of Long Island sometime during the mid-late afternoon hours, which should create enough subsidence (sinking air) in the atmosphere to end the snow across portions of Central, NJ. Eventually, snow will taper off over Northern New Jersey, Long Island and eventually Connecticut towards the evening, with some areas of Connecticut hanging onto the light to moderate snow rates for a little longer. In general. accumulations should range on the lighter side with 1-3″ being commonplace, with locally higher amounts possible in Southern, NY and portions of Connecticut. Regardless, Tuesday should be a wintry day with slick conditions possible for the evening commute, so stay aware of road conditions when driving!

12km NAM showing Precip and MSLP/ 850mb Heights and winds/500mb heights and vorticity/300mb Heights and Winds

Later in the period, our attention turns towards this weekend as a potent shortwave from deep in the Pacific comes ashore along the Oregon/California coast late this week. Like past systems that have affected the Northeast, this shortwave is currently progged to head east while embedded within a relatively fast atmospheric flow, however this wave (if the pattern is favorable enough) may possibly interact with the northern stream that has been quite active as of late. This combination could produce a quick-moving low; and over the past two days most of our reliable guidance has shown us a variety of solutions as well as possible impacts from this system if it reaches our area ranging from snow on Super Bowl Sunday, to a more suppressed system that could miss our area to the south.

The latest trend in the models today has been for more of a flat and progressive flow along with a weaker Pacific shortwave. This would ultimately limit the impacts for our region, but this could very easily change as there are many moving parts with this possible system and none of these pieces will be sampled for days. One of the key pieces to this puzzle will be how much ridging we will have available in the western states, as this will help dictate how much northern stream energy can phase into this system as it heads east. Another key is how strong this system is when it comes ashore later this week, as a stronger storm would likely be more susceptible to a cleaner phase along with more direct and significant impacts for our area. We will continue to monitor the latest guidance over the next few days and provide updates as they become available on this potential threat.

12z GFS (from left to right) showing the PNA ridging in the west, key northern stream energy in Canada, and the position of the shortwave over the Ohio Valley (valid: February, 6th)

Be sure to stay tuned throughout the next 24 hours to get the latest on the low pressure system that will be producing area-wide light snow for our area. Posts like this one are available multiple times each day to Personal and Commercial clients, including Zone Forecast subscribers. Contact us today for more info!

Have a great evening!

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