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Nor’easter likely to spare our area major impacts this weekend

After a few days of concern, forecast models have trended more progressive and weaker with a Nor’easter which will pass off the coast of the Mid Atlantic and eventually New England this weekend. While models have been in good agreement that the storm itself will occur, inconsistencies have been common in regards to the exact track and intensity of the storm system. A convoluted atmospheric setup has wreaked havoc on even the most reliable forecast models.

A few days ago we highlighted the main players in the storm systems evolution. As of tonight, forecast models continue to fine tune the exact evolution of these features. Most interestingly, a lead disturbance ahead of the main storm system is now expected aid it de-amplifying the mid level height field. In simple terms, this will help to suppress the main coastal storm farther to the southeast.

NAM model showing the atmospheric setup in th mid levels as the storm evolves this weekend.

NAM model showing the atmospheric setup in th mid levels as the storm evolves this weekend.

The other main players remain on the field: A large central Canadian block, a west coast ridge, and two main mid level disturbances which are going to interact over the Ohio Valley and Northeast states. Forecast models today have come into better agreement that this evolution will take place in a slightly more progressive manner, and with a slower/weaker phase between two disturbances.

The result is a lead disturbance bringing the possibility of light snow as early as late Saturday, shifting east/northeast rather quickly off the coast. Precipitation with this disturbance should remain rather light — moderate at times — before it shifts off the coast to the northeast. The secondary coastal storm will develop over time, likely during the day on Sunday. Models are still up in arms in regards to the main coastal storms evolution.

Most notably the GFS and NAM (American models) keep the storm system farther east and southeast, with very minimal impacts in our area. The ECMWF and CMC (European, Canadian models) bring the storm closer to the coast, with light to moderate snowfall accumulations throughout the area from Sunday into Monday morning.

Storm Total Snowfall Forecast issued 9pm March 18th. This map is likely to change with further data on Saturday AM.

Storm Total Snowfall Forecast issued 9pm March 18th. This map is likely to change with further data on Saturday AM.

Regardless of the uncertainty, there are a few takeaways here: The large, powerful Nor’easter solution which was depicted on many models a few days ago now seems very unlikely. However, the secondary coastal storm may still cause wintry precipitation from Sunday into Monday. Still, there is the possibility that this storm remains weak and farther southeast with minimal impacts to our area. Even light to moderate snowfall is expected to bring only (no pun intended) light to moderate impacts to the area as the storm system occurs.

Over the next 12 to 24 hours, stay tuned for fine tuning and details in regards to banding, localized snowfall totals, and mesoscale trends. Our overall forecast leans slightly toward the European model guidance, but also accounts for a less amplified solution, leading generally to a light snowfall throughout the area with less accumulations both in the interior and near the coast, where warmer surface temperatures are expected.

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