Cold air, winter weather returns to the forecast

Par for the course this winter, as one storm exits we are already looking ahead at another system which is modeled to potentially bring additional winter weather to the Northeast US. On the heels of a major winter storm for interior and northern New England, which brought a significant cold front and 30-40 degree temperature drop Thursday morning, forecast models are honing in on Pacific energy which will eject into the Southwest US later this week into the weekend. With a lobe of the Polar Vortex hanging around to our north providing cold air, any energetic or moisture filled disturbance would bring the potential for snow. The disturbance late this weekend could do exactly that.

Much of the forecast, however, hinges on the exact positioning and strength of the disturbance as it ejects northeastward from the Southwest US towards the Mid Atlantic. And not surprisingly, forecast models are up in arms as to exactly how consolidated the system will be as it does so. The Canadian, SREF and DGEX extension models all like the idea of the system ejecting as one consolidated trough with significant moisture, while the Euro and GFS are adamant in the idea that the system will be faster and split into multiple pieces.

GFS model showing the important piece of energy entering the Western US and Rockies.

GFS model showing the important piece of energy entering the Western US and Rockies.

A matter of consolidation, and progression

Should the energy eject from the southwest US in one singular piece, the result would be a more significant storm system developing towards the Eastern US. The consolidated energy will help draw in much more moisture from the southern stream, which will surge northward into a dome of cold air settled in to the north of our area. In addition, the developing surface low would be able to enhance lift in the Northern Mid Atlantic and New England, allowing for a broad area of snowfall impacts.

The Canadian, DGEX extension and SREF/NAM show this scenario unfolding over the next 3-5 days. When glancing at the Canadian upper air panel below, it is not difficult to see the consolidated energy and enhanced support for a significant event in the Northeast US. In simple terms, this is the evolution which needs to occur aloft if there is to be a significant winter storm in the Eastern or Northeast US at some point from late this weekend into early next week.

Canadian model valid for early next week. Notice the consolidated energy aloft and resulting winter storm.

Canadian model valid for early next week. Notice the consolidated energy aloft and resulting winter storm.

That being said, the “powerhouse” forecast models (GFS, ECMWF) are not at all enthused about this idea. Both models have a much more progressive pattern evolution, and it begins with the lead shortwave disturbance which is forecast to be located over the Central United States by this weekend. The GFS and ECMWF are both more progressive and farther east with this feature.

As a result, the disturbance which dives into the Western US out of the Pacific moves southward and separates from that aforementioned lead energy. As this occurs, the lead disturbance slides eastward and the disturbance which is diving southward into the US from the Pacific is compressed and then shifts eastward as a weak/strung out disturbance.

GFS model forecasting a more separated and progressive pattern this weekend, resulting in no winter storm threat.

GFS model forecasting a more separated and progressive pattern this weekend, resulting in no winter storm threat.

The resulting solution in terms of sensible weather produces no significant storm, just a weak low pressure system which shifts fairly harmlessly offshore. There will be no winter weather impacts in our area if this evolution occurs in the mid levels of the atmosphere.

A lean toward progression

We won’t sugar coat it: This is a difficult forecast. To make things worse, forecast models are not helping with their wildly differing opinions on how the pattern will shake down. That being said, our current forecast calls for a more progressive solution. With a continued fast Pacific pattern, minimal high latitude blocking to “slow down” the pattern and a relatively narrow window for a bigger system, we blend mostly the ECMWF and GFS into our forecast package at this time.

Nevertheless, confidence in the forecast for this weekend is quite low. We’ll be carefully monitoring model trends over the next few days and, with a good understanding of the pattern as highlighted above, fine tuning our forecast as we move through the weekend.

Comments

comments