Prospects for a Significant Winter Storm Increasing (Saturday, January 29, 2022)

Computer forecast models continue to come into strong agreement (with consistency) that a significant storm will evolve moving into the upcoming weekend. After a challenging past few winters in the forecasting department which makes me skeptical about raising awareness for storms several-days out, the evolution of the pattern and pieces involved give me enough confidence to communicate the idea of a rather significant storm. The past few winters have been characterized by a rather fast jet stream with many embedded pieces of shortwave energy. This results in chaos and high model uncertainty as more pieces involved, the longer (and more challenging) it takes for forecast models to resolve. A comparable example is that of a puzzle. If you're doing a puzzle which is only 50-pieces, you have less pieces to work with and it's going to be easier to (re)solve the puzzle. However, if you have a puzzle that's 500-pieces or 1,000-pieces, you have more pieces to resolve and it will take longer to complete. 

For the upcoming potential this weekend, there are really two MAIN pieces of shortwave energy we're watching. (Note: While I am using GFS model output in below images this does NOT mean I am favoring the GFS or forecasting solely off the GFS. I am just using for illustrative purposes).

As we progress through the week a large ridge of high pressure builds into the western United States with a vigorous trough amplifies (strengthens) across the eastern-third of the United States. Forecast models indicate a piece of shortwave energy traverses the eastern periphery of the ridge with this shortwave energy (becoming associated with the southern branch of the jet stream) amplifying as it digs into the Gulf Coast states (shortwave #1). Moving towards the end of the week, forecast models indicate shortwave energy diving through the upper-Great Lakes region in association with the northern branch of the jet stream (shortwave #2):

Forecast models indicate a positively-tilted trough (with the trough axis digging into Mississippi/Georgia) becoming more neutrally-tilted to slightly negatively-tiled  as it traverses the southeast. This is a very favorable scenario for rapid low pressure development just off the southeast coast and also favors a storm track closer to the coast. Shortwave #2 is very important here because depending on the interaction, shortwave 2 can further enhance rapid development and it can act as a means to keep this storm closer to the coast as well:

In addition to these two pieces of shortwave energy the evolution and structure of the ridge within the West may have huge implications, especially with how the trough evolves in the East. A stronger ridge could result in the trough axis shifting east a bit increasing the likelihood of a farther west track (coast or just inland) while a bit weaker or more flat ridge could push the trough axis east, increasing the potential for a track off the coast. In this scenario, phasing of the two shortwaves will be huge as this could open the window for a missed phase and storm track well off the coast. At this stage that is appearing more unlikely. 

As low pressure develops and moves up the coast (this is a big vague here as the exact track is far from certain. Up the coast in this sense means anywhere from just inland to anywhere just offshore enough to still bring impacts inland) rapid cyclogenesis (deepening) is expected thanks to incredibly favorable upper-level dynamics. Forecast models indicate a powerful 150+ knot upper-level jet streak may transpire across northern New England moving into Saturday. This jet stream structure and jet streak would favor tremendous upper-level divergence over the Northeast into the mid-Atlantic with the result being rapid deepening of the ow pressure and blossoming of precipitation:

Forecast model ensembles (as well as operational runs) are suggesting storm tracks and potential for favorable evolution which would bring significant storm impacts. This includes extremely heavy snowfall and significant totals, high winds with the risk for power outages, rain along immediate coastal areas (particularly eastern Massachusetts), and devastating coastal flooding. Below is the 12z European Forecast Model Ensemble with each "L" (Low Pressure) the forecast of a specific model-member. At this stage, there is strong agreement in a track very close to the benchmark and that historically can result in very heavy snows for much of Connecticut:

Depending on exact storm track and evolution, there will likely be a very step temperature gradient established between warmer east east of the storm and colder air west of the storm. This will likely favor a corridor of extremely heavy upward vertical motion and subsequent heft precipitation rates. This will occur perhaps 50-75 miles northwest of the surface, 850mb, and 700mb low tracks. One second area to watch (more so getting into eastern Massachusetts) will be a very strong surface temperature gradient where the coastal front sets up. That boundary will be the difference between zero snow and perhaps quite a bit.

Given we are 4-5 days out it is impossible to get into specifics and details such as exact storm track, exact storm evolution (where the 850mb and 700mb lows develop, track, and how they evolve), and potential amounts. However, at this juncture, based on the signals, the potential is rapidly growing for a very significant storm. 

An updated blog post will come forth early Tuesday evening. This will provide a storm update along with getting into a bit more of the specifics (positives and negatives).