Wednesday, March 9, 2022 Connecticut Snow Event

An area of low pressure moving off the mid-Atlantic and passing just south of Long Island results in a cute little snowfall event for Connecticut Wednesday. Snowfall accumulations are expected to be on the minor side given marginal boundary layer and surface temperatures with the greatest accumulations occurring across the northwest and northeast hills. 

As low pressure moves northeast off the mid-Atlantic coast passing just south of Long Island, the combination of a strengthening system, favorable upper-level dynamics to support large-scale lift, and a large temperature gradient across the region will yield the rapid blossoming of precipitation and snow across the state moving through Wednesday morning. Temperatures at 850mb (~5,000 feet above the ground) will be as warm as +10C to +12C just off the mid-Atlantic coast with 850mb temperatures as cold as -5C to -10C across New England resulting in a large temperature gradient which favors enhanced upward vertical motion. This will be further enhanced by a strong 150+ knot upper-level jet streak north of New England:

Forecast models also indicate we'll see some very strong frontogenesis move across the state Wednesday afternoon (evident by the red and spots of black below). This is important as this will help achieve heavier snowfall rates which will make accumulations more possible especially within the hills and road surfaces within the hills:

However, in order to maximize the heavier snowfall rates we'll have to get this lift to occur within the dendritic snow growth zone. This should be around 15,000 -20,000 feet Wednesday (slightly higher than what is preferred). Below is the 18z/08 NAM bufkit for New Haven, CT indicating the snow growth zone (yellow/purple contours) and omega (negative values or red contours indicate upward vertical motion...lift). Here we see omega values as low as -10 to -15 and even higher later in the afternoon:

What we're looking at for Wednesday is due to boundary layer temperatures which will be above-freezing and surface temperatures climbing into the mid-30's this will make snow difficult to stick to paved surfaces, especially when snowfall rates are on the light side. Under areas of much stronger lift when precipitation rates will be heavier, accumulations become more likely, especially on colder surfaces and now untreated surfaces. The depth of the warm-layer, however, is on the shallower side this is why despite the surface temperatures being in the mid-30's precipitation will be snow. A shallower warm-layer gives less time for melting. Also, temperatures as low as 1,000 feet off the ground are quite cold (~ -3C to -4C). This cold layer so low will help with the greatest accumulations occurring across the hills (elevations above 500 feet and especially above 800 feet). 

Below is what to expect:

• Light snow breaks out across the state during the morning with areas and periods of moderate-to-heavy snow occurring at times.
• Snowfall rates between 0.5''-1'' per hour under the heaviest band of snow and where snow rates are highest.
• Timing for heaviest snow rates will be from late morning through late afternoon. 
• Greatest accumulations within the northwest and northeast hills. Across lower elevations and the valley, majority of snow accumulations will be on grassy and untreated surfaces.
• Significant travel disruptions aren't likely, but roads will be slick so give yourself extra time traveling.