What a boring weather pattern! While 99% of the public is loving life right now us snow lovers are just despondent!
Yeah – not so exciting right? It looks like weak storm that approaches (that shears out and really just falls apart) will deliver very little precipitation – less than 0.25″ and most of that won’t be snow!
While at the onset of the event the atmosphere will be cold enough to support snow a lack of forcing/lift combined with the possible lack of ice in the clouds will make it very hard to drop much snow. Lack of ice? Huh? Take a look at this forecast sounding from the 18z NAM for Hartford tomorrow night.
While this sounding shows subfreezing temperatures from the tropopause to the ground this is not a snow sounding! So how the hell do you get snow or ice in a cloud? It’s actually pretty complicated.
Supercooled water droplets make up a cloud. Those cloud droplets (unless it’s super, super cold) turn into ice crystals by heterogeneous nucleation when ice forms on a particle (known as a nuclei) such as sea salt, dust, pollen, clay, etc. Salt can jump start the process as warm as -4C but generally you need to be near -8 or -10C to even get ice in the cloud! In the above sounding the red line (temperature) and green line (dew point) race apart above about -5ºC at 650mb. It’s bone dry above that!!
Once you get the ice crystal it grows through either accretion, aggregation, or deposition. The latter, deposition, is how snow crystals really grow! This is maximized between -12ºC and -18º or what we refer to as the “snow growth zone”. Deposition is simply a change in phase from vapor to solid of water on an ice crystal – this is maximized around -15ºC.
With the above sounding it’s perfectly plausible that we may go through most of the storm with little if any snow. It could be mainly freezing rain/freezing drizzle which isn’t too pleasant. The good news is DOT/Public Works crews will have plenty of time to start treating the roads before the Monday AM commute.
Anyway – here’s what to expect with this poor excuse for a “storm”…