Another Lame Looking Storm

What a boring weather pattern! While 99% of the public is loving life right now us snow lovers are just despondent!

snow

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.

noice

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”…

headlines

lowimpact

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Ice Today, Snow Friday

Another winter storm!!!

Today’s storm won’t be quite as disruptive as the last two. Snow and sleet has transitioned to freezing rain across Connecticut. Northerly and northeasterly winds are locking in low level cold while warm air has surged inland aloft. This is a recipe for freezing rain.

Most towns won’t see temperatures reach freezing today so expect ice to continue. Power outages are possible in some areas where ice buildup brings down trees and limbs. The storm looks relatively disorganized, however, so I’m not expecting enough freezing rain to fall and cause widespread problems. More sporadic problems are likely.

Some indications are growing for another major snowstorm on Friday. Too soon to get too specific. Hope to have more on this tonight. Keep in mind many areas will come close to record monthly snowfall if this storm is a big one.

Ryan

Overnight Ice

1z Surface Map

What will be a major rainstorm will begin as some ice in parts of Connecticut. Temperatures have dropped off quickly this evening and faster than computer models forecasted.

18z NAM 6 hour Surface Temperature Forecast

Given the fact temperatures are so far below what was forecasted it seems likely a period of ice will overspread Connecticut late tonight. Easterly winds will develop and bring in warmer air quickly, but areas in Litchfield County could pick up 0.1″ of freezing rain. This is certainly enough to cause problems on untreated roads.

Once the freezing rain ends Sunday will be  a soaker. 1″-3″ of rain is expected with locally higher amounts possible.

Where’s the Snow?

Not here! Skiers have been waiting for a burst of snow but unfortunately the cold pattern we’ve just entered will not produce.

Tonight, freezing rain and sleet will muck up the ski slopes in Vermont, but thankfully there will be little melting with temperatures in the low 30s. I am expecting travel problems Friday morning especially on the east slopes of the Green Mountains away from the Connecticut River Valley where subfreezing cold will stay longest. On the left is a temperature forecast for 7 a.m. Friday morning from the 12z NAM.  You can see the 32 degree isotherm straddling the spine of the Greens down to the Massachusetts border with the coldest weather on the east slopes and especially across New Hampshire. Freezing rain is likely for a period of time early Friday across a large chunk of northern New England.

Beyond Friday I’m expecting a solid 48-72 hours of snowmaking weather in the higher elevations of southern and central Vermont. Daytime highs will stay below freezing about 3000 feet with overnight lows in the teen. Very low dew points and relatively light winds will make conditions good for the snow guns.

Early next week looks good with fair weather, light winds, cold nights and seasonable days. Rain may enter the picture on Thursday but we’ll deal with that when it arrives. I’m still hopefully we can squeeze out a snow event sometime in the first 10 days of December.

Big Thanksgiving Questions

Our computer models are all over the place with the Thanksgiving storm. A highly anomalous pattern featuring large blocks in the upper levels of the atmosphere is making this storm a difficult one to forecast.

Last night’s 00z Euro run sent a fairly intense storm way west, cutting through the Great Lakes, and sending warmth and rain into all of New England late Thursday and into Friday. The run showed freezing rain and sleet at the onset in Vermont but even there temperatures wind up warming well above freezing before the storm ends. This map valid Thanksgiving evening shows the storm moving through Wisconsin! Unless there is a stronger secondary storm that forms near southern New England  to lock in the cold this setup is no good for snow in New England. In fact by Friday morning the Euro has temperatures near 60 degrees in New London and the 32 degree isotherm in southern Quebec!

On the other hand the GFS has been consistently taking a weaker and more sheared out storm south of New England producing a much colder and wintry scenario. The 06z GFS produced a decent snowstorm (probably 6″ of so) for the higher elevations of Vermont and New Hampshire with even some snow and sleet in parts of interior Connecticut and Massachusetts (not much accumulation) on Thanksgiving.

It’s most likely the truth will lie somewhere in between the Euro and GFS with snow, sleet, and freezing rain likely across Vermont and maybe northwest Massachusetts with mainly rain in Connecticut after a brief and light wintry mix to start. If the storm is able to hold on to enough cold air in mid levels of the atmosphere a light to moderate snow is possible in the higher elevations of southern Vermont but it’s too early to say anything with much confidence.