Freak October Snowstorm Becoming More Likely

Hello, Snow!

This evening’s snow is a rare enough event. It looks as if the greater Hartford area has picked up measurable snow in October for the first time since 1979 and for only the 4th time in the last 100 years. We will need to wait to hear from the weather observer at Bradley Airport to get the official word.

This may be just a prelude for a significant and high impact winter storm that appears to be brewing for the weekend. All day I’ve spoken to meteorologist friends who have all said the same thing, “I’ve never seen anything like this.”

Obviously things can change and a variation in the track could mean only a little bit of snow. As of right now, however, the model consensus is a major winter storm that has the potential to bring down trees, tree limbs, and power lines given the amount of foliage still on the trees.

As we’ve seen tonight even though it’s October the sun angle is quite low and given a heavy enough snow rate snow can accumulate on the grass and on the roads. The GFS and the NAM computer models along with the Euro show substantial snow totals (most certainly “plowable”) even down to the shoreline.

For entertainment purposes here’s a look at the >12″ snow probability from our SREF guidance suite. The blue shading is 25 percent chance. Obviously this isn’t what I’m forecasting but this shows just how incredibly bizarre, rare, and unusual this storm could be.

By midday Friday we should have a better handle on this storm. At this point it looks like this storm has the potential to be unlike anything we’ve seen in recent memory.

Thursday Evening Snow

Most areas in Connecticut haven’t seen a frost and most certainly haven’t seen a hard freeze! All that will change Thursday as a burst of cold will move south as a departing storm heads into the Atlantic.

18z NAM 3-Hour Precipitation Forecast 00z Friday

While the NAM computer model drops temperatures fast enough to change rain to accumulating snow just about everywhere the GFS is much milder. As is typical the NAM Is likely too cold and the truth will lie in the middle.

At this point it seems like a slushy coating to an inch of snow is possible in the northwest and northeast hills Thursday evening. For the valley locations some places may see some wet snowflakes mix in but that’s just about it. One of the differences in the model is that the stronger solutions develop stronger northerly winds at the surface which is able to tug colder air to the coast much faster. This will be something to watch.

15z SREF 1" Snow Probability

The 15z SREF snowfall probabilities are pretty similar to previous runs with about a 50% chance of >1″ of snow in the higher elevations of Litchfield County. The green shading is probability over 50% and red is over 75%. As you can see there is a low probability of >1″ of snow in some of the lower elevations but at this point that is rather unlikely.

Even a slushy accumulation could make roads slippery as temperatures drop below freezing in the hills. Watch for some black ice as well early Friday morning.

As for Saturday’s storm… stay tuned! At this point it looks like a rain/snow mix glances by Connecticut but there are some indications the storm could be closer to the coast and much more powerful.

Winter Weather Porn… Already…

Computer modeling has improved forecasts immensely over the last several decades. In the last 10 years the improvement has been remarkable. Many of our computer models are run out to 10 days or 15 days. While the specifics are frequently wrong on a 10 or 15 day forecast the general trends can be used to predict whether the temperature will be above normal or below normal, whether the pattern will be stormy or quiet, etc.

10/28 ECMWF Forecast Courtesy: WSI

This mornings weather porn winner goes to the European model. The model is our most accurate (by almost every standard of verification) and updates twice a day. The run from last night develops a hurricane over the Caribbean, moves it over south Florida, and then up the coast as a nor’easter with a rain storm changing to snow in southern New England. Still this forecast is 7-8 days out so take it with a grain of salt. The odds of this verifying are slim to none!

Incidentally one of our other computer models, the GFS, develops a hurricane over the Caribbean around the same time but sends it way out to sea. It does develop a separate storm/nor’easter that drops some snow in northern New England.

There’s no question there will be a lot to watch by the end of next week as the weather pattern becomes active. It’s too early to start diving into specifics but if I were you I wouldn’t get too excited about the blizzacane just yet.

Major Snowstorm on the Way (Again)

It’s been a snowy start to the winter for sure. Though the western part of the state has cashed in the most in recent storms I think everyone gets hit hard by this storm and right now I’m forecasting 8″-14″ of snow.

The SREF (short range ensemble forecast) probabilities show greater than an 80% chance for 8″+ of snow. That’s extremely impressive. The 00z NAM is going bonkers with this storm (as usual) dropping 15″ or more of snow statewide. This is likely overdone (a good rule of thumb is to cut the NAM forecast by about 25%) but can sometimes signal the potential for the storm to really go to town.

700mb NAM 36 Hour Forecast

One thing to watch here is how quick and how close to the coast the mid level low forms. If the mid level low really goes bonkers along the Jersey Shore like the 00z NAM does than I expect 12″-20″ of snow across the state. If, however, the mid level low takes a bit longer to organize and scoots a bit east I think the heaviest snow will wind up northeast of Connecticut (just west of Boston?). This seems like the most likely scenario at this point. The 00z GFS continues the trend from previous GFS runs with a track a solid 75 or 100 miles east of the overly-amped NAM.

Wherever the cold conveyor belt starts to rip someone in southern New England is going to get hit very hard and probably pick up 18″ or so. At this point I think 8″-14″ is a reasonable forecast for most areas though I wouldn’t be surprised if those numbers are bumped up in some areas, particularly northeast of Connecticut.

One additional note. Unlike the last storm blizzard conditions are unlikely. The heaviest wind and snow will likely be out of phase so even though snow totals will likely be more impressive than the blizzard after Christmas the wind will not arrive until the heaviest snow ends.

Weekend Storm Threat

72 Hour 18z GFS Forecast (Valid 18z Friday)

Here we go again. Another week and another threat for snow. This threat appears to be a bit less than the previous two.  The big question with this storm is where does a big upper level low track. See the big low (closed black circle) near Buffalo?  That low’s position will determine how much snow we see. If the low winds up south of Connecticut then there’s the potential for a major snowstorm. Yesterday some of our computer models said this was a distinct possibility. Now, however, most models indicate that the low will remain west or even just over us which would prevent a big storm from dumping snow on us.

At this point it appears a couple inches of snow is a good possibility as weak low pressure forms offshore. The big storm will remain east and north of us and spare us from a major nor’easter. We’re still over 72 hours out from the main event so things could change but the odds of a blockbuster (>12″) storm are pretty low at this point. A light to moderate event is more likely. Don’t be surprised if some parts of Connecticut see a 3″-6″ or 4″-8″ kind of event Friday into Saturday.