With respect to our rare October snow, this is truly the first winter event of the season, and winter isn't giving us any breaks forecasting this one. This is a very difficult first test.
Winter Storm Watches are up for Tolland and Windham Counties, the area we highlighted earlier today on Facebook as having the best chance for highest accumulations. A Winter Weather Advisory is up for northern Litchfield County and I expect additional headlines from the National Weather Service tonight for other parts of the state.
The setup is fairly straightforward. A weak system is currently zipping along in the south and will phase with the northern stream to create a powerful and rapidly intensifying coastal storm tonight and tomorrow.
It will be a fast mover, but will pack a real punch for parts of the state. This was originally a long shot for snowfall due to the very poor (read: warm) airmass ahead of the storm, but because phasing looks to happen early enough cold air will be produced by dynamic cooling taking place as the low rapidly intensifies and drops heavy precipitation. Snow lovers are lucky to even be in this position. Unlucky break for those that dislike snow.
First let's talk about the overall progression of the storm, and then go through the impact elements we'll be grading ourselves on.
Along the shoreline and points just inland, it is likely going to be tough to flip to accumulating snow soon enough to bring an impactful event.
For inland areas, there is likely to be accumulating snow and it may be plowable the further north and east you are. Because we're looking at heavy wet snow and windy conditions, power outages are possible.
For hilly areas in NW CT, this is likely to be a significant event with plowable snowfall for most. We will be closely watching how quickly you change over (it could be early morning) and where the best banding sets up. We expect breezy conditions, but maybe not as strong as areas further east and along the shoreline, as is usually the case.
In NE CT, we have our highest confidence in a significant to major event. Currently, the best dynamics look to be over this region, and it will likely produce a period of heavy snow tomorrow morning and afternoon before clearing from west to east. With wind and heavy wet snow, there is a significant possibility of power outages.
Before going to specific impacts, a caveat. This is heavily dependent on banding and timing. If this storm fails to "bomb" fast enough, there could be little snow outside of the NE hills. If it develops faster, it could mean more snow for virtually everyone. This is a classic thread the needle event, but here's our forecast.
C-2" Zone: As you can see above, we're not expecting much. The further inland (and higher elevation) you are in this zone the more likely you are to see the higher end of this forecast. The shoreline is unlikely to see any accumulation.
2-4" Zone: This covers most of CT geographically. The further north and east you are, the more likely you are to end up on the higher end of this range. Banding will be critical in this zone. Wherever it rips, you will see accumulation. Ground temperatures don't matter nearly as much when it's snowing at .5-1" an hour.
3-6" Zone: What may be lost in the lack of best banding could be made up for with an earlier onset of snow. This is a tricky zone, as a more compact storm or east track could give many in this zone lower amounts. For now, we agree this is a secondary zone of higher snowfall in large part due to elevation.
5-10" Zone: This is the "jackpot zone". Not everyone will see the highest end of this. This area has a lot of potential though, and has been the most consistently strong part of the forecast. The further north you are, the more likely you see higher end amounts.
C-2" Zone: This is the area least likely to flip to snow, but even here we think that areas outside of the immediate shoreline will flip to snow. Unfortunately for snow lovers, it will be the last to flip, most likely changing to snow in the early afternoon.
2-4" Zone: Rain will change to snow from NW to SE, likely during the mid to late morning hours. This should provide a few hours of snow, some of which may be heavy at times, before the storm departs late afternoon/early evening.
3-6" Zone: Rain flips to snow on the earlier side, perhaps early morning. It will also end faster as the storm departs to the east. Snow should be tapering off early afternoon.
5-10" Zone: Rain flips to snow during the mid morning hours and snow departs by mid-evening.
C-2" Zone: It's looking windy. It's likely windiest in SE CT, but the whole shoreline could see some gusts during the late morning and early afternoon. I think the maximum gusts are between 40-50 mph which is windy but manageable, especially with little snow.
2-4" Zone: It is also windy here, but a little less, with maximum gusts between 30-40 mph. That could cause some issues if there is a higher snowfall here.
3-6" Zone: Maximum wind gusts between 25-35 mph. The could be some issues, but not a ton without higher snowfall or wind gusts.
5-10" Zone: Some of the guidance suggests that there could be some strong wind gusts here, especially further east areas, so I am going with maximum gusts between 35-45 mph.
C-2" Zone: No significant power issues expected. Just watch out if you lose power in common wind events.
2-4" Zone: I expect isolated to scattered power issues here. If you are in SW CT I expect fewer issues as you see less snow, but in central and eastern CT I expect more scattered issues.
3-6" Zone: I expect isolated to scattered power issues here.
5-10" Zone: Here is where trouble is possible, with heavy wet snow and wind, we could see scattered to widespread power outages. Be ready if you live in this zone.
C-2" Zone: Little impact. This is a nuisance event at best as currently forecast.
2-4" Zone: Low-Moderate impact. Although there's not a lot of snow expected, the combination of wind and high snowfall rates will make this a fairly impactful early season event. Lower impact in SW CT. More moderate in north-central and eastern CT.
3-6" Zone: Moderate impact. I expect higher snow totals here, but the snow may be more fluffy and there should be less wind. Road impacts may be higher due to colder temperatures.
5-10" Zone: High impact. Everything suggests that this will be a significant to major event in NE CT due to the combination of heavy wet snow, significant accumulation, and strong winds.
Overall, a mixed bag of impacts for CT. I'll be biting my nails all the way to the end on this forecast as there is higher uncertainty than usual in northern CT. Here's hoping we pass the first test of the winter season!
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