What a difference a few weeks make. After a fast start to our winter in December with a major snowstorm, we saw a big break in winter with a warm Christmas storm and warm first three weeks of January. Since then, we've seen historic cold in much of the central US and a very active pattern for storms in the east.
That has put us well above normal snowfall for this point in the winter season.
Before we get into the forecast, we should talk about this pattern, which we don't see often. For much of January, we actually saw a favorable winter pattern aloft, but for a variety of reasons, mostly because of the Pacific teleconnection pattern being hostile, we did not see a break back toward winter until the last week of the month, where it brought us a major storm and a colder pattern.
Below, we see the same map, looking at February so far. This is about as extraordinary a reversal as you'll ever see, with extreme cold across much of the central US and a very large section of the US with colder than normal temperatures.
Fargo, ND has not been above 0 degrees since February 5.
The AO, or Arctic Oscillation, has been negative since December (which hasn't been the case the last few years) and has taken an extreme drop since the beginning of February.
In addition, we've seen a negative NAO, which if you recall from our winter forecast that has gone up in flames, is a harbinger of potentially big storms. The NAO hasn't been extreme, but it's been negative enough to give us three significant snow events thus far this winter.
In the east, these storms are poised to impact us, albeit differently from our earlier storms that brought mostly snow. We're now turning our attention to icing early in the week and a potential snow/mix/rain even later in the week. Now that we have a better understanding of the pattern, let's dive in.
The Monday-Tuesday storm is actually two waves, but for the purposes of this forecast, we want to view them in tandem. We think this period will bring most of CT a significant winter storm, with icing as the biggest threat. Note that we're not using the word major here, as we do not yet have high confidence in a widespread high impact event yet.
Winter storm watches are now up for the northern four counties, while winter weather advisories are up for the southern four counties.
Unlike snow, forecasting ice is a very difficult forecast, as it requires precise temperature projections in multiple parts of the column of air aloft. Before diving into the details, let's break out a SCW favorite, explaining different types of wintry precipitation.
We expect scattered light precipitation to begin in the hours before dawn on Monday. That means not everyone will see precipitation when they wake up. The best chance of seeing light precip is in southern CT. Although there may be a few flakes mixed in early, we expect things to quickly change to sleet or freezing rain statewide.
As the day progresses, we will likely see more widespread mixed precip across the state, though it doesn't look to be heavy. There is likely to be a break in precipitation during the evening hours, but we will see the radar fill in quickly between 10pm and 2am as the second and more meaningful wave arrives. Tuesday morning looks very messy and early afternoon could see some lingering precipitation before the storm departs.
This one is always tough to predict, but we think we're going to see significant sleet and freezing rain, especially in areas that are not along the immediate shoreline. Although we will see some minor icing tomorrow, the bulk of the accumulation will occur on Tuesday morning.
For the immediate shoreline, we think we see total icing of a glaze to 0.10". That's enough to cause problems on roads and untreated areas.
For interior southern CT (inland areas of the southern 4 counties), we think we see between 0.10 - 0.30" of ice accretion along with a possible layer of sleet. Again, the majority falls on Tuesday, but some glaze is possible tomorrow. This is enough to cause road and untreated area issues, and possible power outages and limb damage with higher accretion in this range. One caveat here is to watch out in northern/western sections of Fairfield and New Haven Counties. There is some guidance that puts you more into the northern CT icing category.
For northern CT, we think we see some snow early, followed by sleet and then freezing rain. This means you can expect a layer of sleet and then icing on top. Icing accretion may be between 0.30 - 0.50. This is on the cusp of a more major event, but for now, we're going to hedge a bit more conservative in case things warm a bit more than expected. Higher end icing on this scale could cause widespread road problems, scattered tree damage, and scattered power outages.
This is where we are likely to see the highest impacts. we cannot emphasize enough that it only takes a little bit of icing to make road conditions truly hazardous. In Texas, it took road icing as thin as a dime to cause a massive pileup. Across CT, tomorrow morning looks decent for travel, but again, if there is precipitation falling in your area or you see wet spots on the road, assume it's icy and take appropriate driving precautions. Widespread delays are possible tomorrow, especially if precipitation is falling. The evening commute could be messy as well. Fortunately, many are home for the holiday tomorrow.
Tuesday is worse. I expect widespread cancellations on Tuesday. The roads are likely to be hazardous across CT. Definitely during the morning and possibly into the early afternoon as freezing rain falls.
Fortunately, we are not expecting a lot of wind, which would have an impact on power outages. Right now, we are just expecting isolated to scattered power outages, with more outages where we see the higher end of our icing forecast (areas closer to 0.50" of icing) verify.
Right now, we think this is a moderate event overall, with high impact on the roads. Monday isn't ideal but it doesn't look high impact, but Tuesday is really the period to watch. If we see the second wave come in stronger, we won't hesitate to declare this a major event.
Wednesday brings a break in between storms. Importantly, we might see a reinforcing shot of cold that sets the stage for our next storm.
This period brings our next storm, which looks messy. Unlike Monday-Tuesday, this one looks like we could see a burst of heavy snow on Thursday, followed by mixing/icing and then rain depending on the track of the system. At first glance, this looks like another significant storm with high impact potential. That's all for now, as our focus is on Monday-Tuesday and there's still uncertainty over track and the antecedent cold for this event.
For now, let's just say we look relatively quiet. There is likely to be another reinforcing shot of cold, which could come into play late Sunday and Monday as another storm may be on the horizon. This active pattern continues...
Monday: Mostly cloudy with light mixed precipitation. Highs in the low to mid 30s. Chance of precipitation low early and rising to 70% late.
Tuesday: Sleet, freezing rain, and rain (shoreline). Highs in the low to mid 30s. Chance of precipitation 100%.
Wednesday: Mostly sunny and seasonably cold with increasing clouds late. Highs in the upper 20s to low 30s.
Thursday: Mostly cloudy with snow. Snow may be heavy at times. Highs in the upper 20s to low 30s. Chance of snow 60%.
Friday: Mixed precipitation early followed by rain. Highs in the low to mid 30s. Chance of precipitation 50%.
Saturday: Decreasing clouds and cold. Highs in the mid to upper 20s.
Sunday: Increasing clouds with a chance of snow late. Highs in the upper 20s to low 30s. Chance of snow 30% late.
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