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We are gaining a bit more confidence in the forecast for our nor'easter, which is named Winter Storm Riley but several questions still remain. We'll explain to you the uncertainty regarding this forecast and our actual forecast. We will continue to update our forecast, so please check back to this article Friday morning for any possible changes.
Current Alerts:
High Wind Warning in effect until 6am Saturday
Winter Weather Advisory (inland) in effect until 6am Saturday
Flood Watch in effect until 6am Saturday
Coastal Flood Advisory (coast) in effect from 11pm Fri through 2am Saturday
Coastal Flood Watch (coast) in effect from 6am Saturday through 2pm Sunday
Timing:
Friday: Rain is expected to changeover to snow midday
Friday night: Snow from the evening through early-Saturday morning
Temperatures:
Friday: Dropping from the mid/upper 30s to around freezing
Friday night: Hovering around freezing
Specific Threats:
Rain: Between 1 and 2 inches through Friday morning before rain likely changes over to snow
Snow: Most areas receive 3-6 inches, 1-3 inches at coast
Wind: Winds will be the strongest Friday into Friday night with gusts as high as 60 mph at coast, 55 mph inland. This will lead to scattered to potentially widespread power outages.
Coastal Flooding: Minor to moderate flooding expected
Discussion:
Precipitation:
The models continue to show disagreement between what will actually happen. Earlier in the day on Thursday, I tweeted out what three of the main models forecasters look at when predicting storms like these, and this disagreement remains the same today (Friday):
As you can tell, the model guidance still doesn't have much of a clue due to this large spread and disagreement. Based on past storms, however, the NAM model has been the most accurate, so I am going to base my forecast mainly off from this model as well as the ensemble guidance from the European model. The main reason for these disagreement is due to the timing of the transfer of energy from the first low pressure over the Great Lakes region to the secondary low currently over the Tennessee Valley, which will become our nor'easter. Because of these timing differences, they will have implications on our forecast. What has become more certain is the track of this nor'easter. This storm will be a slow-mover, allowing for impacts to be maximized. Our low will begin to rapidly develop Friday morning as it tracks toward Cape Cod before stalling off the coast for the entire day. It will then take a track out to sea in the southeast direction beginning Friday evening, but it will continue to bring precipitation and wind to southern New England Friday night. By this time, our storm will likely be a hurricane-force low or a "bomb cyclone," which is when a storm intensifies by at least 24 millibars (pressure) in less than 24 hours.
Now let's talk about the forecast and how it will impact you: Rain will begin Thursday evening and will persist through all of Thursday night. This rain will be steady with intensities light to moderate, adding up as much as 2 inches before the rain likely changes over to snow. This will allow for the ground to become super-saturated, which will make it easier for the winds to take down trees. That leads us to Friday. This will be the big day with the biggest impacts but also the most uncertainty. Snow is likely to fall, but the question is when does that rain changeover to snow? Based on the latest guidance, that may happen as early as 6am for inland areas or as early as 9am for the coast. This changeover to snow should happen by 1pm for all, I'm thinking. Once that rain turns into snow, it will be a doozy. It will be a very wet, heavy snow due to marginal temperatures in the low to mid 30s. Along the coast, the precipitation may go through waves of rain then snow then back to rain then back to snow, so that's why not as much snow is forecast there due to that potential. That may make you think why will it snow with above-freezing temperatures? The reason is because most of the air column will be below 32 degrees. Temperatures are expected to be at or below freezing just a few hundred feet up from the ground. Therefore, the snow won't have time to melt when it gets to the ground, and the heavy snowfall rates expected, the snow will likely be able overcome the marginal temperatures and will be able to accumulate on all surfaces. This snow will persist into much of the overnight hours of Friday before coming to an end by 5am Saturday. Based on all the guidance we have looked at, here's how much snow you can expect. There is bust-potential to this forecast so understand there is a fairly good chance more or less snow falls than the range I am forecasting. There is the chance the coast receives only a trace to one inch of snow. Please check back to this article Friday morning for any possible changes.
Wind:
Now let's talk about the wind: Winds will likely be damaging especially at the coast. The combination of the strong winds, saturated soil, and heavy snow on the trees, that a perfect recipe for widespread power outages, which is what we're forecasting. Winds will gradually increase Thursday night as our coastal storm begins to form. Winds will gust up to 35 mph during this time period. Then from Friday into Friday night, especially in the afternoon and evening, winds are forecast to gust to as much as 65 mph as the coast and 60 mph inland. At least we're not on Cape Cod where winds may gust as much as 90 mph, which is hurricane-force! Due to these winds combined with falling snow, blizzard conditions are possible. As we get into the weekend, the winds will remain gusty up to 45 mph on Saturday and 35 mph on Sunday.
Coastal Flooding:
The latest threat is coastal flooding. Winds will mainly be coming out of the northeast, which would push the water toward Long Island instead of the Connecticut coast, but there may be more of an easterly component to the wind at times, which would lead to minor to moderate coastal flooding. There are four to five more high tide cycles where coastal flooding is possible: Friday night, midday Saturday, Saturday night, Sunday afternoon. and possibly even Sunday night. The biggest crest so far occurred midday Friday, and now the National Weather Service isn't expecting as severe of a crest in the future high tide cycles, which is some good news. There will still be minor flooding, however.
Please stay with Jackson's Weather through the extent of this storm. We'll have LIVE updates throughout the storm on Twitter (no account needed).