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UPDATES AS OF 5AM THURSDAY:
Unfortunately, the models are still not an really any sort of agreement this morning, thus continuing to make this an extremely difficult forecast. We are standing with our forecast for now but will have an update at 3PM today. This storm is also now named Winter Storm Riley.
We're tracking what will become a multi-faceted coastal storm, which will impact the Northeast from Thursday night through this weekend in some way, bringing snow, rain, coastal flooding, damaging winds, and rough surf to parts of the Northeast. Riley, the name of this storm that is yet to develop, has been and still is very difficult to predict due to tremendous uncertainty and inconsistency among the model guidance, which is a great tool to use for forecasting. I came out with a general overview of the various threats this storm poses to the Northeast Thursday morning, but now I believe it is time to come up with an actual forecast. Please please please stay updated. I will keep the article up-to-date as we hopefully gain more confidence with this storm because this forecast is subject to change. All of the information I will present to you below are my current thoughts but understand this will change.
Current Alerts:
Flood Watch in effect from 6am Friday through 6am Saturday
High Wind Watch in effect from 7am Friday through 6am Saturday
Coastal Flood Advisory in effect from 10am through 1pm Friday
Timing:
Thursday: Rain moves in between 5 and 8pm
Thursday night: A steady light to moderate rain persist throughout the night
Friday: Rain is expected to changeover to snow midday (highly subject to change)
Friday night: Snow from the evening through early-Saturday morning
Temperatures:
Thursday: Highs in the mid 50s
Thursday night: Lows in the mid 30s
Friday: Dropping from the mid 30s to around freezing (as low as 29F)
Friday night: Hovering around freezing
Specific Threats:
Rain: Up to two inches through Friday morning before rain likely changes over to snow
Snow: Most uncertain but I'm thinking 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 power outages.
Coastal Flooding: Minor to moderate flooding expected
Discussion:
There are so many different components to this coastal storm that is making it so tough to forecast. A first area of low pressure currently over the Plains will track into the Great Lakes region through Thursday night. By this time period, our coastal storm will begin to develop and will rapidly strengthen as energy from the storm over the Great Lakes weakens and transfers to the coastal low. At first, pressures with this offshore low will be around 1000 millibars, which is not strong at all. By Friday night, this storm will "bomb out," thus making it a "bomb cyclone." Pressures will fall from 1000 mb Thursday night down to around 970 mb by Friday night. This would meet the criteria of a rapidly-intensfiying storm.
So why should I care about a strengthening storm? This soon-to-be powerful storm will determine all of our impacts. Let's first talk about the rain. Rain will move in Thursday evening and will continue throughout Thursday night. There will be a good deal of moisture streaming all the way up from the Caribbean, so there will be pockets of moderate to perhaps heavy rain at times into Friday morning. Therefore, between one and two inches of rain is expected to fall before the anticipated
changeover to heavy, wet snow on Friday. I stress the word, "anticipated," because snow is not guaranteed with this storm. This is when the models differ. The EURO (European) model is more bullish and happens to be the more accurate model. It shows a changeover to snow across our entire area by noon. This solution is very similar to the NAM (North American) model as well, which is actually has the snowiest solution. Meanwhile the GFS (American) model shows a warmer scenario throughout this entire event until a brief period of snow moves in Friday night. Based on this, I have to lean toward the EURO and the NAM models based on their accuracy this winter. Therefore, expect rain to start the day Friday but then the snow to arrive during the midday hours. Specifically, I'm thinking that changeover will happen between 9am and 3pm from northwest to southeast. We may also be in a very favorable spot for snow and heavy snow at that, just north of the closed-off upper-level low pressure, as shown below. Once the snow begins, it likely won't stop. It will persist through much of Friday night before coming to an end early-Saturday morning.
That leads me to talk about the winds. I think the wind will be the biggest threat with this storm. There is a very reasonable chance the coast experiences wind gusts up to 60 mph along the coast and up to 55 mph inland Friday into Friday night. So with these winds combined with falling snow, blizzard conditions are possible Friday afternoon and evening. Those winds will also persist into the weekend with gusts up to 35-45 mph. This February was the wettest February on record in our area with about 6.5 inches of precipitation recorded. Therefore, the ground is super saturated and the heavy rain will make the ground even softer. Once those winds kick in and heavy snow, it will be fairly easy for trees to be knocked down, allowing for the threat for power outages.
Lastly, there is the concern for coastal flooding. Winds will mainly be out of the northeast from this coastal storm or nor'easter, so that will push the water toward Long Island. There will be a more easterly component to the wind at times, however, so the water may pile up along the coast, allowing for minor to moderate flooding, as shown on this forecast tide graph below for Bridgeport. There will also be higher than normal tides due to the high moon, so that will also make the situation worse. There will be four rounds of high tide that may lead to flooding, which will be between Thursday evening and midday Saturday.
Last but not least: the dreaded snowfall forecast. This is a very hard forecast to make because it depends on when exactly the rain will changeover to snow. What is pretty certain is that this snow will be wet and heavy. As of now, I'm thinking most areas receive between three and six inches of snow. The best chance for around half a foot is inland, especially north of Danbury. The NAM model is forecasting a widespread foot of snow. While that solution is unlikely, it doesn't mean that won't happen. Stay tuned to Jackson's Weather as this forecast will likely change.
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