- Winter storm to affect New Jersey Saturday night into Sunday morning
- Mixed bag of precipitation with snow, sleet, freezing rain, winds and flooding rain
- Travel impacts and power outages likely in northern, possibly central New Jersey
- Arctic cold ushered in behind the storm on Sunday, sub-zero wind chills
Our weekend winter storm has taken shape as of Friday evening, currently centered in Oklahoma and sliding east towards the lower Ohio Valley. The sub-tropical jet stream is supplying copious moisture, allowing our Saturday night storm to tap both the Pacific Ocean and Gulf of Mexico as sources for the rain, sleet, and snow it will spread across the state Saturday night. Our Ohio Valley low will pull this moisture plume across the mid-Atlantic and spread up to 2 inches of liquid equivalent in various forms beginning late Saturday afternoon.
Overnight Friday temperatures will slip back into the brisk 20s, with mostly cloudy skies. High clouds are already filtering in from the west and will thicken throughout the day Saturday. Precipitation begins mid to late afternoon and falls in earnest beginning around 6 p.m. I think south of 195 there could be a quick burst of snow capable of putting down a quick coating to an inch, but the transition to plain rain will be swift. Furthest north, in the elevated portions of northern New Jersey, enough cold air may hang in to keep precipitation as snow and sleet through the duration of the event. It’s the part of the state in the middle that is tricky to call as to when snow changes to sleet or freezing rain, and how much accumulates before that transition occurs. It’s not surprising, this is the traditional historic dividing line between snow and “other” precipitation.
As the night goes on, the snow/mix line will creep north. I am most concerned about the icing potential between the Routes 1 and 78 corridors. For the duration of this storm, as well as immediately in its wake, a very cold Arctic air mass lingers just to our north. Cold air sinks, and so I think it will be pretty difficult for this weak surface low to pull enough warm air to scour out sub-freezing temperatures in the lowest layers of the atmosphere. That spells the recipe for a prolonged period of sleet or freezing rain. The former occurs if the layer of cold air is deeper. If there is a very shallow layer of air just above the surface, that’s the recipe for freezing rain. I think there could be a stripe of ice accrual somewhere in central or northern NJ with ice accrual of a quarter inch, which is when you start seeing power outages become more than sporadic.
Further south, plain rain can cause its own problems. The ground is frozen solid across much of the state, and so water will runoff and flood in low lying areas. Look for ponding on roads and creek flooding, with up to 2 inches of rain falling over a 12 hour period.
As the night progresses, the snow/mix line will eventually reach the point where it goes no further into that Arctic air to the north. This probably occurs along or just north of the Route 80 corridor. By daybreak the back edge of precipitation is approaching from the west. A brief burst of snow could herald the leading edge of this cold air, which will spill across the state in the wake of the storm. It crashes in quickly, and any water or slush is liable to a “flash freeze,” creating the potential for the roads to ice up, even as skies clear and conditions look improved. Winds will gust to 30 mph in places, and as temperatures tumble throughout the day, the wind chill will fall below zero before the sun goes down. Sunday night will be painfully cold, with widespread single digit readings, and wind chill values of warning criteria. Monday won’t be any better, with highs only climbing into the teens.
Snow and sleet should accumulate up to 12 inches in the northernmost parts of the state. Look for 3-6 inches in central New Jersey and the northern parts of Philadelphia and New York. If snow transitions to plain rain overnight, you’re likely to wake up to some of this washed away. Ice accrual could happen anywhere, but I think it’s most likely somewhere in Hunterdon and Somerset Counties, or between Routes 78 and 80.
Whatever you have in your driveway or sidewalk Sunday morning, clear it right away. Once the cold air moves in, it will turn into a block of ice and really tough to shovel! Also, since the weather will be fair Saturday morning and most of the afternoon, make sure you’re prepared to lose power for a day or two. I don’t think we will see anything like the outages last March, but even sporadic power loss could affect you, and with dangerous cold in the wake of the storm it’d be best to not leave yourself vulnerable to unpreparedness.