Bitter cold start to the day As of 5 AM Tuesday, the low temperatures ranged from -14° at Estcourt Station to +7° in Sanford, with temperatures in between. Even the offshore islands were flirting with 0°. Portland's record for the date was -14° set in 1902, and for Caribou, -16° in 1986. Thankfully, the breeze is light. The Arctic high over the region moves east in the morning, setting up a southerly flow that will modify temperatures over the next two days. Still, below-normal cold continues to be the trend over the weekend and into next week. Light snow overnight into Wednesday morning Tuesday 7 PM (00z Wednesday) to Wednesday 10 AM (15z) - A decaying warm front moving in from the west interacts with a weak area of low pressure offshore to give it a bit of life Tuesday evening. The southerly wind flow off 46° ocean gives the weak boundary some lift, which will bring some snow that may be locally heavy at times along the MidCoast and DownEast shorelines overnight and after sunrise on Wednesday.  A general 1-3" is expected for coastal Sagadahoc County up the coast to the east of Bangor, with locally higher amounts in the 4-5" range is possible by the time precipitation ends Wednesday morning. Inside runner for Wednesday afternoon into the eveningFor the new followers, a quick definition. An "inside runner" is a low-pressure area that tracks along the St. Lawrence River in Quebec. Perhaps the most famous recent inside runners were the twin January 2024 storms that caused widespread shoreline damage and wiped out winter that season with heavy rainfall. If it were an "outside runner", it would essentially be a NorEaster, with snow as the primary precipitation type. I would consider this inside runner to be on the lazy side. There is not much in the way of moisture with it, roughly ¼" of liquid equivalent for the south to ½-¾" for the north by the time it ends late Wednesday night. The "lazy" part of this is important because, where stronger storms better define precipitation type, systems like this one introduce variability. That may be the case here. Exhibit A, the European idea...  Wednesday 10 AM (15z) to Thursday 7 AM (12z) - The European model idea has been relatively consistent: low-level cold persists due to return flow from the Wednesday morning system feeding it. This brings the concept of more snow closer to the coast on Wednesday afternoon. As the system intensifies upon departure, the coastal front makes a greater intrusion. This brings rain to the coast and perhaps a light junky mix along the boundary over the coastal interior. Exhibit B, The NAM3...  Wednesday 10 AM (15z) to Thursday 7 AM (12z) - The NAM3 short-range idea is not as bullish on the cold hanging on at the lower level as it predicts a slightly stronger system upon arrival, along with a more southerly track. This would allow rain to work deeper into the interior. There is agreement that steady precipitation is on track to end late Wednesday evening over the south, west, and east, and around 1-2 AM over the north. The Quebec border region can expect snow showers into Thursday. With cold air working in on the backside of either solution, any liquid is likely to freeze as temperatures drop. Black ice is possible for the overnight travelers and the morning commute on Thursday.  The coastal front is always the wildcard, and it will do as it pleases, no matter what the models think. Wetter snow is likely along the cold side of the boundary. There could be a sharp gradient between those that receive a few inches of snow and those that receive none. Expect a smooth ride home for those traveling over the interior and for those who work along the coast and travel inland. This will be monitored and updated. A peaceful shoreline escape awaits, |
Mike Haggett
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