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Our weak snowmaker slides to the east Sunday morning, tapering off precipitation from southwest to northeast by midday. Snow showers are expected to continue in the mountains through this evening, bringing some light additional accumulations there. Temperatures are expected to rise above freezing over the south and east, quickly melting what snow fell. Expect the northwest wind to pick up a bit and add a bit of bite to the air as the storm exits Sunday afternoon. For more short term details, check the PTW Weather Wall. Buckle up for a rough week I am not one to jump on the hype train with storms very easily. A busted forecast from around this time 13 years ago irritated me enough to begin my meteorological pursuit of understanding. Since then, I continue to be a student studying the atmosphere and how forecast guidance interprets it. There are times when patience is demanded due to model disagreement, and then there are times when the pattern sets up in a way that advance notice needs to be sent out for folks to plan and prepare. Short term memory refers to the December 18, 2023 storm that brought historic flooding over parts of western Maine and thousands of power outages around the region. While I am not going to predict that kind of outcome here at this point, folks that weathered through that should keep that in mind in preparation for this one. There are some strong similarities of that storm in play here which should be respected. The table setter Monday 4 PM (21z) to Wednesday 7 AM (12z) – A warm front works to muscle its way into the state from the southwest later in the day Monday into Tuesday. With all the cold air around, it will meet resistance as there is a strong signal for cold air damming. The idea at this point is for 1-3” of snow to fall over southwestern areas Monday night into early Tuesday. While warm air intrudes aloft, cold air at the surface could bring pockets of patchy freezing drizzle or rain over interior areas Tuesday into early Wednesday. While there is not much in the way of liquid equivalent precipitation to speak of at ± ¼”, it could be enough to ice up cold windshields and untreated surfaces. As the storm to the south gets better organized and heads north, warm air washes out the cold at the surface, and the precipitation turns to all liquid form and will melt what ice developed. Heavy rain, strong wind, and shoreline implications Monday 1 PM (18z) to Thursday 10 AM (15z) – A look at precipitable water values (moisture in the air column) in the eyes of the European deterministic run from Saturday night. With the advancement of the warm front entering the region Monday night, the region sits in the warm sector on Tuesday. Moisture from the south surges to the northeast Wednesday morning as the trough to the west drives down to the Gulf of Mexico. The stream of moisture depicted here is roughly around normal for July but runs between 300-400% of that for December. The stream has an atmospheric river flair to it, and this is similar to the storm the region experienced a year ago.  Tuesday 7 PM (00z Wednesday) to Thursday 10 AM (15z) – An area of low pressure forms along the long wave frontal boundary and intensifies as it heads north through central New England. The forecast track on this continues to move westward to this point, which if that trend continues, would guarantee a heavy rain event from the high hilltops to sea level, as the European model depicts here. Rain could be heavy at times, and there is also the risk of embedded thunderstorms and a damaging downdraft wind component within them. While I am showing one solution here, it’s important to note that there is room for changes, and the forecast will be fine-tuned.  The general idea is for a 2”+ rain event over much of the state. A more westward track could raise those amounts and less with a more easterly track.  The Weather Prediction Center has already flagged the eastern half of New England in the slight risk of flash flood potential in combination with the heavy rain and the likelihood of efficient snowmelt. A rough guesstimate from what data I’ve eyeballed indicates there is roughly 2-3” of water locked into the snowpack, which, when melted, will add to the amount of water the sky provides. With frozen ground, that water is headed for brooks, rivers, streams, and flood-prone basements. Driveway and trail washouts are possible, along with urban street flooding. We could see a few roads wash out if the forecast trend continues.  Wednesday 7 AM (12z) to Thursday 10 AM (15z) – A look at the low level jet in the eyes of the GFS model from Saturday night indicates the risk of hurricane force wind speeds at roughly 2000 feet. This is concerning for power outages as heavy rain and thunderstorms assist in bringing strong wind to the surface. The shorelines and higher elevations run the greater risk. A word to the wise… if you lost power in either the December 18, 2023 storm or the twin January storms from earlier this year, make preparations to lose it again, and keep in mind that you could be out for days. Track of the storm will dictate the overall impact and outcome for the wind and will be fine tuned.  Wednesday 10 AM (15z) to Friday 7 AM (12z) – The shorelines are likely to face a beating with the storm. A full moon is on the way next Sunday (December 15th), and the astronomical tides creep up during the week. Early estimates on seas range from 8-11 footers south to 13-18 feet DownEast and those will face revision. Beach erosion and splash over are likely, with storm surge and coastal flooding implications to be determined as timing is key there. Stay tuned for updates! Make it routine to check the PTW Weather Wall for updates Appreciation for financial help to keep the coffee pot going, help me pay the bills, and train future forecasters Always have MULTIPLE ways to receive weather alerts. Stay aware, stay on alert, and stay safe. - Mike PRINT MEDIA: Feel free to quote and cite my work here for your stories. Please give me the professional courtesy of knowing that you are referencing my material so I can read your final product and acknowledge it on my media and link it on the PTW IN MEDIA page here on the website. Feel free to send me a message via the Facebook page or Twitter (X) to get my phone number if necessary. Thank you! NOTE: The forecast information depicted on this platform is for general information purposes only for the public and is not designed or intended for commercial use. For those seeking pinpoint weather information for business operations, you should use a private sector source. For information about where to find commercial forecasters to assist your business, please message me and I will be happy to help you. |
Mike Haggett
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