As the trough digs... A sharp, deep trough has developed to the south and has fired up low pressure that will head northeastward Sunday into Monday. I brought up the long-range outlook in Saturday's post, and looking at forecast trends, these troughs over the east will be the norm over the next couple of weeks at least. It's that time of the year where Old Man Winter will show himself across the hemisphere in the form of strong ridges and deep troughs that breed strong storms. Rainy and breezy through Monday Sunday Noon (17z) to Tuesday 1 AM (06z)-- Cold air damming continues to be a concern over the interior areas through Sunday afternoon and into the wee hours of Monday morning. Pockets of freezing drizzle and freezing rain are locally possible as a warm front builds in from the south during the day and into the overnight. As the region sits in the warm sector after the warm front passes north, areas of fog are likely to break out where there is snowpack, reducing visibility. The mist will help ripen the snowpack, allowing for melting as rain moves in on Monday. Rain could be heavy at times and may contain a rumble of thunder as it passes to the east. The faucet shuts down from southwest to northeast Monday afternoon into the evening, ending over the north soon after midnight Tuesday.  A strong low-level jet will assist in throwing rain against the mountains, bringing the most rainfall to that region. With the ripened snowpack, the melting will add to the liquid runoff and could bring localized flooding to the small rivers, brooks, and streams. There is a limited threat of ice jams on the waterways well inland. The dew points are expected to drop to around freezing on Tuesday, which will slow or stop the melting temporarily. Those will rise again as rain re-enters the region for New Year’s Day.  The one thing that cold air damming is good for is cutting down on the wind, as it acts as an inversion. While the low-level jet at roughly 2500’ could produce wind speeds at 60-80 knots, the cold at the surface acts as a cap to keep the strong gusts aloft. The shorelines are exposed to the higher speeds given the warmth of the ocean, and that is where gusts could reach 30-40 mph as the heavier rain moves through the region Monday. Once the rain shuts off, the wind threat drops along with it. Given the state of the power grid, isolated power outages are possible along the coastline, with MidCoast and DownEast areas seeing a better chance for it. Another round of rain to start the year New Year’s Eve celebrations should be a dry affair across much of the region, with the possible exception of southwestern areas by the time of the ball drop. It appears to be seasonably chilly away from the shorelines by the midnight hour. Southwestern areas could see rain showers with the chance of freezing rain away from the shorelines heading into the wee hours of New Year’s Day. An east-southeast wind flow may make the outdoor celebrations a bit raw for the southern coastal communities. Expect fine-tuning on the forecast, and stay tuned.  The rain moving in Sunday into Monday appears to be the wetter of the two systems, but by the time the rain shuts off on Thursday, a good portion of the state picks up 1”+ of rain with 2-3” possible for the higher terrain. While cold air storms back into the region Thursday, the rivers will need to be monitored for some minor flood potential through Friday. Temperature and outlook through SaturdayIn the wake of the midweek system, cold air settles back in. The ski hills begin to rebuild in the form of snow showers Thursday through Saturday. The next storm idea comes around the Monday January 7th timeframe, and perhaps another later in the week, and both could be snowy affairs. Stay tuned!  Check The PTW Weather Wall the morning |
Mike Haggett
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