Tuesday Night Into Wednesday Morning
Looking at short term guidance shown above, it appears the main threat for icing will be across the western foothills through southern Aroostook county. The timeline for the threat to end will be early morning for the west and by mid-morning for the east. As the coastal low intensifies and enters into the Gulf of Maine is where the forecast turns complicated.
For those of you who took the time to read through my update from yesterday. I mentioned the fine line between forecasting sleet and freezing rain.
Here is an example of two SKEW-T model forecast images from the NAM guidance from earlier to this morning. Both models accurately show the mid-level warm air inversion which begins at roughly 20,000 feet above ground level then maxes out in temperature between 7,500 – 6,500 feet above ground level before sharply turning back to below freezing by the time the precipitation reaches the ground.
At first glance, it would appear that the thermal profiles are almost identical. The subtle difference is the freezing rain profile has a few extra feet of above freezing temperatures to work with, and is a shade warmer before it reaches the surface, and that is all the difference. This is the fine line here, and this is why it is extremely difficult to know for sure exactly how this will play out away from the shorelines of the state tonight. What is even more trying with this forecast is these two images are within a handful of miles of each other based in the western mountains.
Like an engine, there are many moving parts. Same rule applies to weather. There are a lot of moving parts in the atmosphere. Where you may read a forecast calling for sleet, understand that if the outcome is freezing rain, it was caused due to a whisker warmer temperatures aloft, and a few extra feet of warmer air to work with.
No Changes To Snowfall Idea
Based on current trends through Tuesday, I see no reason to alter this snowfall idea. As I mentioned in the previous update, sleet and freezing rain may knock these numbers down an inch or two away from the shorelines, but it looks good for the mountains on north.
Be advised for coastal areas, many are under wind advisories. Check with your local NWS office for the latest bulletins on this storm. Links are provided below.
The Year Off To Typical Start Wednesday Onward
The timeline for precipitation to end over the state appears to be on track, as I posted in the previous update. Steady wintry elements end over southern areas by around 7 AM, central Maine sees the tapering off by around 9 AM, and the last of it exits northern Maine just after noon.
Southern and eastern areas have the best chance for sun as the morning turns into the afternoon. Highs for the day range just below freezing for the crown to the mid to upper 40s for coastal areas. An occluded frontal boundary arrives late afternoon into the early evening that may spin off a snow shower north or a rain shower south and behind it, the wind picks up heading into the morning on Thursday.
Back To The Freezer Heading Into The Weekend
As the storm pulls to the northeast and intensifies, westerly winds begin to crank up as a strong area of high pressure moves southeast. Temperatures will struggle to make any headway from the overnight lows. Southwest shoreline areas may come close to 30°, but that appears to be about it. The wind subsides toward early evening. Friday at this point appears cooler than Thursday with the mercury having difficulty reaching the mid 20s for the shorelines and single digits to teens appear plentiful for the north and mountains.
A Look At The Weekend
A departing coastal low well offshore of the region Friday drags in even colder air for the region for Saturday. A bit early to tell if warnings or advisories for the windchill will be needed, but temperatures appear to be in that ballpark idea. Many areas of the mountains and north start the day below zero, and some of those same areas may struggle to get to zero during the day. Single digits / teens are likely to be the highs for the south and east.
While arctic high pressure appears to be in control for the northeast as well as most of the top two thirds of North America, a storm appears to form over the southeast and begin to track northeastward during the day on Saturday. At this point, the storm stays out to sea where southern, western and northern areas escape it. The question remains if eastern areas get in on the action. At this point, a chance for snow for coastal Washington county appears possible.
~ Mike Haggett
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Special thanks to Tropical Tidbits and Pivotal Weather for their written permission to use their graphics in this post. Use of WeatherTAP images used within their written permitted terms of media use policy. Additional forecast information supplied by the National Weather Service, WeatherBELL Analytics and AccuWeather Professional.
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