Snow changes to rain, Windy afternoon

10:10 AM, Dec 21, 2012   |    comments
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"________________________"-Insert unoriginal joke about the Mayans being wrong here.

Ok moving on.

Today: Messy morning out there with coastal rain, inland snow and a mix in between. As promised, however, the rain/snow line is making a strong march to the northwest and all but the mountains will be changed over to rain by noon. (The reason? This storm is an inside runner, tracking to our west, which is allowing a strong southeast flow to develop. Southeast flow + water temperatures in the mid 40s=Rain FTW!) Through the afternoon the concerns will be heavy rain and very strong winds. There is an area of torrential rain just entering southern MA right now...that will get into Maine this afternoon and bring some downpours. I can't even rule out some thunderstorm activity as the atmosphere is warming SO rapidly that it will be able to support thunderstorms. (The mountains that hang on to snow will accumulate 3-6" by the way)

A more widespread concern: strong winds. The National Weather Service has issued a Wind Advisory for the entire coastline from Eastport down to Boston and there is a High Wind Watch for the Midcoast and Downeast, where winds will be even stronger. I expect the strongest wind gusts to arrive early this afternoon over southern coastal Maine, with gusts up to 50 MPH there. By later afternoon and early evening the axis of strongest winds will shift to the Midcoast and Downeast, wind gusts there could top 60 MPH. Generally speaking wind gusts over 50 MPH create some power outages, so I'd expect some this afternoon. The wind direction for those wondering will be east-southeast.

Tonight: Rain ends from southwest to northeast this evening as the low spins north. Southern Maine will see an end to the heavy precipitation by around dinner, but the Midcoast and Downeast will hang onto downpours through 10 PM. The last area to clear the storm out will be northern Maine where it will still be snow and sleet; they won't clear out until after midnight.

Saturday: The storm will be gone but still kind of with us (Sounds like a line from a Lifetime movie). What I mean is that the heavy precipitation will have passed but the low pressure system itself will continue to spin directly overhead in a weaker state. The presence of the low will mean mostly cloudy conditions statewide with scattered showers. The showers will be snow west of I-95 and mainly rain closer to the coast. The mountains could pick up another 1-2" of snow with these showers. Temperatures will top out in the low to mid 40s.

Sunday: The low finally lifts north, allowing for a mixture of sun and clouds with dry conditions. However, as the low moves out it will drag in some strong northwest winds. We could see gusts up to 40 MPH by Sunday afternoon, adding a bite to the air. The actual temperatures won't be too bad, in the low to mid 30s.

Monday: Mostly sunny but chilly. Highs only in the upper 20s to low 30s with a biting windchill.

Right now I'm keeping Christmas Day dry but a weak storm will be passing JUST to our south so I reserve the right to put some light snow in across southern zones if things change. Otherwise it's worth noting if you are heading anywhere south of Boston for the holiday. Not a big storm at all, just a 1-3" deal.

A much larger storm is being depicted by all major computer models on Thursday but of course it's too early to say if it'll be rain or snow. Nonetheless I ended up included in a classic "WSI nerd email thread" about that storm this morning. Enjoy:

Nerd 1: "I wouldn't get too excited for the storm next week yet.  12z ECWMF still has an inside runner.  Of
course you believe the GFS more.  Mean trough position has been too far W all along."

Nerd 2: "Use ensembles. You should know better than to use an op prog past 6 days out.

Sent from my iPhone"

Nerd 1: "00z ECMWF...low goes right over us.  Quick changeover.  You forget the SSTs are still in
the upper 40s in BOS Harbor as well.
If you note the 500 on the ECMWF, the upper low cuts off way W over TX and then
starts to lift NE.  That not a good mean trough position for a solid coastal storm snow
in SNE."

Welcome to my world's a scary place.

Twitter: @KeithCarsonWCSH


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