Currently: A cold front, currently moving to near State College, PA, will bring a line of showers with it, then rapidly cooling weather conditions.
Tonight: Precipitation seems to be taking its time advancing eastward. So later start times are being incorporated into this forecast. Cold air will rapidly move in once the precipitation commences. As far as any changeover to snow is concerned, I will keep any mention of snow out of the forecast south of I 84. North of I 84, some flurries or even a burst of snow is possible as the precipitation comes to an end. No real accumulations are expected, but it wouldn't be a shock to get some coatings on car tops, especially in the highest elevations. At any rate, it will rapidly turn colder and windier tonight. Cold air rushes in after the precipitation ends. The NAM guidance was generally followed for its higher resolution and is generally a bit cooler than the GFS. Expect lows generally near 30 degrees.
Tomorrow: Sunny, windy, and much colder. A couple of old-school forecasting rules conflict each other tomorrow. The first rule is that when temperature guidance is in perfect agreement in the very short term, you don't buck the trend. However, the second rule is that model guidance is often way too warm on sunny days with strong cold air advection. For now, I'll go close to the guidance and accept it. However, if I am off, I will likely be too warm. So I'll go with highs near 40 degrees. It will feel even colder, as winds will gust in the 35-40 MPH range.
Tomorrow Night/Sat: The coldest air mass of the season settles into the region. At least the northern half of the state will make it into the teens. I am a little torn on what to do with temperatures tomorrow night. At the current time, I'll go close to or a touch warmer than guidance. I think guidance dies the winds off too fast and decouples us too fast, resulting in temperatures colder than reality. However, I could be very wrong here and if winds die down early, my forecast lows from the upper teens to the mid 20s (except upper 20s in New London County) could be 3 to 5 degrees too warm. Saturday will be sunny but chilly. With high pressure overhead, I see no reason to make any changes to guidance, which is in excellent agreement. Highs should be in the low 40s.
Long Term (Sunday and beyond): Most of the energy on the long term portion of this forecast will be focused on the storm threat for Tuesday. Before that, expect generally moderating temperatures for Sunday and Monday, as high pressure gradually pushes offshore. Sunday should be the warmest day, as colder air filters in for Monday, due to increasing cloudiness and a cold frontal approach.
Now, for the Tuesday system... "Foreign guidance" Tracks the low pressure system west of the area Tuesday, which would make it mainly a rain event, with some snow at the end, and yes, accumulations possible. American guidance has the storm significantly further east and would result in an all-snow solution for the area. With the depth of the cold air coming in, an the strength of the high pressure system to our north, and my personal belief that the lobe of high pressure depicted by the GFS over Ontario is real, I am going to go with the colder solutions. Therefore, I think Tuesday will have accumulating snow over the area. It seems like one way or another, the area will get at least a light accumulation. All guidance, even the foreign guidance, trended east some today. If today's trends continue, a significant snowstorm may in fact be realized. I don't personally like forecasting a significant snowfall in November 5 days out. However, this is not your run of the mill November air mass. The cold air coming in during and after the next storm threat is significantly deeper and colder than the air mass coming in tonight! Now, if I'm wrong and the storm does track to the west, accumulations would be significantly less. However, even in that scenario, I think most would still see a light accumulation.
Based on the above, and the assumption that there will be at least a little snowcover, and add to that the fact that models notoriously overestimate temperatures on strong cold air advection regimes this far out, I have significantly adjusted temperatures lower than guidance throughout the long term, with the exception being Sunday, since we're ahead of the cold front on Southwesterly winds. This will be a historic cold air mass for the time of year. In fact, looking up climatological records across the northeast reveals that air this cold has not been seen in these parts in November since 1875, and even that was more toward the end of the month! We really are in uncharted territory here! So now I'll list the high temperatures to expect across the area during the long term:
Sunday: Low 50s
Tuesday: around freezing
Wednesday: near 30, but warmer in the CT Valley, maybe 33 or so
Thursday: Mid to upper 30s, but cooler in the NW hills, (33 or so there)
Looking out into the longer range, the mean pattern of a trough in the east and ridge in the west looks to continue as far out as I can see. Therefore, expect below to much below normal temperatures to continue. However, just because it's ludicrous to expect this kind of cold to continue, I also wouldn't look for it to be consistently as cold as it will be this coming week!
Now let's take a look at some weather systems to affect the area in the coming week. We'll do something a little different today. Since tonight's cold front is imminent and precipitation is not that impressive, we'll focus on Saturday morning's lows and the Tuesday storm. Regarding Saturday morning, note that the GFS is "only" showing CT to get into the 20s, with teens extending into W MA. However, these maps typically verify too warm on clear mornings. So expect at least the northern half of CT to be in the teens!