Tonight: As mentioned, expecting lots of clouds, but no precipitation. Models are in excellent agreement regarding temperatures, so a compromise forecast can be used. Therefore, will call for low temperatures from the low 40s to near 50 statewide. There is a small chance that someone in the far NW corner of the state could reach the upper 30s, especially if they can clear out for a few hours.
Tomorrow: A more potent upper level system will approach. This could provide a trigger for widely-scattered showers and thunderstorms to fire. To complicate matters, there could be something of a marine layer along the immediate coast. Marine layers tend to bring in cooler and more stable air into the area. Therefore, the chance of legitimate showers and thunderstorms should generally be north of the Merritt Parkway. South of there, in the marine layer, just a few sprinkles will be possible. As for temperatures, they should make a run for 70 in most of the state, but in the aforementioned marine layer, stay a bit cooler (mid to upper 60s) along the immediate coast. It should be noted that the freezing level is rather low. This would make it easier for any of the stronger cells to produce hail. Typically, these systems do not produce severe weather. But they can produce small hail. Under any of the stronger cells, typically what happens is, you can get some pea size hail and rapidly falling temperatures, so be aware of that!
Tomorrow night into Friday, as has been the theme this spring so far, we get brief shots of warmer weather that don't last very long, only to be replaced by atypical weather- more typical of late winter or very early spring. This appears to be the case again. A brief warm-up will occur tomorrow night into Friday as high pressure shifts offshore and sets up a return flow. Return flows typically pump warmer and sometimes more humid air into our area, depending on the source of the air mass. It will not be humid this time around, as has been the case this spring. Temperatures on Friday should top out generally in the 70-75 degree range. Friday's temperatures should be fairly uniform, since return flows produce more of an onshore flow, thus reducing potential high temperatures in that region.
Long Term: As we get into the long term period, all attention turns to a developing coastal storm. This discussion is going to read a lot more like a discussion you'd typically see in winter, minus any mention of snow, but this system resembles something you'd typically see in winter. There is actually much worse model agreement at this time than yesterday. To make matters worse, the models basically switched positions from 24 hours ago. Yesterday at this time, the ECMWF model was the most aggressive with the northward extent of the heaviest rain, while the GFS had little measurable precipitation reaching the state and the GGEM was somewhere in between. Today, it's the GFS that is very aggressive bringing the heavy rain and high winds further north, with the ECMWF bringing little affects to the state. The GGEM model being in between is actually the most consistent. At this time range, when there is very little model agreement, the general course of action is to go with the most consistent model and take a compromise. As I mentioned, the GGEM model has been the most consistent. What makes this a bit confusing is that the GGEM has far worse verification scores than the ECMWF or GFS, so it isn't easy to ride the GGEM. Historically, the ECMWF has been the best model with handling east coast systems. However, at least from what I have been able to assess, the ECMWF has been very unreliable since it was "upgraded". Therefore, with a high level of trepidation, I'll make my forecast fairly close to the GGEM. I should add that this forecast is subject to significant changes in the coming days.
So what does this all mean for sensible weather and affects from the coastal storm for Connecticut? For now, I think the "significant" affects of the storm are most probable from roughly I 84 on south. The immediate south coast may get it in on at least a period of heavier rain. With a pretty strong gradient in place, strong winds could also occur. Astronomical tides will be quite a bit higher than normal, so there is also a coastal flooding concern. All of this will need to be updated/refined later in the week.
After the coastal storm pulls out, it will actually meander offshore for several days. As it does so, it will spawn a "child" of sorts. This new low will strengthen quickly and try to move Northwestward. Depending on how far northwest it gets would determine whether or not appreciable rainfall makes it back into Connecticut early next week. Once again, areas further to the south would be favored.
Beyond that, it looks like a pattern resembling something you'd expect to see more this time of year takes shape. However, I'd like to caution that we've seen phantom "warm spring patterns" materialize on models around ten days out for the last six weeks or so, and besides infrequent, short-lived intrusions of warmer air, they have been mostly model hallucinations.
Here is a look at a forecast and expected conditions across the state from Saturday through next Wednesday.
Saturday: Cloudy with rain developing, especially south. Highs 60 to 65.
Sunday: Morning rain, especially south, then some clearing. Scattered showers and thunderstorms in the afternoon. Highs 65 to 70.
Monday: Mostly sunny, perhaps some increasing clouds late on the south coast. Highs around 70, cooler along the shore.
Tuesday: Increasing clouds. A chance of rain, especially south. Highs 65 to 70, warmest north.
Wednesday: Decreasing clouds. A chance of morning rain, especially south. Highs 70 to 75, warmest north.
We'll look at some graphical images now, to illustrate this forecast, but they will all be focused on the weekend coastal storm potential. We'll show you "The big Three" computer models, to illustrate the points I made in the discussion. First, here is the GFS model.
Anyway, that's all for now! Enjoy the rest of your week!