Currently: High pressure near Richmond, VA, is dominating our weather today. Yesterday's low pressure system that passed south of the area is well out to sea.
Tonight: Temperatures will probably settle close to, but perhaps a bit lower than guidance. This could be either because of early radiational cooling before clouds move in, or late evaporational cooling, as light rain moves in. There could be light rain toward morning in far SW CT. It should be noted that the NAM has nothing, while the GFS has measurable making it to the south coast. Because yesterday's event, also a southern scraper, was closer to what the GFS printed out than the NAM, I'll go with about an 80% GFS-based solution, so I'll go with chancey pops for Srn Fairfield County only toward dawn. For temperatures, I'll go with lows right around 40 degrees.
Tomorrow: If there is any measurable rain, it will be along the immediate S coast, think S of the Merritt Pkwy. It all ends by noon. Warmer air then moves in. Because of the potential for clouds to linger, I'll go just a smidge below guidance. So we'll go with highs in the upper 50s.
Tomorrow Night/Sat: The next wave of low pressure will approach the area. This one will have a significant amount more rain than its predecessor. Although light rain is possible at any time, steadier, heavier rain should wait until the 2nd half of Sat, and continue into the night. I like colder temps for Saturday than guidance is advertising, only because we usually stay colder than normal in this situation, both due to evaporational cooling and some in-situ CAD that usually develops. For these reasons, I'll take the coldest (NAM) guidance and then subtract 3 degrees from that. Highs should be near 50, but most places should probably end up on the lower end of that range.
Long Term (Sun and beyond): There is lots of uncertainty in this period, unfortunately. This can be seen by how model solutions change drastically from one run to the next.
First, for Sunday, forecast concerns revolve around how far N the warm front makes it. I hate to take the "cop-out" solution because realistically, it usually doesn't work out like that, but it is "the course of least regret" with regards to temps, in that the bust potential on either side is lower. Therefore, we'll run the warm front up to somewhere between the Merritt and I 84 (maybe thinking that the first elevated area can stop the Nwd progress of the front). The NAM holds the front much further S, not even clearing NYC, but it is very unreliable at this range. The GFS gets it up to about the Mass Pike, but tends to be overagressive at this range. So maybe my "preliminary location" won't be that bad after all. Some of these fronts have a very sharp gradient, so if I am off by only 30 miles (which is very little in medium-range meteorology), some folks will bust. I will try the best I can here and compromise the GFS and NAM, but go a bit closer to the GFS, given the NAM's unreliability at this range. This yields highs around 50 degrees, but closer to 55 in the I 91 corridor.
Now the second potential problem is precipitation chances. Most rain should taper off by dawn. After that, there's a slight chance of a pop-up shower at any time. With the cold frontal passage, there could also be a line of showers and thunderstorms late in the day and early in the evening.
For Monday thru Wednesday: An upper level low will affect the region. This upper level low will send little spokes of energy thru the area, that could produce showers at any time, although the vast majority of these three days should be dry. As far as temperatures, I'll go 1-3 degrees below guidance all three days, since upper levels are cold, and any time temperatures rise this should lead to the formation of showers. There may even be a precipitation type question with this. Anything that falls on Monday is rain. On Tuesday, there could be a mix with snow or sleet to I 84, and perhaps all the way to the coast on Wednesday.
Monday should also see gusty winds to 30-35 MPH. As for temperatures, look for highs in the mid to upper 50s Monday. upper 40s Tuesday, and only 40 to 45 Wednesday.
One more note about this period, there is a coastal low modeled to stay well south of the area on Wednesday. Most modeling is in agreement that this stays to our south. However, any shift of the upper level low out of the region faster than modeled could lead to this low coming further north than currently modeled, which would result in a rainier and windier solution than currently advertised. This is NOT currently forecast, but something to watch.
Thursday clears out with nicer weather moving in regardless. Guidance may be a degree or two too cold, given full sun. Highs should be 50-55, but could be warmer than that along I 91.
Now, let's take a look at some of the systems slated to affect our area in graphical form. I will show Saturday's system and Wednesday's potential (squashed) system. First, for Saturday: look at the swath of rain over NJ and PA, basically along I 80, headed toward the area. This image is valid late Saturday afternoon.