Currently: Strong (1042) high pressure was located right about over Dulles Airport. This is keeping fair weather in place across our area.
For tonight, this is a good radiative night, and as such, temperatures will not be uniform. With nearly no wind, expect big differences between the urban corridor and outlying areas. We won't radiate to full maximum potential, because high clouds will increase toward morning. However, still expect a big range in temperatures, from the upper teens to the upper 20s. Some places along the SE coast may not get below 30.
Tomorrow: Precipitation arrives in the mid to late afternoon hours, from W to E. With warmer air rapidly filling in and daytime arrival of precipitation, this should be just light plain rain everywhere. However, it will be a chilly rain. With low dew points to start, I'll go a few degrees below all temperature guidance and call for highs in the low 40s.
Tomorrow Night/Sat: Most of the steadiest and heaviest rain should end by dawn on Saturday. However, it will largely be a cloudy day and a brief rain shower is possible at any time, with a better chance for a quick round of showers later in the afternoon. Although it will not be cold, I'll go a couple degrees cooler than all guidance due to clouds and precipitation. Even so, temperatures should rise to near 50 degrees.
Long Term (Sunday through most of next week); The main focus of the long term period revolves around a storm system slated for later Monday into part of Tuesday. This storm should bring wintry weather to all of the state, with an emphasis on NW areas.
First, for Sunday, The GFS, as it has done recently in events like this, refuses to believe there is strong cold air advection occurring, despite it showing NW winds gusting to 35 MPH. Therefore, I'll undercut its max temperatures by 3 to 5 degrees. This results in high temperatures in the mid 40s.
For Monday, clouds will increase, but the day should be dry. Any precipitation from the next system should hold off until nighttime. Guidance temperatures do not look too bad. Highs should be in the mid to upper 30s.
Now, for the next storm threat.... models are coming into a bit better agreement with this system, but still have their differences. The GFS is playing into its usual bias of kicking the cold air out too quickly. After reviewing all available data, the best forecast I can come up with at this time would be for a burst of snow to develop everywhere Monday night. That snow will then quickly change to rain along the south coast, but sleet and freezing rain elsewhere. Significant accumulations of ice are possible from Route 84 northward, with accumulations of lesser impact down to about the Merritt Parkway. Stay tuned, as updates could be forthcoming to refine this thiking. Precipitation then tapers off during the day on Tuesday. In far NE CT, a band of snow showers or squalls is possible later in the day, possibly with coatings. With the GFS tendency to scour out the surface cold too fast, I'll undercut its guidance by a few degrees. This results in high temperatures in the mid 40s on Tuesday.
For Wednesday, very cold air will move in around the back side of the low. With a breeze, high temperatures will only be around 30 and feel even colder! More of the same is expected Thursday next week, with highs only in the upper 20s. I undercut temperature guidance a few degrees both days, as temperature guidance does not do well with strong cold air advection that far out.
Looking into the longer range, the pattern continues to look very wintry, with storm threats just before and just after Christmas. The storm just before Christmas happens to look extremely potent. Of course, we're a long way out and things can (and will) change, but the pattern definitely seems to offer plenty of winter weather chances in the long range, as of this writing!
Now, let's take a look at some of the weather systems slated to affect our area in the upcoming week. We'll start with tomorrow evening's system, since that is first up. This map, valid Friday night at midnight, already shows light rain falling across the state, with heavier rain getting ready to move in from the south.