2 storms Possible in the Near Term, First Arctic Outbreak Possible in the Long Term?

A very good evening to you from Southern Connecticut Weather!



Today was a picture perfect late fall day across the state of Connecticut, with highs topping out in the low to mid 60s along with mostly sunny skies and calm winds making for fabulous weather to be outside enjoying some of the last days of summerlike weather before we move into the winter season.

Three events highlight tonight’s forecast: A rainstorm encompassing parts of Thursday and Friday, another potential system for early next week, and a general turn towards much colder temperatures in the long range relative to normal. Let’s work through the forecast day by day, going more into depth into these events as they approach.

Tomorrow looks pleasant and uneventful, with high temperatures in the low to mid 60s expected along with building clouds ahead of Thursday’s rain. No precipitation is expected.

Now, we turn to the first of the three events highlighting the forecast: a rainstorm for parts of Thursday and Friday. All models are in agreement on the general track of the storm being it coming down from the lakes/upper Midwest on Thursday morning before transferring to a secondary low somewhere off the Northeastern coast on Thursday evening. Here’s an image from the NAM model showing the transfer in progress, notice the primary low over Western NY is still stronger than the secondary low forming just at the eastern tip of Long Island. 

This is keeping the precipitation concentrated towards the primary low, leaving our area in a dryslot between the two lows. The primary variable that will determine the amount of rain that we get will be where this transfer takes place; if it takes place south of us or further west, we can get stronger rains from the secondary since it will have taken over before it reaches our area, if it takes place to the north or east, we get rains from the primary before the transfer, and if it takes place right over us, we get little/nothing. As of now, the model seem to agree that option number one is out, which leaves us with either a transfer over our heads or one to our east. This makes a great deal of difference in the sensible weather. Right now, as seen above, the NAM model is showing the dryslot taking place over our area, leading to precipitation totals of generally less than a half an inch, as shown on the total precip map below. The NAM has agreement from the GFS model in this case, which also transfers right over the area.

On the other hand, we have the GGEM and the EURO models, both of which transfer the low further east than the GFS and NAM combo do, leading to less of a dryslot across the state and higher rainfall totals as a result, on the order of half an inch to an inch of rain being expected in total. Below is the total precip map from the GGEM, the EURO looks generally similar.

So, which camp is right? Both are perfectly valid meteorological solutions, but I’m inclined to side with the GGEM/EURO camp for two reasons. First, the NAM has a notorious bias towards being overamped in events, and usually places features too far north and west of where they actually occur. As a result, given this usual bias from the NAM and the fact that it is in this case the most NW of the models, we are inclined to toss it. We then have the GFS vs the EURO and GGEM, and given the various track records of the three models, I’d be much more inclined to side with the latter solution. As a result, we’re expecting .50-1” of rain for most of the state, although those amounts could and will be lower if a solution like the NAM or GFS verifies.  Higher totals are possible, but would require a more significant shift in modeling, which we are not expecting at this time considering the relative run to run consistency of the models and the fact that we are now less than 48 hours out.

So, as far as a timeline goes, rain looks to move in over the course of the morning to early afternoon on Thursday, and be generally light and showery and nature before increasing in intensity and coverage during the evening and overnight hours. Rain lessens throughout the day on Friday and departs during the mid day hours, bringing dramatically colder temperatures in it’s wake. It’s possible that we could see precipitation end as flurries/snowshowers in NW areas, but this is a low probability and any accumulations would be non-existent to minimal. Temps look to be below normal, in the low to mid 50s Thursday and mid 40s to lower 50s Friday, coldest in the NW hills.

Looking at next weekend, Saturday looks to be the nicer day of the two, with sunny skies and yet chilly temps, with highs 5 to 10 degrees below normal in the upper 40s. The next system in the pipeline approaches for Sunday, and has been all over the map in terms of model representations the last few days. Todays models show it as a weak northern stream system passing over our area that fails to capture with a southern stream system around the same time, but previous days had the two systems eventually phasing into a stronger coastal storm. Will go with a broadbrushed chance of rain from Sunday into Monday at this time, and will refine the forecast later in the week as models begin to hone in on a solution. Below is a representation of the event on todays 18z GFS, showing the strong storm to the south escaping out to sea and the weak northern stream wave that would be about to impact us.

Looking ahead in the pattern, signs are beginning to emerge of perhaps our first arctic blast of the season, as all modeling is developing a strong trough in the east in the extended forecast, opening the door for the conveyor belt of arctic air to begin to move it’s way southward and eastward. As with most cold shots, this one looks to begin and be strongest in the plains and Midwest before weakening as it moves east, but both the EURO and GFS show impressive anomalies in the ~10 day lead time. We’ve posted below several images images of the averaged temperature departure at 850mb(EURO) and surface(GFS) over a 5 day period from various models. The first, the GFS from day 6 to day 11, shows the train of cold air coming from western Canada down into the central US. Look a few days later, at day 8 to 13, and you can see the center of the cold air has moved east, bringing the colder departures into our region.

Here’s the same D6 image from the EURO model. It doesn’t run past 10 days, but we can see through it’s ensembles and the movement at d10 that it would progress the strongest anomalies east much like the GFS does.

As with most cold outbreaks, this one verbatim has one or two well below normal days, with more moderate, but still cold days on either side.  While it should go without saying that this is over a week out and models will continue to flip and flop, It’s also important to note that since normal temps are much higher in November than the average arctic outbreak in the winter months, the actual readings likely will not be as impressive compared to those seen later in the winter. It’s a sign of winter to come though in terms of the pattern setting up for those times when we do have colder climo, and will certainly feel quite chilly compared to what we’ve been seeing recently!

That just about does it for this update, so until next time, have a wonderful evening and thanks for reading Southern Connecticut Weather!
-SA