This winter’s outlook is the hardest one I’ve had to work out out of the last 3 or 4. There are factors that support different outcomes, although they do tend to appear to lean in a particular direction. To start, I’ve often mentioned that the weather pattern from late October and especially November can be a good indicator of the pattern for the upcoming winter, and in recent years the correlation of mild November to mild winter and cold November to cold winter has been pretty solid (last year being an exception). This November (with a few days left) is running up to a few degrees colder than normal so that would support a colder winter. One missing factor is an influence of either El Nino or La Nina, as we are going to sit in basically neutral ENSO territory. This tends to limit the activity in the subtropical jet stream, often the fuel for winter storms. However, limited activity still leaves the door open for some events to occur. Factors that support colder and/or snowy weather include solar minimum, which is very low sunspot activity, a large area of warmer than average water in the northeastern Pacific which tends to promote high pressure ridging in the western US and a colder trough further east, some warmer water in the northern Atlantic which can help promote high pressure there and induce a blocking pattern, early season rapidly advanced snowcover in Siberia and Canada which builds a cold reservoir, and lower than average sea ice in the Arctic which tends to warm the polar region and send lobes of colder air southward. Also watching a somewhat persistent tendency for the western Indian Ocean to be stormy while the east is rather dry, and this will impact one of the wildcard indices, MJO, which played havoc with last year’s forecast, even though many factors were different, and could very well do so again. You’ll hear that talked about during the season in blog discussions and comments. Another wildcard for the upcoming winter is the possibility of a sudden stratospheric warming event, one that is often forecast but does not always behave as forecast. This event can trigger polar vortex disruption as well and send lobes of much colder air southward. This does not always mean your particular region is going to end up in one of them, as there can be a misconception that this event means cold/stormy everywhere. So this and the MJO lurk like 2 atmospheric and oceanic bullies waiting to kick all the pieces around on your board game. How will it impact the winter forecast below? Time will tell. *** It’s important for me to note here that the biggest wild card to me is the stratospheric warming event and its timing and impact, which could essentially result in nearly a reversal of the expected January & later winter patterns, as what I have noted for February could occur earlier, and then a pattern similar to what I describe for January could occur coming out of that later in the winter. So with lower confidence than I’ve had the last few years, here’s an attempt at a month-by-month breakdown and seasonal overview of what I think is most likely for December 2019 until late March 2020.

DECEMBER
Making a strong case for the “as goes November, so goes the winter” correlation, the pattern for December looks like it wants to hold onto a lot of what November showed us, a lot of chill, a few storm events, but not persistently unsettled. But there is also a little bit of “remember October” in this pattern too, with the tendency for a ridge in the Southeast to want to be there at times. For New England, this pattern would likely result in regular passages of disturbances carrying Pacific moisture across the country but lacking re-energizing from the Gulf of Mexico, and this time with a more significant reservoir of cold air just to the north to either work with or pull down into the region after passage, depending on storm track details. A little more Southeast ridge, and we see a longer mild spell with shorter cold, while a little less Southeast ridge would lead to a more northwesterly flow and colder air more of the time here. We should see a bit of both, with the second scenario being slightly dominant. Something to watch in a pattern like this is the ability of a boundary to set-up west-to-east, parallel to the upper level flow, which can lead to larger areas of unsettled weather, even without a strong storm. This makes forecasting precipitation a little difficult, because I’d want to lean drier due to less subtropical moisture, but closer to normal because of the activity in the polar jet stream. And then you have the question of whether or not your precipitation episodes time with colder air (for frozen precipitation) or milder air (for rain). Coming out of the gate somewhat uncertain is not a great sign for forecasting deeper into the winter, but it is what it is. I’m going to rely on an old friend, “pattern persistence”, and go with a combination of weather patterns we saw progressing through the autumn.
Temperature: Slightly below normal as cold shots slightly outweigh milder interludes.
Precipitation: Slightly above normal, relying on one elongated boundary weather event to push totals up to achieve this.
Snow: Slightly above normal (but will need good timing of moisture & cold air to achieve this).

JANUARY
The changes in the large scale impacts talked above will be few, but subtle changes in things such as the wet west / dry east Indian Ocean pattern and the location of the warmer water in the northeastern Pacific and North Atlantic, as well as impacts from the possible SST warming event will all play roles. Since these are uncertain, the forecast itself carries a high degree of uncertainty, so I’ll have to rely on a little bit of climate modeling, some of which has indicated a relaxation of the Indian Ocean situation with a little less activity west and more east, but just a lesser degree of what is going on there now. This could allow MJO’s influence to become more prominent. Time the favorable-for-snow phases with some cold air and perhaps a temporarily active southern jet stream and we could grab ourselves a classic snowstorm. I think that’s going to be hard to do and we’ll have to rely on polar jet clipper type systems at least to start out the new year. Perhaps with time some things come together for a larger system from the south, which could just as easily track further west and be a bigger rain producer as it could be an offshore classic snowstorm. It’s a gamble and a guess with so many factors that can pull one way or another this particular season. I think if we end up with a snowy month this winter, this is going to be the one. ** See note about January / February patterns at the end of the discussion above. **
Temperature: Near to below normal.
Precipitation: Near normal.
Snow: Slightly above normal.

FEBRUARY
This is the month that I think things can come together for the greatest chance of blocking, because I feel that when all is said and done our SST event will be delayed and locations of warm waters in the Pacific and Atlantic will combine to produce our coldest weather, relative to normal. I’m also still relying on a quiet southern jet stream and dominant polar jet stream, which itself may end up suppressed to the south due to stronger blocking. This would end up a colder, drier pattern if it came together that way. Very minor wildcard is that we have seen some climate model indications that our ENSO neutral conditions may actually dip into weak La Nina territory by late winter.
** See note about January / February patterns at the end of the discussion above. **
Temperature: Below normal.
Precipitation: Below normal.
Snow: Slightly below normal.

MARCH
Plenty of lingering snow across Canada and the possible emergence of weak La Nina, and some persistence of the late winter pattern would lead me to think the March pattern would be chilly but on the drier side of normal, at least to start out. But this part of the forecast is worth very little more than just tossing darts and is really just a stretch / educated guess.
Temperature: Below normal early month, near normal later month.
Precipitation: Below normal.
Snow: Below normal.

WINTER SEASON OVERALL
Temperature: Slightly below normal.
Precipitation: Slightly below normal.
Snow: Near normal.
-Boston 40-50 inches
-Worcester 50-60 inches
-Providence 35-45 inches
-Hartford 45-55 inches