In Depth: Beyond the 10 Day

ROCHESTER, N.Y. (WHEC) — Here is the update to "Beyond the 10 Day" for Sunday December 26th. Currently across the United States, a trough is over the Western Us with a small ridge over the Eastern US. The jet stream is dipping into Southern California and into the Rockies before moving north through the Ohio river Valley and out over the Atlantic. Overall this has been much of the pattern so far this December, and it will continue through the end of the year before potential switch in the pattern occurs as we ring in 2022.

With that said above, not much is expected as we push through this week. No significant weather is on the way through the work week until we hit the new year. This week, troughing over the Western US will keep the storminess out West and ridging over the Eastern US will cause storms to move to our north. We do have a couple of chances for a wintry mix early this week but nothing significant is expected. Across North America, blocking over Greenland and Alaska will persist until we head towards the end of the week which is when things may turn active locally and when the shift in the overall pattern may take place. Ridging over Alaska, which has predominately been just to the south and west of Alaska, will begin to move north. This is significant because the northward advancement of this ridge will allow a trough to slide underneath and lock in the pattern once again. This pattern lock will be important in just a moment. This movement of the ridge over the Bering Strait will also help eject the trough, that has been stuck over the Western US, eastward towards the Eastern US and open the door for colder and stormier weather locally and across the Northeast. Also during this time, models are signaling a potential breakdown of the blocking over Greenland. There is inconsistency with this as GFS is showing a continuation of the blocking while the Euro breaks it down. Overall, the GFS has faired much better than the Euro in the medium range so far this season, which makes me favor the it slightly. It is also worth noting that the GFS does signal weaker blocking than what has occurred this month, but enough of a block to allow the cold to sit across the Northeast. What also leads me to lean more towards the GFS is the fact that the Euro has consistent cold for us locally without a block, which does not make too much sense dynamically. All these factors mentioned above will play into our storm chances as we enter the New Year and the month of January.

Our first time period to watch will come on New Years. At this moment, both models have winter outcomes for us locally. The Euro is a bit warmer with rain to start before a transition over to snow, while the GFS is all over a big snowstorm. Still too early, being 6-7 days away, to talk rain or snow but the dynamics right now look impressive. This first storm chance is a result of the trough over the Western US being ejected east. With that being said, there will be a lot of energy with it and the possibility of a big snowstorm does it exist. HOWEVER this does not mean there will be, but if everything over the next few days trends in the right direction then we are in play for it. Jet stream dynamics look good on this system with the main jet streak to our south and there is ensemble support at this moment. At the surface, I would like to see high pressure to the north come in a touch stronger than what is shown now, but not too strong as that will suppress it and keep everything south. This is one of, if not the best looks we have had so far this season. To note though, a few weeks ago we had a good look for some wintry weather the Tuesday before Christmas and what happened was a miss. The southern stream of energy out ran the northern stream of energy and we were left with partly cloudy skies. We will see what trends occur over the next few days, but the overall pattern looks good this morning. As I mentioned before, a trough will try and slide underneath the ridge over the Bering Strait and lock the pattern, this is important for our next storm chance later that week.

Our next storm chance will likely come towards the end of the first week of 2022. Models are signaling an area of low pressure moving into the Ohio River Valley and then either moving north or east once again. Track will obviously determine precipitation type, but the dynamics of the atmosphere will dictate the track. The pattern lock will be important. If the trough slides underneath the ridge then we will lock ourselves in for a cooler and stormier pattern for January. If not, then January has the potential to be a repeat of December. A lot of this will be determined by another atmospheric force known as the Madden-Julian Oscillation or MJO. This oscillation has 8 phases and has been locked in phase 7 since the start of December. This has been the dictator to our boring winter weather in December, but may make a switch towards phase 8 as we head into the new year. Phases 8,1, & 2 are colder phases during the Winter for the Eastern US and what you would want for increased snowier patterns locally. Phase 7, which we have been stuck in, is a much warmer outlook for the East with snow for the West. Forecasting for the MJO is difficult as the bulk of the oscillation occurs over the Pacific and Indian Oceans where there is little data being ingested and put into numerical modeling. With that said there is a lot of uncertainty of this phase shift in the MJO towards the new year, but the overall pattern in the upper levels does favor this shift. If the MJO does not shift, we will have our chances for snow, but prolonged cold across our region will be significantly hindered and will ultimately impact the rest of winter to come. With all that said our next update will come on Wednesday December 29th, and a better understanding of how those pieces will fall will likely occur.

Temperatures: Generally near or slightly above average before turning cooler late next week.

Precipitation: Slightly above average the next two weeks.

Time Periods to Watch:

Jan 1st-3rd: Low pressure tracking into the Ohio River Valley. Does it track north form there or along the East Coast? I’d like to see high pressure come in a bit stronger, but not too, to get a sure fire snow event. Right now, rain and snow on the table with breezy conditions.

Jan 7th-Jan 9th: Another potential low making its way into the Ohio River Valley. Track will determine precipitation type, but cold air likely available with the pattern potentially changing across the US.