In Depth: Beyond the 10 Day

ROCHESTER, N.Y. (WHEC) — Welcome to the Wednesday, December 29th update for "Beyond the 10 Day" as we continue to try and find when Winter will make an appearance locally.

Currently across the United States a deep trough is located over the Western US with a weak ridge over the Eastern US, contributing to our mild weather locally.

Looking a little further out over North America and we continue to have ridging near Alaska and near Greenland which has contributed to the atmospheric block throughout the month of December and locked our mild pattern in place. Typically, a block over Greenland brings us cooler air locally, but due to the continuous troughing out west we have been stuck in a mild pattern as the Southeast Ridge has persisted. The good news is that things will change as we head into next week, but the bad news is that there remains uncertainty as to if the cold air will make it into the eastern half of the nation towards mid-January.

As we go through the rest of 2021, the mild weather will remain across the region with highs in the low and mid 40s before unsettled weather moves in for New Year’s weekend. We have continued to track this time period over the last couple of weeks for unsettled weather to move in during this time period which may have travel impacts. It is all but certain that we will see unsettled weather across the region, but uncertainty remains on what kind of precipitation type.

This is a complicated system as it will not be a two part storm. The first part comes on Saturday, and it does look almost certain at this moment that we will be on the milder side of things with scattered rain showers before a second area of low pressure tries to develop to the south.

This is where the uncertainty lies as it will matter significantly where this second low pressure tracks. This area of low pressure will slide to our south, but just how far south is the question. Temperatures behind a cold front will come crashing down enough for snow to fall, but will we see lake effect snow or widespread synoptic snow? If this area of low pressure hugs closer to the East Coast and near New York, NY then we will see a greater chance for snow accumulations and a greater chance for travel issues across the region on Sunday. If low pressure tracks south near the Delmarva, even with a hug along the coastline, it will be too far south for us to see widespread snow but lake effect will be possible.

Models continue to differ, the GFS is further south and less snow for us while the Euro remains north and a closer hug to the coast. Model spread continues on both ensemble switch each models showing the different solutions, but it does look like things will come to consensus near northern New Jersey.

With that said we will likely see some snow on Sunday, but overall our snow that comes out of this will be from some lake effect that sets up late Sunday and lasts into Tuesday morning. How much snow from that is in question, but just be prepared for some issues on the roads early next week.

As this system continues to bring impacts across the Eastern US, things will be changing in the atmosphere. Last update, we talked about the ridge near Alaska migrating to the north and the Greenland block beginning to decay. These two pieces are likely to do just that starting this weekend and into next week. The migration of the ridge will begin to eject the persistent troughing out west towards the Eastern US.

Also, an area of low pressure will slide underneath the ridge and lock the atmosphere in place once again. Although the breakdown of the ridge over Greenland will hurt for snow chances moving forward, the new look of the pattern come late next week will favor colder air to be in place across the Great Lakes and our region locally. There still remains uncertainty on how quick this change occurs. The Euro is a bit quicker with this change and has the cooler air moving in towards the end of next week while the GFS is still a bit slower and hesitant in moving the pattern.

This pattern change will hinder a lot on what the Madden Julien Oscillation does. MJO is still in phase 7, which is the warmer phase, but uncertainty remains on whether it makes a push for phase 8 or remains in phase 7. As mentioned last update, phase 8 is a cooler phase for the Eastern US and it would be what you want for the increase chances for snow. Models have the MJO going into phase 8 early next week but remain uncertain as to if it will remain there or revert back to phase 7. This is why the GFS has been hesitant with the change compared to the Euro. This will have implications on our temperatures moving forward and what we see locally with our next couple of storm chances into the middle of January.

Our next storm chance will come in the middle of that potential pattern change, and towards the end of next week. What was supposed to be the change this weekend, has now been pushed for change towards January 7th. This is our next chance for unsettled weather and our next chance for snow.

However, I have questions with this because models are signaling a good look for something along the East Coast now, but so was our New Year’s weekend storm a week out. At this moment and with the lack of blocking in place at the time over Greenland, I would expect this system to either slide over us or to the north with rain showers over to a bit of lake effect on the backside. Then if the pattern does or does not flip, we will be tracking another shot for unsettled weather early the following week, near January 10th. Our precipitation type will depend on the pattern switch.

If things do swing in the colder direction I do expect a decent shot of seeing some snow, however if the pattern shift continues to be pushed back or does not happen then we will likely once again be on the milder side of things.

Our next update will come this Sunday, January 2nd with a better outlook on the potential pattern flip ahead but overall do be prepared for some roadway issues with some lake effect Sunday and Monday.

Temperatures: Near average before turning cooler next weekend.

Precipitation: Above average the next two weeks.

Time Periods to Watch:

January 1st-January 3rd: 2 part storm. First comes on Saturday, second on Sunday. Scattered showers likely Saturday with first area of low pressure sliding over us or just to our south. Colder air moves in on backside for Sunday with a wintry mix over to snow which will be either lake enhancement or lake effect. Just be aware of possible roadway impacts.

January 6th-January 8th: Potential for low along East Coast is there, but blocking over Greenland breaks down. Possibly a rain to snow shower event again, but be aware for unsettled weather around this time.

January 10th-January 12th: Depends on potential pattern change. If the pattern does change than chances for snow will increase, but if not expect another warm system with rain showers.