A Thanksgiving Day Storm Is Likely

Share on facebook
Share on twitter
Share on pinterest

Good morning Weather2020 bloggers,

We have made it to Thanksgiving week and on this Sunday morning, just four days away from the big holiday, we have a very complex weather pattern developing. The models will continue to have a hard time with what happens between now and next weekend. There is a good chance of some brief blocking developing near the west coast with the formation of a high over low block. How this develops will help determine what kind of weather you experience on Thanksgiving Day and the holiday weekend. There will likely be some impacts on travel, one of the biggest weekends for getting to and from your relatives and friends locations.  Let’s take a look.

1This first map shows the flow aloft over North America, which is valid Monday night. You can click on the map for a larger view.  The flow aloft is unblocked with a broad trough over New England and a digging trough off the Pacific Northwest coast. This energy is going to dive south and form into a rather strong upper low. As this happens, it will provide great conditions for snow at many ski resorts out west. This is something that we have not been able to say in years, especially for California. This is still not a storm coming in with a lot of  moisture as it is coming in from the northwest and not the west or southwest, which may happen later this winter.

2This second map shows the 500 mb flow (18,000 feet up) valid Wednesday night at 6 PM.  The flow aloft is still unblocked. Look closely at the eastern Pacific Ocean. A big ridge is developing and if this closes off into an upper high, then we will finally get the flow to block up a bit.  As the flow does begin blocking, what happens next is way too complex for the models to handle and figure out. The upper low is going to be ejected out into the plains and in this process it is likely going to fall apart.

3This third map shows the evolution of the high over low block near the west coast. The big upper low is forecast to get kicked out and absorbed into the flow.  And, a new upper low is forecast to begin developing over California. This upper low and evolution will also be influenced by the system way off the west coast as it gets caught in the southern branch heading towards California as well. This is really a complex development.

There is a well defined northern branch and the developing southern branch.

4

This fourth map, above, shows the developing high over low blocking well. The models, by this point have many different solutions. The way this pattern develops in the next week is rather obviously complex.  There is a lot to monitor here. There is also a tropical system sneaking into the equations south of Cabo san Lucas.

Now what does all of this mean to you? For Thanksgiving Day a strong cold front will have developed and it will only be inching its way eastward. That will be a very cold air mass with some Arctic Air Mass characteristics.  Temperatures will likely be below zero near the center of that air mass up north.

5

Look at where the front is lining up at 6 PM Thanksgiving Night:

6

Now, imagine you are me, or you are one of the 100,000 people thinking of going to see and experience the tradition of the Plaza Lighting that takes place every Thanksgiving Night at just before 7 PM?  This is a forecast map valid at 6 PM Thursday.  If this solution is exactly right, then the forecast would be for a 100% chance of rain around that 6-7 PM time frame. And, that front is strong. If it is six hours slower, then it will likely by in the lower 60s for the Plaza Lighting. If it’s six hours faster, then it would be in the 30s.  Maybe now you can see why Kansas City was the #1 most unpredictable city in America for big cities in the United States.  We have a big challenge ahead.

What would slow it down?  That upper low needs to sit back over the southeast and hold together just 12 more hours. Let’s see how today’s models handle this interesting development.

Have a great Sunday. Thank you for reading and participating in this LRC Forecast Experience Blog. Have you entered the forecast contest yet? We are forecasting for the the week of Christmas.

Gary

Share this post with your friends

Share on facebook
Share on google
Share on twitter
Share on linkedin

Leave a Reply

avatar
  Subscribe  
Notify of
Bill in Lawrence
Guest
Bill in Lawrence

Gary: Happy Monday to you sir!!! This is probably a Get Smart Comment in that the new blog will be up as I type this, but looking at the AO forecast, it appears more and more likely that the first of December will see the return of the AO dip into the negative that we saw in October. There has been some consistence in the past few days of the AO possibly going as low as negative 2 in this time frame. The cold air intrusion into the plains after this week’s storm would seem to coincide with the beginning… Read more »

Gary H
Guest
Gary H

Very good blog post, Gary. The next couple of days will be fun watching the models trend and converge.

Mr. Pete
Guest
Mr. Pete

Rockdoc yeah I’m in the old part of PV where there are lots of big trees and power lines are above ground. A ice storm would be terrible in this part of town. Go Chiefs!

Rockdoc
Guest
Rockdoc

Thanks Mr. Pete. I live south near 95th. Most lines appear buried, but a lot of big trees with a lot of leaves. Sure hope the temps stay up and no ice.

joe
Guest
joe

Gary,

I used the LRC and predicted our first inch of snow on Dec. 1st. Wasn’t sure of the cycle length to go with so I picked the one in the middle. Looks like it may have a chance at verifying!

Rickmckc
Guest
Rickmckc

Wow, I can’t remember seeing that kind of action on the west coast in a long, long time. I’d prefer snow here in KC but even if the weather is just interesting (like this pattern appears to be), I’ll be happy!

Mr. Pete
Guest
Mr. Pete

Does Friday evening look dry Gary?

Rockdoc
Guest
Rockdoc

Hi Mr. Pete. I live in PV 2, so it is good to know another weather follower. I hope we don’t get any ice/snow on possible Monday system post Turkey Day. Since I’m not sure about PV electric distribution/possible outages in storms I just bought 2 bundles of wood and plan to get another 8-10 to compliment what I have heading into this winter. Any info on previous ice/snow storms here?

Michael
Guest
Michael

I just want to know what the possibility of snow is with this system. Any chance? If so, how much?

Dale
Guest
Dale

It still looks like KC gets the small version of cold late this week. The true cold air never makes it here. Just looks like a cold rain again.

Rockdoc
Guest
Rockdoc

Good Sunday Morning Gary. Wow, what a crazy setup. That low off the southeast does not look too strong if I’m reading it right. Too bad the rain may not hold off for the Plaza lighting. Can you imagine if all that rain was snow? We’d possibly be looking at buckets of snow! How much would it be based on the current modeled rainfall? Looking forward on the GFS, it looks like the surface low out in the Pacific off of California will visit us late Sunday into Monday and possibly bring us some ❄❄❄, but the 2m temps may… Read more »

stl78
Guest
stl78

Great write up gary! Do u see any chance of freezing rain? I noticed the wx1 app shows a chance

terry mercer
Guest
terry mercer

Gary you said we can get some blocking up north what dose that help do if it do? You said that the models would have a hard time handling it. Dose that help with the Very cold air to build up?