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Last week we began talking extensively about the warm-up for this week. It began today with low 30s at Mitchell Airport in Milwaukee, and will continue for the rest of this week. Wednesday and Thursday still look like the warmest days this week with highs well into the 30s.
Since the forecast is quiet this week, let’s take a look at the January weather pattern. Back on December 29th I made a forecast for the entire month of January based on the LRC.
The LRC is a theory that says the weather pattern sets up from October 1 to November 10 each year, and then begins to cycle. The LRC uses the large scale weather pattern, determining the locations of the long term long wave ridges and troughs across the northern hemisphere. The best way to study the pattern is at 500mb, or the middle of the atmosphere. The pattern can be translated down to the surface, but a seasonal shift of the jet stream, moisture content, snow pack, etc. all need to be considered when looking ahead. By December when the weather pattern generally repeats for the first time, the cycle length can be determined, thus allowing for fairly accurate long range forecast to be made. For this LRC season(winter, spring, summer) the cycle length is roughly 60 days.
Before we look ahead…let’s look back to where we have been. Again, anything that references the January forecast that I made was done on December 29.
Here is what I was forecasting for January 8-15:
The second week of January will look a lot like the first week in terms of precipitation to start. A clipper should arrive somewhere around the 7-9th window bringing light snow or flurries and a push of cold air. This should be a pretty quick hit of cold, before a warm-up ahead of the next potential storm. The end of this period around the 15th give or a take a day should bring a bigger change to the region.
The big question for this time around in the cycle is how will this storm move. Back in November this storm never really ejected or lifted north into the upper Midwest. It became cut-off and traveled east. This is one storm that could bring us a good snow, but if the cold air wins and it stays south then little or no snow. For this forecast I will lean in the direction of this not being a major storm for us, but one that we should watch.
I identified the clipper and brief cold snap that followed, but did not recognize the lake effect snow that resulted in heavier snow totals. Again, the theory that I use is not able to predict lake effect snow weeks out, just like in the summer it would not be able to forecast a single thunderstorm over a given location for hours producing inches of rain. It is the general pattern that I focus on. So, now that the warm-up is in sight as mentioned above, where is the storm around the 15-17?
Let’s first look back to November 17 at the 500mb chart. This is exactly how things looked on the 17th. A well defined upper low near the Missouri and Arkansas border, a split flow in the jet stream, and a trough near the Pacific Northwest.
Let’s now fast forward and look at that same storm roughly 60 days later, or the cycle length of the pattern this LRC year. The map below is from the 12Z GFS and is valid for January 16…roughly 60 days after the map above on November 17.
Looking at the map below for January 17 the upper low is shifted more to the south, which is expected due to the seasonal shift of the jet stream. There is also a trough present over the Pacific Northwest. Due to the split flow that will be present, the storm will stay to our south, and temperatures will remain average to a little above average.
Overall, this part of the forecast has worked out pretty well, and if you look back to the entire January forecast that I made, I also included the map comparison of this upcoming storm that will miss us to the south.
So the big question is, will another major storm hit us this month. Right now I will continue my thinking from back on December 29 and say yes. Here is what I said then.
The last week of January looks to be the most exciting and wettest of the month for our area. If we are going to see a major winter storm during January, I think this would be the storm and timeframe for our area. Again, the question will be where does it move, but unlike the storm around the middle of the month, this one should lift north into our region. This storm could be rain, sleet, snow, or all of the above. This storm should be followed by a push of arctic air that likely will end the month cold.
One of our long range models that we use forecasts out 384 hours. To be honest, with most models once you get past about 3-5 days their accuracy is not very good. But since we know the pattern and that a storm should be around the region roughly 60 days from November 24, we can expect something fairly large to be around Milwaukee somewhere around January 24.
The model that forecasts out long range is now locking onto a pretty impressive storm on the 24th! This is not how the storm will look on the 24th, but this certainly supports my thinking! I do think when this part of the pattern repeats we could see rain, sleet, or snow. So get ready, the most exciting part of January may still be ahead!
So what are your thoughts on the rest of January? Do you think we will see a storm around the 24th?
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