A Change Is Coming

Last week there were a couple of model runs, especially the Euro that showed a storm trying to develop in our area. Those couple of model runs turned out to be anomalies, it is likely the small system won’t make it over the continental divide, in a best-case scenario flurries fall over the 550 passes Saturday.  A change is coming but it’s 5-8 days away.

So far, November has had a trough in the midwest and east and a ridge in the west.  To determine these forecasters look at a 500 mb height map (mb stands for millibars, which is a unit for measuring air pressure). These maps are very good for getting a picture of the large-scale “weather pattern” over the United States, North America, or even the Northern Hemisphere. 500 mb maps are especially nice for studying wintertime weather patterns in the middle latitudes (between about 30° and 60° latitude).  The colors correlate with air-pressure NOT TEMPERATURE. So red doesn’t necessarily mean warm nor does blue mean cold. Red means above-average heights (ridge) and blue means below-average heights (trough). Ridge’s are usually associated with tranquil weather and troughs are associated with stormy weather.

Here is the current 500 mb height map

GFS500current.png

As I said earlier the pattern has looked similar to this all month.

The pattern will start to change at the beginning next week and one week from now is forecasted by the GFS model to look like this.

gfs5001121.png

Here is the current GFS run for next Thursday using different parameters that you are more familiar with seeing on this site.

gfs-deterministic-namer-instant_ptype-4337600

You can clearly see the low pressure in Arizona, in the northeast and a massive, nasty storm in the Bering Sea, in weather terms, this storm is “bombing out” and is the equivalent of a category 3 hurricane in intensity. It is not at all unusual to sea storm like this in the Bering Sea, they usually are the result of a recurving typhoon from the SW Pacific.

Here is a zoomed-in version of the map above.

zoom.png

There are four circles, one over the four corners one in southern Arizona one in New Mexico and one in eastern Colorado and western Kansas. Those are closed areas of circulation of low pressure. Above the low pressure over the four corners, you see a red line and if you follow along the red line you will see a 552, which tells me that below the 552 line the snow level will be approximately 8,000 feet. The red line above the 552 is the 546 line which is important for us because the snow level drops to 6500 feet.

All said and done here is what the GFS is currently showing for snow from that storm

GFSsnow.png

Here is the Euro

eurosnow.png

 

When we are this far out the models will often agree with outcomes but disagree with how they arrive at that outcome. That is exactly what is going on right now, they are seeing the strong potential for this event but one or all of the models will likely be right, for the wrong reasons. That happened several times during the 2016-2017 winter. So I would not take this to the bank yet but it is sure fun to see on the maps.

Looking out for the rest of November is exciting if you like stormy weather

Now that you know how to interpret the upper air pattern maps check out the last week of November.

gfs-ensemble-all-avg-namer-z500_anom-1573711200-1574445600-1575093600-40

Check back on Saturday for my next update. Thanks for following and supporting the site!

 

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