Sunday October 17, 2021

We finally got back into a real autumn weather pattern. Going from the 80s to slightly below average may make you just want to catch your breath.  While we have a warm up on the way back to the 70s this week, it won’t last.  So when I mention the first frost of the season here, I am not getting ahead of myself. We are due!

Jet Stream

This snapshot of the upper air pattern for next weekend shows the progressive pattern.  By progressive, I mean cold air aloft will continue to get reinforcements, and try to make up for lost time (our warm start to October).

Next weekend we will be back into a trough, cool air aloft.  Looking westward or upstream across the US, and we see a weak ridge, followed by yet another surge of colder with with the Pacific Trough.  Things are about to get interesting….

Note: The 500 mb height is around 18,000 Feet above the ground. That is here the main river of air we call thee Jet Stream is located. There are different layers and air flow we track even higher. 

Jet Stream – Long Range Animation

7 AM Mon Oct 18 to 7 AM Sun Oct 31

This is a Two-Week Outlook

The snapshot above is the middle of this loop, so you can track that next trough across the US. This may spawn a fast moving storm system for Us Halloween Weekend. This pattern is what may be more common with a La Nina start into winter.

Also See: La Nina Advisory To Start Winter

Temperature Trend

8 AM Mon Oct 18 to 8 AM Sun Oct 25

Just for fun, I wanted to plot the animation of temperatures.   Here you can see the warm afternoons midweek, followed by the progressive cold next weekend. 

Timing is in the upper right corner. 

Universal Time Code: 12Z Mon = 8 AM Mon.  00Z Tue = 8 PM Mon

First Frost or Freeze?

Temperatures Snapshots: Next Weekend

Saturday October 23

Hint of 30s in the northern suburbs. This first surge may come with gusty winds, limiting potential frost formation. Noticeably warmer by the water of the Chesapeake Bay. But it will be getting colder. 

Sunday October 24

Winds will be higher as the core of this air mass settles in place.  That will allow more widespread cold, and a better chance for frost to form inland (west and north) of Baltimore. 

This may be the first morning below freezing in the high mountains of western Maryland and West Virgina.

Model Spotlight: ECWMF Temperatures 

Note: This European Model plot is for the weather station at BWI Airport.  Often, temps are cooler just a few miles inland west and north. This is why I see high potential for frosty 30s next weekend. 

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