The Washington Post

Jet stream plunge to foster fall sneak preview

I’m so fired up by Sunday’s weather map, I’m sharing it six days ahead of time. Look at how big the simulated dip in Sunday’s jet stream is.


Sunday’s upper level weather map showing the jet stream (Unisys weather)

A big area of low pressure over the Hudson Bay, and its associated counterclockwise circulation is driving cool air from the Arctic southeastward.

Here’s how NOAA’s Hydrometeorological Prediction Center describes the pattern:

A FAIRLY DEEP MEAN TROF [DIP IN THE JET STREAM] SHOULD SETTLE OVER EAST-CENTRAL NORTH AMERICA WITH AN ANCHORING CLOSED LOW OVER OR JUST SOUTH OF HUDSON BAY...

Our local forecast office in Sterling says:

LOW HEIGHTS [PRESSURES] SUGGEST UNUSUALLY COOL AIR MASS WILL BE FOUND FROM THE GREAT LAKES TO APPALACHINS ...WITH MAXIMA IN OUR FORECAST AREA IN UPR 70S-LWR 80S BOTH SAT AND SUN.

After so many sweltering summer days, will you welcome a day when highs struggle to reach 80 with widespread 50s at night (Sunday)?

Jason is the Washington Post’s weather editor and Capital Weather Gang's chief meteorologist. He earned a master's degree in atmospheric science, and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association.
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