The stubborn weather pattern that just won’t quit

Explaining the 'cut-off upper low that’s bringing a week of clouds and rain

The stubborn weather pattern that just won’t quit
Upper Low getting kicked off to the east (Source: NBC12)

RICHMOND, Va. (WWBT) - We saw this coming last week - a cool, cloudy, rainy pattern that would stick around for a while. Here it is on the water vapor map from the National Weather Service:

This is a classic example of a Cut-Off Low. Here’s the definition from the NWS’s online glossary:

“A closed upper-level low which has become completely displaced (cut off) from basic westerly current, and moves independently of that current. Cutoff lows may remain nearly stationary for days, or on occasion may move westward opposite to the prevailing flow aloft (i.e., retrogression).”

It’s called an upper-level low because it’s not at the surface. It’s at the jet-stream level (20 to 40 thousand feet up). I’ve drawn the upper low on the surface map below, which shows it’s displaced far the west of the surface low that’s set to bring us a round of soaking rain Thursday night and early Friday.

The "cut off" low that's bring us rain, clouds, and cool temperature
The "cut off" low that's bring us rain, clouds, and cool temperature (Source: NBC12)

In this case, it’s a classic. The jet stream is displaced WAY to the North so the low has just been sitting and spinning...inching to the east and waiting for the jet stream to scoop it up and kick it offshore.

That kick is finally coming. This loop is a jet stream level forecast through early Saturday morning, showing a dip in the jet stream swinging in from the west. It’ll scoop up the cut off low and sweep it out to sea.

Upper Low getting kicked off to the east
Upper Low getting kicked off to the east (Source: NBC12)

Just in time for the holiday weekend!

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