Wednesday May 20

Our weather is being dominated by a large upper level Low Pressure system that is cut off from the jet stream. This nearly stalled pattern keeps dumping heavy rain and flooding across the MidWest. Off the coast, Arthur helped to created the traffic jam in the atmosphere, it is no longer a tropical storm. But it has added moisture aloft with the chilly east wind to keep clouds around and hold our temps in the 60s.

Water Vapor Satellite: Cut Off Low

I wanted to highlight this image, before you see the loop below.  The blue, white, and green colors represent moisture at higher levels of the atmosphere. The yellow shade are dry air. Circulation around the Cut Off Low is what’s pumping moisture into the same areas. We are getting a steady east wind. That keeps us chilly and taking cloud tops from Arthur to dim the sky.

May 20 Cut Off Low


Water Vapor Satellite Loop




Chicago has had their wettest May on record so far with 8.3 inches. This is the thirds year in a row with a new May rainfall record. There are still 11 days left in the month to add to it.

Michigan had a dam break from their heavy rain, and needed to lift COVID19 restrictions for evacuation proceedings.


What does this mean for us?


Chilly Afternoon Temperatures 

May 20 maryland weather Wednesday high temperatures


The upper level flow may develop a band of sprinkles or light rain. This model is not perfect, but I am showing this for the idea of what we might see develop across the region.

May 20 maryland weather Wednesday rain


Also see: Today’s Weather Collection Lab

May 20 maryland weather Wedneday morning📋Observations yesterday 

🌡 Climate data today 

🗺 Weather Map


☀️ Sunrise and sunset times

🌙 Moon phase





This model is trying to drop morning temps into the 30s across southern PA. If there is frost, it would depend on the winds going light.  But this does suggest the sky to the north will clear.

May 20 maryland weather Thursday low temperatures


Rain: Once again the staled Low should keep the rain in place across southwest Virginia.

May 20 maryland weather Thursday rain


May 20 maryland weather Thursday high temperatures


Friday: Our Rain Day

This is when the Cut Off Low slowly spins our way. Rain and some thunderstorms are possible. This rain chance may last through the weekend.

May 20 maryland weather Friday morning rain


May 20 maryland weather Friday ECMWF morning rain


Rain Animation

The GFS Model shows the rain spreading in Friday, with showers lingering on Saturday.  The rain should get pushed back west into the mountains by Sunday. This leaves the weather locally better for the second part of the weekend.

Beaches: The persistent EAST WIND will keep temps in the 60s and rip currents through Memorial Day Monday.



Temperature Outlook

May 20 maryland weather temperature outlook Friday


Also See:

New Video Series: What is this cloud?

First installment about a weather prediction instrument I want to test

2020 Tropical Storm and Hurricane Names and Naming History

Tropical Storm Hurricane History


Atlantic Tropical History: Maps of Origin Regions Every 10 Days

13_Tropical Storm Formation Sep11_20

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