History looks to repeat itself when it comes to the weather through early next week in the region. The upcoming pattern shows strong signals similar to that of late June 2006.
The pattern setting up late this weekend across the Washington metropolitan area is reminiscent of one a few summers ago at around the same time.
In late June 2006, a cold front approached the East Coast and then began to retrograde back to the west towards the Ohio Valley. This front was stretched out north to south and brought copious Gulf of Mexico moisture north as well as tapping plenty of Atlantic moisture.
Note the first image below; it shows a stationary front bisecting the region on June 24, 2006.
The upper level chart from late June 2006 shows a sprawling ridge in the West, which contributed to above average temperatures. The ridge was so persistent in June 2006 that Phoenix ended up with its warmest June on record with an average temperature of 94.6 degrees.
Even more striking, look at how the upper-level pattern is very similar to the setup we have now.
Now look at the next image showing the front retrograding west into the Midwest. This helped bring a surge of warm, moist Gulf of Mexico and Atlantic moisture into the region, helping to fuel very heavy rain.
Finally, look at the atmosphere profile similarity between the 2006 event and what is going on now. The dry air, evident by the far separation of the thick black lines at the 500 level (mid-levels of the atmosphere) on the second sounding below will become more saturated early next week as moisture returns in abundance. Winds are well-aligned in both profiles below and the amount of water, indicated by the PWAT number is very similar.
In all, this set up contributed to record rain across the District seven years ago in late June. Take a look at the daily record rainfall set across the Washington, D.C. – Baltimore corridor during this late June event.
While these numbers may not be achieved this time around, precipitation is already at a surplus for June and the year, so it won’t take much to push streams and creeks out of their banks and cause flooding in poor drainage areas as these strong downpours head our way.
This is the latest look at how much rain would be needed in 1 hour to produce flash flooding. Much of the region only needs 2.0 to 2.75 inches in 1 hour to cause flash flooding.
The heavier showers and storms could easily drop that much in an hour or less over the next few days. Be sure to never cross a flooded roadway because the water is typically deeper than it appears.
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