TRACKING JOAQUIN: Deeper look into storm's potential impact on DC this weekend

- The FOX 5 Weather Team continues to monitor the potential for a significant rain event late this week, primarily on Friday and Saturday.

The jet stream, which has been held to the north for the majority of the week, will take a sharp dive southward across the eastern half of the country by Thursday afternoon. The result will be cooler air spilling into the region, with D.C. trading early week highs in the warm and humid 80s for cooler 60s as early as Thursday.


The change will not bring much in the way of quieter weather however, as the jet stream will dip far enough southward to tap into some tropical moisture, which is then directed right back toward the Mid-Atlantic region. The position of this jet stream is vital, as it looks run up the coastline and then push inland across the applications.

This leaves D.C. in a zone which favors the rapid development and strengthening of areas of low pressure, which means the potential for more rain for the region.

The Mid-Atlantic’s position relative to the jet stream is also important because models currently forecast us to be in what is often referred to as a “capture region.” This is where storms riding up the coastline can get pulled inland and enhanced due to the high winds of the jet stream.

With strengthening Tropical Storm Joaquin (likely a hurricane by Wednesday) out in the Atlantic, we are watching the potential for the storm to take a turn towards the East Coast potentially in our neck of the woods.

Many remember Hurricane Sandy, which was a storm that was also captured and pulled inland back in late October 2012. While this is a risk, it is not yet our forecast, but is something the weather department will be keeping a close eye on as the week goes on.

Regardless of the track of Joaquin, the end of the week still looks to be quite wet. On Thursday, an area of low pressure moves northward out of the Carolinas and becomes enhanced by the jet stream. This brings the D.C. region their next shot at some moderate rainfall.

However, the main event is a separate area of low pressure that will develop on Friday and slowly traverse the region through early Sunday morning. This system will have a very strong moisture flow coming up from the south, and weather models have been forecasting widespread 3-6” rain amounts, with localized amount of 8” or more possible.

Make no mistake, D.C. does need the rain. After the second wettest June on record where almost a foot of rain fell over the month, the pattern turned dry for most of July, August and September and Reagan National Airport is currently running about a 2.5” deficit on September alone.

What is not needed is all that rain at once. When it falls heavily and consistently over the course of a couple of days, the majority of the water is not absorbed by the soils. Instead, it becomes runoff, which leads to flooding, and chances are that flooding will indeed be a major story come the weekend.

While the forecast is still uncertain, one certainty is that you can count on the FOX 5 Weather Team to bring you the latest information over the next several days. Stay tuned!

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