Washington, D.C. is abnormally dry, on the brink of drought?

Since a soggy June and start to July, rain has been scarce in the D.C. area.   During both August and September, rain has been roughly half of normal in the region and the U.S. Drought Monitor has placed much of the region under its “abnormally dry” designation.

U.S. Drought Monitor as of Wednesday, September 25.

U.S. Drought Monitor as of Wednesday, September 25.

Since August began, Reagan National Airport has received just 2.56 inches of rain whereas the normal amount is 6.01 inches (for this 57-day period).  The story is similar for much of the region with totals generally 26-50 percent of normal, as the map below indicates.

Precipitation compared to normal over the last 60 days (National Weather Service)

Precipitation compared to normal over the last 60 days (National Weather Service)

Rainfall deficits were even greater at this time last week, but Saturday’s rain to the tune of around an inch helped chip away at them a bit.

The forecast for the next week or so is for little to no rain. The GFS model, shown below, simulates less than one-tenth of an inch of rain in the next 168 hours (or 7 days) in the D.C. area.

Simulation of total precipitation over the next 168 hours from the GFS model (WeatherBell.com)

Simulation of total precipitation over the next 168 hours from the GFS model (WeatherBell.com)

If the dry pattern persists through October, moderate drought conditions could emerge in areas.  The drought would be of the agricultural variety due to parched soils, not a hydrological drought – which requires a longer-term precipitation deficit.  Despite the lack of rain since July, annual rainfall is very close to normal.

October precipitation outlook. EC=Equal Chances of above or below normal precipitation. (National Weather Service)

October precipitation outlook. EC=Equal Chances of above or below normal precipitation. (National Weather Service)

The Climate Prediction Center’s precipitation outlook for October (above) calls for equal chances of above or below precipitation – so there are few strong clues as to whether these dry conditions will persist beyond the next week.

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