Cooling Down Late Week but Indian Summer to Return

Precipitation: The image below (courtesy NOAA) shows the thirty-day departure from average with much of the Washington Region experiencing rainfall deficits of 1 to 3 inches.

The extended forecast models keep our area under the influence of high pressure through the next 7 to 14 days.  High pressure will begin delivering much cooler air on Thursday evening through early next week with highs remaining in the 70s and lows dipping into the 50s.  Some of our far outer exurbs could even dip into the 40s later this weekend.

European Ensemble keeps high pressure in control through much of the extended period:

Orange colors represent 500-mb height anomalies (or areas of high pressure in the mid levels of the troposphere).

After a brief trough swings through (blue colors) this weekend, a strong upper-level area of high pressure is forecast to set up shop over southeastern Canada and northern New England

European Ensemble 850-mb temperature anomalies:

The late September heat wave will break down this weekend into early next week but a ridge of high pressure will build back to the north and temperatures will once again climb above average during the middle to later half of next week.

Rain chances would increase if a tropical system forms underneath the upper-level ridge and tracks up the east coast.  While September through November is on average our driest time of year we could use a soaking rain to settle the dust and clear out the mold spores.

 

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