The approach of the autumnal equinox this week will correspond to a weather pattern change for the Fredericksburg area.
Wednesday, Sept. 22, ushers in the beginning of astronomical autumn for the Northern Hemisphere. The equinox that occurs on that day means that the entire Earth’s surface experiences roughly the same number of hours of sunshine (see graphic). After that, Fredericksburg-area residents will see daylight hours dwindle from 12 hours down to 9 hours at the winter solstice in December.
Meanwhile, today (Monday) started with an “I-95 divide” regarding sunshine. Areas west of the interstate dawned under overcast skies while eastern portions of the Fredericksburg vicinity had bright sunshine. Overall, today will wind up partly cloudy, with afternoon temperatures topping out at or just above 80 degrees, pretty close to average for this date in September.
The milder conditions are due to Sunday’s cold front passage, which is allowing high pressure over New England to exert its influence on the Fredericksburg area. Cool air filtering down the Eastern seaboard is a typical signal of cold air damming, which has been a relatively rare event in recent months. One result of this current setup is to keep moisture from the remnants of Nicholas (remember it?) from creeping north into the area today.
However, the moisture lurking over the southern U.S. won’t be delayed very long. Tonight clouds will roll back overhead and Tuesday looks to be mostly cloudy. Shower chances will arrive during the afternoon hours, with Fredericksburg-area thermometers reaching 80 degrees once again. Rain chances will increase Tuesday night, with Wednesday looking pretty damp as a strong cold front approaches the region from the west.