The latest observations show temperatures that are way above normal for this time of year in the Mid-Atlantic I-95 corridor with 80 degrees at Reagan National Airport in DC, 76 degrees in Philly, and 72 degrees at Central Park in New York City. Despite the impressive warmth of today in this region, there is actually an outside chance that sleet and/or snow are seen in these same locations tomorrow evening as much colder air pours into the area.
A powerful cold front will be moving from west-to-east towards the east coast on Tuesday and this will result in some dramatic temperatures drops behind the front as well as some significant differences across the frontal boundary zone. For example, during the mid-day hours on Tuesday, temperatures may be close to the 70 degree mark in southeastern Pennsylvania while, at the same time, they are in the 20’s in the northwestern part of the state. This frontal system will be accompanied by significant rainfall (1-2 inches) in DC, Philly and New York City along with persistently strong winds and there can be a few thunderstorms mixed into the picture.
As the colder air pours in early tomorrow night behind the passage of the frontal system, lingering rain showers can mix with or change to sleet and/or snow - even into the big cities along the I-95 corridor - but the greatest chance for this changeover to occur before the precipitation ends will be in the western and northern suburbs. In the interior, higher elevation regions of the Northeast U.S., there can even be a few inches of slushy snow later tomorrow (e.g. Appalachian Mountains). By Wednesday morning, temperatures will be at or below freezing throughout the Mid-Atlantic region and patchy frost will be possible early Thursday morning and perhaps even early Friday morning. Temperatures will then modify noticeably by the weekend.
One final note: there is a total lunar eclipse early tomorrow morning, but clouds are very likely to obscure the view in the Mid-Atlantic region; however, there will be another chance in September.