This video shows why cooler air is coming to the Northeast (with the exception of some coastal spots where the westerly winds will be a bit warmer than the ocean winds were during the weekend).
This map shows the pressure analysis for the Northeast and Great Lakes. The gusty flow on the west side of the low pressure (where the lines are closest together) area adds a real autumn feel to the air.
Thunderstorms were widespread yesterday and last night as near-ground air was warm and humid while the air aloft was cooling.
More than 184,000 lightning strokes are plotted.
This map shows the pressure pattern earlier this morning. You can see the extensiveness of the area of west to east winds. As a storm north of the Upper Great Lakes moves eastward, the flow will become more northwesterly.
This year, the "slight" category has been divided in two: slight and enhanced. When seen together on an SPC map, the progression makes sense. When the term "enhanced" is used alone, it can be a challenge, at least until we get used to it.
This map shows the pressure analysis and locations of fronts and low pressure areas at 9 a.m. EDT today. Places from Philadelphia northeastward will only warm up if and when the warm front in Delaware passes any given spot. Chill air follows the front in Indiana.
This map shows the GFS forecast for Monday at 2 p.m. ET. If correct, rain will hold off for the Boston Marathon. However, you can see that any speedup of the rain would prove that idea to be wrong.
Another high pressure area will build over the Northeast during the weekend, so sunshine with mild afternoons can be expected. However, this forecast map for next Monday evening shows how extensive and wide ranging the next storm may be.
These maps show how the US model handles the disturbance now causing rain in Tennessee. On the 1st map (for tomorrow), it is embedded in a southwesterly flow. However the 2nd map (for late tomorrow night) shows it turning more toward the course that would take it out to sea.