Tuesday 10 a.m.
There's quite a contrast in conditions between Michigan and Massachusetts. At mid-morning, Detroit had some sunshine with south to southwest winds bringing in milder air. Meanwhile, in the I-95 corridor from Boston to Baltimore, dreariness greeted the dawn and dampness lingered. The surface pressure pattern helps explain this. Along the East Coast, the flow is coming from the Atlantic. The isobars bend around over the Appalachians, and the flow west of there is from southwest to northeast. The lines become closer together as you move north through Michigan, and the wind increases to match that. Finally, the isobars at the far upper-left corner of the map peel away from their tight packing and assume more of a west to east orientation. The change occurs along a cold front that will speed to the east and off the New England coast tomorrow night.
This video explores the current situation and how things should progress for the rest of the week and this weekend.
The cold front is embedded in a large area of clouds, showers and thunderstorms covering the middle of the country. It will advance past the Northeast coast by the end of the day Sunday. The frontal zone is shown on this picture from late morning Friday.
When weather systems are relatively weak, small scale variations cause forecast uncertainty because several different weather types (such as showers, sunshine, cloudiness, etc.) can coexist in the same region and change constantly. This map shows such a pattern:
Some of the thunderstorms can become severe, with damaging wind and brief cloudbursts of rain. The greatest chance for locally severe storms should be in the "S" areas highlighted on this map (based on the NWS Storm Prediction Center's guidance).
There is a slight risk for severe thunderstorms later today from north-central Tennessee up across Indiana and Ohio to Michigan and eastern Wisconsin (shown by the "S" area on the map below. Thunderstorms are not predicted for areas near the coast from Delaware to New England.
It is not going to snow any time soon, but in any type of weather the flag is a symbol of freedom. This holiday weekend we celebrate the contributions of those who were there to defend the freedoms we enjoy in these times.
Once again, the rain will miss much of central and northern New England. The region has been in a dry spell, as evidenced by its appearance on this U.S Drought Monitor map.