Friday 10:40 a.m.
Chilly air is advancing into the Northeast this afternoon, and in many locations, tonight's chill will rival all-time records for the date. That's because the high pressure area marking the center of the chilly air mass will be right over the I95 corridor tomorrow morning, causing clear and calm conditions. Then, once the high moves to the east, a south to southwest flow of warmer air will become established. By Sunday afternoon, temperatures will be in the 60s throughout southern New England and 70 or higher farther south.
Strong thunderstorms from the middle of the country will head toward the western Great Lakes. The severe weather section at accuweather.com can be very helpful in explaining how these storms may affect you.
Tomorrow morning will be chilly in the Middle and North Atlantic states. Sam The Dog seems to like his early trip outside on cold mornings. I think it makes him appreciate the great usefulness of his fur coat.
The current surface pattern clearly shows the flow that is bringing ocean-cooled air in from the east. If the high pressure area to the north expands southward as expected by tomorrow, this flow will be weakened and perhaps cut off.
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.